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From: email@example.com (Tom Bruhns)
Subject: Re: Low jitter xtal oscilliator
Date: 21 Nov 2002 16:33:29 -0800
References: <firstname.lastname@example.org> <email@example.com>
NNTP-Posting-Date: 22 Nov 2002 00:33:29 GMT
Martin Griffith wrote in message news:...
> from various doc's in my archive
> "It can be easily demonstrated that most people have the ability to
> detect and identify tones which are buried 25 dB or more below white
> noise (A-Weighted). Therefore, it is necessary to keep jitter induced
> side bands at least 25 dB below the A-Weighted THD+N of the converter,
> OR, it is necessary to depend upon psycho-acoustical masking to hide
> these side bands. At Benchmark Media Systems, we have chosen the first
> approach. "
I don't follow the "therefore" above. Why would I expect (almost
certainly random) jitter to produce sidebands which are pure tones?
And anyway, we're not talking about the ability to detect a tone in
white noise, we're talking about the ability to detect jitter-produced
noise in the presence of something which is almost certainly NOT white
Looks a bit like the old shell game to me.
OK, you do NOT want to be fm modulating your oscillator with some
deterministic signal. You should be feeding the oscillator with a
clean power supply. But that's a different problem than building an
oscillator with super good phase noise.
(Man, am I tired of looking at phase noise sidebands [in a digitizer
system, even] today! And I hate working in an environment where I'm
given noisy supplies with no headroom to re-regulate. Grrrr.)
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