54118-mt----advanced Digital Signal Processing

NR

Code No: 54118/MT M.Tech. – I Semester Supplementary Examinations, September, 2008

ADVANCED DIGITAL SIGNAL PROCESSING (Common to Digital Electronics & Communication Systems/ Wireless & Mobile Communication) Time: 3hours

1.a) b) c)

Max. Marks:60

Answer any FIVE questions All questions carry equal marks --Prove the circular convolution property of DFT. Explain how DFT is used for linear FIR filtering a long sequence. The exponential signal: X a (t ) = e −t t ≥ 0 t<0 0 is sampled at the rate Fs=20 samples per second and a block of 100 samples is used to estimate its spectrum. Determine the spectral characteristics of the signal Xa(t) by computing the DFT of the finite duration sequence.

2.a)

b) 3.a)

Compute the eight point DFT of the sequence 1 1 1 1  x(n) =  , , , , 0, 0, 0, 0,  2 2 2 2  using the in-place radix-2 decimation-in-time. Explain how chirp-z transform is used to compute the DFT of signals. Determine the system function H(z) of the lowest-order chebysheu digital filter that meets the following specifications: i) 1-dB ripple in the pass band 0 ≤ W ≤ 0, 3 π . ii)

b) 4.a) b)

At least 60 dB attenuation in the stop band 0.35 π ≤ W ≤ π use

the bilinear transformation. Draw and explain the lattice structure for an all-pole IIR system. Explain the design of digital FIR filter band in wiener filter method. 1 1 1 Given a three-stage lattice filter with coefficients k1 = , k2 = , k3 = , 4 4 3 determine the FIR filter coefficients for the direct form structure. Contd…2.,

Code No: 54118/MT

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5.a) b)

Explain the method of reducing sampling rate by a factor D. Explain how the polyphase filters are used in Interpolation?

6.a)

What is the need for spectral estimation? What are the limitations of non-parametric methods in spectral estimation? Determine the power spectra for the random processes generated by x(n)=w(n)-x(n-2) Where w(n) is a white noise process with variance σ 2 .

b)

7.a) b)

Explain the power spectrum estimation using Burg method. Explain how AR Parameters are obtained by using linear prediction.

8.a)

What is the need for quantisation? Obtain an expression for the variance of the round-off quantization noise. Explain the effect of finite word length in FIR digital filters.

b)

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