Xref: utzoo rec.ham-radio:8094 sci.electronics:4803
Path: utzoo!attcan!uunet!lll-winken!ncis.llnl.gov!helios.ee.lbl.gov!nosc!ucsd!ucsbcsl!amadeus!grosen
From: grosen@amadeus.ucsb.edu (Mark D. Grosen)
Newsgroups: rec.ham-radio,sci.electronics
Subject: Re: Hilbert filters
Message-ID: <1131@hub.ucsb.edu>
Date: 21 Jan 89 02:43:08 GMT
References: <1078@ns.UUCP> <13547@bellcore.bellcore.com>
Sender: news@hub.ucsb.edu
Reply-To: grosen@amadeus.UUCP (Mark D. Grosen)
Organization: University of California, Santa Barbara
Lines: 23


[Phil talks about Hilbert transformers (filters)]

Actually, a Hilbert transformer is  linear-phase, just discontinuous
at w = 0.  It's phase response is -j for 0 < w < pi and +j for -pi < w < 0.
It's magnitude is 1 for all frequencies.  Analog people call it a 90deg.
phase shifter.

An FIR filter can realize the phase response exactly, but can only
approximate the magnitude response.  One approach to  a design is to
window the ideal impulse response of (2sin**2(pi n / 2))/ (pi * n).

An IIR filter can achieve the unit magnitude characteristic (all-pass),
but can only approximate the phase characteristic.  One advantage of IIR
is less overall delay.

Mark

Mark D. Grosen		ARPA: grosen@amadeus.ucsb.edu
Signal Processing Lab / Communications Research Lab
ECE Dept.
University of California
Santa Barbara, CA  93106