Digital Communication - Study Mode

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[#101] The Nyquist sampling rate for the signal $$sleft( t
ight) = frac{{sin left( {500pi t}
ight)}}{{pi t}} imes frac{{sin left( {700pi t}
ight)}}{{pi t}}$$ xa0 xa0xa0 is given by

(A) 400 Hz

(B) 600 Hz

(C) 1200 Hz

(D) 1400 Hz

Correct Answer

(C) 1200 Hz

[#102] The bit rate of digital communication system is R kbits/s. The modulation used is 32-QAM. The minimum bandwidth required for |S| free transmission is

(A) $$frac{R}{{10}}Hz$$

(B) $$frac{R}{{10}}kHz$$

(C) $$frac{R}{5}Hz$$

(D) $$frac{R}{5}kHz$$

Correct Answer

(B) $$frac{R}{{10}}kHz$$

[#103] Consider a binary digital communication system with equally likely 0's and 1's. When binary 0 is transmitted the detector input can lie between the levels -0.25 V and +0.25 V with equal probability: when binary 1 is transmitted, the voltage at the detector can have any value between 0 and 1 V with equal probability. If the detector has a threshold of 0.2 V (i.e., if the received signal is greater than 0.2 V, the bit is taken as 1), the average bit error bit error probability is

(A) 0.15

(B) 0.2

(C) 0.05

(D) 0.5

Correct Answer

(A) 0.15

[#104] Which of the following is worst affected by Noise?

(A) PPM

(B) PCM

(C) PWM

(D) PAM

Correct Answer

(D) PAM

[#105] Which type of encoding is used in USB?

(A) NRZ

(B) RZ

(C) Manchester Encoding

(D) NRZI with bit stuffing

Correct Answer

(D) NRZI with bit stuffing