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APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY
SIXTH SEMESTER B.TECH DEGREE EXAMINATION(R&S), MAY 2019

Course Code: EC302

Course Name: Digital Communication

PARTA
Answer any two full questions, each carries 15 marks

Prove that sampled signal can be reconstructed by passing the samples through a
low pass filter.

If X(t) is a random process with mean 3 and autocorrelation of 9+4e°7*. Find the
mean square value of the random process X(t).

Determine the Nyquist rate and Nyquist sampling interval for the signal,

8)8 = sinc? 100६

Derive the impulse response and frequency response of modified duobinary
encoder.

A signal g(t) = 2௦08 400zt + 6cos 640zt is ideally sampled at f, = 500 Hz. If the

sampled signal is passed through an ideal LPF with a cut-off frequency of 400 Hz,
what frequency components will appear in the filter output?

Explain different line coding schemes with neat sketches.

What is raised cosine spectrum?

A sinusoidal voice signal g(t)=cos6000zt is to be transmitted using either
PCM or DM. The sampling rate for PCM is 8 kHz and for transmission with
DM, the step size is decided to be 31.25 mV. The slope overload distortion
is to be avoided in DM. Assuming that the number of quantization levels
for the PCM system is 64. Determine the bit rate. Which scheme is to be
chosen for this application, PCM or DM?

Explain the distortions associated with Delta modulation.

PART छ
Answer any two full questions, each carries 15 marks

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Duration: 3 Hours

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