Digital Communication System MCQs

Question 1

Companding is used

Accepted Answer

to protect small signals in PCM from quantizing distortion

Answer

to overcome quantizing noise in PCM

Answer

in PCM transmitters, to allow amplitude limiting in the receivers

Answer

In PCM receiver, to overcome impulse noise.

Question 2

Which one of the following system is analog

Accepted Answer

PAM

Answer

PCM

Answer

delta

Answer

differential PCM

Question 3

If the sampling time is less than the Nyquist interval

Accepted Answer

simpler filters can be used to obtain the original signal

Answer

bandwidth increases

Answer

channel capacity increases

Answer

guard time becomes less

Question 4

A signal of maximum frequency of 10 kHz is sampled at Nyquist rate. The time interval between two successive samples is

Accepted Answer

50 ns

Answer

100 gs

Answer

1000 is

Answer

5 is

Question 5

A narrowband signal occupying a frequency range of nfo to (n + 1) fo is to be sampled. The maximum sampling rate is (Taken to be an integer)

Accepted Answer

2f0

Answer

2nfo

Answer

2(n + 1)f0

Answer

None of the above

Question 6

The minimum required bandwidth for transmission of n signals, each band-limited to fm Hz, is

Accepted Answer

2nfm Hz

Answer

fm Hz

Answer

2fm Hz

Answer

mfm Hz

Question 7

TDM is preferred because

Accepted Answer

more than noe messages can be transmitted simultaneously over a common channel

Answer

it requiresless power

Answer

it needs lesser bandwidth

Answer

none of these

Question 8

Two orthogonal signals s1(t) and s2(t) satisfy the following relation :

Accepted Answer

0 si (t) s2 (t) dt = 0 s1 (t)

Answer

s2 (t) dt = 1 si (t)

Answer

s2 (t) dt = co s1 (t)

Answer

s2 (t) dt =71

Question 9

In communication, the sampling technique leads to

Accepted Answer

higher speed of communication

Answer

higher efficiency

Answer

cheaper equipment

Answer

all of the above