Digital Communication MCQ Questions & Answers

11

A coherent binary phase-shift keyed (BPSK) transmitter operates at a bit rate of 20 Mbps. For a probability of error (P_e) of 10^-4 and given carrier-to-noise $$\left( {\frac{{\text{C}}}{{\text{N}}}} \right)$$ density ratio of 8.8 dB, determine energy of bit-to-noise $$\left( {\frac{{{{\text{E}}_{\text{b}}}}}{{{{\text{N}}_0}}}} \right)$$ density ratio for a receiver bandwidth equal to the minimum double-sided Nyquist bandwidth.

A) 23 dB B) 2.3 dB C) 8.8 dB D) 0.88 dB

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Answer & Solution

Answer: Option C

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12

In . . . . . . . . the position of a pulse relative to its unmodulated time of occurrence is varied in accordance with the message signal.

A) PWM B) PCM C) PDM D) PPM

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Answer & Solution

Answer: Option D

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13

An analog signal has significant spectral components from 1 kHz to 5 kHz. What is the Nyquist sampling rate of this signal?

A) 5 k samples/s B) 4 k samples/s C) 8 k samples/s D) 10 k samples/s

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Answer & Solution

Answer: Option D

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14

In PCM if the transmission path is very long

A) repeater stations are used B) pulse width may be increased C) pulse amplitude is increased D) pulse spacing is reduced

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Answer & Solution

Answer: Option A

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15

Which of the following modulation schemes gives the maximum probability of error?

A) ASK B) BFSK C) DBPSK D) PSK

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Answer & Solution

Answer: Option A

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16

In QPSK the average probability of bit error in AWGN channel is obtained as

A) $${P_{eQPSK}} = Q\left[ {\sqrt {\frac{{2{E_b}}}{{{N_o}}}} } \right]$$ B) $${P_{eQPSK}} = {Q^2}\left[ {\sqrt {\frac{{2{E_b}}}{{{N_o}}}} } \right]$$ C) $${P_{eQPSK}} = Q\left[ {\sqrt {\frac{{{E_b}}}{{{N_o}}}} } \right]$$ D) $${P_{eQPSK}} = Q\left[ {\frac{1}{2}\sqrt {\frac{{2{E_b}}}{{{N_o}}}} } \right]$$

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Answer & Solution

Answer: Option A

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17

A signal x(t) = 100cos(24π × 10³)t is ideally sampled with a sampling period of 50 µsec and then passed through an ideal lowpass filter with cutoff frequency of 15 kHz. Which of the following frequencies is/are present at the filter output?

A) 12 kHz only B) 8 kHz only C) 12 kHz and 9 kHz D) 12 kHz and 8 kHz

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Answer & Solution

Answer: Option D

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18

In a M-ary PSK digital communication system, it is required to transmit the data with 80 Mbps bit rate within maximum allowable channel bandwidth of 16 MHz. The value of M is

A) 1024 B) 256 C) 512 D) 2048

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Answer & Solution

Answer: Option A

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19

To overcome slope overload problem which type of integrator is used in delta modulation?

A) Fixed slope integrator B) Variable slope integrator C) Linear slope integrator D) Bipolar integrator

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Answer & Solution

Answer: Option B

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20

A comparison of frequency division and time division multiplexing system shows that

A) FDM requires a lower bandwidth, but TDM has greater noise immunity B) FDM has greater noise immunity and requires lower bandwidth than TDM C) FDM requires channel synchronization, while TDM has greater noise immunity D) FDM requires more multiplexing while TDM requires band pass filter

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Answer & Solution

Answer: Option C

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Digital Communication MCQ Questions & Answers | ECE