Exercise: Communication Systems

Questions for: Communication Systems

Consider the draw backs
  1. Slope overload
  2. Serration noise
  3. Granular noise
Which of these draw backs does Delta modulation have?
A:
1 and 2 only
B:
2 and 3 only
C:
1 and 3 only
D:
1, 2, 3
Answer: C

In delta modulation the, recovered waveform may be dc whereas the original signal is not dc. This noise is called granular noise.

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If γ = (S0/N0)/(Si/Nm) where S0 and S1 are signal power output and signal power input and N0 and Nm are noise power output and noise power input, the value of γ for SSB-SC and DSB-SC amplitude modulated system respectively are
A:
1 and 1
B:
1 and 2
C:
2 and 1
D:
0.5 and 0.5
Answer: A

SSB - SC and SSB - DB have γ = 1 and are similar from noise point.

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A signal m(t) with bandwidth 500 Hz is first multiplied by a signal g(t) where . The resulting signal is then passes through an ideal low pass filter with bandwidth 1 kHz the output of the low pass filter would be
A:
δ(t)
B:
m(t)
C:
0
D:
m(t) δ(t)
Answer: B

Multiplication in time domain is equivalent to convolution. According to the property of impulse signal, convolution of a signal m(t) with δ(t) is signal itself.

m(t) x g(t)

m(t).

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A balun provides an impedance transformation of
A:
16 : 1
B:
8 : 1
C:
4 : 1
D:
2 : 1
Answer: C

Balun has turn ratio of 2 : 1. Therefore, impedance transformation is 4 : 1.

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An FM wave is made to pass through a frequency tripler. If original modulation index is mf, the output of tripler has a modulation index equal to
A:
mf
B:
mf
C:
3 mf
D:
mf
Answer: C

Frequency tripler makes modulation index three times.

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