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Path: utzoo!attcan!uunet!ginosko!gem.mps.ohio-state.edu!apple!kchen
From: kchen@Apple.COM (Kok Chen)
Newsgroups: sci.crypt,sci.electronics
Subject: Re: Noise generator (hardware)
Message-ID: <35357@apple.Apple.COM>
Date: 7 Oct 89 21:22:40 GMT
References: <281@hhb.UUCP> <131@arinc.UUCP> <29071@obiwan.mips.COM> <9018@batcomputer.tn.cornell.edu>
Organization: Apple Computer Inc., Cupertino, CA
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eacj@batcomputer.tn.cornell.edu (Julian Vrieslander) writes:

>There is a good discussion of the basics of digital pseudo-random noise
>generators in chapter 9 of "The Art of Electronics," by Horowitz and Hill
>(I have the 1st edition, have not checked the new one).

>They include a complete schematic for an adjustable bandwidth p-r noise
>source, and claim that it is similar to the method used in the Hewlett
>Packard 3722A.
>-- 
>Julian Vrieslander 


For the "bible" on PN Generators (PN = Pseudo-noise), take a look at 

	Solomon W. Golomb, "Shift Register Sequences,"
	Holden Day, San Francisco. 1967.

Sorry, no ISBN number on my copy of the book (preceeded the introduction
of ISBNs :-).

I have used this method to generate a noise comb for an antenna 
resistance noise-bridge pretty successfully, instead of using the
standard zener knee method.  The biggest advantages are 1) it generates
a *huge* signal compared to the zener, and 2) a simple D.C. voltmeter
[measuring the TTL voltage level at the load when the PN sequence is
not running] is all it takes to get a very good estimate of the 
noise density. (Well, it takes a calculator too, because there is
a sin(x)/x envelope :-) But, since it was for a home project, and I
don't own an oscilloscope, this became the most convenient noise
generator to build.

Caveat: Take great care if you want to use this as a pseudo-random number 
generator for image dithering, for example.  You have been warned :-).

-- 
----
Kok Chen			kchen@apple.COM
Apple Computer, Inc.