Question A mammography service examined 327 patients during the third calendar quarter of 1996. 719 films were exposed during this period, eight of which were repeats. What is the repeat rate?
Answer 1.1%
A type of luminescence where the visible light is emitted only during the stimulation of the phosphor. If a heart measures 12.5 cm from side to side at its widest point, and its image on chest radiograph measures 14.7 cm, what is the magnification factor?
Fluorescence
Radiation doses in the range of approximately200 to 1000 rad produce the
Hematologic syndrome
Ratio of incident to transmitted radiation through a grid ratio of patient dose with and without grid A radiographic single-phase unit installed in a private office has a maximum capacity of 100 milliseconds of 120kVp and 500mA. What is the power rating?
Bucky factor
Who completes the development of first computed tomographic (CT) scanner (EMI, Ltd.) in 1973? It is the study of the response of an image receptor to x-rays Ratio of radiographic contrast with a grid to that without a grid. Analysis of persons irradiated therapeutically with superficial x-rays has shown that the skin erythema dose required to affect 50% of persons so irradiated is about
Hounsfield
ECG recording requires a bandwidth of 0.05 to ____ Hz Find the potential generated if blood flowing in a vessel with radius 0.9 cm cuts a magnetic field of 250 G. Assume a volume flow rate of 175 cubic cm per second.
100
Period during which heart contracts. Apparatus for measuring blood pressure
Systole Sphygmomanometer
1.18
42 kW
Sensitometry contrast improvement factor 600 rad
309 uV
Given the energy level of 6.624x10^-18 J imparted to an electron stream by an X-ray device, calculate the frequency in MHz.
10^10 MHz
10^10 MHz It was first noted by Heinrich Hertz in 1887 and won Albert Einstein the Nobel Prize in 1905. It refers to the emission of electrons from a clean metallic surface (phototube) when electromagnetic radiation (light waves or X-rays) falls onto that surface. Unit of radiation exposure or amount of X-ray radiation that will produce 2.08x10^9 ion pairs per cubic centimetre of air at standard temperature and pressure (STP).
Photoelectric effect
An optical electronic device that measures the color concentration of a substance in solution. Recording of heart sounds Recorder for measuring galvanic skin resistance
colorimeter
It consists of 36 unique codes representing the 10 digits and 26 uppercase letters. The first fixed- length character code developed for machines rather than for people The early pioneer in the development of errordetection and correction procedures The most reliable convolutional coding scheme for error detection For the given parameters, determine the energy per bit-to noise power density ratio C = 10e-12 W fb = 60 kbps N = 1.2 x 10e-14`W B = 120 kHz
code 39
A signal at the input to a mu-law compressor is positive with its voltage one-half the maximum value. What proportion of the maximum output voltage is produced?
0.876Vmax
Inaccuracies caused by the representation of a continuously varying quantity as one of a number of discrete values.
quantizing errors
Roentgen
phonocardiography electrodermograph
Baudot Code Richard W. Hamming CRC 22.2 dB ;
Circuit for digitizing voice at a low data rate by using knowledge of the way in which voice sounds are produced A coding scheme that records the change in signal level since the precious sample Distortion created by using too low a sampling rate when coding an analog signal for digital transmission A network with bandwidth of 10 Mbps can pass only an average of 12000 frames per minute with each frame carrying an average of 10000 bits. What is the throughput of this network? A telephone subscriber line must have an SNRdB above 40. What is the minimum number of bits?
vocoder
delta modulation either a or b a. aliasing 2 Mbps
b. foldover distortion
= 2 Mbps 6.35 SNRdB = 6.02nb + 1.76 = 40 n = 6.35
The thick coaxial cable implementation of standard Ethernet A bit pattern or a character added to the beginning and the end of a frame to separate the frames An IPv4 has an address space of how many?
10 Base 5 Flag 4294967296 232 = 4294967296
What is the bit rate of STS – 1? A block coding technique in which four bits are encoded into a five bit code A national standards organization that defines standards in the United States In asynchronous transmission, one or more bits to indicate the end of transmission What is the overhead (number of extra bits) in the DS3 service? The minimum sampling rate according to Nyquist Theorem It is used in wireless applications in which stations must be able to share the medium without interception by an eavesdropper and without being subject to jamming from a malicious intruder An error detection method which uses one’s complement arithmetic It is a connecting device between two internetworks that use different models It is an undesired shift or width change in digital bits of data due to circuitry action which causes bits to arrive at different times In PCM system, it is the ratio of the maximum input voltage level to the smallest voltage level that can be quantized A multiplexer combines four 100-kbps channels using a time slot of 2 bits, determine the frame duration.
51.84 Mbps 4B/5B Encoding ANSI stop bit 1.368 Mbps twice the highest frequency of a signal spread spectrum
Checksum Gateway Jitter
Dynamic range
20s The link carries 50,000 frames /sec The frame duration = 1/50,000 = 20s
Determine the Hamming distance for the codewords Two (10101, 11001) 10101 XOR 11001 = 01100 ( presence of two 1) An address space is the total number of addresses used by the protocol, such as IPv4 and IPv6. What 2128 is the address space of IPv6? It is a standard designed by ITU to allow telephones in H.323 the public telephone network to talk to computers/terminals connected to the internet A computer monitor has a resolution of 1200 by 1000 12 Megabits pixels. If each pixel uses 1024 colors, how many bits are needed to send the complete contents of a screen? 1,200 times 1000 pixels x 10 bits = 12 Mb
Combination of compression at the transmitter and expansion at the receiver of communications system. A device launches or receives a wave in a transmission line or waveguide in one direction only. A type of linear-beam microwave tube that uses velocity modulation of the electron beam A series of pulses in which the amplitude of each pulse represents the amplitude of the information signal at a given time. _______________ is used to position samples of the different message signals in non-overlapping time slots. A ___________ is similar to a phasor diagram except that the entire phasor is not drawn. It was the first fixed length character code. It involves transmitting each character twice. The __________ provides the mathematical justification for using a Gaussian Process as a model for a large number of different physical phenomena in which the random variable, at a particular instant of time, is the result of a large number of individual random events. A set of communication facilities allowing direct access to 64kpbs data streams (or multiples of) for drop and insert. A form of cell relay, supports B-ISDN. A series of pulses, in which the timing of each pulse represents the ampltitude of the information signal at a given time. A line of sight radio link operating at a frequency of 6GHz has a separation of 40km between antennas. An obstacle in the path is located 10km form the transmitting antenna. By how much must the beam clear the obstacle?
1024 colors requires 10 bits , 2 10 = 1024 Companding directional coupler Klystron PAM
TDM
constellation diagram Baudot Code Redundancy Central Limit Theorem
Asynchronous transfer mode (ATM)
Pulse Position Modulation
11.6m
R = 11.6m Variation in received field strength over time due to changes in propagation conditions.
Fading
The atomic weight of an element is approximately determined by Of the following substances the worst conductor is The volt is the standard unit of Which of the following antenna types is not designed for transmitting at 10 Ghz The type of radio wave responsible for long distance communications by multiple skips is the: Line of sight communications is not a factor in which frequency range? It refers to the rate of change of a signal on the transmission medium after encoding and modulation have occurred. It was the first fixed-length character code developed for machines rather than people. A receiver-transmitter station used to increase the communications range of VHF, UHF and microwave signals is called a(n): It represents the simplest whole number ratio of the various types of atoms in a compound. It is a term that is often misunderstood and commonly confused with bit rate (bps) Defined as the optimum level of a test tone on a channel at same point in a communication system. Duplicating each data unit for the purpose of detecting errors is a form of error detection called ______. Determine the wavelength of a 4 Ghz signal. What is the device that converts energy from one form to another? It may be defined as any undesired voltages or currents that ultimately end up appearing in the receiver output. The channel capacity of a 5 kHz bandwidth binary system is ____ bits/s. Assuming no noise. Microwaves are frequencies above _____ GHz. The government agencies that regulates radio communications in the US is the ________. A wave guide acts a/an _______ filter Coax is not used beyond frequencies of about ______ GHz. Data Communications refers to the transmission of _______. Determine the peak frequency deviation for a binary FSK signal with a mark frequency of 49 kHz, space frequency of 51kHz and an input bit rate of 2kbps.
It is often used to compare the performance of one digital modulation technique to another. It is the process of converting an infinite number of possibilities to a finite number of conditions.
the number of protons Air electromotive force Zepp antenna Direct Wave HF Baud
Baudot Code Repeater
empirical formula Baud transmission level point Redundancy 0.075m Transducer Electrical noise
10,000 1 FCC High-pass 6 all of the above a. voice 1 kHz
b. video
bandwidth efficiency Quantization
c. Computer data
For a PCM system with a maximum analog frequency of 4kHz, determine the minimum sample rate.
8 kHz
It is another relatively simple form of redundancy error checking where each character has a numerical value assigned to it. It is a modulation and multiplexing technique that distributes the signal and its sidebands over a very wide bandwidth. The computers that hold shared files, programs and the network operating system. They also provide access to network resources to all the users of the network. It is defined by the ITU-T as a service that provides transmission channels capable of supporting transmission rates greater than the primary data rate. It is the only error-correction scheme that actually detects and corrects transmission errors when they are received without requiring a transmission.. This OSI Layer is responsible for network availability, data storage and processor capacity. It also determines the type of dialogue available. It is often defined as the loss incurred by an electromagnetic wave as it propagates in a straight line through a vacuum with no absorption or reflection of energy from nearby objects. What do you call the accumulation of additional sounds such as wind, street noise, other voices that contribute to what the listener hear? It is a single transmission path from transmitter to receiver with line of sight range. It is defined by the average rate at which energy is carried out per unit area. What happens to the frequency of the wave and to its wavelength when a sound wave produced in one medium enters another medium with a different speed? The process of combining multiple audio signals into one track is called? The speed of sequence of musical notes is called? If the frequency of a sound is increased, what will happen to its pitch? A type of microwave protection system where each working channel has a dedicated back up or spare channel. Also known as Pin 21 of the RS-232 interface on D connector, this connection allows signals to be transmitted from the DCE to the attached DTE whenever there is a high probability of an error in the received data due to the quality of the circuit falling below a predefined level.
Checksum
Spread spectrum
Servers
Broadband ISDN
Forward Error Correction
Session layer
free space path loss
Ambience
Hop Intensity the frequency of the wave stays the same while the wavelength changes.
audio mixing Tempo Increases Hot Standby
signal quality detector
______ which means that 2 or more bits in the data unit have changed.? It is a four-wire Gigabit Ethernet implementation. It is a digital process that allows several connections to share the high bandwidth of a link. EEE 802.11 is define in which MAC sublayer?
It is the oldest microwave tube design which is commonly used in radar transmitters where they can generate peak power levels in the megawatt range. A modulation process wherein both frequence and phase remains constant while the amplitude changes. It is the most powerful redundancy checking technique which is based on binary division. What do you call the element with electrical properties between those of an insulator and a conductor? In pulse-code modulation, it translates the quantized samples into digital code words. It is an error detection technique in which a redundant bit is appended to every data unit so that the total number of 1s in the unit (including the parity bit) becomes even. A local area network topology in which the individual terminal, microcomputers or workstations are connected directly to a central computer. The only way to achieve high data rates with a narrowband channel is to increase the number of bits per symbol, the most reliable way to do this is to use a combination of amplitude and phase modulation known as Find the maximum dynamic range for a linear PCM system using 16-bit quantizing.
burst error 1000 Base-T TDM (b) and (c) B. PCF Magnetron
C. DCF
ASK cyclic redundancy check Semiconductor Encoder vertical redundancy check
Star
quadrature amplitude modulation
98.08 dB DR = 1.76 + 6.02m; dB DR = 1.76 + 6.02(16) DR = 98.08 dB
Compute the baud rate for a 72000 bps 64-QAM signal.
12000 baud A 64-QAM signal means that there are 6 bits per signal element since 26 = 64. Therefore, baud rate = 72000/6 baud rate = 12000 baud
A telephone signal takes 2ms to reach its destination. Calculate the via net loss required for an acceptable amount of echo.
0.8 dB
Telephone switch that connects only to other switches, and not to individual customers.
tandem office
VNL = 0.2t + 0.4dB VNL = 0.2 (2ms) + 0.4 dB VNL = 0.8 dB
It is a form of digital modulation similar to PSK except the digital information is contained in both amplitude and the phase of the transmitted carrier. The most common circuit used for demodulating binary FSK signals. We have an audio signal with a bandwidth of 4KHz.What is the bandwidth needed if we modulate the signal using AM? Ignore FCC regulations for now.
QAM
We have an audio signal with a bandwidth of 4 MHz. what is the bandwidth if we modulate the signal using FM? Ignore FCC regulations.
40
For PCM system with the following parameters determine the minimum number of bits used. Maximum analog frequency= 4 khz, maximum decoded voltage=±2.55, Minimum dynamic range= 199.5
8
PLL 8 KHz BW = 2 x 4 KHz = 8 KHz
BW=10x4 = 40 MHz
= 7.63 =8
A network topology in which data circulates from one computer to the next in sequence. Find the maximum dynamic range for linear PCM system using 8-bit quantizing
Ring 49.92 dB DR = 1.76 + 6.02(m) DR = 1.76 + 6.02(8)
What frequencies would be generated by a telephone using DTMF signalling, when the number 8 is pressed? It is a means of transmitting data by shifting the phase angle of the transmitted signal. The name given for a set of standards for communicating among computers in which the primary purpose is to serve as a structural guideline for exchanging information between computers, workstations and networks.
852 Hz and 1336 Hz
Any transmission system which conveys more than one signal simultaneously can experience this type of interference due to the reception of portions of a signal from one channel in another channel. What type of digital modulation scheme uses two or more different output frequencies? It is an error-correcting code used for correcting transmission errors in synchronous data streams. A suite of protocols that allows a wide variety of computers to share the same network. Noise that is primarily caused by lightning. Often called as Static Noise.
Crosstalk
PSK OSI
FSK Hamming Code TCP/IP atmospheric noise
A modulation technique in which the frequency of the modulated signal varies with the amplitude of the modulating signal Is a form of constant –amplitude angle modulation similar to standard frequency modulation except the modulating signal is a binary signal that varies between two discrete voltage levels rather than a continuously changing analog waveform. The highest layer in the hierarchy and is analogous to the general manager of the network by providing access to the OSI environment. What is the equation for Hartley’s Law? Network topology wherein individual terminals, microcomputers and workstations are connected directly to a central computer. The loss of data that occurs when two stations transmit at the same time on a network A term used to describe a telephone instrument whose handset is on its cradle, ready to receive a ring signal. The most commonly used digital modulation scheme. Simple form of redundancy error checking where each character has a numerical value assigned to it. The characters within a message are combined together to produce an error checking character. Is an eight-bit fixed length character set developed in 1962 by the International Business Machines Corporation. An attempt is made to transmit base band frequency of 30khz using a digital audio system with a sampling rate of 44.1khz. What audible frequency would result.
AM
Calculate the capacity of a telephone channel that has a S/N of 1023?
30,000 b/s
FSK
Application layer
I=ktB Star
Collision On hook
PCM Checksum
EBCDIC code
14.1KHz fa = fs – fm = 44.1KHz – 30KHz = 14.1 KHz
The telephone channel has a bandwidth of about 3KHz C= BW log2 (1+ S/N) = 3 x 103 log2 (1+ 1023) =30000 b/s
Designed to send characters of the message with the specified bit rate but without any fixed timing relationship from one character to the next. Token Ring Standard It is the process of extracting a phase-coherent reference carrier from a receiver signal. It is a potential problem whenever two metallic conductors carrying different signals are located in close proximity to each other. What is the termed refer as the rapid degradation of output signal quality with channel induced errors?
asynchronous
802.5 Carrier Recovery Crosstalk
threshold effect
What was the first fixed-length character code developed for machines rather than for people? A source whose output satisfies the condition of statistical independence among letters in the sequence is said to be_____. Calculate the minimum data rate needed to transmit audio with sampling rate of 30 Khz and 14 bits per sample. Handles error recovery, flow control (synchronization), and sequencing (which terminals are sending and which are receiving). It is considered the “media access control layer”. A MAC protocol for LANs, with stations connected topologically or logically in a ring. Or the IEEE 802.5 LAN standard. A network topology where each device is connected to a centre point and all data is routed through that point. A lasers use organic dyes enclosed in a glass tube for an active medium, dye is circulated into the tube with a pump. A powerful pulse of light excites the organic dye Codes that have a restriction on the number of consecutive 1s or 0s in a sequence. Contains seven bytes (56 bits) of alternating 0s and 1s that alert the receiving system to the coming frame and enable it to synchronize its input timing Every letter was encoded into fixed length of binary code words of length 5. The composite signal that modulates the FM carrier. It is a simple means of error detection. It involves the addition of one extra bit to the bits that encode a character. A data compression scheme that uses fewer bits to represent more frequently occurring characters or bit patterns and more bits to represent those occur less frequently. Speed at which symbols are transmitted in a digital communication systems. It is the process of converting an infinite number of possibilities to a finite number of conditions. It is the ratio of the largest possible magnitude to the smallest possible magnitude that can easily be decoded by the digital to analog converter in the receiver. It is the institution that developed the ASCII (American Standard Code for Information Intertchange). In early 1900s, he showed that any composite signal is a sum of a set of sine waves of different frequencies, phases and amplitudes. Find the binary equivalent of x8+x3+x+1.
Baudot code Memoryless
420 Kb/s
Data Link Layer
Token Ring
Star network
Liquid Lasers
Run length limited code Preamble
Baudot Code Baseband Parity
Huffman coding
Baud rate Quantization Dynamic Range
ANSI Jean-Baptiste Fourier
100001011 x8+x7+x6+x5+x4+x3+x2+x+k 1
0
0
0
0
1
0
1 1
Given a bandwidth of 6000 Hz for an ASK signal, what is the baud rate?
6000 Hz baud rate = bandwidth 6000 Hz = 6000 Hz
Compute the bit rate for a 2000 baud 16-QAM signal.
It is an electronic device that is used for computer communications through telephone lines. A telephone line has a bandwidth of 4.5 kHz and a signal-to-noise ratio of 40dB. A signal is transmitted down this line using a four level code. What is the maximum theoretical data rate Showed mathematically that it is posssible to reconstruct a band-limited analog signal from periodic samples, as long as the sampling rate is at least twice the frequency of the highest frequency component of the signal. Find the maximum dynamic range for a linear PCM system using 8-bit quantizing.
In operation, many modern codecs achieved compresion by first encoding the signals using a 12bit linear PCM code, then converting the 12-bit linear code into an 8-bit compressed code by discarding some of the bits. This is a simple example of: Sampling of an analog signal using a sample-andhold circuit such that the sample has the same amplitude for its whole duration. The basic building block of the FDM hierarchy. The GSM radio system uses GMSK in a 200kHzchannel, with a channel data rate of 270.883 kbps. Calculate the frequency shift between mark and space. For Ethernet system with a length of 2.5km on coaxial cable with a velocity factor of 0.66. What is the propagation delay?
8000 bps bit rate = baud * 4 2000 * 4 = 8000 bps Modem 18 kbps C = 2Blog2M = 2(4.5x103)log2(4) = 18 kbps Harry Nyquist
49.92 dB DR = 1.76 + 6.02m dB = 1.76 + 6.02(8) dB = 49.92 dB Digital Signal Processing
Flat-topped Sampling
Message Channel 135.4165kHz fm-fs=0.5fb=0.5*270.833kHz=135.4165kHz 12.6µs T=d/(VfC)=2.5km/(0.66*300000000m/s)=12.6 µs
A signal at the input to a µ-Law compressor is positive, with its volatage one-half the maximum value. What proportion of the maximum output voltage is produced? A telephone signal take 2ms to reach its destination. Calculate the via net loss required for an acceptable amount of echo.
0.876 Vo
Who invented the telegraph? The simplest modulation technique, where a binary information signal modulates the amplitude of an analog carrier.
Samuel F.B Morse Amplitude-Shift Keying
Vo=Vo(ln(1+(255*0.5)))/ln(1+255)=0.876 Vo 0.8 dB VNL=0.2t+0.4=(0.2*2)+0.4=0.8
Is the lowest Open System Interconnection hierarchy and is responsible for the actual propagation of unstructured data bits (1s and 0s) through a transmission medium. Error-correction scheme that actually detect and corrects transmission errors when they are received without requiring a retransmission. It allows the overall complexity of the system to be broken down into individual function –layers- that operate essentially by themselves. This are very useful pictorial representations that clearly show the protocol operations such as words or convetional drawings. Pair of wires that connects the central office to the users phone How long does it take to dial the number 784-3745 using pulse dialing with .5s inter digit time?
Physical Layer
Forward Error Correction
Transparency
State Transition Diagram
Local loop 6.8s 0.7 + 0.8 + 0.4 + 0.3 + 0.7 + 0.4 + 0.5 (6x0.5) = 6.8s
Network that connects users who are in the same general location In operation, many modern codecs achieved compresion by first encoding the signals using a 12bit linear PCM code, then converting the 12-bit linear code into an 8-bit compressed code by discarding some of the bits. This is a simple example of: A balanced modulator that will used in conjuction with a microwave generator, power amplifier, and bandpass filter, up-converts the IF carrier to an RF carrier and amplifies the RF to the desired output power. What is the equation for Hartley’s Law?
LAN
The loss of data that occurs when two stations transmit at the same time on a network We have an audio signal with a bandwidth of 5 HHz. What is the bandwidth modulate the signal using FM? Ignore FCC regulation.
Collision
Used to established a point to point connection across a network.
TCP
An attempt is made to transmit a baseband frequency of 25kHz using digital audio system with a sampling rate of 44.1 kHz. What audible frequency would result?
19.1kHz
Defines the rules of the conversation the message passing among the network users Responsible for providing signals to the loop sensing activity and sending phone signals at the end of the loop The typical amount of voltage in dc use in the battery of the central office with respect to ground
Digital Signal Processing
Transmit Modulator
I=ktB
50 MHz BW= 10 x 5MHz =50MHZ
f a = f s - fm = 44.1kHz – 25kHz = 19.1kHz network protocol SLIC
-48
A network that is composed of a smaller lan that are closely link. It is needed for areas spread out geographically How many central office allotted for each exchange? It is a method of switching that provides a separate physical path for each symbol The central office detects a request for service from a telephone by: The OSI Layer responsible for data tracking as it moves through a network. It controls and ensures the end – to – end integrity of the data message propagated through the network between two devices. It is used on long – distance circuits, in an effort to overcome echoes caused by circuit imbalances. The sensitivity of a radio receiver is given in terms of dBm. If the receiver is receiving 200 mW, what is the corresponding dBm of this signal? An antenna with a noise temperature of 75 Kelvin is connected to a receiver input with a noise temperature of 300 K. Given the reference temperature T0 = 290 K, find the noise figure of the system. modulation index of an AM radio station is 0.75. If the carrier power is 500W, what is the total transmitted power?
WAN
An FM transmitter system is using a 1MHz crystal oscillator to generate a very stable 108MHz final carrier frequency. The output of the crystal oscillator is fed to a x36 multiplier circuit then mixed with a 34.5 MHz signal. The sum output of the mixer is filtered out, while the difference is fed to another multiplier in order to generate the final carrier frequency. What is the multiplier value? A/an _______ is a range of frequency in which the upper frequency is double the lower frequency. Determine the worst-case output S/N for a narrowband FM receiver with deviation maximum of 10 kHz and a maximum intelligence frequency of 3 kHz. The S/N input is 3:1.
72
A small variable capacitance in parallel with each section of ganged capacitor is called _______. How many wavelengths long are required for a pair of conductors to be considered as a transmission line? Determine the time taken for a signal to travel down a 10 m transmission line, if its velocity factor is 0.7.
1 space switching a flow of loop current Transport
Echo Suppresors 23 dBm dBm for 200 mW = 10 log (200mW/1mW) = 23 dBm 3.6 dB
641 W
m2 Pt Pc1 2
Octave 10 Φ = sin-1 (1/3) = 19.5 or 0.34 rad δ = Φ x fi = 0.34 x 3 kHz = 1 kHz The S/N will be 10 kHz/ 1 kHz = 10 Trimmer 1/10λ 47.6 ns T= L/ (Vf x Vc) T= 10 m/ (0.7)(3x108 m/s) T= 47.6 ns
The maximum voltage standing wave of an RG-11/U foam coaxial cable is 52 V and its minimum voltage is 17 V. How many percent of the incident power is the reflected power? At exactly one-quarter wavelength, the short-circuited transmission line behaves as a(an) ________ circuit. Determine the phase-shift represented by a 75 ns delay of a 4 MHz signal to a 75-ft cable with a dielectric constant of 2.3.
26%
Which of the following is a flat conductor separated by an insulating dielectric from a large ground plane that is usually one-quarter or one-half wavelength long? One complete revolution around a Smith Chart represents _________ wavelengths. A mismatched transmission line is also referred to as a ___________ line. It is the ratio of the speed of propagation on a line to that of light in free-space. Which of the following is the most widely used UTP cable that can carry baseband data at rates up to 100 Mbps at a range up to 100m? The modulated peak value of a signal is 125V and the unmodulated carrier value is 85V. What is the modulation index?
Microstrip
The total transmitted power of an AM broadcast transmitter with a carrier power of 50kW when modulated 80 percent is:
One of the advantages of DSB is the savings of great deal of power. Which of the following is the reason why it is not widely used? If the input in a transmitter is collector-modulated, the system is called a _______________________. The input to an FM receiver has a S/N of 2.8. What is the frequency deviation caused by the noise if the modulating frequency is 1.5KHz and the permitted deviation is 4KHz?
What circuit is used to return the frequency response of a signal to its normal, “flat” level? It is the most common means of overcoming the problems of quantizing error and noise. ____ means that the characteristics and performance of an antenna are the same whether the antenna is radiating or intercepting an electromagnetic signal. Which of the following methods is used to lower the resonant frequency of a shortened vertical antenna?
parallel-resonant 108 degrees Θ = 360 td / T T =1/f = 1 / 4MHz = 250 ns Θ = 360 (75) / 250 = 108 degrees
½λ Resonant velocity factor CAT 5
0.47 m = Em/ Ec Emax = Ec + Em ; Em = Emax – Ec = 125 – 85 = 40 V m = 40V/ 85V = 0.47 66kW Pt = Pc ( 1 + m2/2) Pt = 50,000 ( 1 + 0.82 /2) Pt = 66,000 W Pt = 66kW the signal is difficult to demodulate
high-level modulator 547.8 Hz = fm = sin -1 N/S = sin -1 1/2.8 = 0.3652 = (0.3652)(1.5KHz) = 547.8 Hz de-emphasis Companding antenna reciprocity
top hat loading
Calculate the gain (isotropic) of a parabolic antenna that has a diameter of 3 m, an efficiency of 60% and operates at a frequency of 4 GHz.
39.8 dBi
It is a phenomenon caused by any support insulators used at the ends of the wire antenna. Which of the following is not a reason why most halfwave antennas are mounted horizontally at low frequencies? The shape of the electromagnetic energy radiated from or received by an antenna is called the Antennas that transmit an equal amount of energy in the horizontal direction are called The ability of an antenna to send or receive signals over a narrow horizontal directional range is referred to as A basic antenna connected to a transmission line plus one or more additional conductors that are not connected to the transmission line form a An antenna made up of a driven element and one or more parasitic elements is generally referred to as a Which antennas usually consist of two or more halfwave dipoles mounted end to end? A stacked collinear antenna consisting of half-wave dipoles spaced from one another by one-half wavelengths is the When the characteristic impedance of the transmission line matches the output impedance of the transmitter and the impedance of the antenna itself, A one-quarter wavelength of coaxial or balanced transmission line of a specific impedance connected between a load and a source in order to match impedances is
end effect
By how much should two antennas be separated for space diversity in the 11 GHz band?
5.5 m
G = 2 D2/ 2 = 3x108/ 4MHz = 0.075 m G = 0.62(3)2 0.0752 G= 9474.8 G = 10 log 9474.8 G = 39.8 dBi
more cost-effective
radiation pattern Omnidirectional Directivity
parasitic array
Yagi antenna Collinear broadside array
maximum power transfer will take place
a Q section
m 200 3 x 108 200 c s d 200 5.5 m f 9 11x 10 s
What is the phase velocity of a rectangular waveguide with a wall separation of 3 cm and a desired frequency of operation of 6 GHz?
5.43 x 108 m/s
A transmitter and a receiver is 45 km apart. Suppose that there is an obstacle midway between the transmitter and receiver. By how much must the path between the towers clear the obstacle in order to avoid diffraction at a frequency of 11 GHz?
10.51 m
How far from the transmitter could a signal be received if the transmitting and receiving antennas where 40 m and 20 m, respectively, above level terrain?
44.5 km
A signal propagated in a waveguide has a full wave of electric intensity change between two further walls, and no component of the electric field in the direction of propagation. The mode is An isolator has a forward loss of 0.7 dB and a return loss of 26 dB. A source provides 1 W to the isolator, and the load is resistive with an SWR of 3. How much power is dissipated in the load?
TE20
An isolator has a forward loss of 0.7 dB and a return loss of 26 dB. A source provides 1 W to the isolator, and the load is resistive with an SWR of 3. How much power returns to the source?
638 mW
1W
Po u t
0. 7 anti log 10 SWR 1 0 .5 SWR 1
851.14 mW
PLOAD Po u t 1 2 638.35 mW 5.43 x 108 m/s
1W
Po u t
anti log
0.7 10
851.14 mW
SWR 1 0.5 SWR 1
PLOAD Po u t 1 2 638.35 mW Pre f le cte d Po u t 2 212.78 mW Pre tu rn e d
212.78 mW 534.49 W 26 anti log 10
It is a microwave device that allows RF energy to pass through in one direction with very little loss, but absorbs RF power in the opposite direction. A metal wrapped around the parabolic antenna aperture to eliminate sidelobes interfering nearby stations is called The wavelength of a wave in a waveguide _________. Geostationary satellites are located at ____ with respect to the equator. The quality of a space-link is measured in terms of the ______ ratio. Why does the downlink frequency appear to vary by several kHz during a low earth orbit satellite pass? The most ambitious LEO constellation to date is ______. A satellite-dish owner has a 3 meter dish designed for C-band (4 GHz) operation. The owner wants to use the same dish with a new feedhorn, for Ku-band (12 GHz) satellites. What effect will the change in frequency have on the gain and beamwidth of the antenna? The moon orbits the earth with a period of approximately 28 days. How far away is it? Assume circular orbit.
isolator
What is the length of the path to a geostationary satellite from an Earth station if the angle of elevation is 300?
39000 km
What is the nominal uplink frequency for the Ku band? To cover all inhabited regions of the earth, the number of polar-orbit satellites required is A dipole antenna has a radiation resistance of 67 ohms and a loss resistance of 5 ohms, measured at the feedpoint. Calculate the efficiency. Two antennas have gains of 5.3 dBi and 4.5 dBd, respectively. Which has a greater gain? A half-wave dipole is sometimes called: An antenna's beamwidth is measured "Ground Effects" refers to the effects on an antenna's radiation pattern caused by An antenna can be matched to a feed line using
14 GHz 1
As the length of a "long-wire" antenna is increased
Shroud
is greater than in free space 00 latitude G/T The distance between the satellite and ground station is changing, causing the Doppler effect Teledesic Gain increases by 9.54 dB, beamwidth decreases to 1/3 of its former value.
384 Mm
93% Efficiency = Rr / Rt = 67 / (67 + 5) = 93% The second antenna has a higher gain. Hertz antenna between half-power points radio signals reflecting off the ground all of the choices a. a shorted stub b. an LC network c. a loading coil the number of lobes increases
LPDA stands for Field strength at a distance from an antenna is measured with A receiving antenna with a built-in preamplifier The height above mean sea level of a satellite in a geosynchronous orbit around Earth is: The location of a satellite is generally specified in terms of A point in the orbit of an object orbiting the earth that is located closest to Earth. Find the velocity of a satellite in a circular orbit 500 km above the earth’s surface.
Log-Periodic Dipole Array a field-strength meter active antenna 35,786 km latitude & longitude Perigee 7.6 km/s Formula : v
4x1011 d 6400
Where : v = velocity in meters per second d = distance above earth’s surface in km
4x1011 v = 7.6 km/s (500 6400)
Find the orbital period of a satellite in a circular orbit 36,000 km above the earth’s surface if the earth’s radius is 6400 km.
1440 mins
Formula :
C v
Where :
T = orbital period C = circumference v = orbital velocity C = 2r = 2 ( 6400 + 36,000 ) = 266.4 x 10 6 m
4 x1011 3.07km/s (36,000 6400) C 266.4 x106 m T 24hrs or 1440 mins v 3.07x103 m /s
v
Footprint The outline of a communications satellite antenna pattern on the earth is known as: 39,000 km Calculate the length of the path to a geostationary satellite from an earth station where the angle of elevation is 30.(earth’s radius = 6400 km, height of d (r h) 2 (r cos ) 2 r sin satellite above earth is 36 X 103 km) A satellite access technique where each earth station TDMA ( Time Division Multiple Access) transmits a short burst of information during a specific time slot. An earth station antenna look angle is determined by : azimuth & elevation An ITU radiocommunication standards for satellite services which provides information on the range of frequencies that can be used by fixed satellite service systems for emergency and disaster relief operations.
ITU-R S.1001-2
As per Philippine standard, frequency allocation of AM Radio Broadcasting is from…
526.5 to 1705 kHz
Part of broadcasting in a day that refers to that period of time between 1000 UTC to 2200 UTC. UTC stands for Universal Time Coordinates. An AM broadcast service area in which groundwave field of 1mV/m (60dBu) is not subject to objectionable interference or objectionable fading. In antenna mast or tower construction, the required obstruction painting and/or lighting must be imposed on mast or tower more than … from the ground level. Regarding the design of AM antenna, what should be the polarization of the radiator? As per Phillipine standard, what is the minimum frequency separation in any service area for adjacent AM radio stations? What is the maximum power allowable for remote pick-up stations used as broadcast auxillary services for AM and FM broadcast stations? What is the classification of an FM station having an ERP not exceeding 30kW? What is the modulation used for the stereophonic subcarrier of FM composite baseband signal? What is the pilot subcarrier frequency used in FM stereophonic transmission? The output power of an FM transmitter is 5 kW. If the power loss in transmission line is around 10 W and the antenna has a power gain of 6 dB, what is the ERP of the station in kW?
Frequency allocation of FM broadcast in the Philippines… What is the color TV system adopted by the Philippines? Exact value of color subcarrier frequency (MHz) is … Determine the visual carrier frequency of TV channel 9.
What is the maximum allowable ERPs for channels 7 – 13 in Metro Manila and Metro Cebu? At NTSC standard, the number of lines per frame = ________ lines/frame At NTSC standard, line frequency = 15734.264 Hz. What is the equivalent line period?
nighttime period
primary service area
150 ft
Vertical 36 kHz
35 W
Class B AM DSB SC 19 kHz 19.96 kW GANT = 6 dB = 4 ERP = (5000 – 10) x 4 = 4990 x 4 = 19,960 W or 19.96 kW 88 – 108 MHz NTSC 3.579545 Mhz 187.25 MHz 186 MHz, low band frequency of channel 9 186 + 1.25 = 187.25 Mhz 1 MW 525 63.556 usec fH = 15734.264 Hz H = 1 / fH = 1 / 15734.264
Nominal RF bandwidth of NTSC TV channel… A land mobile station used for the transmission of TV program materials and related communications from the scenes of events occuring at remote points from TV broadcast station studios to TV broadcast station. For a total capacity of 36 Mbps and 64-QAM of digital modulation, what is the ideal RF bandwidth?
H = 63.556 x 10-6 = 63.556 usec 6 MHz TV Pick-up station
6 MHz
What is the mode of radio wave propagation that utilized ionosphere as a medium of transmission and / or reception of radio signals? What is the wavelength of a radio signal travelling at a frequency of 220 MHz in a coaxial line having Teflon foam as its dielectric, εr = 2? What is the angle of refraction in a Teflon (ε r2 = 2) medium of a radio wave from air (ε r1 = 1.0) if its angle of incidence is 45°?
An ionosphere layer also termed as “absorption layer” because it absorbs most of the frequencies above 100 kHz is known as the … layer. As per ITU-R Recc. V.431-6 Tables 1 & 2 Wavelength Classifications, what is the classification of Super High Frequency? What is a diversity scheme that uses two (2) separate antennas and receivers for each single transmitter? What is a diversity scheme that uses two (2) different frequencies in a simplex path? What is the critical frequency of a layer if the maximum value of electron density is 2 x 10 6 per cm3?
sky wave
0.96 m Vp = Vf C vf = 1 / sqrt (εr) λ = vP / f = 0.96m 30° Using Snell’s Law… Sqrt (εr1) sin θi = Sqrt (εr2) sin θr Sqrt (1) sin 45° = Sqrt (2) sin θr θr = sin-1 [(Sqrt (1) sin 45°) / Sqrt (2)] = sin-1 (0.5) = 30° D
Centimetric
space diversity frequency diversity 13 MHz Nmax = 2 x 106 per cm3 = 2 x 106 x 106 per m3 = 2 x 1012 per m3
fc = 9 x sqrt (Nmax) = 9 x sqrt (2 x 1012) fc = 12.73 MHz or 13 MHz approx. A radio communication link is to be established via the ionosphere. The maximum virtual height of the layer is 110 km. at the midpoint of the path and the critical frequency is 4 MHz. If the distance between the radio stations is 500 km, what is the suitable value for the optimum working frequency? Use flat terrain analysis.
8.4 MHz For flat terrain analysis, tan i = d/2h v i = tan-1 [d/2hv] = tan-1 [500/2(110)] = tan-1 [2.273] = 66.25° angle of incidence MUF = fc x sec i = fc / cos i = 4 / cos 66.25° = 4 / 0.40275 = 9.932 MHz via Secant Law
The power density is inversely proportional to the square of the distance from the source. This law is known as… The lowest portion of the ionosphere that is useful for long-distance communication by amateurs; about 100 to 115 km above the earth is known as the… layer. This is often termed as the Kennely-Heavyside layer. A graph which shows the radiation in actual field strength of electromagnetic fields at all points which are at equal distance from the antenna is known as…
OWF = 0.85 x MUF = 0.85 (9.932) = 8.4422 MHz or 8.4 MHz approx. Inverse Square law
E
Radiation Pattern
The efficiency of an antenna is 82 %. Its radiation resistance is 30 Ω. What is the value of its loss resistance?
A phenomenon on the surface of the sun with appearance and disappearance of dark irregularly shaped areas. What should be done to increase the transmission distance at frequencies higher than HF bands? Which of the following factors must be considered in the transmission of a surface wave to reduce attenuation?
A radio station operates at 11 meter wavelength. What is the designated band of station’s frequency?
What is the total radio horizon distance between an 80 ft transmitting station and a 20 ft receiving station?
A power density of 1.57 x 10-4 W/m2 is measured 50 meters from a test antenna whose directive gain is 2.15 dB. How much power was fed into the test antenna?
6.58 Ω η = Rd/(Rd + Rloss) 0.82 = 30/(30 + Rloss) 0.82 (30 + Rloss) = 30 = 24.6 + 0.82 Rloss Rloss = (30 – 24.6) / 0.82 = 6.5854 Ω or 6.58 Ω approx. 11-year sunspot
increase antenna height All of the choices a. electrical properties of the terrain b. frequency c. antenna polarization HF c = 3 x 108 m/sec λ = 11 m = c / f f = 3 x 108 / 11 = 27 MHz approx., which is within 3 – 30 MHz range designated as HF band 18.97 mi dRH (TOT) = sqrt (2 x hT) + sqrt (2 x hR) dRH (TOT) = sqrt (2 x 80) + sqrt (2 x 20) dRH (TOT) = 18.97 mi 3W PR = PD x 4πd2 = 1.57 x 10-4 x 4π(50)2 = 4.93 W approx. is the radiated power GANT = log-1 [2.15 dB/10] = 1.64 PR = PFED x GANT PFED = PR / GANT = 4.93 / 1.64 = 3.007 W or 3 W approx.
Identical telephone numbers in different parts of a country are distinguished by their ___.
area codes
Telephone traffic is measured ____.
in erlangs
In a cellular telephone system, each cell site contains a ____.
Repeater
When the signal from a mobile cellular unit drops below a certain level, what action occurs?
the unit is “handed off” to a closer cell
In a cellular telephone system, group of cells is called ___.
Cluster
In Celluar Telephone Systems, these are transmissions from base stations to mobile units (Downlink)
forward links
A CDMA mobile measures the signal strength from the base as -100 dBm. What should the mobile transmitter power be set to as a first approximation, considering - 76 dB at mobile power contol?
A telephone signal takes 2ms to reach its destination. Calculate the via net loss required for an acceptable amount of echo.
250 mW PT = -76 dB - PR Where: PT = transmitted power in dBm PR = received power in dBm PT = -76 dB - PR = -76 dB – (-100dBm) = 24 dBm = 250 mW 0.8 dB VNL = 0.2t + 0.4 dB = 0.2 X 2 + 0.4 = 0.8 dB
The typical voltage across a telephone when on-hook is: Central offices are connected by:
48 volts DC
In telephony, call blocking is:
occurs when the central office capacity is exceeded
The cable used for local loops in telephone system is mainly: In DTMF, the four vertical frequencies are ____.
twisted-pair copper wire
In DTMF, the Horizontal frequencies are
1209Hz, 1336Hz,1477Hz,1633Hz
In Celluar Telephone Systems, these are transmissions from mobile units to base stations (Uplink) In DTMF, the horizontal frequencies is also known as
reverse links
In DTMF, the Vertical frequencies is also known as
low group frequencies
The bandwidth of voice-grade signals on a telephone system is restricted in order to: This is the highest-ranking office in the DDD network in telephony in terms of the size of the geographical area served and the trunking options available. In Cellular Radio, AMPS stand for:
allow signals to be multiplexed
In Cellular Radio, BSC stands for:
Base Station Controller
In Cellular Radio, MSC stands for:
Mobile Switching Center
In GSM, voice channels are called:
traffic channels
In Mobile Communications, GSM uses:
frequency hopping
In Mobile Communications, IMSI stands for:
International Mobile Subscriber Identification
An acoustical phenomenon wherein the sound continues to persist after the cause of sound has stopped resulting in repeated reflections is called…
Reverberation
trunk lines
697Hz,770Hz,852Hz,941Hz
high group frequencies
regional center
Advanced Mobile Phone Service
A group of filters has 1/3 octave of spacing. If the initial frequency is 25 Hz, what is the next frequency available for the filter? + 26 dBu is how many volts?
A type of microphone that uses the principle of a capacitor as a means of transduction. It uses a polarizing voltage of between 9 and 48 V of DC supply applied to its diaphragm by an external power supply Determine the sound power in Watts produced by the bank’s alarm if a by-stander heard the alarm at a sound pressure level of 100 dB-SPL. The by-stander is 100 ft away from the bank.
A loudspeaker produces an SPL of 85dB-SPL at 1 meter distance and input electrical power of 1 W. How loud is the SPL at distance of 20 meters if this speaker is driven to 10 W of electrical power?
A number from 0 to 1 representing the ability of a surface material to absorb sound energy is known as… The difference in dB between the loudest level of sound and the softest passage of sound is known as _ The highest frequency that can be used for skywave propagation between two specific points on earth’s surface. Variation in signal loss caused by natural weather disturbances. Determine the radio horizon for a transmit antenna that is 200 m high and a receiving antenna that is 100 m high The height above the earth’s surface from which a refracted wave appears to have been reflected… Electromagnetic waves that are directed above the horizon level. The most common light used in fiber-optic links is In the telecommunications industry, the most commonly used fiber(s) are The abrupt change in refractive index from core to cladding of fiber-optic cable is called the A technique that is used to minimize the pulse dispersion effect is to
31.5 Hz f2 = 2x f1 where x = 1/3, fraction of an octave f2 = 21/3 x 25 = 31.5 Hz 15.5 V V (dBu) = 20 log [ voltage in Volts / 0.775 Volts ] 26 = 20 log [ voltage in Volts / 0.775 V ] 26 / 20 = log [ voltage in Volts / 0.775 V ] = 1.3 Voltage = log-1 (1.3) x 0.775 V Voltage = 15.5 V Condenser
58.65 W PWL = SPL + 20 log D(m) + 8 PWL = 100 + 20 log (100/3.28) + 8 = 137.68 dB-PWL 137.68 = 10 log W + 120 W = log-1 [(137.68 – 120)/10] W = 58.65 Watts 69 dB-SPL SPL@1m/1W = 85 dB-SPL (given) SPL@20m/1W = 85 - 20 log (20m/1m) = 59 dB-SPL SPL@20m/10W = 59 + 10 log (10W/1W) = 69 dBSPL Absorption Coefficient
dynamic range
Critical Frequency
Fading 99.5 km D = √ 17ht + √ 17hr = √ 17(200) + √ 17(100) = 99.5 km virtual height sky waves Infrared 50 and 62.5 micron Step index Minimize the core diameter
Which is not an important characteristic of a light detector? The dispersion of light in fiber-optic cable caused by a portion of the light energy traveling in the cladding is called Recent laser developments for fiber-optic communication include Which of the following considerations is important when deciding between using a diode laser or an LED? In 1815, the correct explanation of diffraction was given by It is the central part of the optical communication system The light energy that is always emitted or absorbed in discrete units Which of the following Ethernet fiber optic standard uses synchronous, Centralized Clock? It is a mixed, multiple-service standard to allow the transmission of voice and video over an FDDJ network. It is a layer of plastic that surrounds a fiber or group of fibers The angular separation between the two half-power points on the power density radiation pattern. Refers to the direction in space of electric vector of the electromagnetic wave radiated from an antenna and is parallel to the antenna itself. Placing a metallic array on the antenna effects to increase the current at the base of the antenna, and also to make the current distribution more uniform. What is this called? What principle that states that the properties of an antenna are independent of whether it is used for transmission or reception. Calculate the beam width between nulls of a 2-m paraboloid reflector used at 6GHz. Note: such reflectors are often used at that frequency as antennas outside broadcast television microwave links. This is often used to cure the problem of great thickness required of lenses used at lower microwave frequencies or for strong curved wavefronts. A structure-generally metallic and sometimes very complex-designed to provide an efficient coupling between space and the output of a transmitter or input to a receiver. The ratio comparing the power density generated by a practical antenna in some direction, with that due to an isotopic antenna radiating the same total power. Any array that is directional at right angles to the plane of the array is said, by inference, to have ____. The ratio of the focal length to the mouth diameter is called __________ of the parabola, just as in camera lenses.
Power consumption Waveguide dispersion
Distributed feedback (DFB) and vertical cavity surface emitting (VCSEL) Response time
Fresnel Optical Fiber Quanta 10 Base-FB (Backbone) FDDI – II
Buffer Tube Beamwidth Polarization
Top loading
Principle of reciprocity 3.50 Φ0= Φ0=3.50 Zoning
Antenna
Directive gain
Broadside action Aperture
Corresponds to a resonant transmission line, and the dipole antennas describe so far have been resonant. An optic fiber is made of glass with a refractive index of 1.55 and is clad with another glass with a refractive index of 1.51. Launching takes place from air. What numerical aperture does the fiber have?
An optic fiber is made of glass with a refractive index of 1.55 and is clad with another glass with a refractive index of 1.51. Launching takes place from air. What is the acceptance angle?
For a single-mode optical cable with 0.25-dB/km loss, determine the optical power 100km from a 0.1-mW light source.
For an optical fiber 10km long with a pulse-spreading constant of 5ns/km, determine the maximum digital transmission rates for return-to-zero. In fiber optics, it is a measure of the conversion efficiency of a photodetector. It is the ratio of the output current of a photodiode to the input optical power and has the unit of amperes per watt A phenomenon also called stress corrosion resulting if the glass fiber is exposed to long periods of high humidity? The theory which states that when visible light or highfrequency electromagnetic radiation illuminates a metallic surface, electrons are emitted. The science of measuring only light waves that are visible to the human eye The process of constructing an ILD that is similar to LED except that the ends are highly polished. A phenomenon in optical fibers communication system that is caused by the difference in the propagation times of light rays that take different paths down the fiber. For an electronic device operating at a temperature of 17°C with a bandwidth of 10 kHz, determine the thermal noise power in dBm .
Resonant antenna 0.352 ∆=(n1-n2)/n1 =(1.55-1.51)/1.55 =0.0258 NA=n1√(2∆) =1.55√[(2)(0.0258)] = 0.352 20.6◦ ∆=(n1-n2)/n1 =(1.55-1.51)/1.55 =0.0258 NA=n1√(2∆) =1.55√[(2)(0.0258)] = 0.352 Θ0(max)=sin-1NA= sin-10.352=20.6◦ -35dBm P =0.1mW x 10-{[(0.25)(100)]/(10)} =1 x 10-4 x 10{[(0.25)(100)]/(10)] =(1 x 10-4)(1 x 10-25) =0.316µW P(dBm)= 10log = -35dBm 20Mbps Fb=
=20Mbps
Responsivity
Static fatigue Planck’s law
Photometry Lasing Pulse spreading
-134dBm N = KTB N(dBm) = 10log (4 x 10-17) = -134 dBm 0.001
A 300Ω resistor is connected across the 300Ω antenna input of a television receiver. The bandwidth of the receiver is 6MHz, and the resistor is at room temperature .Find the noise voltage applied to the receiver input. The signal power at the input to an amplifier is 100µW and the noise power is 1 µW. At the output, the signal power is 1W and the noise power is 30mW. What is the amplifier noise figure, as a ratio?
5.4 µV VN = = 4(1.38 x 10-23 J/K)(293 K)(6 x 106 Hz)(300 Ω) = 5.4 x 10-6 V = 5.4 µV 3 (S/N)p = 100µW 1µW (S/N)o = 1W 0.03W NF (ratio) = 100 33.5
It is desired to operate a receiver with NF = 8dB at S/N = 15 dB over a 200-KHz bandwidth at ambient temperature. Calculate the receiver’s sensitivity.
-98dBm
A Satellite receiving system includes a dish antenna ( Teq = 35 K) connected via a coupling network (Teq= 40 K) to a microwave receiver (Teq=52 K referred to its input). What is the noise power to the receiver’s input over a 1-MHz frequency range? Equivalent temperature of a passive system having the same noise power output of a given system. The noise voltage produced across a 50Ω is input resistance at a temperature of 302°C with a bandwidth of 6 MHz is ______.
1.75 x 10-15
Determine the worst-case output S/N for a broadcast FM program that has a maximum intelligence frequency of 5 kHz. The input S/N is 2
30
= 33.3 =3
S = Sensitivity = -74dBm + NF + 10log∆f + desired S/N S = -174 + 8 + 10log(200,000) + 15 S = -98 dBm
PN = KT∆f = 1.38 x 10-23 J/K (35 + 40 + 52)K (1MHz) = 1.75 x 10-15 W noise temperature 2.24µV VN = = 4(1.38 x 10-23)(302)(6 x 106)(50) = 2.24µV ᵟ = φ x fi = 0.5 x 5 kHz = 2.5 kHz 75 kHz 2.5 kHz
The technique that uses the BPSK vector relationship to generate an output with logical 0s and 1s determined by comparing the phase of two successive data bits is A special digital modulation technique that achieves high data rates in limited-bandwidth channels is called FSK systems are much superior to two-tone amplitude-modulation systems with respect to Using an oscilloscope to display overlayed received data bits that provide information on noise, jitter, and linearity is called a(n) The type of radio transmission that uses pseudorandomly switched transmissions is known as The acronym CDMA refers to ________.
= 100
= 30
DPSK
Quadrature amplitude modulation (QAM) Ionospheric fading characteristics Eye pattern
Spread spectrum Code-division multiple-access systems
The acronym OFDM refers to ________.
Orthogonal Frequency Division Multiplexing
Using radio to transmit gathered data on some particular phenomenon without human monitors is known as The acronym for the form of data transmission in which the modulating wave shifts the output between two predetermined frequencies is _____. Pseudorandom implies a sequence that can be _____ but has the properties of randomness. ______ implies that both analog and digital signals share the same channel bandwidth. Telemetry may be defined as _____ metering.
Radio telemetry
Which is not a type of pulse modulation?
Pulse-frequency modulation (PFM)
PPM and PWM are superior to PAM systems in
Noise characteristics
A procedure that decides which device has permission to transmit at a given time is called The major difficulty faced by delta modulators is
Line control
The AT&T T1 lines
Use 8-bit PCM code and include 24 voice channels
The ground wire in a USB cable is ______.
Brown
A(n) ________ is used to allow a digital signal to be transmitted on an analog channel.
Modem
The bit ________ is the amount of power in a digital bit for a given amount of time. The relationship for bit rate to ________ bandwidth is defined by the Shannon-Hartley theorem. In an S/H circuit, the time that it must hold the sampled voltage is Error signals associated with the sampling process are called A(n) ________ is a single LSI chip containing both the ADC and DAC circuitry. The NRZ digital signal-encoding format has a ________ component in the waveform. Reed–Solomon codes utilize a technique called ________ to rearrange the data into a nonlinear ordering scheme to improve the chance of data correction. The electric field intensity is measured in:
Energy
It is a result of an increase in the charge density in dielectric materials. It refers to the maximum antenna gain.
Polarization
The maximum horizontal distance between the transmitter and the receiver for line of sight propagation is known as: Typical mode of radiation of helical antenna is:
radio horizon
FSK
re-created Hybrid Remote
Slope overload
Channel Aperture time Foldover distortion and aliasing Codec Dc Interleaving
V/m
Directivity
end fire
The electric field is perpendicular to the earth’s surface, the polarization is: In what major RF band is ground wave basically applied? A measure of mismatch in a transmission line
Vertical
The highest frequency that can be set back to earth by the ionosphere, if wave is sent vertically upward. Travel in a straight line from the transmitting antenna to the receiving antenna. VLF waves are for some types of services because
critical frequency
It is the distance between two wave fronts having the same phase at any given instant. It is a piece of transmission line which is normally short-circuited at the far end. A 50 ohms transmission line is connected to a 30 ohm resistive load. Calculate the reflection coefficient.
Wavelength
The characteristic impedance of a transmission line does not depend upon its Characteristic impedance of a transmission line is the impedance measured at the _______ when its length is infinite. Which region of the ionosphere is mainly responsible for long-distance night time communications? Which is properly terminated antenna?
MF (Medium Frequency) standing wave ratio
space wave they are very reliable
Stub 0.25 Ref Coeff = (30 – 50)/(30 + 50) = 0.25 Length Input
F layer Rhombic
Occurs when the radio beam is at point of grazing over an obstacle. A microwave communications system, space loss calculation formula is
diffraction
Is an OSI Layer which is responsible for providing error-free communications across the physical link connecting primary and secondary stations (nodes)
Data Link layer
Is the ratio of the largest possible magnitude to the smallest possible magnitude that can be decoded by the digital-to-analog converter. Is a PCM system which uses a single bit PCM code to achieve digital transmission of analog signals. Is a redundancy error detection scheme that uses parity to determine if a transmission error has occurred within a message and is sometimes called message parity. Is an n-bit data register inside the UART that keeps track of the UART’s transmit and receive buffer registers. Is an access method used primarily with LANs configured in a bus topology. IP version 4 address length is
Dynamic range
Is a multiport bridge that provides bridging function.
Switch
92.4 + 20log F + 20 log D
Delta modulation Longitudinal redundancy check
Status Word register
CSMA/CD 32 bits
Is a device which operates in the Network layer and it makes forwarding decisions on the basis of network addresses. OC-1 (STS-1) line rate is
Router
Is one in which all computers share their resources with all the other computers on the network.
Peer-to-peer client/server network
Is used to interface DTEs to digital transmission channels
Channel service unit
Modulation which combines encoding and modulation to reduce the probability of error.
TCM
Is an empirical record of a system’s actual bit error performance
BER
Is an error-correcting code used for correcting transmission errors in synchronous data streams.
Hamming code
51.84 Mbps
