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How does modwpt details provide zero phase filtering ?

Asked by HIMANSHU SANDHIBIGRAHA on 17 May 2018
Latest activity Answered by Wayne King
on 28 May 2018
I have used MODWPT for getting the wavelet coefficients for a given signal. But the resulting coefficients are shifted by some phase difference. Rather than that by using MODWPT details I am getting zero phase filtering. How does this result in zero phase difference? What are the changes in filter coefficients inorder to get this result?

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1 Answer

Answer by Wayne King
on 28 May 2018

MODWPTDETAILS actually projects the signal onto the various wavelet packet subspaces, that is what provides the zero-phase filtering because you are using not only the analysis filters but also the synthesis filters. MODWPT does have a time-aligned option that will provide an approximation to this using just the analysis filters (coefficients), but it is not exact like MODWPTDETAILS. The MODWPT with time-aligned does have the advantage of still conserving the signal energy though. The similarity between MODWPT and MODWPTDETAILS is analogous to MODWT and MODWTMRA.

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