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A6802 Pages: 2

APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY
SIXTH SEMESTER B.TECH DEGREE EXAMINATION, APRIL 2018
Course Code: EC302
Course Name: DIGITAL COMMUNICATION (EC)

PARTA
Answer any two full questions, each carries 15 marks.

Define autocorrelation function of random process and explain its properties.

Find power spectral density of the WSS process if its autocorrelation function is given
by

Ry (7) = ‏مه وق ۹ء‎ < 7 > ००.

Explain the need for anti-aliasing filter in a digital communication system.

What is a matched filter? Derive an expression for the impulse response of a matched
filter.

Derive impulse response for Duobinary encoder.

Consider a random process X(t) = Acos(2zf,t+o) where A and fc are constants and 0 is
uniformly distributed over the interval (ர, ஐ). Check whether the given random process
is WSS.

A baseband digital system uses 4-level PAM along with the raised cosine pulse. The
system has a frequency response of 3.2 kHz. If the binary data is transmitted at 9600 bps
data rate, then what would be the symbol rate and roll-off factor of the transmitted pulse
shape for zero ISI?

PART 8
Answer any two full questions, each carries 15 marks.

Given the signals s,(t),s,(t),s,(t) and 8, (1) shown in Figure. Use the Gram-Schmidt
orthogonalization procedure to find an orthonormal basis for the set of following signals:

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Find mean and variance of received signal x(t), if signal si) was transmitted which is
corrupted by AWGN with zero mean such that x(t)= 50 +w(t),where w(t) is AWGN.

Derive an expression for probability of error for BPSK.

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Duration: 3 Hours

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