RE: Help-octave Digest, Vol 43, Issue 52

[dastew]

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Date: Mon, 26 Oct 2009 10:24:22 +0530
Subject: Re: Help-octave Digest, Vol 43, Issue 52
From: address@hidden
To: address@hidden


Hi all,
          I am trying to use the butterworth filter.  After filtering the signal I feel there is a slight phase shift.  HOw can this be removed?.

There IS going to be a phase shift. All filters ( That I know.) have a phase shift, and unless you have a FIR filter they will all produce some phase distortion. That is -- Different frequencies have a different phase shift. So if different frequencies have a different time delay going through your filter then you will  have a hard time removing the phase shift. If you have only one frequency going through the filter then it is possible to compensate for the delay-- just change your time reference.
 


 Also how to specify the order of the filter.
eg; butter(1,fc/nysq) , does this mean a first order butterworth filter?.


Yes
and
butter(5,fc/nysq)     this is a 5th order filter.

You owe me a virtual coffee also :-)

Doug Stewart

 
Thanks and regards




--
Nuncio.M
Research Scientist
National Center for Antarctic and Ocean research
Head land Sada
Vasco da Gamma
Goa-403804