# Digital Communications Questions and Answers – PAM, PWM and TDM

This set of Digital Communication Question Bank focuses on “PAM, PWM and TDM”

1. Flat top sampling of low pass signals
a) Gives rise to aperture effect
b) Implies over sampling
d) Introduces delay distortion

Explanation: Flat top sampling of low pass signals gives rise to aperture effect.

2. In a delta modulation system, granular noise occurs when the
a) Modulating signal increases rapidly
b) Pulse rate decreases
c) Pulse amplitude decreases
d) Modulating signal remains constant

Explanation: In a delta modulation system, granular noise occurs when the modulating signal remains constant.

3. A PAM signal can be detected using
a) Low pass filter
b) High pass filter
c) Band pass filter
d) All pass filter

Explanation: A PAM signal can be detected by using low pass filter.

4. Coherent demodulation of FSK signal can be performed using
a) Matched filter
b) BPF and envelope detectors
c) Discriminator
d) None of the mentioned

Explanation: Coherent demodulation of FSK signal can be performed using matched filter.

5. The use of non uniform quantization leads to
a) Reduction in transmission bandwidth
b) Increase in maximum SNR
c) Increase in SNR for low level signals
d) Simplification of quantization process

Explanation: The use of non uniform quantization leads to increase in SNR for low level signals.

6. Which of the following requires a synchronizing signal?
a) Single channel PPM system
b) PAM
c) DM
d) All of the mentioned

Explanation: PAM requires a synchronizing signal.

7. A PWM signal can be generated by
a) An astable multi vibrator
b) A monostable multi vibrator
c) Integrating a PPM signal
d) Differentiating a PPM signal

Explanation: A PWM signal can be generated by a mono stable multi vibrator.

8. TDM is less immune to cross-talk in channel than FDM.
a) True
b) False

Explanation: False because different message signals are not applied to the channel simultaneously.

9. In an ideal TDM system, the cross correlation between two users of the system is
a) 1
b) 0
c) Infinity
d) -1

Explanation: In an ideal TDM system, the cross correlation between two users of the system is 0.

10. TDM requires
a) Constant data transmission
b) Transmission of data samples
c) Transmission of data at random
d) Transmission of data of only one measured

Explanation: TDM requires transmission of data samples.

Sanfoundry Global Education & Learning Series – Digital Communications.

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