Electronics and Communication Engineering - Electromagnetic Field Theory

16. 

Consider a 300 Ω, quarter wave long at 1 GHz transmission line as shown in figure. It is connected to a 10 V, 50 Ω source at one end is left open circuited at the other end. The magnitude of the voltage at the open circuit end of the line is

A. 10 V
B. 5 V
C. 60 V
D. 60/7 volt

Answer: Option A

Explanation:

γ = a + jβ a = 0 γ = jβ

Propagating wave

v = VI e-rz + VR erz

No change in the voltage at the open end it will same,

vr = 10 volt.


17. 

The phase angle corresponding to λ/4 in a standing-wave pattern is

A. 30°
B. 90°
C. 135°
D. 180°

Answer: Option B

Explanation:


18. 

A hollow rectangular waveguide has dimensions a = 2b. Calculate the amount of attenuation, if the frequency is 3 GHz, and b = 1 cm.

A. 49
B. 47.33
C. 50.33
D. 50

Answer: Option B

Explanation:

Since, wave is attenuated hence β = 0

and Take, dominant mode m = 1,

n = 0

.


19. 

Calculate the directivity of an antenna for θE = 30°, θH = 60

A. 46
B. 23
C. 50
D. 100

Answer: Option B

Explanation:

.


20. 

Most antenna consisting of a 50 meter long vertical conductor operates over a perfectly conducting ground plane. It is base fed at a frequency of 600 kHz. The radiation resistance of the antenna in ohms is

A.
B.
C.
D. 20p2

Answer: Option C

Explanation: