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Digital Gommunication Max. Marks:100

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Time: 3 hrs.

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PART

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Note: Answer FIVE fwll questions, selecting at least TWO questions.from euch purt"

A

Explain sampling theorem of low pass signals and derive the interpolation formuia"

(08 Marks)

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be recovered.

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c. d band pass signal g(t) with a specirum shown in Fig.Ql(c) is idealtry sampled. Si
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Derive the expression for signal to quantization noise ratio (SNR) and show that for uniform (08 Marksi quantization, each bit in the codeword of a PCM contributes 6 dB to SNR. : For a binary PCM signal, determine L if the compression parameter pr 100 and the (06 Marks) minimum ISNR]6 dB : 45 dB. Deterrnine the ISNR]g dB wittri this value of L" With a neat block diagram and waveform, explain time division multiplexing. (05 Marks)

a.

b.

of delta modulator. With relevant flgure and rnathematical (08 Marks) expressions, explain the functioning of DM transmitter and recetver. For a binary sequence i 1100011010i draw the digital format waveforms corresponding to: (06 Marks) i) Bipolar NRZ waveform and ii) 8-ary signaling waveform. plot the sarne Derive an expression for power spectral density of bipolar l{RZ format and (05 Nlarks) with respect to &equency. Explain the principies

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(86 Marks)

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X(f) given by,

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pass signal x(t) has spectrum

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What is correlative coding? Explain duo binary coding with and without precoding. (08 Marks) The binary data 011100101 are applied to the input of a rnodified duo binary system: i) Construct the modified duo binary coder output and corresponding receiirer output without a precoder. i, Suppose that due to error in transmission, the level produced by the tirird digit is reduced ta zero. Construct a new receiver output. {07 Marks) (05 Nlarks) With a neat block diagram, explain the concept of adaptive equalization.

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5a. b.

PART _ B With neat block diagram, explain DPSK transmitter and receiver. Illustrate the generation of differentially encoded sequence for the binary input sequence 00100110011110. (12 Marks) A binary data is transmitted over an AWGN channel using binary phase shift keying at the rate

of 1 Mbps. it is desired to have

average probability

of error P. s i0-4. Noise power

Write

a note on Gram-Schmidt orthogonalizatronprocedure.

(08 Marks)

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6 a. b"

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spectral density is Noz : 19-12 WlHz. Determine the average carrier power required at the receiver input, if the detector is of coherent type. Take erfc(3.5) : 0.00025. (08 Marks)

Consrder the signal sr(t), s2(t), s3(t) and s4(t) as given below in Fig.Q6(b).

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Fig.Q6(b) Find an ofihonormatr basis for these set of signals using Gram-Schmidt orthogonahzation procedure. (12 Marks)

b"

Draw and explain the block diagram of correlation receiver. Show that the probability of bit error of a matched

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are they classified? Explain properties of PN sequence. A slow FF{/MFSK system has the following parameters: The number of bits/MFSK symbol :4 The number of MFSK symbols per hop : 6 Calculate processing gain of the system.

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Wrat is spread spectrum technique? F{ow

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(08 Marks)

filter receiver is given

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