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Digital filters in signal processing

Waldmann thinklab at rummelplatz.uni-mannheim.de
Mon Sep 5 01:14:36 EST 1994

Hello out there !

Preparing for a doctoration thesis on event related brain potentials
evoked from the lower gastrointestinal system, I'm about to leave the
stage of paper-pencil solutions. I will have to evaluate the relative
merits of digital filter methods, but actually I'm a psychologist and
not much of a programmer. That's why I'm looking for your advice.

ERP waveforms are most frequently modeled as a determistic signal
plus (independent) random noise. Filters are used to improve the 
signal-to-noise ratio prior to feature extraction and interpretation,
they can be formulated equivalently in both time and frequency domain
of time series analysis. Common methods are conventional ensemble
averaging, minimum mean square error filters, cross-correlation based
filtering / latency correction, and time-varying filters. There seems 
to be kind of trade-off between restrictiveness in assumptions and 
computational nicety. It's not the understanding of these methods but 
their realization that my problem lies with. I've heard that some 
toolkits for actually designing and implementing digital filters are 
available from the Digital Signal Processing Committee of the IEEE 
(1979), but I feel that I should not rely on my poor understanding of 
algorithms and their derivation alone. So I'd like to ask:

    *  Are their any software packages or stand-alone solutions
       that can be recommended for biosignal processing, perhaps
       with an emphasis to EEG / ERP filtering ? I understand 
       the basics of C / C++ and I'm ready to learn.
    *  Is there someone experienced in the realization and validation
       of the methods cited who will be so kind to give some hints ? 
    *  Maybe there is some researchers' group that wants to establish
       a regular exchange-of-ideas via Usenet/Internet. I'm currently
       working in the Laboratory for Clinical Psychophysiology (Otto-
       Selz-Institute) at the University of Mannheim, Germany.  

If you want to support me with your advice or have any suggestions as 
regards alternative methods (I'm also thinking about neural nets in this 
context, reconceiving a filter's job as sort of pattern recognition), 
please post to the current newsgroup or send (e)mail to

    Hans-Christian Waldmann   |   internet:         
    Falkenstr. 21 A           |  
    68307 Mannheim            |   thinklab at rummelplatz.uni-mannheim.de   
    Germany                   |

                 --  THANK YOU IN ADVANCE  --

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