JNTU
JNTU B.Tech III DIGITAL SIGNAL PROCESSING Previous Question Paper (November/December - 2017 - R13)
Part A is compulsory which carries 25 marks. Answer all questions in Part A. Part B consists of 5 Units. Answer any one full question from each unit. Each question carries 10 marks.
Part A
Discuss the stability criterion for digital filter.
Answer
A linear time-invariant (LTI) digital filter is stable if its impulse response h(n) is absolutely summable, i.e., Σ|h(n)| < ∞. In terms of the Z-transform, this requires that all poles of the system function H(z) must lie strictly inside the unit circle in the z-plane (|z| < 1).
Explain region of convergence and its properties.
Answer
The Region of Convergence (ROC) is the set of all values of z for which the Z-transform of a sequence converges. Properties include: 1) The ROC is a ring or disk centered at the origin in the z-plane. 2) The ROC contains no poles. 3) For a finite-duration sequence, the ROC is the entire z-plane (except possibly z=0 or z=∞). 4) For a right-sided sequence, the ROC extends outward from the outermost pole. 5) For a left-sided sequence, the ROC extends inward from the innermost pole.
What is zero padding? What are its uses?
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Differentiate between Decimation-in-time and Decimation-in-frequency.
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Why is the Butterworth response called a maximally flat response?
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What is warping effect? What is its effect on magnitude and phase response?
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What is Gibbs phenomenon?
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Explain the procedure for designing FIR filters using windows.
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What is overflow oscillations?
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What is the need for anti-aliasing filter prior to down sampling?
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Part B
Explain the method of obtaining the frequency response of linear shift invariant systems.
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For the following discrete time signals, determine whether or not the system is linear, shift invariant, causal and stable: (i) y(n)=x(n+7) (ii) y(n)= x^3(n)
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Derive the relationship between impulse response and frequency response of a discrete time system.
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Draw the structures of cascade realization of H(z) = [1 - z^-1] / [(1 - 0.5z^-1)(1 - 0.125z^-1)].
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Determine the 8 point DFT of the sequence.
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Compare overlap-save method and overlap-add method.
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What are the advantages of FFT over DFT?
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Compute the FFT for the sequence x(n) = n^2 + 1 where N=8 using DIT algorithm.
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What are the steps to design an analog Chebyshev low pass filter?
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Apply bilinear transformation to H(s) = 2/{(s+1)(s+2)} with T=1 Sec and find H(z).
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Design a digital Butterworth filter that satisfies the following constraint using bilinear transformation. Assume T=1sec: 0.9 ≤ |H(e^jw)| ≤ 1 for 0 ≤ w ≤ π/2; |H(e^jw)| ≤ 0.2 for 3π/2 ≤ w ≤ π.
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Using a rectangular window technique, design a low pass filter with pass band gain of unity, cut-off frequency of 1000Hz and working at a sampling frequency of 5 KHz. The length of the impulse response should be 7.
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What is the necessary and sufficient condition for linear phase Characteristics in FIR filter?
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What is a Kaiser window? Explain the design of a FIR filter using Kaiser window.
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What are "decimation", "decimation factor" and "down sampling"?
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The sequence x(n) = [0,3,6,9] is interpolated using interpolation sequence bk=[1/3,2/3,1,2/3,1/3] and the interpolation factor of 3. Find the interpolated sequence y(m).
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What are the effects of finite word length in digital filters?
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Explain limit cycles in recursive structures.
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