From: Alan Horowitz <alanh@infi.net>
Date: Wed, 24 Jul 1996 15:57:07 +0800
To: jim bell <jimbell@pacifier.com>
Subject: Re: Digital Watermarks for copy protection in recent Billbo
In-Reply-To: <199607232200.PAA25339@mail.pacifier.com>
Message-ID: <Pine.SV4.3.91.960723200613.144A-100000@larry.infi.net>
MIME-Version: 1.0
Content-Type: text/plain


> However, what is somewhat less 
> well-known is the fact that in order to keep higher frequencies from being 
> "aliased" (reflected to lower frequencies by heterodyne processes) it is 
> necessary to remove (by filtering) any frequency content above that maximum, 
> before sampling is done.

   Well, fudge sticks. That sounds like this thing called an "image" in 
heterodyne analog RF receivers. I know how those work.

What is the physical basis for "aliasing" as you describe, in the 
sampling theater of operations?