Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!cs.utexas.edu!swrinde!ucsd!ucbvax!hplabs!hpl-opus!hpnmdla!hpsad!toma
From: toma@hpsad.HP.COM (Tom Anderson)
Newsgroups: comp.dsp
Subject: Re: Designing the analog filter adendum
Message-ID: <9520004@hpsad.HP.COM>
Date: 28 Sep 89 21:03:19 GMT
References: <1989Sep27.030845.2927@ivucsb.sba.ca.us>
Organization: HP Signal Analysis Division - Rohnert Park, CA
Lines: 15


> However, we do have a phase problem.  My Chebychev design has a
> phase lag of 180 degrees at 20kHz.  The phase starts taking off
> at about 2kHz.  This is no big deal for me, as I am dealing with
> yucky movie and TV signals, but for those hi-fi nuts who buy
> expensive cable and interconnects, this is bloody murder...

Can't you fix up the phase of the analog anti-aliasing filter with
a digital filter that has flat frequency response and the opposite
phase of the analog filter?  For that matter, maybe you could fix
up the amplitude flatness at the same time.

Tom Anderson       toma@hpsad.hp.com       "Its only hardware"
Hewlett-Packard
Opinions expressed are my own and not Hewlett-Packard's.