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Quiz Questions Pool for Week 9


Q1. Consider the following second order FIR filter with the two zeros on the unit circle as shown below.

Quiz9Q1.jpg

The transfer function for this filter is given by $ H(z) = (1-e^{j\theta}z^{-1})(1-e^{-j\theta}z^{-1})=1-2\cos(\theta)z^{-1}+z^{-2} $

a. Find the difference equation of this filter.
b. Find the frequency response $ H(w) $ by the following two approaches:
i. apply the input $ e^{jwn} $ to the difference equation describing the system,
ii. find the DTFT of the impulse response,
and verify that both methods lead to the same result.
c. Find the response of this system to the input
$ x[n]=\left\{ \begin{array}{rl} 1, & \text{ if }n=-2,\\ 1, & \text{ if }n=0,\\ 1, & \text{ if }n=2,\\ 0, & \text{ else. } \end{array} \right. $
d. Is this filter a lowpass, highpass, bandpass or a bandstop filter?
e. An interference signal modulated at 2kHz and sampled at 8kHz is being inputted to this system and you want to eliminate this interference. What must be the value of $ \theta $ to eliminate this signal?

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