Apologies if this is too basic.
I need to implement a band-pass filter, for a realtime system. Not sure what to use. FIR? IIR? Something else ?
Any tips would be highly appreciated.
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1$\begingroup$ What do you mean by real-time? Please provide the maximum allowable delay, sampling frequency, and filter requirements. All these are interdependent. $\endgroup$– JuanchoCommented Dec 27, 2012 at 12:14
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$\begingroup$ Sampling frequency 512Hz. Filter 1Hz-30Hz and as minimum delay as possible. It's EEG data BTW. Thanks @Juancho! $\endgroup$– DovCommented Dec 27, 2012 at 12:59
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1 Answer
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For an EEG signal, I suppose you need to keep the shape of the signal. Therefore the filter should have linear phase, so the reasonable way to go is a FIR filter.
If shape (transients) don't matter much for your application, then an IIR filter would be preferable since it will give less end-to-end delay in general.
Note that suprressing 0 - 1 Hz, inevitably gives a group delay of at least 1 second, depending on how sharp the transition should be, so your real-time requirements may conflict with the start frequency.
You may try some filter design tools (e.g. from matlab) to find a reasonable compromise between frequency response and group delay.
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$\begingroup$ Could you please elaborate a bit about the "group delay problem" you have mentioned, not 100% sure why it's happened (I Probably missing something very basic ) Thanks this is all very helpful! $\endgroup$– DovCommented Dec 27, 2012 at 22:46
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$\begingroup$ Could you please elaborate a bit about the "group delay problem" you have mentioned, not 100% sure why it's happened (I Probably missing something very basic ) Thanks this is all very helpful! $\endgroup$– DovCommented Dec 28, 2012 at 10:29