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Help with FFT and wvtool

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Leor Greenberger
Leor Greenberger on 9 Mar 2013
Hi All,
I am stumped on this one. I created a filter and used wvtool on it.
w_k = kaiser(K,9.5*pi);
wvtool(w_k)
I then set the analysis parameters as follows:
And I get the plot shown below. I have tried every which way to recreate this myself so that I can calculate the main lobe width of various filters to no avail. Ideally, I want the magnitude normalized and response in dB (see first image), but when I couldn't get those plots, I tried to just copy what I have pasted here. My code is as follows (although I have tried many variations of normalizing the FFT to no avail):
K = 512;
Fs = 1E6;
w_k = kaiser(K,9.5*pi);
W_n = fft(w_k,K);
W_n = W_n(1:K/2+1);
W_n = abs(W_n);
W_n = 2*W_n;
n = 0:1:K/2;
freq_n = Fs*n/K;
figure
plot(freq_n/1E6,W_n);
Thanks for the help!
  3 Comments
Leor Greenberger
Leor Greenberger on 11 Mar 2013
Hi Honglei,
I am not sure what the time domain plot is based on, but I set 512 points in the FFT, as shown in the first image, and this is the length I am using in the script.

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