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

Tuesday, 30 April 2013 03:15Web

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AMIETE – ET (OLD SCHEME)

Code: AE21 Subject: DIGITAL COMMUNICATIONS

**Time:**three Hours Ma

**x.**

**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

**(**quaternary.

**A)****(**trinary.

**B)****(**binary.

**C)****(**M-ary.

**D)****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

**(**2-bit messag

**A)****e.**

**(**4-bit message.

**B)****(**3-bit messag

**C)****e.**

**(**5-bit message.

**D)****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

**(**getting a high noise power at the destination.

**A)****(**increasing the probability of a bit fault.

**B)****(**the detection and correction of errors.

**C)**Earning: Approval pending. |