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From: whit@milton.u.washington.edu (John Whitmore)
Newsgroups: comp.dsp,sci.electronics
Subject: Re: 180 deg phase shift
Message-ID: <1991May15.055011.5823@milton.u.washington.edu>
Date: 15 May 91 05:50:11 GMT
References: <1991May8.222501.19572@syd.dms.CSIRO.AU> <1991May10.003817.5593@milton.u.washington.edu> <625@fudd.dataco.UUCP>
Organization: University of Washington, Seattle
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In article <625@fudd.dataco.UUCP> mcphail@taarna.UUCP (Alex McPhail,DC ) writes:
>  Since any periodic function is always measured against time, 
>shifting the function's phase is also a time-related operation.  
>
> .... frequency and Fourier components
>have nothing to do with phase shifting.

	I disagree.  In discussing networks (or filters), one usually
refers to the Bode plot of amplitude and of phase shift plotted
against frequency.  The normal meaning in the context of
filters of the phrase 'phase shift' is the phase part of that
representation, and 'constant 180 degree phase shift' is
clear and unambiguous.  It means amplitude inversion.

	What earthly use are 'degrees' in describing the phase
of something which is not a circular function?

	And, why do you refer to 'any periodic function' in
this discussion?  To the best of my recollection, there
was never any statement made that the function under discussion
was periodic.  Phase shifts are well-defined in the absence
of periodicity, though easier to measure and display in the
case of periodic test waveforms.

	John Whitmore