Thread View: comp.dsp
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Started by Todd Day
Wed, 27 Sep 1989 03:08
Designing the analog filter adendum
Author: Todd Day
Date: Wed, 27 Sep 1989 03:08
Date: Wed, 27 Sep 1989 03:08
16 lines
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1242 bytes
I forgot to mention what analog filter I chose and why. I chose Chebychev because it has no ripple in the passband and takes half as many poles as the Butterworth. Each complex pole pair can be done with one op-amp, so the fewer pairs, the better. 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... -- Todd Day | todd@ivucsb.sba.ca.us | ivucsb!todd@anise.acc.com "Ya know, some day these scientists are going to invent something that can outsmart a rabbit" -- Bugs Bunny
Re: Designing the analog filter adendum
Author: Tom Anderson
Date: Thu, 28 Sep 1989 21:03
Date: Thu, 28 Sep 1989 21:03
15 lines
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> 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.
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