I am monitoring, in real time, geophysical signals related to earthquake prediction. To isolate the frequencies of concern, it is heavily filtered with 60Hz notch and 150Hz low pass.
It is now required that the frequency components within the filtered signal (1-30Hz) be returned to a real time phase relationship with the monitored signal.
Can anyone please advise what might be the most practical design method for achieving this?
Thanking you kindly,
Klaus Jensen
I'm not quite sure what "real time phase relationship" means to you, but
I assume John Larkin et al will drop in with better suggestions :)
martin
Well, if one could characterize the phase-frequency behavior of the filters, then one (same guy, even) could FFT the data, muck the real and imaginary line pairs appropriately, and reverse transform it. That wouldn't be real hard.
John
Are you digitizing this data? If so, I'd plot out the phase variations of your filters then make a nice long FIR allpass filter to correct them. You could even correct for the beginnings of the amplitude rolloff of the notch and the lowpass, if you were feeling frisky.
As long as your filter characteristics stayed pretty constant, this should work just fine at lining all the phases up.
-- Tim Wescott Wescott Design Services http://www.wescottdesign.com Posting from Google? See http://cfaj.freeshell.org/google/ "Applied Control Theory for Embedded Systems" came out in April. See details at http://www.wescottdesign.com/actfes/actfes.html
Just stepping back a bit, I would try and get rid of the interference in the first place. Maybe the OP could tel us more about the interface
martin
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