MATLAB: Does changing the values in the Filter internals pane in the FDATool not affect the displayed step response of the designed filter

fdatoolfilterFilter Design Toolboxinternalsresponse

When using fixed-point arithmetic during filter design with the FDATool, changing Filter Internals does not have an effect on the displayed filter response.

Best Answer

The step response in FDATool does not take into account the specified filter internals.

Additional information has been incorporated into the documentation in Release 2009a (R2009a).

For previous releases, to work around this issue, you can use the FILTER function as follows:

1. Generate a MATLAB file for the filter from the Generate MATLAB file option in the File menu : File --> Generate MATLAB file

2. Save the MATLAB file as filterfile.m or any other valid name of your choice.

3. Use the FILTER command as follows:

CustomFilter= filterfile
plot(filter(CustomFilter, [zeros(1,100) ones(1,100)]))    % Computes and plots step response

Related Solutions

MATLAB: Filter

Code:

   dt = 0.001;         % sampling time (seconds per sample)
   Fs = 1/dt;          % sampling rate (samples per second)
   Fnyq = Fs/2;        % Nyquist frequency (hertz)
   Fco = fm + bw;      % Cut-off frequency (hertz)
   wn = Fco/Fnyq;      % Normalized cut-off (dimensionless)

Explanation:

dt is the sampling time (in seconds per sample)
Fs is the sampling rate (in samples per second)
Fnyq is the Nyquist frequency (in hertz)
Fco is the cutoff frequency (in hertz)
bw = bandwidth (in hertz)
Fc is not needed to compute wn

You should make sure that the following conditions are true:

   bw << fm << fc

and

   bw << fm << Fs

HTH.

Rick

MATLAB: Digital filters

Hi Kim,

Do you have access to the Signal Processing Toolbox in MATLAB? If so, you can use the fdatool to design the filter very easily.

For more information:

doc fdatool