Analog and Digital Communications Mid - I, September - 2014

1.The bandwidth of an AM wave is _____
  • 2fm
  • fm
  • fm/2
  • fm/4
Answer: A
2.The SSB wave can be obtained from balanced modulator by connecting its output to a____
  • clipper
  • clamper
  • filter
  • amplifier
Answer: D
3.A product modulator yields
  • a full AM signal
  • a DSB-SC signal
  • a VSB signal
  • an SSB signal
Answer: B
4.In phase-shift SSB modulator the input signals to one of the balanced modulator are phase shifted by
  • 450
  • 900
  • 1800
  • 300
Answer: B
5.The bandwidth of a narrow band FM signal equals
  • 2Δf
  • 2(Δf+fm)
  • 2fm
  • 2(Δf-fm)
Answer: C
6.The image channel rejection in super heterodyne receiver depends upon
  • IF stage only
  • RF stage only
  • detector and RF stage
  • detector , RF , IF stages
Answer: B
7.An AM super heterodyne receiver with IF of 455kHz is tuned to the carrier frequency of 2000kHz. The image frequency is
  • 1910kHz
  • 1MHz
  • 2910kHz
  • 2000kHz
Answer: C
8.The PAM signal can be detected by
  • BPF
  • band stop filter
  • HPF
  • LPF
Answer: D
9.In PCM , if the number of quantization levels is increased from 4 to 64, then the bandwidth requirement will be approximately be _______
  • 3 times
  • 4 times
  • no change
  • 64 times
Answer: A
10.Which of the following pulse communication system is inherently immune to noise
  • PPM
  • PCM
  • PWM
  • PAM
Answer: B
11.If the carrier of a 100 % modulated AM wave is suppressed, the percentage power saving will be_________
Answer: 66.66%
12.The advantage of SSB-SC system is ___________________
Answer: Power and Bandwidth is reduced
13.The total power relation in DSB-SC is ______________________
Answer: Pt = Pc m2/2
14.The figure of merit for DSB-SC system is ________________________
Answer: 1
15.A preemphasis circuit provides extra noise immunity by _______________
Answer: Amplifying the higher frequencies
16.In frequency modulation if the amplitude of the modulating voltage is doubled the maximum frequency deviation _______________________
Answer: Doubles
17.The modulation index in FM is given by _____________________
Answer: Δf/fm
18.Quantization noise range in PCM is _________________________
Answer: –S/2 to +S/2
19.In delta modulation, slope overload error occurs when the modulating signal changes ___________ than the encoder can follow.
Answer: More rapidly
20.The PWM signal is converted into PPM signal with the help of _______________
Answer: Flip-flop