Principles of Communications Mid - II, November - 2014

1.In a TDM system, each signal is allotted in a frame a unique and fixed
  • Frequency slot
  • amplitude slot
  • Phase slot
  • none
Answer: D
2.In delta modulation the slope overload distortion can be reduced by
  • decreasing the step size
  • decreasing the granular noise
  • decreasing the sampling rate
  • increasing the step size
Answer: D
3.Among the digital modulation systems QPSK, 8-PSK, BFSK, DPSK, the system with lowest bit error probability is
  • 8- PSK
  • BFSK
  • DPSK
  • QPSK
Answer: D
4.A binary communication system is transmitting data at a rate of 10 kbps using NRZ signaling. The Minimum channel bandwidth required for the above system is
  • 10kHz
  • 5 kHz
  • 20 kHz
  • 15 kHz
Answer: A
5.Granular noise in Delta modulation system can be reduced by
  • using a square law device
  • Increasing the step size
  • decreasing the step size
  • adjusting the rate of rise of the base band signal
Answer: C
6.BPSK and QPSK systems are
  • of same bandwidth
  • using same carrier recovery circuit for demodulation
  • of same bit error probability
  • of same symbol duration
Answer: C
7.In BPSK the carrier signal shifts between
  • two angles that are 1800 out of phase
  • two angles that are 1800 in phase
  • two angles that are 900 out of phase
  • two angles that are 900 in phase
Answer: A
8.Band width efficiency is
  • bits/ symbols
  • symbols /bits
  • bits x symbols
  • bits+symbols
Answer: A
9.DPSK may be viewed as
  • absolute phase
  • difference between two successive signaling
  • addition of two phases
  • addition of two successive signaling
Answer: B
10.The bandwidth of DPSK is
  • Less than BPSK
  • greater than BPSK
  • equal to BPSK
  • none
Answer: A
11.A Speech signal, band limited to 4 kHz and peak voltage varying between +5V and -5V, is sampled at the Nyquist rate. Each sample is quantized and represented by 8 bits. If the bits and 1 are transmitted using bipolar pulses, the minimum bandwidth required for distortion free transmission is _____________________________.
Answer: 4 Khz
12.A source generates three symbols with probabilities 0.25, 0.25, 0.5 at a rate of 3000 symbols/sec. Assuming independent generation of symbols, the most efficient source encoders average bit rate is _________________
Answer: 4500 bits/sec
13.A matched filter ________________________________________ the Probability of error
Answer: Minimizes
14.The angular separation between any two adjacent phases in QPSK is ________ degrees
Answer: 900
15.Three analog signals having bandwidth 1200Hz, 600Hz and 600Hz are sampled at their respective Nyquist rates, encoded with 12 bit words, and time division multiplexed. The bit rate for the multiplexed signal is ______________ Kbps
Answer: 57.6 kbps
16.The demodulation of binary ASK wave can be done with the help of ______________ receivers
Answer: Coherent receiver & non coherent receiver
17.The minimum bandwidth of BPSK signal is equal to _________________________________.
Answer: Twice of the highest frequency contained in BBS
18.In 16 PSK the angular separation between adjacent output phases is _____________.
Answer: 22.500
19.In an FSK two sinusoidal waves of the _________ amplitude and ___________ frequencies are used to represent 1 and 0 respectively.
Answer: Same Different
20.If two or more bits are combined in some symbols, then the signaling rate is ________________
Answer: Reduced