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From: karn@ka9q.bellcore.com (Phil Karn)
Newsgroups: rec.ham-radio,sci.electronics
Subject: Re: Hilbert filters
Message-ID: <13547@bellcore.bellcore.com>
Date: 20 Jan 89 07:10:21 GMT
References: <1078@ns.UUCP>
Sender: news@bellcore.bellcore.com
Reply-To: karn@ka9q.bellcore.com (Phil Karn)
Organization: Secular Humanists for No-Code
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>Okay, so what does a Hilbert transform look like?

Because a Hilbert Transformer is not a linear-phase device, by far the
easiest way to build one in DSP is with a FIR (finite impulse reponse)
filter. Just load up the coefficients in a table and run through them like
any other FIR filter. Any of several standard texts on DSP, e.g., Rabiner
and Gold, can tell you how to compute the optimum coefficients for a FIR
Hilbert Transformer of a given length.

The FIR is much preferred over the IIR (infinite impulse response) filter
design you presented, because it allows the kind of precise control over
filter phase characteristics that is the whole point of the Hilbert
Transform.

Phil