Antenna solved exam 2016

Fayoum University Faculty of Engineering Department of Electrical Engineering

EE 422 - Midterm Exam Elective Course (1)  –  Antenna  Antenna Propagation, 2016 Please show all your work for more rational grading. 1. [4 points] Radiation intensity of the antenna is given by:

0       / 9 1     1     / 9       / 3 U  ,   0.342    sin     0   / 3       0     2  (a) Find the total radiated power (b) Directivity of the antenna (dimensionless and in dB)

2. [4 points] A transmitting antenna produces a maximum far-field magnetic field

intensity in a certain direction given by:

 H 

50 I  

r 

e  j t 



jkr 

 A m

where  I  is   is the peak input current at the antenna. The radiation resistance (or input resistance) of the lossless antenna is 100 Ω. Find the effective aperture of the antenna. 3. [6 points] A 2-m-long center-fed dipole antenna operates in the AM broadcast

 band at 1 MHz. The The dipole is made made of copper wire wire with a radius of 1 mm. (a) Determine the radiation efficiency of the antenna. (b) What is the antenna gain in dB? (c) What antenna current is required so that the antenna would radiate 80 W,

and how much power will the generator have to supply to the antenna? 4. [4 points] The directivity of an antenna pattern is given by the following equation:

 ,    D

 D

o

sin 3  

(a) What should the value of the constant  Do  be in order to be a valid

directivity? (b) What is the half power beamwidth of this antenna?

Fayoum University Faculty of Engineering Department of Electrical Engineering

5. [3 points] Calculate the power received by a cellular telephone antenna of gain 1

dBi from a base station radiating 25 W of power at a frequency of 835 MHz. it is given that the gain of the base station antenna is 12 dBi, and the base station is located at a distance of 10 Km from the user of the cell phone. 6. [4 points] A standard FM tower sends 50 kW at 100 MHz. The FM tower antenna

gain is 7 dB - they are designed not to radiate up in the air and more in a horizontal cone. You are 10 kms away from the transmitter. (a) Calculate the path loss to your location (in dB). (b) You are carrying an FM receiver in your cell phone with a miserable antenna

having a gain of -15 dB. Calculate the received power. END OF QUESTION SHEET

TOTAL MARKS FOR THIS EXAM = 25

Fayoum University Faculty of Engineering Department of Electrical Engineering

EE 409 - Midterm Solutions Questio n # 1

Q u e s t i o n # 2  

Fayoum University Faculty of Engineering Department of Electrical Engineering Q u e s t i o n # 3 

Questio n # 4

Fayoum University Faculty of Engineering Department of Electrical Engineering Questio n # 5

Q u e s t i o n # 6