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From: campbell@churchy.ai.mit.edu (Paul Campbell)
Newsgroups: comp.dsp
Subject: Re: Nyquist Rate
Message-ID: <13687@life.ai.mit.edu>
Date: 5 Mar 91 00:36:48 GMT
References: <1991Mar2.230829.21497@eedsp.gatech.edu>
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The Nyquist rate is the rate needed to sample a given bandwidth from zero
up to that frequency but not including that frequency since the frequency
of the sampling introduces harmonics which will be lost, including the
top of the band, and any multiple of the Nyquist rate. This is not as bad
as the frequencies outside of the band, which will be aliased. This is the
whole basis of the Nyquist sampling theorem, to be able to determine what 
sampling rate to use for a given bandwidth. Realistically, for any decent
resolution of the wave, you should sample at four times the maximum, but
the absolute minimum (the limit, which will obviously not work at all)
is the Nyquist rate, or twice the maximum frequency.