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Electronics and Communication Engineering - Communication Systems

Exercise : Communication Systems - Section 6
11.
A narrow band noise n(t) has symmetrical spectrum and has power density spectrum 0.2 x 10-6. The power density of quadrature component is
0.2 x 10-6
10-7
4 x 10-7
5 x 10-8
Answer: Option
Explanation:

.

12.
The radio receivers mostly used now a days are
TRF receivers
super heterodyne receivers
CW receivers
pulsed receivers
Answer: Option
Explanation:

Now-a-days only super heterodyne radio receivers are used.

13.
The reactance of coupling capacitors, for DC quantities, is
zero
low
infinite
zero or low
Answer: Option
Explanation:

For zero frequency capacitive reactance is infinite.

14.
An AM wave is given by s(t)AM = 20 (1 + 0.5 cos 103t + 0.3 cos 104 t cos 106 t) the modulation index of the envelope is
0.5
0.58
0.3
0.8
Answer: Option
Explanation:

.

15.
The modulating frequency in frequency modulation is increased from 10 kHz to 30 kHz. The bandwidth is increased by
6
1/6 times
increase by 30 kHz
increase by 20 kHz
Answer: Option
Explanation:

BW = 2fm(1 + β)

for β >> 1

B.W. a 2fm .

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