Electronics and Communication Engineering - Exam Questions Papers

6. 

An air-filled rectangular waveguide has dimensions 8cm x 10cm . The wavelength of waveguide at frequency 3 GHz

A. 25 cm
B. 100 cm
C. 16.13 cm
D. 23.09 cm

Answer: Option D

Explanation:

λc = 2a = 2(10) = 20 cm

= 1.5 GHz

λg = 23.09 cm.


7. 

NMOS devices have __________ switching speeds and __________ on-state resistance; as compared with PMOS devices.

A. slower, higher
B. faster, lower
C. faster, higher
D. slower, lower

Answer: Option B

Explanation:

In NMOS devices, we have mobility of electrons than holes in PMOS; consequently higher conductivity and lower on-state resistance.


8. 

What is the frequency of pulse at the points a, b, c in the circuit?

A. 3 MHz
B. 7.8 KHz
C. 10 KHz
D. 1 MHz

Answer: Option B

Explanation:

Ring counter is N : 1 divider.

Hence ⇒ 1 MHz

Johnson counter is 2N : 1 divider

Ripple counter 2N : 1

= 7812.5 ∼ 7.8 kHz

Mod 10 = 4 FF ⇒ 24 = 16.


9. 

A lossless transmission line with air dielectric is 6 m long. what is the phase constant?

A. 1p rad/m
B. 2p rad/m
C. 0.2p rad/m
D. 0.1p rad/m

Answer: Option C

Explanation:

.


10. 

The impulse response h(t) of a linear invariant continuous time system is given by h(t) = exp (- 2t) u(t), where u(t) denotes the unit step function. The frequency response H(ω) of this system in terms of angular frequency ω is given by H(ω)

A.
B.
C.
D.

Answer: Option C

Explanation:

H(ω) = e-2t e-jωt