Deemed University 2009 A.M.I.E.T.E Electronics & Communication Engineering Digital communications – et (old scheme) - Question Paper

AMIETE – ET (OLD SCHEME)

Code: AE21 Subject: DIGITAL COMMUNICATIONS
Time: three Hours Max. Marks: 100

NOTE: There are nine ques. in all.
· ques. one is compulsory and carries 20 marks. ans to Q. 1. A must be written in the space given for it in the ans book supplied and nowhere else.
· Out of the remaining 8 ques. ans any 5 ques.. every ques. carries 16 marks.
· Any needed data not explicitly given, may be suitably presumed and said.


Q.1 select the accurate or the best option in the following: (210)

a. In an alphabet of symbols, if K = one the system will be termed

(A) quaternary. (B) trinary.
(C) binary. (D) M-ary.

b. A baud limited signal having no spectral components above hertz can be determined uniquely by values sampled at uniform intervals of

(A) . (B) .
(C) . (D) .

c. In the design of corrrelator and matched filter for the baseband demodulation, if the signal waveform is s(t) of duration T sec, then the impulse response of the filter will be

(A) . (B) .
(C) . (D) .

d. In the implementation of a differential 8-PSK (D8PSK) modulator, to every phase we assign a

(A) 2-bit message. (B) 4-bit message.
(C) 3-bit message. (D) 5-bit message.

e. The probability of a bit-error for coherently detected BPSK system, with usual notations is

(A) . (B) .
(C) . (D) .


f. In waveform coding, the redundant bits added to data sequences can be used for

(A) getting a high noise power at the destination.
(B) increasing the probability of a bit fault.
(C) the detection and correction of errors.

Earning:   Approval pending.