1. The velocity factor of a transmission line depends on A.temperature B. skin effect C. relative permittivity of dielectric D.none of the above Answer & Explanation Answer: Option C Explanation: ∈r of a dielectric changes with humidity.
2. A loss less line of characteristic impedance Z0 is terminated in pure reactance of -jZ0 value. VSWR is A.10 B. 2 C. 1 D.infinity Answer & Explanation Answer: Option D Explanation: A pure reactance does not absorb any power. Therefore VSWR is infinite because |rv| = 1.
3. In a klystron amplifier the input cavity is called A.buncher B. catcher C. Pierce gun D.collector Answer & Explanation Answer: Option A Explanation: A Klystron is a vacuum tube used for generation/amplification of microwaves. An electron beam is produced by oxide coated indirectly heated cathode and is focussed and
accelerated by focussing electrode. This beam is transmitted through a glass tube. The input cavity where the beam enters the glass tube is called buncher. As electrons move ahead they see an accelerating field for half cycle and retarding field for the other half cycle. Therefore, some electrons are accelerated and some are retarded. This process is called velocity modulation. The velocity modulation causes bunching of electrons. This bunching effect converts velocity modulation into density modulation of beam. The input is fed at buncher cavity and output is taken at catcher cavity. In a two cavity klystron only buncher and catcher cavity are used. In multi cavity klystron one or more intermediate cavities are also used. The features of a multicavity klystron are : 1. Frequency range - 0.25 GHz to 100 GHz 2. Power output - 10 kW to several hundred kW 3. Power gain - 60 dB (nominal value) 4. Efficiency - about 40%. A multicavity klystron is used in UHF TV transmitters, Radar transmitter and satellite communication.
4. In a circular waveguide the dominant mode is A.TE01 B. TE11 C. TE20 D.TE21 Answer & Explanation Answer: Option B Explanation: Some applications require dual polarization capability. Circular waveguide has this capability.
These analysis uses cylindrical coordinates. In circular waveguide TE11 mode has the lowest cut off frequency and is the dominant mode. If D is diameter of waveguide λc = 1.706 D for TE11 mode λc = 1.029 D for TE21 mode λc = 0.82 D for TE01 mode λc = 1.306 D for TM01 mode.
5. The reflection coefficient on a line is 0.2 ∠45°. The SWR is A.0.8 B. 1.1 C. 1.2 D.1.5 Answer & Explanation Answer: Option D Explanation:
6. Microwave resonators are used in A.microwave oscillators B. microwave narrow band amplifier C. microwave frequency metres D.all of the above Answer & Explanation Answer: Option D Explanation: They are used in all the devices.
7. Assertion (A): TWT uses a focussing mechanism to prevent the electron beam from spreading. Reason (R): In a TWT the electron beam has to travel a much longer distance than in klystron. A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation Answer: Option A Explanation: In a klystron the resonant structure limits the bandwidth. A TWT is a broadband device. Its main components are electron gun (to produce the electron beam) and a structure supporting the slow electromagnetic wave. The velocity of wave propagation along the helix structure is less than velocity of light. The beam and wave travel along the structure at the same speed. Thus interaction occurs between beam and wave and the beam delivers energy to the RF wave. Therefore the signal gets strengthened and amplified output is delivered at the other end of tube. The main features of TWT are : 1. Frequency range - 0.5 GHz to 90 GHz 2. Power output - 5 mW at low frequencies(less than 20 GHz) 250 kW (continuous wave) at 3 GHz 10 MW (pulsed) at 3 GHz 3. Efficiency - about 5 to 20% 4. Noise - about 5 dB for low power TWT 25 dB for high power TWT TWT is used as RF amplifier in broadband microwave receivers, repeater amplifier in broad band communication systems, communication satellites etc.
8. In a TWT the amplitude of resultant wave travelling down the helix A.increases exponentially B. increases linearly C. decreases exponentially D.is almost constant Answer & Explanation Answer: Option A Explanation: In a klystron the resonant structure limits the bandwidth. A TWT is a broadband device. Its main components are electron gun (to produce the electron beam) and a structure supporting the slow electromagnetic wave. The velocity of wave propagation along the helix structure is less than velocity of light. The beam and wave travel along the structure at the same speed. Thus interaction occurs between beam and wave and the beam delivers energy to the RF wave. Therefore the signal gets strengthened and amplified output is delivered at the other end of tube. The main features of TWT are : 1. Frequency range - 0.5 GHz to 90 GHz 2. Power output - 5 mW at low frequencies(less than 20 GHz) 250 kW (continuous wave) at 3 GHz 10 MW (pulsed) at 3 GHz 3. Efficiency - about 5 to 20% 4. Noise - about 5 dB for low power TWT 25 dB for high power TWT TWT is used as RF amplifier in broadband microwave receivers, repeater amplifier in broad band communication systems, communication satellites etc.
9. Which of the following is not a travelling wave? A.e = Em sin (βx - ωt) B. e = Em cos (βx - ωt) C. e = Em sin (ωt - βx) D.e = Em sin (βx)
Answer & Explanation Answer: Option D Explanation: In a travelling wave both x and t increase simultaneously so that a constant phase point moves in the direction of positive (or negative) x.
10. Both Impatt and Trapatt devices use avalanche effect A.True B.False Answer & Explanation Answer: Option A Explanation: An Impatt diode has n+ - p - i - p + structure and is used with reverse bias. It exhibits negative resistance and operates on the principle of avalanche breakdown. Impatt diode circuits are classified as broadly tunable circuit, low Q circuit and high Q circuit. The impedance of Impatt diode is a few ohms. The word Impatt stands for Impact Avalanche Transit Time diode. The features of Impatt diode oscillator are : frequency 1 to 300 GHz, Power output (0.5 W to 5 W for single diode circuit and upto 40 W for combination of several diodes), efficiency about 20%. Its applications include police radar systems, low power microwave transmitter etc. Avalanche diode can also be operated in large signal high efficiency mode called Trapped Avalanche Transit Time mode. The Trapatt oscillations depend on the delay in the current caused by avalanche process. The avalanche delay makes it possible to increase the diode voltage well above the breakdown voltage. Therefore a very rapid multiplication of charge carriers occurs. A Trapatt diode is also a negative resistance device.
The features of Trapatt diode oscillator are : Frequency 3 to 50 GHz, Power output 1-3 W, efficiency about 25%. Its applications are low power doppler radar, microwave beacon landing system etc. 11. In a directional coupler A.isolation (dB) equals coupling plus directivity B. coupling (dB) equals isolation plus directivity C. directivity (dB) equals isolation plus coupling D.isolation (dB) equals (coupling) (directivity) Answer & Explanation Answer: Option A Explanation: Isolation equals coupling plus directivity.
12. As the frequency is increased, the charging MVAR in a cable A.decreases B. increases C. remain the same D.decreases or remains the scheme Answer & Explanation Answer: Option B Explanation: Charging current and MVAR are proportional to frequency.
13. Loss angle of a good quality cable is about A.1° C. 70° Answer & Explanation
B. 30° D.90°
Answer: Option A Explanation: For ideal dielectric loss angle is zero. For good quality cables, loss angle is very small, about 1° only.
14. In a three cavity klystron amplifier, the oscillations are excited in A.input cavity B. output cavity C. intermediate cavity D.both (a) and (b) Answer & Explanation Answer: Option C Explanation: A Klystron is a vacuum tube used for generation/amplification of microwaves. An electron beam is produced by oxide coated indirectly heated cathode and is focussed and accelerated by focussing electrode. This beam is transmitted through a glass tube. The input cavity where the beam enters the glass tube is called buncher. As electrons move ahead they see an accelerating field for half cycle and retarding field for the other half cycle. Therefore, some electrons are accelerated and some are retarded. This process is called velocity modulation. The velocity modulation causes bunching of electrons. This bunching effect converts velocity modulation into density modulation of beam. The input is fed at buncher cavity and output is taken at catcher cavity. In a two cavity klystron only buncher and catcher cavity are used. In multi cavity klystron one or more intermediate cavities are also used. The features of a multicavity klystron are : 1. Frequency range - 0.25 GHz to 100 GHz 2. Power output - 10 kW to several hundred kW 3. Power gain - 60 dB (nominal value) 4. Efficiency - about 40%. A multicavity klystron is used in UHF TV transmitters, Radar transmitter and satellite
communication.
15. In the given figure reflection coefficient at load is
A.0.6 B. - 0.6 C. 0.4 D.- 0.4 Answer & Explanation Answer: Option B Explanation:
16. Which of the following lines is non-radiating? A.Open two wire B. Coaxial C. Both D.None of the above Answer & Explanation Answer: Option B Explanation: Since fields are confirmed within a coaxial cable it is non-radiating.
17. Assertion (A): The impedance of a matched load is equal to characteristic impedance of line. Reason (R): A matched termination absorbs all the power incident on it. A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A
C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation Answer: Option A Explanation: Matched load means no reflections.
18. Skin effect is more pronounced at high frequencies. A.True B.False Answer & Explanation Answer: Option A Explanation: Skin effect increases as frequency increases.
19. Assertion (A): The phenomenon of differential mobility is called transferred electron effect. Reason (R): GaAs exhibits transferred electron effect. A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation Answer: Option B Explanation: A Gunn diode uses GaAs which has a negative differential mobility, i.e., a decrease in carrier velocity with increase in electric field. This effects is called transferred electron effect. The impedance of a Gunn diode is tens of ohms. A Gunn diode oscillator has a resonant cavity, an arrangement to couple Gunn diode to cavity, biasing arrangement for Gunn diode and arrangement to couple RF power to load.
Applications of Gunn diode oscillator include continuous wave radar, pulsed radar and microwave receivers.
20. Which of the following devices uses a helix? A.Klystron amplifier B. Klystron oscillator C. TWT D.Both (a) and (b) Answer & Explanation Answer: Option C Explanation: In a klystron the resonant structure limits the bandwidth. A TWT is a broadband device. Its main components are electron gun (to produce the electron beam) and a structure supporting the slow electromagnetic wave. The velocity of wave propagation along the helix structure is less than velocity of light. The beam and wave travel along the structure at the same speed. Thus interaction occurs between beam and wave and the beam delivers energy to the RF wave. Therefore the signal gets strengthened and amplified output is delivered at the other end of tube. The main features of TWT are : 1. Frequency range - 0.5 GHz to 90 GHz 2. Power output - 5 mW at low frequencies(less than 20 GHz) 250 kW (continuous wave) at 3 GHz 10 MW (pulsed) at 3 GHz 3. Efficiency - about 5 to 20% 4. Noise - about 5 dB for low power TWT 25 dB for high power TWT TWT is used as RF amplifier in broadband microwave receivers, repeater amplifier in broad band communication systems, communication satellites etc.
21. Which of the following parameters is negligible in transmission lines? A.R B. L C. C D.G Answer & Explanation Answer: Option D Explanation: Shunt conductance can be neglected in most of calculations.
22. The width of a radio beam from a 1 m diameter parabolic antenna at 10 GHz is about A.100° B. 50° C. 5° D.1° Answer & Explanation Answer: Option C Explanation:
23. The diagram to show distance time history of electrons in klystron amplifier is called A.apple gate diagram B. asynchronous diagram C. bunching diagram D.velocity modulation diagram Answer & Explanation Answer: Option A Explanation: Applegate diagram is distance time plot. 24. Impedance level of Impatt diodes is generally lower than that of Gunn diodes A.True B.False Answer & Explanation Answer: Option A
Explanation: An Impatt diode has n+ - p - i - p + structure and is used with reverse bias. It exhibits negative resistance and operates on the principle of avalanche breakdown. Impatt diode circuits are classified as broadly tunable circuit, low Q circuit and high Q circuit. The impedance of Impatt diode is a few ohms. The word Impatt stands for Impact Avalanche Transit Time diode. The features of Impatt diode oscillator are : frequency 1 to 300 GHz, Power output (0.5 W to 5 W for single diode circuit and upto 40 W for combination of several diodes), efficiency about 20%. Its applications include police radar systems, low power microwave transmitter etc.
25. A quarter wave line open circuited at far end behaves as A.inductance B. L and C in parallel C. capacitance D.L and C in series Answer & Explanation Answer: Option D Explanation: A quarter wave line o.c. at far end behaves as a series tuned circuit. 26. A line has Z0 = 300 ∠ 0° Ω. If ZL = 150 ∠ 0° Ω, reflection coefficient is A.0.5 B. 0.3333 C. -0.3333 D.-0.5 Answer & Explanation Answer: Option C Explanation:
Reflection coefficient
27. Assertion (A): A backward wave oscillator has an internal positive feedback. Reason (R): A positive feedback is necessary for sustained oscillations. A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation Answer: Option B Explanation: It is somewhat similar to TWT and can deliver microwave power over a wide frequency band. It has an electron gun and a helix structure. However the interaction between electron beam and RF wave is different than in TWT. The growing RF wave travels in opposite direction to the electron beam. The frequency of wave can be changed by changing the voltage which controls the beam velocity. Moreover the amplitude of oscillations can be decreased continuously to zero by changing the beam current. It features are: 1. Frequency range - 1 GHz to 1000 GHz. 2. Power output - 10 mV to 150 mW (continuous wave) 250kW (pulsed). It is used as signal source in transmitters and instruments.
28. In a microstrip transmission the signal can be easily redirected by changing the centre strip. A.True B.False Answer & Explanation Answer: Option A Explanation: A Microstrip line has a single dielectric substratc with ground plane on one side and a strip
on the other face. Its special feature is easy access to top surface so that minor adjustments can be made after circuit fabrication. The high dielectric constant of the substrate reduces guide wavelength and circuit dimensions. A microstrip line is the most commomly used transmission structure for microwave integrated circuits.
29. The frequency of oscillation in a backward wave oscillator can be changed by A.varying the voltage which controls beam velocity B. varying the beam current both by varying the beam current and by light varying the voltage which controls beam C. velocity D.changing the rate of thermionic emission Answer & Explanation Answer: Option A Explanation: It is somewhat similar to TWT and can deliver microwave power over a wide frequency band. It has an electron gun and a helix structure. However the interaction between electron beam and RF wave is different than in TWT. The growing RF wave travels in opposite direction to the electron beam. The frequency of wave can be changed by changing the voltage which controls the beam velocity. Moreover the amplitude of oscillations can be decreased continuously to zero by changing the beam current. It features are: 1. Frequency range - 1 GHz to 1000 GHz. 2. Power output - 10 mV to 150 mW (continuous wave) 250kW (pulsed).
It is used as signal source in transmitters and instruments.
30. A line has a phase constant of 29.8 rad/m. At 1000 MHz the wavelength is A.29.8 m B. 2.98 m C. 2.1 m D.0.21 m Answer & Explanation Answer: Option D Explanation:
. 31. In the given figure the time taken by the wave to make one round trip is
A.10 ns B. 20 ns C. 30 ns D.40 ns Answer & Explanation Answer: Option D Explanation:
32. For a 50 Ω resistor for 3 GHz application, the stray capacitance should be less than A.1 μF B. 1 nF C. 1 pF
D.0.1 pF Answer & Explanation Answer: Option D Explanation: XC should be at least ten times greater than R. Therefore for 50 Ω resistor at 3 GHz, C should be less than 0.1 pF.
33. In a travelling wave tube distributed interaction between an electron beam and a travelling wave takes place A.True B.False Answer & Explanation Answer: Option A Explanation: In a klystron the resonant structure limits the bandwidth. A TWT is a broadband device. Its main components are electron gun (to produce the electron beam) and a structure supporting the slow electromagnetic wave. The velocity of wave propagation along the helix structure is less than velocity of light. The beam and wave travel along the structure at the same speed. Thus interaction occurs between beam and wave and the beam delivers energy to the RF wave. Therefore the signal gets strengthened and amplified output is delivered at the other end of tube. The main features of TWT are : 1. Frequency range - 0.5 GHz to 90 GHz 2. Power output - 5 mW at low frequencies(less than 20 GHz) 250 kW (continuous wave) at 3 GHz 10 MW (pulsed) at 3 GHz 3. Efficiency - about 5 to 20%
4. Noise - about 5 dB for low power TWT 25 dB for high power TWT TWT is used as RF amplifier in broadband microwave receivers, repeater amplifier in broad band communication systems, communication satellites etc.
34. The fabrication of microstrip line is done by A.photo etching B. printed circuit technique C. oxidation D.cladding Answer & Explanation Answer: Option B Explanation: Printed circuit techniques is used for micro strip line.
35. The condition of minimum distortion in a transmission line is A.RL = 1 B. R = 0 C. D. Answer & Explanation Answer: Option D Explanation:
The condition for minimum distortion is found by equating 36. The action of backward wave oscillator is similar to that of A.klystron amplifier B. reflex klystron oscillator C. TWT D.magnetron Answer & Explanation Answer: Option C
The result is
.
Explanation: It is somewhat similar to TWT and can deliver microwave power over a wide frequency band. It has an electron gun and a helix structure. However the interaction between electron beam and RF wave is different than in TWT. The growing RF wave travels in opposite direction to the electron beam. The frequency of wave can be changed by changing the voltage which controls the beam velocity. Moreover the amplitude of oscillations can be decreased continuously to zero by changing the beam current. It features are: 1. Frequency range - 1 GHz to 1000 GHz. 2. Power output - 10 mV to 150 mW (continuous wave) 250kW (pulsed). It is used as signal source in transmitters and instruments.
37. In the given figure the reflection coefficient at source end is
A.1 C. 1/3 Answer & Explanation Answer: Option C Explanation:
B. -1 D.-1/3
.
38. Assertion (A): Artificial transmission lines are frequently used in laboratories. Reason (R): An artificial transmission line can be used to represent an actual line and can also be used as a delay circuit, as attenuator, as filter network etc. A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation Answer: Option A Explanation: Artificial transmission lines have many applications. One of the applications is to simulate an actual line in the laboratory.
39. In a backward wave oscillator the wave travelling along the line winds itself back and forth A.True B.False Answer & Explanation Answer: Option A Explanation: It is somewhat similar to TWT and can deliver microwave power over a wide frequency band. It has an electron gun and a helix structure. However the interaction between electron beam and RF wave is different than in TWT. The growing RF wave travels in opposite direction to the electron beam. The frequency of wave can be changed by changing the voltage which controls the beam velocity. Moreover the amplitude of oscillations can be decreased continuously to zero by changing the beam current.
It features are: 1. Frequency range - 1 GHz to 1000 GHz. 2. Power output - 10 mV to 150 mW (continuous wave) 250kW (pulsed). It is used as signal source in transmitters and instruments.
40. A line is excited by a 100 V dc source. If reflection coefficients at both ends are 1 each then A.there will be no oscillations on line B. there will be only 1 or 2 oscillations on line C. there will be a finite number of oscillations on line D.the oscillations will continue indefinitely Answer & Explanation Answer: Option D Explanation: Because rv = 1 at each end, the line voltage will not reach a steady value and oscillations will continue indefinitely. 36. The action of backward wave oscillator is similar to that of A.klystron amplifier B. reflex klystron oscillator C. TWT D.magnetron Answer & Explanation Answer: Option C Explanation: It is somewhat similar to TWT and can deliver microwave power over a wide frequency band. It has an electron gun and a helix structure. However the interaction between electron beam and RF wave is different than in TWT. The growing RF wave travels in opposite direction to the electron beam. The frequency of wave can be changed by changing the voltage which controls the beam velocity. Moreover the amplitude of oscillations can be decreased continuously to zero by changing
the beam current. It features are: 1. Frequency range - 1 GHz to 1000 GHz. 2. Power output - 10 mV to 150 mW (continuous wave) 250kW (pulsed). It is used as signal source in transmitters and instruments.
37. In the given figure the reflection coefficient at source end is
A.1 C. 1/3 Answer & Explanation
B. -1 D.-1/3
Answer: Option C Explanation:
.
38. Assertion (A): Artificial transmission lines are frequently used in laboratories. Reason (R): An artificial transmission line can be used to represent an actual line and can also be used as a delay circuit, as attenuator, as filter network etc. A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation
Answer: Option A Explanation: Artificial transmission lines have many applications. One of the applications is to simulate an actual line in the laboratory.
39. In a backward wave oscillator the wave travelling along the line winds itself back and forth A.True B.False Answer & Explanation Answer: Option A Explanation: It is somewhat similar to TWT and can deliver microwave power over a wide frequency band. It has an electron gun and a helix structure. However the interaction between electron beam and RF wave is different than in TWT. The growing RF wave travels in opposite direction to the electron beam. The frequency of wave can be changed by changing the voltage which controls the beam velocity. Moreover the amplitude of oscillations can be decreased continuously to zero by changing the beam current. It features are: 1. Frequency range - 1 GHz to 1000 GHz. 2. Power output - 10 mV to 150 mW (continuous wave) 250kW (pulsed). It is used as signal source in transmitters and instruments.
40. A line is excited by a 100 V dc source. If reflection coefficients at both ends are 1 each then A.there will be no oscillations on line B. there will be only 1 or 2 oscillations on line C. there will be a finite number of oscillations on line
D.the oscillations will continue indefinitely Answer & Explanation Answer: Option D Explanation: Because rv = 1 at each end, the line voltage will not reach a steady value and oscillations will continue indefinitely. 36. The action of backward wave oscillator is similar to that of A.klystron amplifier B. reflex klystron oscillator C. TWT D.magnetron Answer & Explanation Answer: Option C Explanation: It is somewhat similar to TWT and can deliver microwave power over a wide frequency band. It has an electron gun and a helix structure. However the interaction between electron beam and RF wave is different than in TWT. The growing RF wave travels in opposite direction to the electron beam. The frequency of wave can be changed by changing the voltage which controls the beam velocity. Moreover the amplitude of oscillations can be decreased continuously to zero by changing the beam current. It features are: 1. Frequency range - 1 GHz to 1000 GHz. 2. Power output - 10 mV to 150 mW (continuous wave) 250kW (pulsed). It is used as signal source in transmitters and instruments.
37. In the given figure the reflection coefficient at source end is
A.1 C. 1/3 Answer & Explanation
B. -1 D.-1/3
Answer: Option C Explanation:
.
38. Assertion (A): Artificial transmission lines are frequently used in laboratories. Reason (R): An artificial transmission line can be used to represent an actual line and can also be used as a delay circuit, as attenuator, as filter network etc. A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation Answer: Option A Explanation: Artificial transmission lines have many applications. One of the applications is to simulate an actual line in the laboratory.
39. In a backward wave oscillator the wave travelling along the line winds itself back and forth A.True B.False Answer & Explanation
Answer: Option A Explanation: It is somewhat similar to TWT and can deliver microwave power over a wide frequency band. It has an electron gun and a helix structure. However the interaction between electron beam and RF wave is different than in TWT. The growing RF wave travels in opposite direction to the electron beam. The frequency of wave can be changed by changing the voltage which controls the beam velocity. Moreover the amplitude of oscillations can be decreased continuously to zero by changing the beam current. It features are: 1. Frequency range - 1 GHz to 1000 GHz. 2. Power output - 10 mV to 150 mW (continuous wave) 250kW (pulsed). It is used as signal source in transmitters and instruments.
40. A line is excited by a 100 V dc source. If reflection coefficients at both ends are 1 each then A.there will be no oscillations on line B. there will be only 1 or 2 oscillations on line C. there will be a finite number of oscillations on line D.the oscillations will continue indefinitely Answer & Explanation Answer: Option D Explanation: Because rv = 1 at each end, the line voltage will not reach a steady value and oscillations will continue indefinitely. 41. Assertion (A): A coaxial line is a non-radiating line. Reason (R): In a coaxial line the electric and magnetic fields are confined to the region between the concentric conductors.
A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation Answer: Option A Explanation: Since the fields are confined, there is no radiation.
42. Reflex klystron oscillator is essentially a low power device A.True B.False Answer & Explanation Answer: Option A Explanation: It uses a single cavity resonator for generating microwave oscillations. Its parts are electron gun, resonator, repeller and output coupling. It operates on the principle of positive feed back. The repeller electrode is at negative potential and sends the partially bunched electron beam back to resonator cavity. This positive feedback supports oscillations. Its feature are: 1. Frequency range - 2 to 100 GHz 2. Power output - 10 MW to about 2 W 3. Efficiency - 10 - 20 % Its applications include radar receivers, local oscillator in microwave devices, oscillator for microwave measurements in laboratories etc.
43. A 10 km long line has a characteristic impedance of 400 ohms. If line length is 100 km, the characteristic impedance is
A.4000 Ω B. 400 Ω C. 40 Ω D.4 Ω Answer & Explanation Answer: Option B Explanation:
and is independent of line length.
44. A matched generator (Zg = Z0) with 1 Ω available. If all ports are matched, the power delivered at ports 1, 2, 3 respectively are A.0.5 W, 0.5 W, 0 W B. 0 W, 0 W, 1 W C. 0.33 W each D.0 W, 0.25 W, 0.25 W Answer & Explanation Answer: Option A Explanation: Since all ports matched, input SWR = 1. No power is reflected and Pin = P4 = 1 W. This power splits between ports 1 and 2. Therefore P1 = P2 = 0.5 Ω, P3 = 0.
45. Which TM mode in rectangular waveguide has lowest cutoff frequency? A.TM11 B. TM01 C. TM10 D.TM21 Answer & Explanation Answer: Option A Explanation: Hz = 0
Ex = ± ZTM Hy Ey = ± ZTM Hx where E0 is the amplitude of the wave. The expressions for β, λc, fc, λg, a are the same as for TE waves. For TM wave the lowest cut off frequency in rectangular wave guide is for TM11 mode.
If , the cutoff frequency for TM11 mode is about 12% more than that for TE20 mode. 46. A resistive microwave load with ZL = 150 Ω is connected to 50 Ω coaxial line. SWR is A.more than 3 B. less than 3 C. equal to 3 D.either (a) or (c) Answer & Explanation Answer: Option C Explanation:
47. Which of the following devices uses a slow wave structure? A.Klystron two cavity amplifier B. Klystron multicavity amplifier C. Reflex klystron oscillator D.TWT Answer & Explanation
Answer: Option D Explanation: In a klystron the resonant structure limits the bandwidth. A TWT is a broadband device. Its main components are electron gun (to produce the electron beam) and a structure supporting the slow electromagnetic wave. The velocity of wave propagation along the helix structure is less than velocity of light. The beam and wave travel along the structure at the same speed. Thus interaction occurs between beam and wave and the beam delivers energy to the RF wave. Therefore the signal gets strengthened and amplified output is delivered at the other end of tube. The main features of TWT are : 1. Frequency range - 0.5 GHz to 90 GHz 2. Power output - 5 mW at low frequencies(less than 20 GHz) 250 kW (continuous wave) at 3 GHz 10 MW (pulsed) at 3 GHz 3. Efficiency - about 5 to 20% 4. Noise - about 5 dB for low power TWT 25 dB for high power TWT TWT is used as RF amplifier in broadband microwave receivers, repeater amplifier in broad band communication systems, communication satellites etc.
48. In a turnstile antenna two-half wave resonant wire radiators are placed at 90° to each other in the same plane and are excited A.in phase B. in phase opposition C. 90° out of phase with each other D.45° out of phase with each other Answer & Explanation Answer: Option C
Explanation: Since the two wire radiators are at 90° to each other, they have to be excited 90° out of phase with each other.
49. A waveguide section in a microwave circuit acts as A.LP filter B. Bandpass filter C. HP filter D.Band stop filter Answer & Explanation Answer: Option C Explanation: It allows high frequencies.
50. In a klystron amplifier dc electron velocity is v0 and dc electron charge density is r0 the dc beam current is A.r0v0 B. r0/v0 C. v0/r0 D.(v0/r0)2 Answer & Explanation Answer: Option A Explanation:
= coulomb |sec|m2 = current density. 1. The directivity in a receiving antenna 1. increases the intercept area in forward direction 2. reduces the noise picked up from other sources 3. provides a means of discriminating against undesired signals originating in directions other than in which the desired transmitter lies. Which of the above statements are correct? A.1 only B. 1 and 2 only
C. 1, 2 and 3 D.2 and 3 only Answer & Explanation Answer: Option C Explanation: All the three are correct.
2. Assertion (A): PIN diode can be used as attenuator and limiter. Reason (R): PIN diode has a thin intrinsic layer. A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation Answer: Option B Explanation: A PIN diode has an intrinsic (i) layer between p and n layers. When reverse bias is applied depletion layers are formed at p-i and i-n junctions. The effective/width of depletion layer increases by the width of i layer. It can be used as a voltage controlled attenuator. At high frequencies the rectification effect ceases and impedance of diode is effectively that of i layer. This impedance varies with the applied bias. It is used in high frequency switching circuits, limiters, modulators etc.
3. The bunching action which occurs in multicavity klystron amplifier can be represented by Applegate diagram A.True B.False Answer & Explanation Answer: Option A
Explanation: A Klystron is a vacuum tube used for generation/amplification of microwaves. An electron beam is produced by oxide coated indirectly heated cathode and is focussed and accelerated by focussing electrode. This beam is transmitted through a glass tube. The input cavity where the beam enters the glass tube is called buncher. As electrons move ahead they see an accelerating field for half cycle and retarding field for the other half cycle. Therefore, some electrons are accelerated and some are retarded. This process is called velocity modulation. The velocity modulation causes bunching of electrons. This bunching effect converts velocity modulation into density modulation of beam. The input is fed at buncher cavity and output is taken at catcher cavity. In a two cavity klystron only buncher and catcher cavity are used. In multi cavity klystron one or more intermediate cavities are also used. The features of a multicavity klystron are : 1. Frequency range - 0.25 GHz to 100 GHz 2. Power output - 10 kW to several hundred kW 3. Power gain - 60 dB (nominal value) 4. Efficiency - about 40%. A multicavity klystron is used in UHF TV transmitters, Radar transmitter and satellite communication.
4. The cut off wavelength in circular waveguide A.guide diameter B. square of guide diameter C. cube of guide diameter D.square root of guide diameter Answer & Explanation
Answer: Option A Explanation: Some applications require dual polarization capability. Circular waveguide has this capability. These analysis uses cylindrical coordinates. In circular waveguide TE11 mode has the lowest cut off frequency and is the dominant mode. If D is diameter of waveguide λc = 1.706 D for TE11 mode λc = 1.029 D for TE21 mode λc = 0.82 D for TE01 mode λc = 1.306 D for TM01 mode.
5. In Reflex Klystron oscillator the focussing electrode is at a high potential A.True B.False Answer & Explanation Answer: Option B Explanation: It uses a single cavity resonator for generating microwave oscillations. Its parts are electron gun, resonator, repeller and output coupling. It operates on the principle of positive feed back. The repeller electrode is at negative potential and sends the partially bunched electron beam back to resonator cavity. This positive feedback supports oscillations. Its feature are: 1. Frequency range - 2 to 100 GHz 2. Power output - 10 MW to about 2 W
3. Efficiency - 10 - 20 % Its applications include radar receivers, local oscillator in microwave devices, oscillator for microwave measurements in laboratories etc. 6. Consider the following statements 1. 2. 3. 4.
Impedance of Gunn diode is about tens of ohms. Impedance of Impatt diode is a few ohms. Impedance of Impatt diode are of the same order. Impedance of Impatt diode is more than that of Gunn diode.
Which of the above statement are correct? A.all B. 1 and 2 only C. 1, 2 and 3 D.1, 2 and 4 Answer & Explanation Answer: Option B Explanation: A Gunn diode uses GaAs which has a negative differential mobility, i.e., a decrease in carrier velocity with increase in electric field. This effects is called transferred electron effect. The impedance of a Gunn diode is tens of ohms. A Gunn diode oscillator has a resonant cavity, an arrangement to couple Gunn diode to cavity, biasing arrangement for Gunn diode and arrangement to couple RF power to load. Applications of Gunn diode oscillator include continuous wave radar, pulsed radar and microwave receivers. An Impatt diode has n+ - p - i - p + structure and is used with reverse bias. It exhibits negative resistance and operates on the principle of avalanche breakdown. Impatt diode circuits are classified as broadly tunable circuit, low Q circuit and high Q circuit. The impedance of Impatt diode is a few ohms. The word Impatt stands for Impact Avalanche Transit Time diode. The features of Impatt diode oscillator are : Frequency 1 to 300 GHz, Power output (0.5 W to 5 W for single diode circuit and upto 40 W for combination of several diodes), efficiency about 20%.
Its applications include police radar systems, low power microwave transmitter etc.
7. In high frequency circuits impedance matching can be done by 1. open circuited stubs 2. short circuited stubs 3.
transformer
Which of the above correct? A.1, 2 and 3 B. 1 and 2 only C. 1 and 3 only D.2 and 3 only Answer & Explanation Answer: Option A Explanation: All the three can be used for impedance matching in high frequency circuits.
8. The directive gain of a transmitting antenna is proportional to A.its cross-sectional area B. square of cross-sectional area C. square root of cross-sectional area D.cube root of cross-sectional area Answer & Explanation Answer: Option A Explanation:
and is thus proportional to cross sectional area.
9. In a loss line RL < Z0, then A.Reflection coefficient is zero B. Reflection coefficient is ∞
C. Reflection coefficient is negative D.Reflection coefficient is positive Answer & Explanation Answer: Option C Explanation:
Since RL < Z0, rv is negative.
10. Assertion (A): A backward wave oscillator can be used as a sweep generator. Reason (R): The frequency of oscillation of a backward wave oscillator can be changed by varying the voltage which controls the beam velocity. A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation Answer: Option A Explanation: It is somewhat similar to TWT and can deliver microwave power over a wide frequency band. It has an electron gun and a helix structure. However the interaction between electron beam and RF wave is different than in TWT. The growing RF wave travels in opposite direction to the electron beam. The frequency of wave can be changed by changing the voltage which controls the beam velocity. Moreover the amplitude of oscillations can be decreased continuously to zero by changing the beam current. It features are: 1. Frequency range - 1 GHz to 1000 GHz.
2. Power output - 10 mV to 150 mW (continuous wave) 250kW (pulsed). It is used as signal source in transmitters and instruments. 11. If a line having Z0 = 300 ∠ 0 W is open circuited at far end, VSWR is A.0 B. 1 C. ∞ D.2 Answer & Explanation Answer: Option C Explanation:
If line is o.c. |rv| = 1 and VSWR
= ∞.
12. If f is the frequency of electromagnetic wave, fc is cutoff frequency, then in a rectangular waveguide A.attenuation is low when f > fc B. attenuation is low when f < fc C. attenuation is high when f < fc D.either (b) or (c) Answer & Explanation Answer: Option A Explanation: Wavelength should be less than cutoff wavelengths. Therefore frequency should be higher than cutoff frequency for minimum attenuation.
13. Assertion (A): The condition of minimum distortion in a transmission line is L = RC/G. Reason (R): Line loading means addition of inductance to satisfy the condition L = RC/G. A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation Answer: Option B
Explanation: Oscillator circuits using vacuum tubes (triodes, pentodes) have the following limitations at very high frequencies (microwave region). The stray capacitances and inductances become important and affect the operation of the circuit. At low frequencies the transit time between cathode and anode is a small fraction of period of oscillation. However, at microwave frequencies this transit time becomes comparable to time period of oscillations.
14. A magnetron has a cylindrical cathode surrounded by an anode structure having cavities opening into interaction space by means of slots A.True B.False Answer & Explanation Answer: Option A Explanation: It is somewhat similar to TWT and can deliver microwave power over a wide frequency band. It has an electron gun and a helix structure. However the interaction between electron beam and RF wave is different than in TWT. The growing RF wave travels in opposite direction to the electron beam. The frequency of wave can be changed by changing the voltage which controls the beam velocity. Moreover the amplitude of oscillations can be decreased continuously to zero by changing the beam current. It features are: 1. Frequency range - 1 GHz to 1000 GHz. 2. Power output - 10 mV to 150 mW (continuous wave) 250kW (pulsed).
It is used as signal source in transmitters and instruments.
15. The correct sequence of parts in klystron amplifier are A.anode, catcher cavity, cathode, buncher cavity B. cathode, buncher cavity, catcher cavity, cavity C. anode, buncher cavity, catcher cavity, cathode D.cathode, catcher cavity, anode, buncher cavity Answer & Explanation Answer: Option B Explanation: Cathode is the first part and anode is the last. 16. A transmission line has Z0 = 300 Ω and ZL = (300 - j300) ohm. The transmission coefficient is A.1.265 ∠ - 18.43° B. 1.01 ∠ - 10° C. 1.14 ∠ 66.68° D.1.09 ∠ 66.68° Answer & Explanation Answer: Option A Explanation:
Transmission coefficient
= 1.265 ∠- 18.43°.
17. In a reflex klystron oscillator, repeller electrode is at A.low positive potential B. high positive potential C. negative potential D.zero potential Answer & Explanation Answer: Option C Explanation: It uses a single cavity resonator for generating microwave oscillations.
Its parts are electron gun, resonator, repeller and output coupling. It operates on the principle of positive feed back. The repeller electrode is at negative potential and sends the partially bunched electron beam back to resonator cavity. This positive feedback supports oscillations. Its feature are: 1. Frequency range - 2 to 100 GHz 2. Power output - 10 MW to about 2 W 3. Efficiency - 10 - 20 % Its applications include radar receivers, local oscillator in microwave devices, oscillator for microwave measurements in laboratories etc.
18. A quarter wave line short circuited at load end behaves as A.an inductance B. an inductance and capacitance in series C. a capacitance D.an inductance and capacitance in parallel Answer & Explanation Answer: Option D Explanation: A quarter wave line short-circuited at far end behaves as a parallel tuned circuit.
19. A (75 - J50) ohm load is connected to a coaxial of Z0 = 75 ohm at 10 GHz. The best method of matching is to connect A.an inductance at load B. a short circuited stub at load C. a short circuited stub at specific distance from load D.a capacitance at specific distance from load Answer & Explanation Answer: Option C
Explanation: A short-circuited stub is a suitable method of matching.
20. The width of a radio beam from a 1 m diameter parabolic antenna at 1 GHz is about A.100° B. 50° C. 5° D.2° Answer & Explanation Answer: Option B Explanation: Beam width between nulls of a parabolic antenna . Therefore 50° is the nearest value. 21. Which one of the following is transferred locking electron device C antenna? A.BARITT diode B. IMPATT diode C. Gunn diode D.Step recovery diode Answer & Explanation Answer: Option C Explanation: A Gunn diode uses GaAs which has a negative differential mobility, i.e., a decrease in carrier velocity with increase in electric field. This effects is called transferred electron effect. The impedance of a Gunn diode is tens of ohms. A Gunn diode oscillator has a resonant cavity, an arrangement to couple Gunn diode to cavity, biasing arrangement for Gunn diode and arrangement to couple RF power to load. Applications of Gunn diode oscillator include continuous wave radar, pulsed radar and microwave receivers.
22. A magnetron requires an external magnetic field with flux lines parallel to axis of cathode A.True B.False Answer & Explanation
Answer: Option A Explanation: It is somewhat similar to TWT and can deliver microwave power over a wide frequency band. It has an electron gun and a helix structure. However the interaction between electron beam and RF wave is different than in TWT. The growing RF wave travels in opposite direction to the electron beam. The frequency of wave can be changed by changing the voltage which controls the beam velocity. Moreover the amplitude of oscillations can be decreased continuously to zero by changing the beam current. It features are: 1. Frequency range - 1 GHz to 1000 GHz. 2. Power output - 10 mV to 150 mW (continuous wave) 250kW (pulsed). It is used as signal source in transmitters and instruments.
23. When a line short circuited at far end, the minimum voltage occurs at A.far end B. source end C. midway between source and far end D.none of the above Answer & Explanation Answer: Option A Explanation: When a line is short-circuited at far end, the voltage at far end is zero.
24. In a TWT the axial component of electric field advances along the tube A.at a velocity that is almost equal to speed of light
B. at a velocity that is a small fraction of speed of light C. at a velocity that is about 50% of speed of light D.at a velocity that may be even more than speed of light Answer & Explanation Answer: Option B Explanation: In a klystron the resonant structure limits the bandwidth. A TWT is a broadband device. Its main components are electron gun (to produce the electron beam) and a structure supporting the slow electromagnetic wave. The velocity of wave propagation along the helix structure is less than velocity of light. The beam and wave travel along the structure at the same speed. Thus interaction occurs between beam and wave and the beam delivers energy to the RF wave. Therefore the signal gets strengthened and amplified output is delivered at the other end of tube. The main features of TWT are : 1. Frequency range - 0.5 GHz to 90 GHz 2. Power output - 5 mW at low frequencies(less than 20 GHz) 250 kW (continuous wave) at 3 GHz 10 MW (pulsed) at 3 GHz 3. Efficiency - about 5 to 20% 4. Noise - about 5 dB for low power TWT 25 dB for high power TWT TWT is used as RF amplifier in broadband microwave receivers, repeater amplifier in broad band communication systems, communication satellites etc.
25. If other parameter are constant, transmission loss at 5 GHz as compared to that at 0.5 GHz is A.20 dB more B. 20 dB less C. 700 dB more D.100 dB less Answer & Explanation
Answer: Option B Explanation: As frequency increases, transmission loss increases slightly. 26. For a circular wave guide A.cutoff frequency for TE10 and TE01 modes are same B. cutoff frequency for TE10 and TE01 modes are different C. cutoff frequency for TE10 mode = twice the cutoff frequency for TE20 mode D.cutoff frequency for TE10 mode = haf the cutoff frequency for TE20 mode Answer & Explanation Answer: Option A Explanation: When a circular waveguide is rotated by 90°, the configuration remain the same.
27. In the given figure the reflected voltage wave after first reflection is
A.18 V B. -18 V C. 30 V D.-30 V Answer & Explanation Answer: Option B Explanation:
.
28. Assertion (A): A half wavelength line can be used as a 1 : 1 transformer. Reason (R): The input impedance of a half wavelength line is equal to load impedance. A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation Answer: Option A Explanation: Since a half wavelength line has an input impedance equal to load impedance, the impedance transformation ratio is 1:1.
29. The magnitudes of OC and SC input impedances of a transmission line an 100 Ω and 25 Ω. The characteristic impedance is A.25 Ω B. 50 Ω C. 75 Ω D.100 Ω Answer & Explanation Answer: Option B Explanation:
30. A loss less line is terminated in a circular lines are E lines A.SWR = 0 B. SWE = 0 C. SWR is finite D.SWR = ∞ Answer & Explanation Answer: Option C Explanation:
= finite number and VSWR = finite number. 31. Which of the following terminations makes the input impedance of a line equal to characteristic impedance Z0? A.line open circuited at far end B. line terminated in Z0 C. line short circuited at far end D.line terminated in inductance Answer & Explanation Answer: Option B Explanation: If ZL is load impedance and Z0 is characteristic impedance.
Input impedance =
. If ZL = Z0 the input impedance = Z0.
32. In microwave system the function of mode filter is A.to suppress modes with lower cut off frequencies B. to suppress modes with higher cut off frequencies C. to change mode of wave transmission D.both (b) and (c) Answer & Explanation Answer: Option D Explanation: Mode filter suppress modes with lower cutoff frequencies.
33. For the strip line in the given figure the capacitance per unit length =
A. B. C. D. Answer & Explanation Answer: Option A Explanation:
frads/unit length.
34. The total field developed by an antenna array at a distant point is A.phasor sum of fields produced by individual antennas of the array B. algebraic sum of fields produced by individual antennas of the array C. either (a) or (b) depending on type of array D.neither (a) nor (b) Answer & Explanation Answer: Option A Explanation: Since field is a phasor quantity we have to take phasor sum.
35. High speed logic circuits use A.pulses with very small width
B. pulses with very large width C. pulses whose width is neither small nor large D.either (b) or (c) Answer & Explanation Answer: Option A Explanation: High speed means time period is small. Therefore pulses should also have small width. 36. To couple a coaxial line to a parallel wire line it is best to use A.slotted line B. balun C. directional coupler D.λ/4 transformer Answer & Explanation Answer: Option B Explanation: A balun gives 4 : 1 impedance transformation.
37. Assertion (A): A quarter wave transformer is used to match a resistive load to a transmission line. Reason (R): A quarter wave transformer is a transmission line of quarter wave length. A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation Answer: Option B Explanation:
A line of length matching.
If
is called quarter wavelength line. Such a line is used for impedance
A quarter wave line can match a source impedance Zin with load impedance ZL by selecting a proper value of Z0 so as to satisfy equation.
Such a line is also called
transformer.
38. Assertion (A): Magnetron is generally used in n mode. Reason (R): Frequency for p mode can be easily separated from adjacent modes. A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation Answer: Option A Explanation: It is somewhat similar to TWT and can deliver microwave power over a wide frequency band. It has an electron gun and a helix structure. However the interaction between electron beam and RF wave is different than in TWT. The growing RF wave travels in opposite direction to the electron beam. The frequency of wave can be changed by changing the voltage which controls the beam velocity. Moreover the amplitude of oscillations can be decreased continuously to zero by changing the beam current. It features are: 1. Frequency range - 1 GHz to 1000 GHz. 2. Power output - 10 mV to 150 mW (continuous wave) 250kW (pulsed). It is used as signal source in transmitters and instruments.
39. A balun should have A.low SWR at both ports B. high SWR at both ports C. high SWR at input port and low SWR at output port D.low SWR at input port and high SWR at output Answer & Explanation Answer: Option A Explanation: Turn ratio is so selected as to give low SWR at both ports.
40. Assertion (A): The velocity factor of a line is the ratio of wave velocity on the line to speed of light. Reason (R): If the conductors of a line are immersed in a non magnetic insulating liquid, the wave velocity increases. A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation Answer: Option C Explanation: R is wrong because wave velocity decreases. 41. In mode filter of the given figure which of the following modes is unaffected
A.TE01 B. TE10 C. TE11
D.all TM Answer & Explanation Answer: Option A Explanation: TE01 mode is unaffected because its horizontally oriented electric field is every where perpendicular to the conducting strips.
42. The directive gain of a transmitting antenna is A.proportional to wavelength B. inversely proportional to wavelength C. proportional to square of wavelength D.inversely proportional to square of wavelength Answer & Explanation Answer: Option D Explanation:
43. A duplexer is used to A.couple two antennas to a transmitter B. isolate the antenna from the local oscillator C. prevent interference between two antennas connected to receiver D.use an antenna for reception or transmission without interference Answer & Explanation Answer: Option D Explanation: Same antenna is used for transmission and reception.
44. A branched duplexer requires A.TR tubes
B. ATR tube C. both TR and ATR tube D.none of the above Answer & Explanation Answer: Option C Explanation: A branched duplexer funds use in narrow bandwidth applications. TR tube stands for transmit-receive tube and ATR tube stands for antitransmit receive tube. Both these tubes are used in branched duplexer.
45. In a backward wave oscillator the wave A.travelling along the line winds itself back and forth B. progresses only in forward direction C. progresses only in backward direction D.either (a) or (c) Answer & Explanation Answer: Option A Explanation: It is somewhat similar to TWT and can deliver microwave power over a wide frequency band. It has an electron gun and a helix structure. However the interaction between electron beam and RF wave is different than in TWT. The growing RF wave travels in opposite direction to the electron beam. The frequency of wave can be changed by changing the voltage which controls the beam velocity. Moreover the amplitude of oscillations can be decreased continuously to zero by changing the beam current. It features are: 1. Frequency range - 1 GHz to 1000 GHz.
2. Power output - 10 mV to 150 mW (continuous wave) 250kW (pulsed). It is used as signal source in transmitters and instruments. 46. A coaxial line has L = 500 nH/m and C = 50 pF/m. The characteristic impedance is A.500 Ω B. 250 Ω C. 100 Ω D.50 Ω Answer & Explanation Answer: Option C Explanation:
.
47. The main feature of a parametric amplifier is A.low noise B. very high gain C. broad bandwidth D.both (b) and (c) Answer & Explanation Answer: Option C Explanation: Since reactance does not contribute thermal noise to the circuit, it is a low noise device.
48. Assertion (A): PIN diode is commonly used for microwave control. Reason (R): A PIN diode uses heavily doped p and n materials. A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation Answer: Option B
Explanation: A PIN diode has an intrinsic (i) layer between p and n layers. When reverse bias is applied depletion layers are formed at p-i and i-n junctions. The effective/width of depletion layer increases by the width of i layer. It can be used as a voltage controlled attenuator. At high frequencies the rectification effect ceases and impedance of diode is effectively that of i layer. This impedance varies with the applied bias. It is used in high frequency switching circuits, limiters, modulators etc.
49. In a vacuum tube, the transit time of electron between cathode and anode is important at A.low frequencies B. high frequencies C. both (a) and (b) D.frequencies which are neither very low nor very high Answer & Explanation Answer: Option B Explanation: At high frequencies transit time is large as compared to the period of microwave signal. 50. Assertion (A): A line of length infinity.
and short circuited at far end has an input impedance of
Reason (R): A line of length and short circuited at far end behaves as a parallel resonant circuit. A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation Answer: Option A Explanation: A parallel tuned circuit has an infinite impedance if R is zero.
1. A cavity resonator is A.a hollow metallic enclosure B. a hollow enclosure having magnetic material as its walls C. a hollow enclosure having dielectric material as its walls D.either (b) or (c) 2. If antenna diameter is increased four times, the maximum range is increased by a factor of A.2 B. 2 C. 4 D.0.2 Answer & Explanation Answer: Option C Explanation: Range of radar is proportional to antenna diameter.
3. Assertion (A): Gunn diode is a transferred electron device. Reason (R): A Gunn oscillator uses the phenomenon of transferred electron effect. A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation Answer: Option B Explanation: A Gunn diode uses GaAs which has a negative differential mobility, i.e., a decrease in carrier velocity with increase in electric field. This effects is called transferred electron effect. The impedance of a Gunn diode is tens of ohms. A Gunn diode oscillator has a resonant cavity, an arrangement to couple Gunn diode to cavity, biasing arrangement for Gunn diode and arrangement to couple RF power to load. Applications of Gunn diode oscillator include continuous wave radar, pulsed radar and
microwave receivers.
4. Atomic and molecular resonance is observed in many substances A.at microwave frequencies B. at low frequencies C. at frequencies used in AM broadcast D.at both (b) and (c) Answer & Explanation Answer: Option A Explanation: Atomic and molecular distances are very small. Therefore resonance can occur only at microwave frequencies.
5. The component in the given figure is
A.attenuator B. T type low pass filter C. T type high pass filter D.phase shifter Answer & Explanation Answer: Option B Explanation: Z01 provides series inductances and teflon filled low impedance line Z02 provides shunt capacitance. 6. The semiconductor diode which can be used in switching circuit in microwave range is A.PIN diode B. Varactor diode C. Tunnel diode
D.Gunn diode Answer & Explanation Answer: Option A Explanation: A PIN diode has an intrinsic (i) layer between p and n layers. When reverse bias is applied depletion layers are formed at p-i and i-n junctions. The effective/width of depletion layer increases by the width of i layer. It can be used as a voltage controlled attenuator. At high frequencies the rectification effect ceases and impedance of diode is effectively that of i layer. This impedance varies with the applied bias. It is used in high frequency switching circuits, limiters, modulators etc.
7. In the given figure the reflected current wave after first reflection is
A.0.18 A B. -0.18 A C. 0.3 A D.-0.3 A Answer & Explanation Answer: Option B Explanation:
8. A line has an attenuation of 0.054 Np/m. The attenuation in decibels is
A.4.7 dB/m B. 0.47 dB/m C. 0.54 dB/m D.5.4 dB/m Answer & Explanation Answer: Option B Explanation: 0.054 x 8.68 = 0.47 dB/m.
9. If a line is open circuited Zin = Z0 tanh (gl). A.True Answer & Explanation
B.False
Answer: Option B Explanation: The quantities required to be measured in microwave circuits are frequency, power and impedance. Microwave frequency measurement is done by slotted line, resonant cavities and transfer oscillator. Microwave power measurement uses bolometers and micromave power meters. A self balancing bridge working on the principle of power substitution is commomly used. Microwave impedance measurement is done by measurement of reflection coefficient and VSWR. A slotted line and probe is a basic tool for these measurements.' Network analyser enables rapid impedance measurement over a broad frequency range.
10. A reflex klystron oscillator uses A.one cavity resonator B. two cavity resonators C. three cavity resonators D.none of the above Answer & Explanation
Answer: Option A Explanation: It uses a single cavity resonator for generating microwave oscillations. Its parts are electron gun, resonator, repeller and output coupling. It operates on the principle of positive feed back. The repeller electrode is at negative potential and sends the partially bunched electron beam back to resonator cavity. This positive feedback supports oscillations. Its feature are: 1. Frequency range - 2 to 100 GHz 2. Power output - 10 MW to about 2 W 3. Efficiency - 10 - 20 % Its applications include radar receivers, local oscillator in microwave devices, oscillator for microwave measurements in laboratories etc. 11. A coaxial RF cable has a characteristic impedance of 50 Ω and C equal to 40 pF/m. The inductance is A.1 μ H/m B. 10 μ H/m C. 0.1 μ H/m D.0.01 μ H/m Answer & Explanation Answer: Option C Explanation:
. 12. In a microwave coaxial line, the maximum operating frequency is f max and breakdown strength of dielectric is Ed' Then maximum power handling capacity is proportional to A. B.
C. D. Answer & Explanation Answer: Option B Explanation: Power handling capacity μ (voltage)2 and is inversely proportional to f2 max.
13. To couple a coaxial line to a parallel wire line it is best to use A.slotted line B. balun C. directional coupler D.λ/4 transformer Answer & Explanation Answer: Option B Explanation: A balun gives 4 : 1 impedance transformation. 14. In a multicavity klystron amplifier the signal to be amplified develops an ac voltage of signal frequency across the gap in buncher cavity A.True B.False Answer & Explanation Answer: Option A Explanation: A Klystron is a vacuum tube used for generation/amplification of microwaves. An electron beam is produced by oxide coated indirectly heated cathode and is focussed and accelerated by focussing electrode. This beam is transmitted through a glass tube. The input cavity where the beam enters the glass tube is called buncher. As electrons move ahead they see an accelerating field for half cycle and retarding field for
the other half cycle. Therefore, some electrons are accelerated and some are retarded. This process is called velocity modulation. The velocity modulation causes bunching of electrons. This bunching effect converts velocity modulation into density modulation of beam. The input is fed at buncher cavity and output is taken at catcher cavity. In a two cavity klystron only buncher and catcher cavity are used. In multi cavity klystron one or more intermediate cavities are also used. The features of a multicavity klystron are : 1. Frequency range - 0.25 GHz to 100 GHz 2. Power output - 10 kW to several hundred kW 3. Power gain - 60 dB (nominal value) 4. Efficiency - about 40%. A multicavity klystron is used in UHF TV transmitters, Radar transmitter and satellite communication.
15. If VSWR is infinite, the transmission line is terminated in A.short circuit B. complex impedance C. open circuit D.either (a) or (c) Answer & Explanation Answer: Option D Explanation:
and ZL = ∞, i.e., line is o.c or s.c.
. Since VSWR = ∞, |rv| = 1. This can happen if ZL = 0 or
16. In a circular waveguide TE21 mode has lowest cutoff frequency A.True B.False Answer & Explanation Answer: Option B Explanation: Some applications require dual polarization capability. Circular waveguide has this capability. These analysis uses cylindrical coordinates. In circular waveguide TE11 mode has the lowest cut off frequency and is the dominant mode. If D is diameter of waveguide λc = 1.706 D for TE11 mode λc = 1.029 D for TE21 mode λc = 0.82 D for TE01 mode λc = 1.306 D for TM01 mode.
17. The number of TV channels which can be accommodated in a spectrum of 300 MHz is about A.5 B. 10 C. 50 D.200 Answer & Explanation Answer: Option C Explanation: A TV channel has a bandwidth about 5 MHz. Hence 300 MHz spectrum can accommodate about 50 channels.
18. The noise figure of multicavity klystron amplifier is very low A.True B.False Answer & Explanation
Answer: Option B Explanation: A Klystron is a vacuum tube used for generation/amplification of microwaves. An electron beam is produced by oxide coated indirectly heated cathode and is focussed and accelerated by focussing electrode. This beam is transmitted through a glass tube. The input cavity where the beam enters the glass tube is called buncher. As electrons move ahead they see an accelerating field for half cycle and retarding field for the other half cycle. Therefore, some electrons are accelerated and some are retarded. This process is called velocity modulation. The velocity modulation causes bunching of electrons. This bunching effect converts velocity modulation into density modulation of beam. The input is fed at buncher cavity and output is taken at catcher cavity. In a two cavity klystron only buncher and catcher cavity are used. In multi cavity klystron one or more intermediate cavities are also used. The features of a multicavity klystron are : 1. Frequency range - 0.25 GHz to 100 GHz 2. Power output - 10 kW to several hundred kW 3. Power gain - 60 dB (nominal value) 4. Efficiency - about 40%. A multicavity klystron is used in UHF TV transmitters, Radar transmitter and satellite communication.
19. Assertion (A): The velocity of electromagnetic waves on overhead lines and coaxial cables is the same. Reason (R): Free space has an intrinsic impedance of 377 ohms.
A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation Answer: Option D Explanation: Velocity of em waves on caoxial cables is less than that on overhead lines.
20. In the given figure the E and H lines in a coaxial cable
A.The radial lines are E lines and circular lines are H lines B. Radial lines are H lines and circular lines are E lines C. The directions of E and H lines are wrong D.Radial lines may be E and H lines depending an direction of current Answer & Explanation Answer: Option A Explanation: H lines are concentric circles around conductor and E lines are radial. 21. Roughly the time required for microwave cooking as compared to conventional cooking is A.about twice B. about half C. about 10 times D.about one-tenth Answer & Explanation Answer: Option D Explanation: Time required for microwave cooking is much less than the time required for conventional
cooking.
22. If the minimum range of a radar is to be doubled, the peak power has to be increased by a factor of A.2 B. 4 C. 8 D.16 Answer & Explanation Answer: Option D Explanation: Range = (power)025.
23. Which mode has the lowest cut off frequency in circular wave guides? A.TE01 B. TE11 C. TE20 D.TE21 Answer & Explanation Answer: Option B Explanation: Some applications require dual polarization capability. Circular waveguide has this capability. These analysis uses cylindrical coordinates. In circular waveguide TE11 mode has the lowest cut off frequency and is the dominant mode. If D is diameter of waveguide λc = 1.706 D for TE11 mode λc = 1.029 D for TE21 mode λc = 0.82 D for TE01 mode λc = 1.306 D for TM01 mode.
24. Assertion (A): Klystron amplifiers use one or more intermediate cavities in addition to buncher and catcher cavity. Reason (R): When one or more intermediate cavities are used the bandwidth can be increased. A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation Answer: Option A Explanation: A Klystron is a vacuum tube used for generation/amplification of microwaves. An electron beam is produced by oxide coated indirectly heated cathode and is focussed and accelerated by focussing electrode. This beam is transmitted through a glass tube. The input cavity where the beam enters the glass tube is called buncher. As electrons move ahead they see an accelerating field for half cycle and retarding field for the other half cycle. Therefore, some electrons are accelerated and some are retarded. This process is called velocity modulation. The velocity modulation causes bunching of electrons. This bunching effect converts velocity modulation into density modulation of beam. The input is fed at buncher cavity and output is taken at catcher cavity. In a two cavity klystron only buncher and catcher cavity are used. In multi cavity klystron one or more intermediate cavities are also used. The features of a multicavity klystron are : 1. Frequency range - 0.25 GHz to 100 GHz 2. Power output - 10 kW to several hundred kW 3. Power gain - 60 dB (nominal value)
4. Efficiency - about 40%. A multicavity klystron is used in UHF TV transmitters, Radar transmitter and satellite communication.
25. A wave Em cos (bx - ωt) is a backward wave. A.True B.False Answer & Explanation Answer: Option B Explanation: It is a forward wave because as t increases, x increases. 26. A reflex klystron oscillator is a A.low power device B. high power device C. high efficiency device D.both (a) and (b) Answer & Explanation Answer: Option A Explanation: It uses a single cavity resonator for generating microwave oscillations. Its parts are electron gun, resonator, repeller and output coupling. It operates on the principle of positive feed back. The repeller electrode is at negative potential and sends the partially bunched electron beam back to resonator cavity. This positive feedback supports oscillations. Its feature are: 1. Frequency range - 2 to 100 GHz 2. Power output - 10 MW to about 2 W 3. Efficiency - 10 - 20 % Its applications include radar receivers, local oscillator in microwave devices, oscillator for
microwave measurements in laboratories etc.
27. Consider the following applications 1. TV tuning 2. Active filter 3. Microwave frequency multiplication In which of above can a varactor diode be used? A.1 2 and 3 B. l and 2 only C. 1 and 3 only D.2 and 3 only Answer & Explanation Answer: Option A Explanation: Varactor diode is used in all the three applications.
28. Consider the following statements 1. 2. 3. 4.
Dissipative attenuator has a fixed value of attenuation. Reflective attenuator has a fixed value of attenuation. Both dissipative and reflective attenuators are available only with fixed attenuation. Both dissipative and reflective attenuators are available with either fixed or variable attenuation.
Which of the above are correct? A.1 only B. 1 and 2 C. 1, 2 and 3 D.4 only Answer & Explanation Answer: Option D Explanation: Both dissipative and reflective attenuators are available with either fixed or variable
attenuation.
29. Impedance inversion may be obtained with A.a short circuited stub B. a quarter wave line C. an open circuited stub D.a half wave line Answer & Explanation Answer: Option B Explanation: Impedance inversion occurs when load impedance is not matched with characteristic impedance of line.
30. Power gain of a multicavity klystron amplifier is A.more than 30 dB B. causes retardation of all electrons C. causes acceleration of some electrons and retardation of others D.none of the above Answer & Explanation Answer: Option A Explanation: A Klystron is a vacuum tube used for generation/amplification of microwaves. An electron beam is produced by oxide coated indirectly heated cathode and is focussed and accelerated by focussing electrode. This beam is transmitted through a glass tube. The input cavity where the beam enters the glass tube is called buncher. As electrons move ahead they see an accelerating field for half cycle and retarding field for the other half cycle. Therefore, some electrons are accelerated and some are retarded. This process is called velocity modulation. The velocity modulation causes bunching of electrons. This bunching effect converts velocity
modulation into density modulation of beam. The input is fed at buncher cavity and output is taken at catcher cavity. In a two cavity klystron only buncher and catcher cavity are used. In multi cavity klystron one or more intermediate cavities are also used. The features of a multicavity klystron are : 1. Frequency range - 0.25 GHz to 100 GHz 2. Power output - 10 kW to several hundred kW 3. Power gain - 60 dB (nominal value) 4. Efficiency - about 40%. A multicavity klystron is used in UHF TV transmitters, Radar transmitter and satellite communication 31. If a short line is terminated in characteristic impedance it behaves as an infinite line. A.True B.False Answer & Explanation Answer: Option A Explanation: In a line terminated by Z0, there are no reflections.
32. Ga As exhibits negative differential mobility A.True B.False Answer & Explanation Answer: Option A Explanation: A Gunn diode uses GaAs which has a negative differential mobility, i.e., a decrease in carrier velocity with increase in electric field. This effects is called transferred electron effect. The impedance of a Gunn diode is tens of ohms. A Gunn diode oscillator has a resonant cavity, an arrangement to couple Gunn diode to
cavity, biasing arrangement for Gunn diode and arrangement to couple RF power to load. Applications of Gunn diode oscillator include continuous wave radar, pulsed radar and microwave receivers.
33. Consider the following statements 1. Bunching of electrons occurs in two cavity klystron amplifier. 2. Bunching of electrons occurs in multi cavity klystron amplifier. 3. Bunching of electrons occurs in reflex cavity klystron amplifier. Which of the above statements are correct? A.1, 2, and only B. 1, 2 and 3 only C. 1 and 3 only D.2 and 3 only Answer & Explanation Answer: Option B Explanation: A Klystron is a vacuum tube used for generation/amplification of microwaves. An electron beam is produced by oxide coated indirectly heated cathode and is focussed and accelerated by focussing electrode. This beam is transmitted through a glass tube. The input cavity where the beam enters the glass tube is called buncher. As electrons move ahead they see an accelerating field for half cycle and retarding field for the other half cycle. Therefore, some electrons are accelerated and some are retarded. This process is called velocity modulation. The velocity modulation causes bunching of electrons. This bunching effect converts velocity modulation into density modulation of beam. The input is fed at buncher cavity and output is taken at catcher cavity. In a two cavity klystron only buncher and catcher cavity are used. In multi cavity klystron one or more intermediate cavities are also used.
The features of a multicavity klystron are : 1. Frequency range - 0.25 GHz to 100 GHz 2. Power output - 10 kW to several hundred kW 3. Power gain - 60 dB (nominal value) 4. Efficiency - about 40%. A multicavity klystron is used in UHF TV transmitters, Radar transmitter and satellite communication.
34. Assertion (A): For high frequency lines inductive reactance is very high as compared to ac resistance. Reason (R): Due to skin effect ac resistance of line is higher than dc resistance. A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation Answer: Option B Explanation: XL = ωL. As frequency increases line resistance increases slightly but XL increases directly as per frequency.
35. Consider the following applications 1. 2. 3. 4.
Switch Attenuator Phase shifter Oscillator
In which of the above can a PIN diode be used? A.1 2 3 and 4 B. 1 2 and 3 only C. 1 and 2 only D.2, 3 and 4 only
Answer & Explanation Answer: Option B Explanation: PIN diode is not used in oscillators. 36. Which one of the following is not a negative resistance device? A.Gunn diode B. Tunnel diode C. Impatt diode D.Varactor diode Answer & Explanation Answer: Option D Explanation: Gunn diode, Tunnel diode and Impatt diodes are negative resistance devices. The limitation of solid state devices at high frequencies include those associated with transit time and junction capacitances. The devices used are : Transferred electron oscillators (Gunn diode), Avalanche diode oscillators (Impatt diode, Trapatt diode, Masters, Lasers, Tunnel diode, Varactor etc).
37. Microwave links are typically 50 km apart A.because of atmospheric attenuation B. because of output tube power limitation C. because of earth's curvature D.to ensure that applied dc voltage is not excessive Answer & Explanation Answer: Option C Explanation: Earth's curvature limits the distance between microwave links.
38. For matching over a range of frequencies in a transmission line it is best to use A.a balun B. a broad band directional coupler
C. double stub D.a single stub of adjustable position Answer & Explanation Answer: Option C Explanation: Double stub is useful for matching over a range of frequencies.
39. Assertion (A): In the interaction region of magnetron an electron is subjected to three forces: force due to electric field, force due to magnetic field and centrifugal force. Reason (R): The mechanism of generation of microwaves, in a magnetron, involves interaction of electromagnetic fields with electrons moving in static electric and magnetic fields oriented at right angles to each other. A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation Answer: Option A Explanation: It is somewhat similar to TWT and can deliver microwave power over a wide frequency band. It has an electron gun and a helix structure. However the interaction between electron beam and RF wave is different than in TWT. The growing RF wave travels in opposite direction to the electron beam. The frequency of wave can be changed by changing the voltage which controls the beam velocity. Moreover the amplitude of oscillations can be decreased continuously to zero by changing the beam current. It features are: 1. Frequency range - 1 GHz to 1000 GHz.
2. Power output - 10 mV to 150 mW (continuous wave) 250kW (pulsed). It is used as signal source in transmitters and instruments.
40. Which of the following is wrong for a magic used to tee? A.E and H arms are decoupled B. coplanar arms are coupled C. all ports are perfectly matched D.A signal into coplanar arm splits equally between E and H arms Answer & Explanation Answer: Option B Explanation: Coplanar arms are decoupled. 41. The expression HZ = C cos(Bx) cos(Ay)yz is for A.TE wave B. TM waves C. both TE and TM waves D.some TE and some TM waves Answer & Explanation Answer: Option A Explanation: In TM mode Hz = 0.
42. Assertion (A): Impedance matching can be done by using stubs. Reason (R): A double stub is used for impedance matching when frequency of signal varies. A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation Answer: Option A Explanation:
Hollow metallic enclosures exhibit resonance behaviour when excited by electromagnetic field. These enclosures are called cavity resonators.
43. Read the following statements about TWT 1. 2. 3. 4.
It uses thermionic emission. It uses an attenuater. It is inherently a resonant device. It has broad bandwidth.
Which of the above are correct? A.1, 2, 3 and 4 B. 1, 2 and 3 C. 1, 3 and 4 D.1, 2 and 4 Answer & Explanation Answer: Option D Explanation: In a klystron the resonant structure limits the bandwidth. A TWT is a broadband device. Its main components are electron gun (to produce the electron beam) and a structure supporting the slow electromagnetic wave. The velocity of wave propagation along the helix structure is less than velocity of light. The beam and wave travel along the structure at the same speed. Thus interaction occurs between beam and wave and the beam delivers energy to the RF wave. Therefore the signal gets strengthened and amplified output is delivered at the other end of tube. The main features of TWT are : 1. Frequency range - 0.5 GHz to 90 GHz 2. Power output - 5 mW at low frequencies(less than 20 GHz) 250 kW (continuous wave) at
3 GHz 10 MW (pulsed) at 3 GHz 3. Efficiency - about 5 to 20% 4. Noise - about 5 dB for low power TWT 25 dB for high power TWT TWT is used as RF amplifier in broadband microwave receivers, repeater amplifier in broad band communication systems, communication satellites etc.
44. If a line having Z0 = 300 ∠ 0 W is short circuited at far end, VSWR is A.0 B. 1 C. ∞ D.2 Answer & Explanation Answer: Option C Explanation: If line is s.c |rv| = 1 and VSWR = ∞.
45. A klystron amplifier generally uses Pierce gun A.True B.False Answer & Explanation Answer: Option A Explanation: It uses a single cavity resonator for generating microwave oscillations. Its parts are electron gun, resonator, repeller and output coupling. It operates on the principle of positive feed back. The repeller electrode is at negative potential and sends the partially bunched electron beam back to resonator cavity. This positive feedback supports oscillations. Its feature are: 1. Frequency range - 2 to 100 GHz
2. Power output - 10 MW to about 2 W 3. Efficiency - 10 - 20 % Its applications include radar receivers, local oscillator in microwave devices, oscillator for microwave measurements in laboratories etc. 46. Assertion (A): PIN diode is used as a fast switch. Reason (R): PIN diode has very high resistance when reverse biased and very low resistance when forward biased. A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation Answer: Option A Explanation: A PIN diode has an intrinsic (i) layer between p and n layers. When reverse bias is applied depletion layers are formed at p-i and i-n junctions. The effective/width of depletion layer increases by the width of i layer. It can be used as a voltage controlled attenuator. At high frequencies the rectification effect ceases and impedance of diode is effectively that of i layer. This impedance varies with the applied bias. It is used in high frequency switching circuits, limiters, modulators etc.
47. A pulsed radar produces 1 μ sec pulses at a rate of 1000 per second. The duty cycle is A.0.001 B. 0.01 C. 0.1 D.1 Answer & Explanation Answer: Option A Explanation: 1 x 10-6 x 1000 = 0.001.
48. Assertion (A): Impedance measurement at microwave frequencies is done by finding SWR. Reason (R): SWR and reflection coefficient depend on the characteristic impedance and load impedance. A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation Answer: Option B Explanation:
49. When a line is loaded the characteristic impedance is equal to A.(R + jωL)(G + jωC) B. C. D.LC Answer & Explanation Answer: Option B Explanation:
or
50. Which device has internal positive feedback? A.Two cavity klystron amplifier B. Multi-cavity klystron amplifier C. Reflex klystron amplifier D.All of the above Answer & Explanation
.
Answer: Option C Explanation: A Klystron is a vacuum tube used for generation/amplification of microwaves. An electron beam is produced by oxide coated indirectly heated cathode and is focussed and accelerated by focussing electrode. This beam is transmitted through a glass tube. The input cavity where the beam enters the glass tube is called buncher. As electrons move ahead they see an accelerating field for half cycle and retarding field for the other half cycle. Therefore, some electrons are accelerated and some are retarded. This process is called velocity modulation. The velocity modulation causes bunching of electrons. This bunching effect converts velocity modulation into density modulation of beam. The input is fed at buncher cavity and output is taken at catcher cavity. In a two cavity klystron only buncher and catcher cavity are used. In multi cavity klystron one or more intermediate cavities are also used. The features of a multicavity klystron are : 1. Frequency range - 0.25 GHz to 100 GHz 2. Power output - 10 kW to several hundred kW 3. Power gain - 60 dB (nominal value) 4. Efficiency - about 40%. A multicavity klystron is used in UHF TV transmitters, Radar transmitter and satellite communication. 1. The domain mode in rectangular waveguide is A.TE01 B. TE02 C. TE10 D.TM11 Answer & Explanation Answer: Option C
Explanation: No answer description available for this question. Let us discuss.
2. The reverse voltage applied to a varactor diode A.is less than avalanche breakdown voltage B. is more than avalanche breakdown voltage C. may be more or less than a avalanche breakdown voltage D.is very high as compared to avalanche breakdown voltage Answer & Explanation Answer: Option A Explanation: The action of varactor diode is due to the capacitance of depletion layer. The thickness of depletion layer depends on the reverse bias which should not cause breakdown.
3. To ensure that only dominant mode TE10 is allowed to propagate in an air filled rectangular waveguide, the lower frequency limit and upper frequency limit are A.about 25% above fc for TE10 and 5% below fc for TE20 mode respectively B. about 50% above fc for TE10 and 25% below fc for TE20 mode respectively C. about 25% above fc for TE10 and 25% below fc for TE20 mode respectively D.none of the above Answer & Explanation Answer: Option A Explanation: No answer description available for this question. Let us discuss.
4. The skin depth at 1000 MHz as compared to that at 500 MHz is A.2 B. 12 C. 0.707 D.0.5 Answer & Explanation Answer: Option C
Explanation: No answer description available for this question.
5. The transit time (in cycles) for electrons in repeller space of reflex klystron oscillator for sustaining oscillations is (n is any integer) A.2(n - 1) B. 2n - 1 C. D. Answer & Explanation Answer: Option D Explanation: No answer description available for this question 6. In a TWT the amplitude of resultant wave travelling down the helix remains constant A.True B.False Answer & Explanation Answer: Option B Explanation: The signal gets strengthened.
7. In the given figure forward current wave has a magnitude of
A.0.45 A B. 0.3 A C. 0.2 A
D.0.1 A Answer & Explanation Answer: Option B Explanation:
8. In an infinite line the input impedance at every point is equal to characteristic impedance. A.True B.False Answer & Explanation Answer: Option A Explanation: No answer description available for this question. Let us discuss.
9. Consider the following time parameters 1. Domain growth time constant. 2. Transit time. 3. Dielectric relaxation time in positive mobility regime. Which of the above are used in connection width transferred electron device? A.1, 2, and 3 B. 1 and 2 only C. 1 and 3 only D.2 and 3 only Answer & Explanation Answer: Option A Explanation: No answer description available for this question.
10. PIN diode has
A.p+ and n layers separated by i layer B. p+ and n+ layers separated by i layer C. p- and n- layers separated by i layer D.none of the above Answer & Explanation Answer: Option B Explanation: No answer description available for this question. 11. The two terms used to describe performance of a directional coupler are A.coupling and directivity B. gain and coupling C. gain and directivity D.gain and isolation Answer & Explanation Answer: Option A Explanation: No answer description available for this question.
12. The number of PM radio channels which can be accommodated in a spectrum of 300 MHz is about A.10 B. 100 C. 500 D.1500 Answer & Explanation Answer: Option D Explanation: No answer description available for this question.
13. Consider the following statements 1. Gunn diode can be used in combinational logic circuits. 2. Gunn diode can be used in sequential logic circuits. 3. Both Gunn diode and GaAs Mesfet can be used in logic circuits.
Which of the above statements are correct? A.1, 2, and 3 B. 1 and 2 only C. 2 and 3 only D.1 and 3 only Answer & Explanation Answer: Option A Explanation: No answer description available for this question.
14. In the given figure shows the equivalent circuit of a magic tee. If all ports are matched
A.nE = nH = 2 B. nE = nH = 0.707 C. nE = 2, nH = 0.707 D.nH = 0.707, nH = 2 Answer & Explanation Answer: Option A Explanation: No answer description available for this question. 15. Assertion (A): Microstrip is very commonly used in microwave integrated circuits. Reason (R): Microstrip has an easy access to the top-surface so that active and passive discrete components can be easily mounted. A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong
D.A is wrong but R is correct Answer & Explanation Answer: Option A Explanation: A Microstrip line has a single dielectric substratc with ground plane on one side and a strip on the other face. Its special feature is easy access to top surface so that minor adjustments can be made after circuit fabrication. The high dielectric constant of the substrate reduces guide wavelength and circuit dimensions. A microstrip line is the most commomly used transmission structure for microwave integrated circuits. 16. A 75 ohm line is first short terminated and minima locations are noted. Then the short is replaced by resistive load and minima location are again noted. If minima location are not altered and VSWR is 3, the value of resistive load is A.25 Ω B. 50 Ω C. 225 Ω D.250 Ω Answer & Explanation Answer: Option C Explanation:
rv
and VSWR
17. The word 'LORAN' means A.long range navigation B. long range TV transmission C. long range cable transmission D.either (b) or (c) Answer & Explanation Answer: Option A
.
Explanation: No answer description available for this question.
18. In the given figure forward voltage wave has a magnitude
A.90 V B. 60 V C. 30 V D.10 V Answer & Explanation Answer: Option C Explanation: No answer description available for this question.
19. The duty cycle of a radar transmitter is equal to A.(PRF) (pulse width) B. (PRF)/(pulse width) C. (pulse width)/(PRF) D.(pulse width) + (PRF) Answer & Explanation Answer: Option A Explanation: No answer description available for this question.
20. In a klystron amplifier the bunching effect
A.converts velocity modulation into current modulation of beam B. converts current modulation into velocity modulation of beam C. both (c) and (b) D.neither (a) nor (b) Answer & Explanation Answer: Option A Explanation: A Klystron is a vacuum tube used for generation/amplification of microwaves. An electron beam is produced by oxide coated indirectly heated cathode and is focussed and accelerated by focussing electrode. This beam is transmitted through a glass tube. The input cavity where the beam enters the glass tube is called buncher. As electrons move ahead they see an accelerating field for half cycle and retarding field for the other half cycle. Therefore, some electrons are accelerated and some are retarded. This process is called velocity modulation. The velocity modulation causes bunching of electrons. This bunching effect converts velocity modulation into density modulation of beam. The input is fed at buncher cavity and output is taken at catcher cavity. In a two cavity klystron only buncher and catcher cavity are used. In multi cavity klystron one or more intermediate cavities are also used. The features of a multicavity klystron are : 1. Frequency range - 0.25 GHz to 100 GHz 2. Power output - 10 kW to several hundred kW 3. Power gain - 60 dB (nominal value) 4. Efficiency - about 40%. A multicavity klystron is used in UHF TV transmitters, Radar transmitter and satellite communication. 21. Out of modes TE20 and TE30 of propagation of electromagnetic engery A.both have the same cutoff frequency
B. TE20 has lower cut off frequency as compared to TE30 C. TE30 has lower cutoff frequency as compared to TE20 D.either (a) or (c) Answer & Explanation Answer: Option B Explanation: No answer description available for this question.
22. A TE10 rectangular waveguide is to be designed for operation over 25-35 GHz and the band centre is 1.5 times the cutoff frequency. The dimension of broadside is A.15 mm B. 10 mm C. 9 mm D.7.5 mm Answer & Explanation Answer: Option D Explanation: No answer description available for this question.
23. In a klystron amplifier the force on all electrons A.causes acceleration of all electrons B. causes retardation of all electrons C. causes acceleration of some electrons and retardation of others D.none of the above Answer & Explanation Answer: Option C Explanation: A Klystron is a vacuum tube used for generation/amplification of microwaves. An electron beam is produced by oxide coated indirectly heated cathode and is focussed and accelerated by focussing electrode. This beam is transmitted through a glass tube. The input cavity where the beam enters the
glass tube is called buncher. As electrons move ahead they see an accelerating field for half cycle and retarding field for the other half cycle. Therefore, some electrons are accelerated and some are retarded. This process is called velocity modulation. The velocity modulation causes bunching of electrons. This bunching effect converts velocity modulation into density modulation of beam. The input is fed at buncher cavity and output is taken at catcher cavity. In a two cavity klystron only buncher and catcher cavity are used. In multi cavity klystron one or more intermediate cavities are also used. The features of a multicavity klystron are : 1. Frequency range - 0.25 GHz to 100 GHz 2. Power output - 10 kW to several hundred kW 3. Power gain - 60 dB (nominal value) 4. Efficiency - about 40%. A multicavity klystron is used in UHF TV transmitters, Radar transmitter and satellite communication.
24. If load impedance ZL >> Z0, then A.Z0 = ZL (VSWR) B. ZL = Z0 (VSWR) C. ZL = Z0 (VSWR - 1) D.ZL = Z0 VSWR Answer & Explanation Answer: Option B Explanation:
If ZL >> Z0, |rv|
and VSWR
. Therefore ZL = Z0(VSWR).
25. The inductance of a twin feeder used to connect antenna to TV receiver is about A.0.2 μ H/m B. 0.6 μ H/m C. 1.6 μ H/m D.10 μ H/m Answer & Explanation Answer: Option C Explanation: No answer description available for this question. 26. When resonant cavities are coupled together the result is A.one resonant frequency B. n resonant frequencies C. resonant frequencies D.either (b) or (c) Answer & Explanation Answer: Option B Explanation: No answer description available for this question. 27. For a rectangular waveguide having width a and height b, the cutoff wavelength for TM11 mode is equal to A. B. C. D. Answer & Explanation Answer: Option B Explanation: No answer description available for this question.
28. The path length between ports 1 and 2 for the two waves in a hybrid ring is A.1 B. C. D. Answer & Explanation Answer: Option C Explanation: The quantities required to be measured in microwave circuits are frequency, power and impedance. Microwave frequency measurement is done by slotted line, resonant cavities and transfer oscillator. Microwave power measurement uses bolometers and microwave power meters. A self balancing bridge working on the principle of power substitution is commonly used. Microwave impedance measurement is done by measurement of reflection coefficient and VSWR. A slotted line and probe is a basic tool for these measurements.' Network analyser enables rapid impedance measurement over a broad frequency range.
29. The radiation resistance of a circular loop of one turn is 0.01 ohm. For 5 turn loop the radiation resistance is A.0.002 Ω B. 0.01 Ω C. 0.05 Ω D.0.25 Ω Answer & Explanation Answer: Option D Explanation: No answer description available for this question.
30. As wavelength decrease the size of high directivity antenna A.decreases B. increases C. is not affected D.either (b) or (c) Answer & Explanation Answer: Option A Explanation: No answer description available for this question. 31. Which of the following modes of transmission will not be supported by a rectangular waveguide? A.TE15 B. TE12 C. TM11 D.TM10 Answer & Explanation Answer: Option D Explanation: No answer description available for this question.
32. In a circular waveguide with radius r, the dominant mode is A.TM01 B. TE01 C. TM11 D.TE11 Answer & Explanation Answer: Option B Explanation: Some applications require dual polarization capability. Circular waveguide has this capability. These analysis uses cylindrical coordinates. In circular waveguide TE11 mode has the lowest cut off frequency and is the dominant mode. If D is diameter of waveguide
λc = 1.706 D for TE11 mode λc = 1.029 D for TE21 mode λc = 0.82 D for TE01 mode λc = 1.306 D for TM01 mode.
33. If 'a' is the width of rectangular wave guide and 'λ' is the wave length, then A. B. C. D. Answer & Explanation Answer: Option B Explanation: No answer description available for this question.
34. A parametric amplifier uses A.non linear resistance B. non linear reactance C. either (a) or (b) D.neither (a) nor (b) Answer & Explanation Answer: Option B Explanation: In a parametric amplifier the non-linear element is varactor diode or inductor.
35. Assertion (A): Impatt diode can be used in both amplifiers and oscillators. Reason (R): Impatt diode has a low resistance. A.Both A and R are correct and R is correct explanation of A
B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation Answer: Option B Explanation: An Impatt diode has n+ - p - i - p + structure and is used with reverse bias. It exhibits negative resistance and operates on the principle of avalanche breakdown. Impatt diode circuits are classified as broadly tunable circuit, low Q circuit and high Q circuit. The impedance of Impatt diode is a few ohms. The word Impatt stands for Impact Avalanche Transit Time diode. The features of Impatt diode oscillator are : frequency 1 to 300 GHz, Power output (0.5 W to 5 W for single diode circuit and upto 40 W for combination of several diodes), efficiency about 20%. Its applications include police radar systems, low power microwave transmitter etc. 36. Which one of the following can be used for amplification of microwave energy? A.TWT B. Magnetron C. Reflex klystron D.Gunn diode Answer & Explanation Answer: Option A Explanation: No answer description available for this question.
37. If ZTE is wave impedance for TE waves, Ed is maximum dielectric strength of insulating material, a and b are the width and height of a rectangular wave guide, the maximum power handling capability Pmax for TE10 mode is A. B.
C. D. Answer & Explanation Answer: Option B Explanation: No answer description available for this question. 38. At frequencies of 10 MHz and higher the impedance represented by ground is primarity A.resistive B. inductive C. capacitive D.partly resistive and partly capacitive Answer & Explanation Answer: Option C Explanation: No answer description available for this question.
39. A disadvantage of microstrip line as the connections of compared to strip line is that former A.do not lend themselves to printed circuit B. are more likely to radiate C. are bulky D.are more expensive and complex Answer & Explanation Answer: Option B Explanation: No answer description available for this question..
40. As frequency increases, the transmission efficiency A.decreases B. increases C. is not affected
D.either (a) or (c) Answer & Explanation Answer: Option B Explanation: No answer description available for this question. 41. A circular polarizer converts a linearly polarized wave into a circularly polarised wave. A.True B.False Answer & Explanation Answer: Option A Explanation: No answer description available for this question.
42. If D is diameter of circular waveguide the cutoff wave-length for TE11 mode is equal to A.1.706 D B. 2.11 D C. 0.82 D D.0.41 D Answer & Explanation Answer: Option A Explanation: Some applications require dual polarization capability. Circular waveguide has this capability. These analysis uses cylindrical coordinates. In circular waveguide TE11 mode has the lowest cut off frequency and is the dominant mode. If D is diameter of waveguide λc = 1.706 D for TE11 mode λc = 1.029 D for TE21 mode λc = 0.82 D for TE01 mode
λc = 1.306 D for TM01 mode.
43. The external magnetic field in a magnetron is such that lines are A.parallel to the axis of cathode B. perpendicular to the axis of cathode C. inclined to the axis of cathode D.either (b) or (c) Answer & Explanation Answer: Option A Explanation: The operation of magnetron is based on interaction of electromagnetic fields with electrons moving in static electric and magnetic fields oriented at 90° with respect to each other. In a magnetron three forces act on electron viz. force due to electric field (equal to - eE), force due to magnetic field [equal to - e (v x B)] and centrifugal force (equal to mv2/r). The path of the electron can be found by balancing these three forces. Magnetron can be of three types i.e., negative resistance device, cyclotron frequency device and travelling wave or cavity device. In negative resistance magnetron use is made of the negative resistance between two anode segments. It has low efficiency and is used at frequencies less than 0.5 GHz. In cyclotron magnetron a synchronism exists between ac component of electric field and periodic oscillation of electrons in a direction parallel to the field. It is used for frequencies higher than 100 MHz. A cavity magnetron has a number of cylindrical cavities in the interaction region. The cavity magnetron is the most common type of magnetron. Its features are : 1. Frequency range - 500 MHz to 10 GHz 2. Power output - 250 kW (pulses) 3. Efficiency - about 50%
It is used in radar systems, industrial heating systems and microwave ovens.
44. Varactor diodes use A.silicon B. GaAs C. either (a) or (b) D.neither (a) nor (b) Answer & Explanation Answer: Option C Explanation: No answer description available for this question.
45. A circular waveguide carries TE11 mode whole radial electric field is given by Er = E0j1(r) sin Φ V/m where r is radial distance in cm from the axis The cut off wavelength is A.10 cm B. 3 p cm C. 2 p cm D.8 cm Answer & Explanation Answer: Option A Explanation: No answer description available for this question. 46. Assertion (A): Impatt diode is an avalanche diode. Reason (R): Avalanche breakdown phenomenon occurs when a p-n junction is reverse biased. A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation Answer: Option B
Explanation: An Impatt diode has n+ - p - i - p + structure and is used with reverse bias. It exhibits negative resistance and operates on the principle of avalanche breakdown. Impatt diode circuits are classified as broadly tunable circuit, low Q circuit and high Q circuit. The impedance of Impatt diode is a few ohms. The word Impatt stands for Impact Avalanche Transit Time diode. The features of Impatt diode oscillator are : frequency 1 to 300 GHz, Power output (0.5 W to 5 W for single diode circuit and upto 40 W for combination of several diodes), efficiency about 20%. Its applications include police radar systems, low power microwave transmitter etc.
47. A radar has a maximum range of 120 km. The maximum allowable pulse repetition frequency for unambiguous reception is A.1250 B. 330 C. 2500 D.8330 Answer & Explanation Answer: Option A Explanation: No answer description available for this question.
48. In a line with finite attenuation A.power transmission is least efficient when there are no standing waves on the line B. power transmission is most efficient when there are no standing waves on line C. Load power depends on phase constant D.standing waves will always exist on the line Answer & Explanation Answer: Option B Explanation:
If standing waves are not there, whole of the power is absorbed by load.
49. In the given figure a short circuited transmission line resonator If n = 1, 2, 3...
A. For series reasonance βl = np and for parallel resonance B.
For series resonance and for parallel resonance βl = np C. βl = np for both series and parallel resonance D.
for both series and parallel resonance Answer & Explanation Answer: Option A Explanation: No answer description available for this question.
50. The electric field in a TWT due to applied signal A.is directed along the helix axis B. is directed radially from helix axis C. is inclined to the helix axis by about 60° D.is inclined to the helix axis by about 45° Answer & Explanation Answer: Option A Explanation: In a klystron the resonant structure limits the bandwidth. A TWT is a broadband device. Its main components are electron gun (to produce the electron
beam) and a structure supporting the slow electromagnetic wave. The velocity of wave propagation along the helix structure is less than velocity of light. The beam and wave travel along the structure at the same speed. Thus interaction occurs between beam and wave and the beam delivers energy to the RF wave. Therefore the signal gets strengthened and amplified output is delivered at the other end of tube. The main features of TWT are : 1. Frequency range - 0.5 GHz to 90 GHz 2. Power output - 5 mW at low frequencies(less than 20 GHz) 250 kW (continuous wave) at 3 GHz 10 MW (pulsed) at 3 GHz 3. Efficiency - about 5 to 20% 4. Noise - about 5 dB for low power TWT 25 dB for high power TWT TWT is used as RF amplifier in broadband microwave receivers, repeater amplifier in broad band communication systems, communication satellites etc.
1. In 8 cavity magnetron the p mode corresponds to a total phase shift equal to A.± 8 p radians around the periphery B. ± 4 p radians around the periphery C. ± 2 p radians around the periphery D.± 16 p radians around the periphery Answer & Explanation Answer: Option A Explanation: No answer description available for this question. 2. Satellite communication systems use the frequency band A.10 to 20 MHz B. 50 to 70 MHz C. 3 to 6 GHz D.100 to 120 GHz
Answer & Explanation Answer: Option C Explanation: No answer description available for this question.
3. The characteristic impedance of a cable is about A.300 Ω B. 50 Ω C. 5 Ω D.2 Ω Answer & Explanation Answer: Option B Explanation: No answer description available for this question..
4. The Q factor of a waveguide resonator is given by (ω0 is resonant frequency, U is energy storage and WL is the power loss) A. B. C. Q = ω0UWL D. Answer & Explanation Answer: Option A Explanation: No answer description available for this question.
5. A TR (transmitter receiver) tube has A.low loss for low power signals and high B. high loss for low power signals and low loss for high level signal
C. low loss for both low level and high level signals D.high loss for both low level and high level signals Answer & Explanation Answer: Option A Explanation: No answer description available for this question. 6. When duct propagation exists A.the line of sight and diffraction. Zone concepts are payable B. the line of sight and diffraction zone concepts are not applicable C. line of sight concept is applicable but diffraction zone concept is applicable D.diffraction zone concept is not applicable but line of sight concept is not applicable Answer & Explanation Answer: Option B Explanation: No answer description available for this question.
7. For l << λ, the equivalent circuit of a microwave resistor is A.
B.
C.
D.
Answer & Explanation Answer: Option B Explanation:
No answer description available for this question.
8. If μr is relative permeability, ∈r is relative permittivity, c is velocity of light fc is cutoff frequency, phase velocity vp (i.e., speed with which a particular phase of the wave travels down a rectangular waveguide at frequency f) is given by A. B.
C.
D. Answer & Explanation Answer: Option A Explanation: No answer description available for this question.
9. If in line the characteristic impedance becomes real. A.True B.False Answer & Explanation Answer: Option A
10. In a microwave coaxial cable the inner conductor radius is a and inner radius of outside conductor is b. For TE11 mode the cut off wavelength is about A.a + b B. p(a + b) C. pa D.pb Answer & Explanation
Answer: Option B
11. In a magnetron the magnetic flux density is of the order of A.1 mWb/s B. 1 Wb/m2 C. 106 m/s D.1012 m/s Answer & Explanation Answer: Option A
12. For a directional coupler the power is in the ratio of A.40 dB B. 30 dB C. 20 dB D.10 dB Answer & Explanation Answer: Option C
13. As regards rectangular and circular waveguides A.both have infinite set of TE and TM modes B. rectangular waveguide has infinite TE and TM modes but not the circular waveguide C. circular waveguide has infinite TE and TM modes but not the rectangular waveguide D.none of the above Answer & Explanation Answer: Option A
14. In a high frequency coaxial line and the length of line characteristic impedance is a function of A.properties of insulating material only B. inner and outer conductor radius only C. both (a) and (b) D.neither (a) nor (b) Answer & Explanation
Answer: Option C
15. Assertion (A): In TE10 mode the cutoff frequency of rectangular waveguide is the broad dimension and c is velocity of light. Reason (R): TE10 mode is the dominant mode in rectangular waveguide. A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation Answer: Option B
16. The usable bandwidth of ridge wave guide A.is lower than that of rectangular waveguide B. is higher than that of rectangular waveguide C. is almost same as that of rectangular waveguide D.is very small as compared to that of rectangular waveguide Answer & Explanation Answer: Option B
17. Assertion (A): In TE mode for rectangular waveguide. Reason (R): In TM mode for rectangular waveguide. A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation Answer: Option B
18. The attenuation characteristics of a loaded line is similar to that of A.low pass filter B. high pass filter
where a is
C. band pass filter D.band stop filter Answer & Explanation Answer: Option D
19. A microstrip line has ∈r = 9. The normalised wavelength A.10 B. 2 C. 1 D.0.4 Answer & Explanation
is about
Answer: Option D
20. If the repeller voltage in a klystron oscillator is increased the transit time of electron A.will be increased B. will be decreased C. will remain the same D.either (a) or (b) Answer & Explanation Answer: Option C 21. In which of the following devices can the operation be visualised in terms of a series feedback loops? A.TWT B. Reflex klystron C. Klystron amplifier D.Backward wave oscillator Answer & Explanation Answer: Option D
22. The first and second subscripts in models of circular waveguides depict the number of full sine wave variations in circumference in direction and Bessel function A. variations in radial direction respectively the Bessel function variations in radial direction and the number of full sine wave B. variations in circumference direction respectively the Bessel function variations in circumference direction and number of full sine wave C. variations in radial direction respectively D.none of the above
Answer & Explanation Answer: Option A
23. In which mode of circular waveguide does the attenuation continuously decrease as frequency is increased? A.TE01 B. TE11 C. TE05 D.TE21 Answer & Explanation Answer: Option A
24. In which mode of rectangular waveguide are all field components zero? A.TM00 B. TM11 C. TM01 D.TM10 Answer & Explanation Answer: Option A
25. A microstrip line has dielectric having relative permittivity ∈r. The effective dielectric constant is A.more than ∈r B. equal to 1 C. less than ∈r D.either a or b Answer & Explanation Answer: Option C 21. In which of the following devices can the operation be visualised in terms of a series feedback loops? A.TWT B. Reflex klystron C. Klystron amplifier D.Backward wave oscillator Answer & Explanation Answer: Option D
22. The first and second subscripts in models of circular waveguides depict the number of full sine wave variations in circumference in direction and Bessel function A. variations in radial direction respectively the Bessel function variations in radial direction and the number of full sine wave B. variations in circumference direction respectively the Bessel function variations in circumference direction and number of full sine wave C. variations in radial direction respectively D.none of the above Answer & Explanation Answer: Option A
23. In which mode of circular waveguide does the attenuation continuously decrease as frequency is increased? A.TE01 B. TE11 C. TE05 D.TE21 Answer & Explanation Answer: Option A
24. In which mode of rectangular waveguide are all field components zero? A.TM00 B. TM11 C. TM01 D.TM10 Answer & Explanation Answer: Option A
25. A microstrip line has dielectric having relative permittivity ∈r. The effective dielectric constant is A.more than ∈r B. equal to 1 C. less than ∈r D.either a or b Answer & Explanation Answer: Option C
26. The rotation of direction of E field of a linearly polarized wave passing through a magnetised ferric medium is called A.Lorentz rotation B. Faraday rotation C. Steinmitz rotation D.Fleming's rotation Answer & Explanation Answer: Option B
27. If air pressure in a rectangular waveguide is increased the maximum power handling capacity A.is decreased B. is increased C. remains the same D.may increase or decrease depending on pressure Answer & Explanation Answer: Option B
28. A directional coupler is used to determine A.rv B. rv and VSWR C. L and C D.wave velocity Answer & Explanation Answer: Option B
29. A square waveguide carries TE11 mode whose axial magnetic field is given by Hz = H0 , where the guide dimensions are in cms. The cut off frequency of the mode is A.5 GHz B. 7.5 GHz C. 6.5 GHz D.8 GHz Answer & Explanation Answer: Option B
30. For air filled circular waveguides A.the attenuation due to imperfect conducting walls is negligible B. the attenuation due to imperfect dielectric is negligible both the attenuation i.e. due to imperfect conducting walls and due to imperfect dielectric C. are significant D.the total attenuation is almost zero Answer & Explanation Answer: Option B 31. A short circuited stub is preferred to an open circuited stub because an open circuited stub A.is more difficult to fabricate and construct B. is made of transmission line of different Z0 C. is liable to radiate D.is incapable of giving full range of reactance Answer & Explanation Answer: Option C
32. If the peak transmitted power in a radar is increased by a factor 81, the maximum range is increased by a factor of A.3 B. 9 C. 27 D.81 Answer & Explanation Answer: Option A
33. Radar is essentially an echo ranging system A.True Answer & Explanation
B.False
Answer: Option A
34. In Gunn diode electrons are transferred from A.Ridge guide is essentially a form of capacitively loaded guide B. low to high mobility energy bands C. valley to domain formation D.domain to valley formation
Answer & Explanation Answer: Option A
35. Consider the following statements about radar Beacon 1. It is also called transponder. 2. It includes pulse transmitter, receiver and antenna. 3. It replies with full power even when the signal receives is weak. Which of the above statements are correct? A.All B. 1 and 2 only C. 2 and 3 only D.2 only Answer & Explanation Answer: Option A 36. Consider the following statements about instrument landing system of aircraft 1. It ensures correct landing under conditions of low visibility. 2. It consists of runaway localizer, glide path equipment and marker beacons. 3. It is basically a blind landing system. Which of above statements are correct? A.All B. 1 and 2 only C. 1 and 3 only D.2 only Answer & Explanation Answer: Option A
37. Effect of loading of line is A.increase in Z0, a and β B. increase in Z0 and β but decrease in a C. decrease in Z0, a and β D.decrease in Z0 and β but increase in a Answer & Explanation Answer: Option B
38. Which mode has the minimum cutoff frequency in rectangular wave guides? A.TE11 B. TE10 C. TE01 D.TE20 Answer & Explanation Answer: Option B
39. As compared to dimensions of most feeds, the skin depth at microwave frequencies is A.of the same magnitude B. much larger C. much smaller D.either (b) or (c) Answer & Explanation Answer: Option A
40. In microwave communication links the fading due to rain occurs. The methods to solve this problem include A.antenna replacement and feed correction B. amplitude trimming and phase correction C. polarization shifting and code diversity D.path diversity and frequency diversity Answer & Explanation Answer: Option D 41. A microwave connector should have high SWR. A.True B.False Answer & Explanation Answer: Option B
42. Assertion (A): A small section of high impedance line is equivalent to a series inductance. Reason (R): A small section of a low impedance line is equivalent to a series resistance. A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct
Answer & Explanation Answer: Option C
43. Assertion (A): Bolometer is frequently used in microwave power measurement. Reason (R): In a bolometer the input microwave power causes a change in resistance. A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation Answer: Option B
44. The radiation resistance of a doublet antenna of length dl is proportional to A.δ l B. (δ l)2 C. (δ l)3 D.(δ l)05 Answer & Explanation Answer: Option B
45. Which of the following statements is not correct regarding modes of electromagnetic energy transmission? In TE mode the direction of electric field is always and everywhere transverse to the A. direction of propagation In TM mode the magnetic field pattern is always and everywhere transverse to the B. direction of propagation The subscripts is TE and TM designations denote the number of half sine wave variations C. of the field components in x and y directions respectively. D.TM11 is called the dominant mode. Answer & Explanation Answer: Option D 46. Oscillations are obtained from a reflex klystron only for combinations of anode voltage and repeller voltage that give a favourable transit time. A.True B.False Answer & Explanation
Answer: Option A
47. In the given figure shows a 10dB directional coupler. If power input at port 1 is 100 mW, power output at port 3 is
A.10 mW B. 15 mW C. 20 mW D.25 mW Answer & Explanation Answer: Option A
48. The noise figure of klystron amplifier is about A.25 dB B. 3 dB C. zero D.1 dB Answer & Explanation Answer: Option A
49. Which one of the following is true for EM wave propagation through rectangular waveguide of cross-section 2a x a A.critical wavelength for TE10 mode is the same as that for TE02 mode B. critical wavelength for TE10 mode is one half of that for TE10 mode C. critical wavelength for TE10 mode is the same as that for TM10 mode D.critical wavelength for TE10 mode is double that for TE01mode Answer & Explanation
Answer: Option C
50. In the given figure the line voltage after a number of reflections will be
A.30 V B. -30 V C. 10 V D.-10 V Answer & Explanation Answer: Option C 1. Which one of the following is also called 'rat race'? A.E plane tee B. H plane tee C. Magic tee D.Hybrid ring Answer & Explanation Answer: Option D
2. Radar principle is used in A.detection of aircraft B. burglar alarms C. garage door openers D.all of the above Answer & Explanation Answer: Option D
3. In an optional fiber the refractive index of cladding material should be
A.nearly 1 B. very low C. less than that of core D.more than that of core Answer & Explanation Answer: Option C
4. In microwave circuits, a mode transducer is used to A.change mode of wave transmission B. change direction of wave transmission C. change polarization of wave transmission D.change mode, direction or polarization wave transmission Answer & Explanation Answer: Option D
5. A waveguide connected to a circularly polarized antenna must be able to efficiently propagate both vertically and horizontally polarised waves. A.True B.False Answer & Explanation Answer: Option A 6. Which of the following is not used as a microwave mixer or detector? A.PIN diode B. Crystal diode C. Schottky barrier diode D.Backward diode Answer & Explanation Answer: Option A
7. Integrated fin line can be utilized as a medium for constructing millimeter wave circuits. A.True B.False Answer & Explanation Answer: Option A
8. The secondary constants of a line are A.Z0 B. Z0 and γ C. Z0, γ and wave velocity D.Z0, γ and L Answer & Explanation Answer: Option B
9. In a loss less line the propagation constant is equal to A.jωLC B. LC C. jωLC D.LC Answer & Explanation Answer: Option A
10. A rectangular wave guide has two stubs each of length stubs are circuited. Then the stubs present A.an infinite impedance in shunt with line B. an infinite impedance in series with line C. a zero impedance in shunt with line D.a finite impedance in shunt with line Answer & Explanation
connected at the source end. The
Answer: Option A 11. Slotted line can be used for measurement of high frequencies A.True B.False Answer & Explanation Answer: Option A
12. In a waveguide the dielectric region is generally A.air B. magnetic material C. brass D.mica Answer & Explanation
Answer: Option A
13. In directional coupler of the given figure, the terms |S14| and |S23| of scattering matrix are nearly
A.1 each B. 0.5 each C. 0.1 each D.1 and 0.5 respectively Answer & Explanation Answer: Option A
14. A line is excited by a 100 V, 200 ohm source and is terminated by 100 Ω resistance. If the voltage on line reaches steady value in 80 ns, the natural resonant frequency is A.100 MHz B. 50 MHz C. 12.5 MHz D.6.25 MHz Answer & Explanation Answer: Option C
15. A line of length slightly longer than A.inductance L B. capacitance C C. L and C in series D.L and C in parallel Answer & Explanation Answer: Option A 16. The most commonly used magnetron is
and open circuited at far end behaves as
A.cylindrical B. parallel plate C. inclined plate D.flat plate Answer & Explanation Answer: Option A
17. The effect of earth's magnetic field on radiowaves is minimum when the electric field lines of radio waves and flux line of earth's magnetic field are in the same A. direction the electric field lines of radio waves and flux lines of earth's magnetic field are at right B. angles the electric field lines of radiowaves and flux lines of earth's magnetic field oppose each C. other D.both (b) and (c) Answer & Explanation Answer: Option A
18. A line of characteristic impedance Z0 branches into two line each with characteristic impedance Z0. The refracted voltage is A.zero B. infinite C. equal to incident voltage D.two third of incident voltage Answer & Explanation Answer: Option D
19. The resistance values of a PIN diode under positive bias and negative bias respectively are about A.a few ohms and a kilo ohms B. about 100 ohms and 1000 ohms C. about 0.1 ohm and 100 ohms D.about 1000 ohms and 10000 ohms Answer & Explanation Answer: Option A
20. A PIN diode can be used A.as a shunt mounted switch B. as a series mounted switch C. both as series or shunt mounted switch D.non of the above Answer & Explanation Answer: Option C 21. What is the numerical aperture an optical fiber when critical angle is 30°? A.0.5 B. 0.704 C. 0.866 D.0.2 Answer & Explanation Answer: Option A Explanation: No answer description available for this question.
22. A line of length slightly less than A.inductance L B. capacitance C C. L and C in series D.L and C in parallel Answer & Explanation
and short circuited at far end behaves as
Answer: Option A Explanation: No answer description available for this question.
23. In TE10 mode of rectangular waveguide A.there is one half sine wave variation along x direction and one along y direction B. there is one half sine wave variation along y direction and one along x direction C. there is one full sine wave variation along x direction and one along y direction D.none of the above Answer & Explanation
Answer: Option A
24. Reflection from the object to be measured is significant only when the wavelength is A.much bigger than the size of object B. much smaller than the size of object C. almost of the size of object D.either (a) or (c) Answer & Explanation Answer: Option B 25. The speed at which axial electric field due to signal advances in a TWT is equal to A.speed of light B. (speed of light) (helix pitch helix circumference) C. (speed of light) (helix circumference helix pitch) D.(speed of light) (helix pitch) (helix circumference) Answer & Explanation Answer: Option B 26. To ensure that only dominant TE10 mode propagates in a rectangular waveguide, the operating frequency A.must be more than cutoff frequency of TE10 mode B. must be less than cutoff frequency of TE20 mode must be more than cutoff frequency of TE10 mode and less than cutoff frequency of TE20 C. mode D.must be less than cutoff frequency of TE10 mode Answer & Explanation Answer: Option C
27. In a microwave power measurement using bolometer, the principle of working is variation of A.inductance with absorption of power B. resistance with absorption of power C. capacitance with absorption of power D.cavity dimension with heat generated by power Answer & Explanation Answer: Option B 28. Z0 = (Zoc Zsc)0.5 A.True Answer & Explanation
B.False
Answer: Option A
29. A microwave junction is matched at all ports if the S matrix A.has all diagonal elements zero B. has all diagonal elements equal but not zero C. has all diagonal elements complex D.is Hermitian Answer & Explanation Answer: Option A
30. Assertion (A): A line of length slightly more than equivalent to an inductive reactance.
and open circuited at far end is
Reason (R): A line of length slightly more than and short circuited at far end behaves as a capacitive reactance. A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation Answer: Option B
31. TE01 mode of propagation of electromagnetic energy A.is merely the TE10 mode rotated 90° B. is merely the TE10 mode rotated 180° C. is the same as TE10 mode D.either (b) or (c) Answer & Explanation Answer: Option A
32. Assertion (A): Slotted line is frequently used for microwave measurements. Reason (R): The unknown impedance is mounted at the end of slotted line. A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A
C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation Answer: Option B
33. Fibers have numerical aperture (NA) in the range of 0.15 to 0.4 Fibers with higher NA value would have A.reduced losses B. high bandwidth C. reduced losses and low bandwidth D.more losses and low bandwidth Answer & Explanation Answer: Option D 34. The following components are used to measure power output of a 2 kW TWT amplifier 1. 2. 3. 4. 5.
TWT Low pass/High pass filter Low power 20 dB attenuator 40 dB directional coupler with matched load Power meter.
The correct sequence of connections of these components is: A.1, 4, 2, 3, 5 B. 1, 3, 4, 2, 5 C. 1, 2, 4, 3, 5 D.1, 4, 3, 2, 5 Answer & Explanation Answer: Option B 35. Which part of radio spectrum is more crowded? A.Lower frequency part B. Higher frequency part C. Both (a) and (b) D.None of these Answer & Explanation Answer: Option D 36. As compared to their values in free space A.velocity of electric wave in dielectric is smaller but wave length of electric wave is more B. both velocity and wave length of electric wave in dielectric are higher
C. both velocity and wave length of electric wave in dielectric are smaller D.wave length of electric wave is less but velocity is more in dielectric Answer & Explanation Answer: Option C
37. A 3 port circulator is in the given figure. Its scattering matrix is
A.
B.
C.
D. Answer & Explanation Answer: Option A
38. Characteristic impedance of a coaxial cable is inversely proportional to ∈r. A.True B.False Answer & Explanation Answer: Option A
39. A rectangular waveguide has a discontinuity in the form of reduced narrow dimension. In the
equivalent circuit this discontinuity can be represented by A.a shunt capacitance at the discontinuity B. a shunt inductance at the discontinuity C. a shunt resistance at the discontinuity D.none of the above Answer & Explanation Answer: Option A
40. Depth of penetration does not depend on frequency. A.True B.False Answer & Explanation Answer: Option B 41. Assertion (A): Inter-digitated geometry is widely used for microwave transistors. Reason (R): Tuning at input and output of transistor uses MOS chip capacitors. A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation Answer: Option B
42. For a 1 cm x 2 cm air filled rectangular waveguide the maximum frequency should be less than about A.1000 MHz B. 5000 MHz C. 14000 MHz D.140000 MHz Answer & Explanation Answer: Option C
43. Hollow waveguides are used as transmission lines at frequencies A.above 1 GHz B. above 5 GHz C. above 10 MHz D.above 1 MHz
Answer & Explanation Answer: Option B
44. If rv is reflection coefficient and VSWR is voltage standing wave ratio, then A. B. C. D. Answer & Explanation Answer: Option B
45. In the given figure the equivalent circuit of a T attenuator. If condition for matched attenuator is
the
A. B. C. D. Answer & Explanation Answer: Option A 46. The total power radiated from an antenna system is determined by imagining that the antenna is at the centre of a very large A.sphere B. rectangle C. square D.ellipse Answer & Explanation
Answer: Option A
47. The AM, PM, and TV broadcast frequencies are A.of the same order as microwave range B. much lower than microwave range C. much higher than microwave range D.either (a) or (c) Answer & Explanation Answer: Option B
48. Assertion (A): For a reciprocal microwave junction the S matrix is symmetrical. Reason (R): In a symmetrical matrix Sij = Sji. A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation Answer: Option B
49. In TE mode of waveguide Ez = 0 A.True Answer & Explanation
B.False
Answer: Option A
50. The primary constants of a transmission line are A.R and L B. R, L and C C. R and C D.R, L, G and C Answer & Explanation Answer: Option D 1. In terms of R, L, G and C the propagation constant γ of a transmission line is
A. B. C. D. Answer & Explanation Answer: Option B
2. The p mode of operation of magnetron signifies that A.the phase difference between adjacent anode poles is p radians B. the phase difference between adjacent anode poles is a multiple of p radians C. the total phase shift around the periphery is p radians D.none of the above Answer & Explanation Answer: Option A
3. Consider the following statements (L is the length of array between centres of end antennas and A is wave-length) 1. Width of major lobe between nulls of broad side array and end fire array are different. 2. Directive gain of broadside array and end fire array are different. 3. Directive gain of broadside array is 4 Which of the above statements are correct? A.1, 2 and 3 B. 1 and 2 only C. 1 only D.1 and 3 only Answer & Explanation Answer: Option D
4. The electrical requirement on wall thickness of rectangular wave guide is A.wall thickness is more than skin depth B. wall thickness is less than skin depth C. wall thickness is equal to skin depth D.either (b) or (c) Answer & Explanation
Answer: Option A
5. If a microstrip is enclosed in a metal enclosure A.the radiation losses are increased B. the radiation losses are reduced RL C. the capacitance becomes zero D.the inductance becomes zero Answer & Explanation Answer: Option B 6. In the given figure power meters at A and B indicate 1 mW and 110 μW respectively. VSWR of line is
A.1.5 C. 2.5 Answer & Explanation
B. 2 D.3
Answer: Option B
7. As frequency is increased, the skin effect A.increases B. decreases C. remains the same D.either (b) or (c) Answer & Explanation Answer: Option A
8. In a rectangular waveguide there is one half wave variation of electric field across the narrow dimension and two half wave variations of electric field across wider dimension. The
dominant mode is A.TM12 C. TE21 Answer & Explanation
B. TE13 D.TM25
Answer: Option C
9. VTM stands for voltage tunable magnetron. A.True Answer & Explanation
B.False
Answer: Option A Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 10. Which of the following is used in integrated circuits? A.Microstrip line B. Coaxial line C. Twin wire line D.Shield cable Answer & Explanation Answer: Option A 11. Which of the following is a balanced line? A.Coaxial line B. Strip line C. Microstrip line D.TV twin lead Answer & Explanation Answer: Option D Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 12. A line of characteristic impedance 400 Ω is terminated by a resistance of 400 Ω. The reflected quantities are
A.zero B. equal to incident quantities C. half the incident quantities D.double the incident quantities Answer & Explanation Answer: Option A Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 13. A magic tee is to be used as CW duplexer. Then port 1, port 2, port 3 (E arm), port 4 (H arm) respectively should be connected to A.matched load, antenna, receiver and CW transmitter B. CW transmitter, antenna, receiver and matched load C. CW transmitter, receiver, antenna and matched load D.CW transmitter, matched load, receiver and antenna Answer & Explanation Answer: Option A Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 14. Wave guides are pressurised above normal atmospheric pressure for A.increasing the power handling capacity B. improving conductivity of walls C. preventing higher modes from propagation D.varying the wave impedance Answer & Explanation Answer: Option A Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum
15. Assertion (A): In a power divider SH = 0, S21 = 0.707 = S3, Reason (R): In a power divider the input port (i.e., port 1) is matched and incident power is equally divided in output ports 2 and 3 A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation Answer: Option A 16. In microwave detector used in laboratory measurements of relative power levels, standing wave ratio is about A.0.1 B. 1.25 C. 5 D.10 Answer & Explanation Answer: Option B Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 17. Microwaves A.get reflected by ionosphere B. are absorbed by ionosphere C. are neither reflected nor absorbed by ionosphere D.are both reflected and absorbed by ionosphere Answer & Explanation Answer: Option C Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 18. In microstrip line has dielectric material most commonly used is A.silicon B. rubber C. plastic D.bakelite Answer & Explanation
Answer: Option A Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 19. In fibre optics the use is made of thin glass fibres for efficient transmission of light. A.True B.False Answer & Explanation Answer: Option A Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 20. Fields are said to be circularly polarized if A.their magnitudes are equal B. their magnitudes are equal and they differ in phase by ± 90° C. their magnitudes are unequal and they differ in phase ± 90° D.their magnitudes are unequal and they are in phase Answer & Explanation Answer: Option B 21. Which mode is called dominant mode in rectangular wave guide? A.TE01 B. TE11 C. TE10 D.TE20 Answer & Explanation Answer: Option C Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 22. In a TWT the loss in attenuator is A.almost equal to forward gain of tube B. much less than forward gain of tube C. much higher than forward gain of tube
D.almost infinite Answer & Explanation Answer: Option A Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 23. To study electromagnetic radiations from astronomical objects, radio astronomers use A.low frequencies B. medium frequencies C. microwaves D.either (a) or (b) Answer & Explanation Answer: Option C Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 24. Radar reciever has high sensitivity and low noise figure A.True B.False Answer & Explanation Answer: Option A Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 25. For a waveguide, which of the following statements is wrong? A.It is usually made of brass or aluminium B. It is usually rectangular or circular in shape C. The dielectric region is usually air D.The wall thickness is very small as compared to skin depth Answer & Explanation Answer: Option D
26. A transmission line discontinuity is defined as any interruption in the uniformity of the line. A.True B.False Answer & Explanation Answer: Option A Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 27. Interference generated by electrical equipment and automobile ignition systems when observed closed to earth is A.horizontally polarized B. vertically polarized C. polarized both horizontally D.not polarized Answer & Explanation Answer: Option B Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 28. The earliest uses of electromagnetic waves were A.point to point communication B. radar C. both (a) and (b) D.neither (a) nor (b) Answer & Explanation Answer: Option C Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 29. At millimeter wavelength the favoured mode in circular wave guide is A.TE01 B. TE11
C. TE20 D.TE21 Answer & Explanation Answer: Option A Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 30. In laboratory experiment the output from reflex klystron is moderated by square wave because A.it is easy to generate a square wave B. crystal diode operates in square law region of i-v characteristics C. it prevents frequency modulation D.detector circuit is less complicated Answer & Explanation Answer: Option B 31. Klystron amplifier is not used to amplifier very weak microwave signals due to A.low gain for weak signals B. low noise for weak signals C. high noise D.both (a) and (b) Answer & Explanation Answer: Option C Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 32. Which of the following modes in circular waveguides are circularly symmetric? A.TE01 B. TE02 C. both (a) and (b) D.neither (a) nor (b) Answer & Explanation Answer: Option C
Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 33. Which of the following lines behaves as infinite line? A.a line terminated in inductance B. a line terminated in capacitance C. a short line D.a line terminated in z0 Answer & Explanation Answer: Option D Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 34. A rectangular waveguide has two stubs each length connected at the source end. The stubs are short circuted. Then A.the longitudinal current is power current and current in stubs is reactive B. the longitudinal current is reactive current and current in stubs is power current C. both power and reactive exists in both longitudinal direction and stubs D.the current in stubs is zero Answer & Explanation Answer: Option A Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 35. Performance of a PIN diode switch is represented by A.insertion loss when switch is off B. insertion loss when switch is on C. insertion loss when switch is on and isolation loss when switch is off D.insertion loss when switch is off and isolation loss when switch is on Answer & Explanation Answer: Option C
36. A circular waveguide has an infinite set of TE and TM modes. A.True B.False Answer & Explanation Answer: Option A Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 37. In TE and TM modes of rectangular waveguides having propagation in z direction A.Ez and Hz are both zero B. In TE mode Ez is zero and in TM mode Hz is zero C. In TE mode Hz is zero and in TM mode Ez is zero D.In both TE and TM modes both Ez and Hz are non-zero Answer & Explanation Answer: Option B Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 38. Which of the following are true for magic tee in the given figure select the answer as per given codes
1. 2. 3. 4.
S13 = S23 S14 = S24 S12 = 0 S34 = 0
A.1, 2 and 3 B. 1, 2 and 4
C. 2, 3 and 4 D.1, 3 and 4 Answer & Explanation Answer: Option C Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 39. The manufacturing technique used to manufacture strip type transmission line is A.photoetching technique B. oxidation technique C. cladding D.epitaxial Answer & Explanation Answer: Option A Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 40. An electromagnetic wave can be completely guided by a dielectric rod or slab. A.True B.False Answer & Explanation Answer: Option A 41. Most electromagnetic transmission in rectangular wave-guide uses A.TE10 mode B. TE01 mode C. TE20 mode D.TE11 mode Answer & Explanation Answer: Option A Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum
42. Loading of a line means A.increasing inductance of line B. increasing distributed inductance of line C. decreasing distributed inductance of line D.decreasing inductance of line Answer & Explanation Answer: Option B Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 43. The frequency of oscillations obtained from a reflex klystron depends mainly on A.resonant frequency of cavity B. repeller voltage C. voltage of focussing electrode D.characteristics of cathode Answer & Explanation Answer: Option A Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 44. The main advantage of TWT over klystron is A.higher bandwidth B. higher gain C. higher frequency D.higher output Answer & Explanation Answer: Option A Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum
45. In a TWT the phase velocity of the axial component of the field on the slow wave structure is kept A.equal to velocity of electron B. slightly less than velocity of electron C. slightly more than velocity of electron D.equal to velocity of light in free space Answer & Explanation Answer: Option A 46. Assertion (A): Two equal and opposite travelling waves result in a standing wave. Reason (R): The ratio of maximum to minimum value of a standing wave is called SWR. A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation Answer: Option B Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 47. When a wave reaches an open circuit A.the voltage at termination is doubled the incident voltage B. the current at termination is doubled the incident voltage C. the voltage at termination is zero D.both V and I at termination are doubled the incident voltage and current Answer & Explanation Answer: Option A Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 48. Assertion (A): In circular waveguide the attenuation of TE01 mode decreases as the operating frequency increases. Reason (R): The wall currents in a circular waveguide in TEQ1 mode are completely circumferential.
A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation Answer: Option B Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 49. Consider the following statements 1. Usable bandwidth of ridge wave guide is more than that of rectangular waveguide. 2. For a given value of TM10 cutoff frequency the cross section of ridge wave guide is lesser that that of rect angular waveguide. 3. Ridge wave guide has higher conductor losser than a rectangular waveguide. 4. Ridge guide has higher conductor losser than a rectangular waveguide. Which of the above statements are correct? A.1 and 2 only B. 1, 2 and 3 only C. 2 and 3 only D.All Answer & Explanation Answer: Option B Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 50. Directive gain of elementary doublet is A.100 C. 1.5 Answer & Explanation
B. 10 D.0.5
Answer: Option C 1. Consider the following statements, SWR of a transmission line is infinite when the load is 1. a short circuit
2. a complex impedance 3. an open circuit 4. a pure reactance Which of the above statements are correct? A.1 and 3 only B. 1, 2, 3 C. 2, 3, 4 D.1, 2, 4 Answer & Explanation Answer: Option A Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 2. In a reflex klystron the output frequency is determined primarily by resonant frequency of cavity. A.True B.False Answer & Explanation Answer: Option A Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 3. The arrangement in the given figure is a hybid T. If 100 mW fed at port 1, the power reflected back at port 1 is
A.0 B. 25 mW C. 50 mW D.100 mW Answer & Explanation Answer: Option C Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 4. In TE10 mode the largest electric field in a rectangular wave guide, occurs A.along centre line of broad wall (i.e. x = a/2) B. along the broad wall (i.e. x = 0 and x = a) C. either (a) or (b) D.neither (a) nor (b) Answer & Explanation Answer: Option A Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 5. Which modes of circular wave guides have circular symmetry? A.TE11 B. TE11 and TE21 C. TE01 D.TE01 and TM01 Answer & Explanation Answer: Option D 6. In rectangular waveguides the ratio of width to height is about A.0.5 B. 1 C. 2 D.4 Answer & Explanation Answer: Option C Explanation:
No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 7. If wavelength in free space is λ0 wavelength in insulator λ, μr is relative permittivity or insulator and ∈r is relative permittivity or insulator, then A. B. C. D. Answer & Explanation Answer: Option B Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 8. In the given figure the circuits for input impedance of a microwave device with output ports match terminated. The device is
A.E plane tee B. H plane tee C. magic tee D.hybrid ring Answer & Explanation Answer: Option D Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum
9. Which of these statements is correct? A.Ridge guide is essentially a form of capacitively loaded guide. B. Ridge guide is essentially a form of inductively loaded guide. C. Ridge guide is essentially a form of resistively loaded guide. D.Ridge guide has higher power handling capacity than rectangular waveguide. Answer & Explanation Answer: Option A Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 10. A rectangular waveguide has width a. Then at the cutoff frequency (with corresponding wave length λc) A. B. a = λc C. D.a = 2λc Answer & Explanation Answer: Option A 11. In a rectangular waveguide cutoff wavelength for TE10 mode is 8 cm. Then cutoff wavelength for TE20 mode is A.8 cm B. 6 cm C. 4 cm D.2 cm Answer & Explanation Answer: Option C Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 12. In a coaxial line A.the characteristic impedance is less than that of two wire line B. the wave velocity is less than that of two wire line
C. both (a) and (b) D.neither (a) nor (b) Answer & Explanation Answer: Option C Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 13. If a and b are the width and height of rectangular wave-guide the cut off wavelength λc for TE20 mode is equal to A.a B. a + b C. a - b D.a2 + b2 Answer & Explanation Answer: Option A Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 14. A TEM wave is incident normally on a perfect conductor. The E and H fields at boundary will respectively be A.minimum and maximum B. minimum and minimum C. maximum and minimum D.maximum and maximum Answer & Explanation Answer: Option A Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 15. The scattering matrix of magic tee is
A.
B.
C.
D.
Answer & Explanation Answer: Option A 16. Frequency range for satellite communication is A.1 kHz to 100 kHz B. 100 kHz to 10 MHz C. 10 MHz to 100 MHz D.1 GHz to 30 GHz Answer & Explanation Answer: Option D Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 17. For a given operating frequency a waveguide has more power handling capacity than a coaxial line. A.True B.False Answer & Explanation Answer: Option A
Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 18. VSWR = Emax/Emin. A.True Answer & Explanation
B.False
Answer: Option A Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 19. Power monitor and reflectometer use the principle of A.directional coupler B. klystron amplifier C. Gunn diode D.TWT Answer & Explanation Answer: Option A Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 20. A line slightly longer than A.an inductance B. a capacitance C. L and C in series D.L and C in parallel Answer & Explanation
length and short circuited at far end behaves as
Answer: Option B 21. Compared to coaxial lines, the advantages of wave guides are A.higher power handling capacity B. lower loss per unit length C. cheaper and simple mechanical structure
D.all of the above Answer & Explanation Answer: Option D Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 22. Standard mismatches are used to calibrate SWR and impedance measuring equipments. A.True B.False Answer & Explanation Answer: Option A Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 23. As compared to LED, LASER has 1. 2. 3. 4.
higher emission efficiency no tuning arrangement narrow spectral width provision for confinement
Of these statements A.1, 2, 3 are correct B. 1, 2, 4 are correct C. 1 and 3 are correct D.1, 3, 4 are correct Answer & Explanation Answer: Option D Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 24. Microwaves are used for
A.telephony B. radio broadcast C. TV systems D.all of the above Answer & Explanation Answer: Option D Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 25. In a shield helix A.the spacing between adjacent turns is very large B. the spacing between adjacent turns approaches zero C. the spacing between adjacent turns approaches zero and wire thickness approaches zero D.the spacing between adjacent turns is very large wire thickness approaches zero Answer & Explanation Answer: Option C 26. Consider the following statements about hybrid ring 1. 2. 3. 4.
Ports 1 and 2 are decoupled. Port 3 and 4 are coupled. A signal entering either port 1 or 2 splits equally between ports 3 and 4. A signal entering either port 3 or 4 splits equally between ports 1 and 2.
Which of the above are correct? A.1, 2, 3 and 4 B. 1, 3 and 4 C. 1 and 2 D.2, 3 and 4 Answer & Explanation Answer: Option B Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 27. TM01 mode in circular waveguide is analogous to A.TM10 mode in square waveguide
B. TM11 mode in square waveguide C. TM20 mode in square waveguide D.TM02 mode in square waveguide Answer & Explanation Answer: Option B Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 28. In microwave system, waveguide twists A.change the plane of polarization of a propagating wave B. change the direction of a propagating wave C. change the mode of a propagating wave D.both (b) and (c) Answer & Explanation Answer: Option A Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 29. Guide wavelength (λg), cutoff wavelength (λc) and free space wavelength (λ0) of a waveguide are related as A. B. C. D. Answer & Explanation Answer: Option A Explanation:
No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 30. A 'rat race' is a A.hybrid junction for microwaves B. a microwave oscillator C. a microwave amplifier D.a microwave antenna Answer & Explanation Answer: Option A 31. A directional coupler is used A.to transmit microwave signals B. to generate microwave signals C. to measure amplitude and phase of a travelling wave D.both (a) and (b) Answer & Explanation Answer: Option C Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 32. Assertion (A): In rectangular waveguide TE01 mode is just TE10 mode rotated by 90°. Reason (R): When a rectangular waveguide is rotated by 90°, the broad and narrow dimensions get interchanged. A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation Answer: Option A Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum
33. Consider the following statements about a magic tee 1. 2. 3. 4.
The collinear arms are isolated from each other. On of the collinear arms is isolated from E arm. On of the collinear arms is isolated from H arm. E and H arms are isolated from each other.
Of the above statements A.1 and 2 are correct B. 1 and 3 are correct C. 1 and 4 are correct D.2 and 3 are correct Answer & Explanation Answer: Option C Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 34. Assertion (A): Hollow waveguides are frequently used as transmission lines at microwave frequencies. Reason (R): Waveguide has high power handling capacity, low loss and simple structure. A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation Answer: Option A Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 35. In p mode of operation of magnetron the spikes due to phase focussing effect rotate at an angular velocity corresponding to A.one pole/cycle B. two pole/cycle C. four pole/cycle D.six pole/cycle
Answer & Explanation Answer: Option B 36. Dielectric constant and conductivity of rocky soil and flat sandy soil are around A.10 and 20 mho/cm respectively B. 20 and 10 mho/cm respectively C. 2 and 5 mho/cm respectively D.0.5 and 2 mho/cm respectively Answer & Explanation Answer: Option A Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 37. The main advantage of using micro waves for communications is A.large bandwidth B. small bandwidth C. low power D.high power Answer & Explanation Answer: Option A Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 38. A line of length less than A.inductance L B. capacitance C C. L and C in series D.L and C in parallel Answer & Explanation Answer: Option B Explanation:
and open circuited at far end behaves as
No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 39. The beam of a radar should be A.very narrow B. very wide C. neither too narrow nor very wide D.either (b) or (c) Answer & Explanation Answer: Option A Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 40. TE10 mode of propagation of electromagnetic energy in waveguides can be thought of as A.three TEM waves travelling along length of wave-guide One TEM wave travelling along length of wave guide and one TEM wave propagation in B. the transverse plane C. One TEM wave travelling along the length of wave guide and two TEM waves D.none of the above Answer & Explanation Answer: Option C 41. Ridge waveguide is essentially a form of capacitively loaded guide. A.True B.False Answer & Explanation Answer: Option A Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 42. In a rectangular waveguide A.the broad width is generally labelled 'a' and height 'b' B. the broad width is generally labelled 'b' and height 'a' C. any one of the dimensions may be labelled 'a' and the other 'b' D.the length is labelled as 'a' Answer & Explanation
Answer: Option A Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 43. Which of the following modes cannot exist in rectangular resonant cavity? A.TE110 B. TE011 C. TM110 D.TM111 Answer & Explanation Answer: Option A Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 44. In a Gunn diode oscillator drift velocity of electron is 107 cm/s and active region length is 10 x 10-4 cm. The natural frequency of oscillation is A.1 MHz B. 10 MHz C. 1 GHz D.10 GHz Answer & Explanation Answer: Option D Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 45. Assertion (A): An artificial transmission line can be used as a pulse generator. Reason (R): A pulse function is used very frequently in network analysis. A.Both A and R are correct and R is correct explanation of A B. Both A and R are correct but R is not correct explanation of A C. A is correct but R is wrong D.A is wrong but R is correct Answer & Explanation
Answer: Option B 46. A waveguide twist is used to change the plane of polarization. A.True B.False Answer & Explanation Answer: Option A Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 47. Consider the following statements about directional coupler shown in the figure
1. 2. 3. 4.
Ports 1 and 2 are decouple Ports 3 and 4 are decoupled Pots 1 and 3 are decoupled Ports 1 and 4 are decoupled
Which of the above statements are correct? A.1 and 2 only B. 3 and 4 only C. 1, 2 and 3 D.2, 3 and 4 Answer & Explanation Answer: Option A Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 48. In a multicavity klystron amplifier the electron velocity of the order of A.10 m/s B. 103 m/s
C. 106 m/s D.1012 m/s Answer & Explanation Answer: Option C Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 49. At a frequency equal to cutoff frequency in a rectangular wave guide A.the flow of electromagnetic energy is zero B. the flow of electromagnetic energy is infinite C. the flow of electromagnetic energy is 50% of maximum D.the flow of electromagnetic energy is 10% of maximum Answer & Explanation Answer: Option B Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 50. Two identical hybrid tees are joined as shown in the given figure. If 16 mW power is fed into port 1, the power output at ports 2 , 3, 1', 2', 3' respectively is
A.8, 4, 2, 2, 0 mW
B. 0, 8, 4, 4, 0 mW C. 0, 8, 2, 2, mW D.8, 2, 4, 2, 0 mW Answer & Explanation Answer: Option B 51. In a microwave resistor the wall thickness is made as small as possible to A.have high value of R B. have low value of R C. minimize capacitive effect D.reduce inductance Answer & Explanation Answer: Option C Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 52. In a klystron amplifier the transit time of electron passing the gap in the cavity should be A.less than one cycle B. less than half cycle C. less than quarter cycle D.more than quarter cycle Answer & Explanation Answer: Option C Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 53. In a cable with ∈r = 4, the wave velocity is A.3 x 108 m/s B. 0.75 x 108 m/s C. 1.5 x 108 m/s D.108 m/s Answer & Explanation Answer: Option C
Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 54. In a backward wave oscillator the efficiency A.is much higher than in TWT B. is much lower than in TWT C. is almost the same as in TWT D.either (a) or (b) Answer & Explanation Answer: Option C Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 55. Consider the following statements 1. Fading of signals is generally greatest near radio horizon. 2. Fading of signals is generally greatest in shadow zone. 3. Fading is small when a good optical path is present. Which of the above statements are correct? A.1, 2 and 3 B. 1 and 2 only C. 1 and 3 only D.2 and 3 only Answer & Explanation Answer: Option A 56. The use of coaxial microwave line should be restricted to frequencies A.below cut off frequency of TE11 mode B. above cut off frequency of TE11 mode C. at frequencies much lower than cut off frequency of TE11 mode D.at frequencies much higher than cut off frequency of TE11 mode Answer & Explanation Answer: Option A Explanation:
No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 57. Generally the wall thickness of rectangular waveguide is A.about 1-5 mils B. about 40-100 mils C. about 0.1 to 0.5 mils D.about 500 mils Answer & Explanation Answer: Option B Explanation: No answer description available for this question. Let us discuss. View Answer Workspace Report Discuss in Forum 58. If QL is loaded Q, QE is external Q and QU is unloaded Q of a microwave resonator, then A. B. C. D.QL = QE + QU Answer & Explanation Answer: Option A
