Highpass Filter does not work

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Michael Werthmann
Michael Werthmann on 28 Feb 2019
Hello,
I meassured a 85 Hz signal with a sampling frequency of 8000 Hz. Now I want to filter out the noise and artifacts below 10 Hz
I created a butter Highpass with designfilt with the following properties:
Samplerate: 1 KHz
Stopband Atten: 60 dB
Passband Edge: 60 Hz
Stopband Edge: 20 Hz
Passband Ripple: 1 dB
This results in the red Spectrum, which represents the filtered...
frequencies.png
Zfilt(1,:) = filter(ans,Zvis(1,:));
Zfilt(2,:) = filter(ans,Zvis(2,:));
%
Zviss=abs(fft(Zvis(1,:))).^2;
Zfilts=abs(fft(Zfilt(1,:))).^2;
%
figure;
f=0:fs/length(Zvis):(length(Zvis)-1)*(fs/length(Zvis));
plot(f,Zviss); hold on;
plot(f,Zfilts,'r');
xlim([1 100]);
Where is my mistake?
Thank You for your help!
Kind Regards
Michael

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