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Phase correction techniques

Discussion in 'Electronic Design' started by Klaus Jensen, Feb 4, 2007.

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  1. Klaus Jensen

    Klaus Jensen Guest

    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
  2. I'm not quite sure what "real time phase relationship" means to you,
    will allow you to do basic analogue filter design.

    I assume John Larkin et al will drop in with better suggestions :)

  3. John  Larkin

    John Larkin Guest

    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.

  4. Tim Wescott

    Tim Wescott Guest

    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

    Posting from Google? See

    "Applied Control Theory for Embedded Systems" came out in April.
    See details at
  5. 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

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