Path: utzoo!attcan!uunet!cbmvax!vu-vlsi!cheung
From: cheung@vu-vlsi.Villanova.EDU (Wilson Cheung)
Newsgroups: comp.sys.amiga
Subject: Re: Sampling at 29KHz (long)
Message-ID: <1615@vu-vlsi.Villanova.EDU>
Date: 31 May 88 19:35:36 GMT
References: <2845@polya.STANFORD.EDU> <734@eos.UUCP> <53788@sun.uucp> <5872@cup.portal.com>
Organization: Villanova Univ. EE Dept.
Lines: 13

In article <5872@cup.portal.com>, doug-merritt@cup.portal.com writes:
> >it are the 44 khz sampling signal used by a CD player:
> >[ waveforms deleted ]
> aliasing. With a sampling rate of A of a sine of frequency B, you'll
> always get two aliased components of frequencies A-B (here 26Khz) and
> A+B (62Khz).
that aliasing is occuring here since 44 Khz is more than double 18 Khz.
What he is looking at is the result of the sampling process, repeated
spectra of the original signal.  To obtain the original signal you must
pick out one of these repeated spectra.  This is done by using a low pass
filter that cuts off around 22 Khz (half the sampling rate).  

			Wilson Cheung