Hello everyone,
I designed a Bandpass Filter using the filterDesigner app. It is an 18th order IIR filter.
Then I export the filter both as df2sos object and "SOS and G" matrices.
Afterwards, I try filtering my data with:
y = filtfilt(Hd,x);
It gives the error: Not enough input arguments.
Well. Why don’t I use:
y = filtfilt(Hd.sosMatrix,Hd.scaleValues,x);
% or
y = filtfilt(SOS,G,x);
These do not work for my filter; they result in unstable filters. Even though my originally designed filter is stable, they give unstable results. Here is the MATLAB page for this issue.
So, how to use FiltFilt function with my df2sos object or my "SOS and G" matrices, without getting an unstable result? I’d really appreaciate some help.
Regards,
Berk

Additional Details:
Here is the code to generate my filter object:
Fstop1 = 0.0001; % First Stopband Frequency
Fpass1 = 0.0004; % First Passband Frequency
Fpass2 = 0.08; % Second Passband Frequency
Fstop2 = 0.12; % Second Stopband Frequency
Astop1 = 50; % First Stopband Attenuation (dB)
Apass = 0.5; % Passband Ripple (dB)
Astop2 = 50; % Second Stopband Attenuation (dB)

h = fdesign.bandpass(‘fst1,fp1,fp2,fst2,ast1,ap,ast2’, Fstop1, Fpass1, …
Fpass2, Fstop2, Astop1, Apass, Astop2);

Hd = designfilt(h, ‘cheby2’, …
‘MatchExactly’, ‘stopband’, …
‘SystemObject’, true);
and the screenshot from the filterDesigner app:Hello everyone,
I designed a Bandpass Filter using the filterDesigner app. It is an 18th order IIR filter.
Then I export the filter both as df2sos object and "SOS and G" matrices.
Afterwards, I try filtering my data with:
y = filtfilt(Hd,x);
It gives the error: Not enough input arguments.
Well. Why don’t I use:
y = filtfilt(Hd.sosMatrix,Hd.scaleValues,x);
% or
y = filtfilt(SOS,G,x);
These do not work for my filter; they result in unstable filters. Even though my originally designed filter is stable, they give unstable results. Here is the MATLAB page for this issue.
So, how to use FiltFilt function with my df2sos object or my "SOS and G" matrices, without getting an unstable result? I’d really appreaciate some help.
Regards,
Berk

Additional Details:
Here is the code to generate my filter object:
Fstop1 = 0.0001; % First Stopband Frequency
Fpass1 = 0.0004; % First Passband Frequency
Fpass2 = 0.08; % Second Passband Frequency
Fstop2 = 0.12; % Second Stopband Frequency
Astop1 = 50; % First Stopband Attenuation (dB)
Apass = 0.5; % Passband Ripple (dB)
Astop2 = 50; % Second Stopband Attenuation (dB)

h = fdesign.bandpass(‘fst1,fp1,fp2,fst2,ast1,ap,ast2’, Fstop1, Fpass1, …
Fpass2, Fstop2, Astop1, Apass, Astop2);

Hd = designfilt(h, ‘cheby2’, …
‘MatchExactly’, ‘stopband’, …
‘SystemObject’, true);
and the screenshot from the filterDesigner app: Hello everyone,
I designed a Bandpass Filter using the filterDesigner app. It is an 18th order IIR filter.
Then I export the filter both as df2sos object and "SOS and G" matrices.
Afterwards, I try filtering my data with:
y = filtfilt(Hd,x);
It gives the error: Not enough input arguments.
Well. Why don’t I use:
y = filtfilt(Hd.sosMatrix,Hd.scaleValues,x);
% or
y = filtfilt(SOS,G,x);
These do not work for my filter; they result in unstable filters. Even though my originally designed filter is stable, they give unstable results. Here is the MATLAB page for this issue.
So, how to use FiltFilt function with my df2sos object or my "SOS and G" matrices, without getting an unstable result? I’d really appreaciate some help.
Regards,
Berk

Additional Details:
Here is the code to generate my filter object:
Fstop1 = 0.0001; % First Stopband Frequency
Fpass1 = 0.0004; % First Passband Frequency
Fpass2 = 0.08; % Second Passband Frequency
Fstop2 = 0.12; % Second Stopband Frequency
Astop1 = 50; % First Stopband Attenuation (dB)
Apass = 0.5; % Passband Ripple (dB)
Astop2 = 50; % Second Stopband Attenuation (dB)

h = fdesign.bandpass(‘fst1,fp1,fp2,fst2,ast1,ap,ast2’, Fstop1, Fpass1, …
Fpass2, Fstop2, Astop1, Apass, Astop2);

Hd = designfilt(h, ‘cheby2’, …
‘MatchExactly’, ‘stopband’, …
‘SystemObject’, true);
and the screenshot from the filterDesigner app: filterdesigner, signalprocessingtoolbox, filtfilt, filter, unstable, df2sos, iir filter, sos g MATLAB Answers — New Questions

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