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Homework Help: Signal Processing help

  1. Nov 2, 2012 #1
    1. The problem statement, all variables and given/known data

    1. We need to design a low pass analog filter using any one of the MATLAB routines: buttap,cheb1ap, cheb2ap,ellipap. Find analog filter's poles, zeros, and gain. Which would be the best to use and why?

    2. Design a digital IIR from the analog filter with the following specs : Pass-band ripple : +/-0.005, Lower pass-band cutoff freq. : 0.115, upper pass-band cutoff freq : 0.325, stop-band ripple : -42 dB, lower stop-band cutoff frequency : 0.082, upper stop-band cutoff frequency : 0.365. I have to use bilinear or spectral transformations - I have to create my own module for this not use the MATLAB routines.

    3. We have been given a specbox.m routine and we have to use THAT to see if the specifications given are satisfied.

    4. We are given a wave file P.wav, we need to use "filter" MATLAB function to test the filter we made. After filtering we need to make "frequency related observations" after listening to the filtered sound. I have no idea how I am going to do that.

    5. Convert my filter into a cascade by using zp2sos and repeat filtering the sound by creating a module that implements the fundamental (direct 1) signal flow graph implementation. Then what are the observations? I need to observe:

    A. Do the two filtered signals sound differently?
    B. What additional test would I need to use to verify the correct functionality of my filter?

    6. I need to find the "unit pulse response" of the system by designing appropriate input/output test - comment on WHY I used this method, its advantages and disadvantages.

    2. Relevant equations

    function specbox(x1,x2,y1,y2,RGB)

    % specbox(x1,x2,y1,y2,RGB)
    % draws an RGB colored box using the given coordinates
    % in the current figure
    % RGB is a vector [r g b] with 3 values between 0 and 1
    line(x1*[1 1],[y1 y2],'Color',RGB);
    line(x2*[1 1],[y1 y2],'Color',RGB);
    line([x1 x2],y1*[1 1],'Color',RGB);
    line([x1 x2],y2*[1 1],'Color',RGB);

    3. The attempt at a solution

    I am using MATLAB for the first time in my life. And the previous project on this same subject I got very low grade. I haven't used any of the functions and I have trouble using them (I will try and find out though), but if anyone can help me it would be great. Thanks :) I think the first part - creating the analog filter is straightforward.

    Particularly, I don't know how to use modules and all, and I am trying to learn but given the way specbox.m has been defined to us, how would I go about verifying the given specs for the filter using that? (question 3). And the second major difficulty I think would be choosing a test to find my unit impulse response (question 6)
    Last edited: Nov 3, 2012
  2. jcsd
  3. Nov 3, 2012 #2
    The buttap routine only allows me to put the order in the input arguments, how do I deal with the rest of the parameters?
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