How to get bode diagram from slx model.
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How to get the bode diagram of digital filter like a FIR LPF designed by Fdatool. That is written in M-file. X axis unit is Hz, not rad/s. Please show me its M file.
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Eeshan Mitra
on 24 Aug 2017
The frequency response of a digital filter can be plotted using the "freqz" function in the Control System Toolbox.
Lets assume that a low-pass FIR filter is designed in the following manner with the following parameters in fdatool:
Filter Order: Minimum order
Fs = 1000 Hz
Fpass = 200 Hz
Fstop = 250 Hz
Apass = 1 dB
Astop =40 dB
The designed filter is then exported to the MATLAB Workspace as a filter object named 'Hd'.
The frequency response can be visualized by typing the following at the Command Window:
>> freqz(Hd)
Alternately if you want to plot the phase and magnitude separately, you can use output arguments with "freqz" to assign the frequency vector and the response for a specific sample frequency. For example:
>> fs = 1000;
>> [h,f] = freqz(Hd,501,fs); % 501 points
>> figure
>> subplot (2,1,1)
>> semilogx(f,20*log10(abs(h)))
>> subplot (2,1,2)
>> semilogx(f,angle(h))
3 Comments
Eeshan Mitra
on 25 Aug 2017
On second thoughts magnitude response should be represented as real(h) rather than abs(h)
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