[Eeglablist] Plugins and bandpass FIR filtering

Brahim HAMADICHAREF bhamadicharef at plymouth.ac.uk
Mon Apr 25 09:36:48 PDT 2005


Hi all,

I also experienced same problems with MATLAB SP2 (version 7.0.4)
but have not managed to find out where the problems comes from.

For the IIR filter design and phase problems ...
Use MATLAB Signal Processing Toolbox with the function
filtfilt for "Zero-phase digital filtering"

"y = filtfilt(b,a,x) performs zero-phase digital filtering by processing
the input data in both the forward and reverse directions. After filtering
in the forward direction, it reverses the filtered sequence and runs it back
through the filter. The resulting sequence has precisely zero-phase distortion
and double the filter order. filtfilt minimizes start-up and ending transients
by matching initial conditions, and works for both real and complex inputs."

Maybe the IIR filtering plugin could be modified to incorporate such method.

For the FIR filter design... you can use the function "firpm" which is the
Parks-McClellan optimal FIR filter design (also called remez) to first
estimate the minimal order of the filter from your specs and then calculate
the coefficients. I have emailed Andreas an example and can give to anyone
by email request.

Best regards

Brahim HAMADICHAREF
Signal Processing and Multimedia Communications research Group
Plymouth, Devon, UK
http://www.tech.plym.ac.uk/spmc/





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