Application of the Sptool filter
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Hi all, As a part of my project, i require a lowpass filter of cut off frequency 50 Hz. This I was able to design using the SPTOOL in matlab.The designed filter was an IIR Butterworth filter.My problem is the fact that I want to use the generated filter in my code.Currently, what I do to use the filter is that I import the signal to be filtered from the matlab workspace to sptool, apply the filter to it and export it back to the workspace.However, I dont want the GUI but want that filter to be applied in my code itself.The m file generated contains objects and such which I am not familiar with.The important thing for me right now is how to use the generated m file of the filter on the array .Is it possible to do such a thing?Thanks in advance
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Accepted Answer
Vieniava
on 11 Feb 2011
Your generated mfile suppose to look like this
%UNTITLED Returns a discrete-time filter object.
% M-File generated by MATLAB(R) 7.8 and the Signal Processing Toolbox 6.11.
%
% Generated on: 11-Feb-2011 13:01:59
%
% Butterworth Lowpass filter designed using FDESIGN.LOWPASS.
% All frequency values are in Hz.
Fs = 48000; % Sampling Frequency
Fpass = 9600; % Passband Frequency
Fstop = 12000; % Stopband Frequency
Apass = 1; % Passband Ripple (dB)
Astop = 80; % Stopband Attenuation (dB)
match = 'stopband'; % Band to match exactly
% Construct an FDESIGN object and call its BUTTER method.
h = fdesign.lowpass(Fpass, Fstop, Apass, Astop, Fs);
Hd = design(h, 'butter', 'MatchExactly', match);
% [EOF]
Now you should copy those lines into your script:
Fs = 48000; % Sampling Frequency
Fpass = 9600; % Passband Frequency
Fstop = 12000; % Stopband Frequency
Apass = 1; % Passband Ripple (dB)
Astop = 80; % Stopband Attenuation (dB)
match = 'stopband'; % Band to match exactly
h = fdesign.lowpass(Fpass, Fstop, Apass, Astop, Fs);
Hd = design(h, 'butter', 'MatchExactly', match);
Dont be afraid of objects. Filtering is simple now, you can use Hd filter object whenever you need to filter any signal:
Sfiltered=filter( Hd, S);
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