MATLAB: Error with using filter

Question

Hi all,

I have to filter few signals and I wrote the following code:

Fpass = 40;   % Passband Frequency
Fstop = 45;   % Stopband Frequency
Apass = 1;    % Passband Ripple (dB)
Astop = 80;   % Stopband Attenuation (dB)
Fs    = 100;  % Sampling Frequency
h = fdesign.lowpass('Fp,Fst,Ap,Ast', Fpass, Fstop, Apass, Astop, Fs);
Hd = design(h, 'butter','MatchExactly', 'stopband','SystemObject', true);
a=rand(1000,1);
a=filter(Hd,a);

I get the following error:

Undefined function 'filter' for input arguments of type 'dsp.BiquadFilter'.

Why do I get that error?

Thanks

Regards

Pietro

Answer 1

dsp.BiquadFilter is a System object, so its main method is step(). Try

a = step(Hd,a)