Path: utzoo!utgpu!cunews!cognos!alzabo!rob
From: rob@alzabo.ocunix.on.ca (Robert Hilchie)
Newsgroups: comp.dsp
Subject: Discreet Sampling
Message-ID: <1991Feb28.194203.27097@alzabo.ocunix.on.ca>
Date: 28 Feb 91 19:42:03 GMT
Organization: Midnight Software Inc.,  Ottawa,  Canada
Lines: 15

I hope this question isn't too elementary for this newsgroup.

It is claimed that any signal sampled at a rate of 2s can be reproduced exactly,
provided that the original signal did not contain frequencies above s.

Now suppose the sampling rate is 40 kHz and the signal being sampled is a
sine wave of constant amplitude at 19 999 Hz. At some point the samples will
occur near the peaks and troughs of the sine wave, while, half a second later,
the samples will occur at the midpoints between the peaks and troughs. Thus,
the reproduced signal will fluctuate in amplitude every second.

How can this "beating" be avoided? Thanks in advance,

Rob Hilchie
rob@alzabo.ocunix.on.ca