MATLAB: Difference between fvtool and freqz

filterfreqzfvtool

Hi,
I am currently using a few notch filters, however a lot of the time I notice different results depending on if I am using freqz or fvtool to plot (eg. the magnitude of fvtool is 10 times or twice that of freqz), I don't seem to understand what is wrong with my code, or if there is any difference between how the magnitude is calculated. code: %======================
close all;
clear all;
wo = 60/(1000/2); bw = wo/35;
[b,a] = iirnotch(wo,bw);
fvtool(b, a);
freqz(b, a);
%======================
Thank you.

Best Answer

There is really not much difference between the two. If you are referring to the differences between the null depths, it is because the two use different default values of FFT points. The default of freqz is a 512-point FFT while for fvtool, it's 8192 points. If you use
freqz(b,a,8192)
You should see similar results.
HTH
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