VTU Electronics and Communication Engineering (Semester 5)
Digital Signal Processing
December 2015
Total marks: --
Total time: --
INSTRUCTIONS
(1) Assume appropriate data and state your reasons
(2) Marks are given to the right of every question
(3) Draw neat diagrams wherever necessary


1 (a) Define N-point DFT and IDFT of a sequence.
3 M
1 (b) Find the 8-point DFT of the sequence x(n)= {1, 1, 1, 1, 1, 1, 0, 0}.
8 M
1 (c) Find the IDFT of X(K) = {4, -2j, 0, 2j}.
6 M
1 (d) Obtain the relation between DFT and Z-transform.
3 M

2 (a) State and prove circular convolution property.
6 M
2 (b) For x(n) = {7, 0, 8, 0}, find y(n), if Y(K)= X((K-2)).
6 M
2 (c) Let x(n) = {1, 2, 0, 3, -2, 4, 7, 5}. Evaluate the following: \[ i) \ X(0) \\ ii) X(4) \\ iii) \sum_{K=0} X(K) \\ \sum_{K=0}|X(K)|^2 \]
8 M

3 (a) In the direct computation of N-point DFT of x(n), how many
i) Complex multiplications,
ii) Complex additions
iii) Real multiplications
iv) Real additions and
v) Trigonometric function evaluations are required.
10 M
3 (b) Find the output y(n) of a filter whose impulse response h(n)={1, 2} and input signal x(n)= {1, 2, -1, 2, 3, -2, -3, -1, 1, 1, 2, -1} using overlap save method.
10 M

4 (a) Develop 8-point DIF-FFT radix-2 algorithm and draw the signal flow graph.
10 M
4 (b) Find 8-point DFT of a sequence x(n)= {1, 1, 1, 1, 0, 0, 0, 0} using DIT-FFT radix-2 algorithm. Use butterfly diagram.
10 M

5 (a) Given \( |H_a(j\Omega)|^2 = \dfrac {1}{(1+4\Omega^2)}, \) determine the analog filter system function Ha(s).
8 M
5 (b) Let \( H(s) = \dfrac {1}{(s^2 + \sqrt{2s}+1)} \) respect transfer function of a low pass filter with a pass band 1 rad/sec. Use frequency transformation to find the transfer function of the analog filters.
i) A LPF with pass band of 10 rad/sec.
ii) A HPF with cut-off frequency of 5 rad/sec.
8 M
5 (c) Compare Butterworth and Chebyshev filters.
4 M

6 (a) Realize the FIR filter \( H(z)= \dfrac {1}{2}+ \dfrac {1}{3}z^{-1}+ z^{-2}+ \dfrac {1}{4}z^{-3}+ z^{-4}+ \dfrac {1}{3}z^{-5} + \dfrac {1}{2}z^{-6} \) in direct form.
4 M
6 (b) Obtain direct form-I, direct form-II, cascade and parallel form realization for the following systems: y(n)=0.75 y(n-1)-0.125y(n-2)+6x(n)+7x(n-1)+x(n-2).
16 M

7 (a) A LPF is to be designed with frequency response. \[ H_d(e^{j\omega}) = H_d(\omega) = \left\{\begin{matrix} e^{-j2\omega}& |\omega| < \frac {\pi}{4} \ \ \ \ \ \ \\0, & \frac {\pi}{4} <|\omega|<\pi \end{matrix}\right. \] Determine hd(n) and h(n) if ω(n) is rectangular window, \[ \omega_R(n)= \left\{\begin{matrix} 1 &0\le n \le 4 \\0 & \text {Otherwise} \end{matrix}\right. \] Also, find the frequency response. H(ω) of the resulting FIR filter.
10 M
7 (b) Explain the design of linear phase FIR filter using frequency sampling technique.
10 M

8 (a) Explain the design of IIR filter by using Impulse Invariance Method (IIM) technique also explain mapping of analog to digital filter by IIM.
10 M
8 (b) Convert the analog filter with system function, \( H_a(s)= \dfrac {s+0.1}{(s+0.1)^2+16} \) into a digital IIR filter by means of bilinear transformation (BJT). The digital filter is to have a resonant frequency of \( \omega_r = \dfrac {\pi}{2} \).
10 M



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