[time-nuts] Short-Term Stability

Mike Feher mfeher at eozinc.com
Thu Mar 16 17:17:05 UTC 2006


Poul -

OK, I glanced through the paper. Similar concept to what we used to do with
adding analog noise prior to quantization to improve overall dynamic range.
I do not understand however what this has to do with reducing spurious in a
DDS. Are you saying that you need an extra bit in the wave shaping ROM that
goes to the MSBs of the accumulator and then feeds the D/A? That of course
would mean an additional bit in the D/A as well, and that is where the
problem is. If you could have an extra bit in the D/A then you would
theoretically pick up 6 dB improvement in spurious anyway. - Mike    

 
Mike B. Feher
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960
 
 

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Poul-Henning Kamp
Sent: Thursday, March 16, 2006 12:02 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Short-Term Stability

In message <006601c64919$75bfc530$0201a8c0 at n4fs>, "Mike Feher" writes:
>Poul -
>
>Unfortunately the technology does not yet allow having a 69 tap FIR running
>data at a 2 GHz clock rate.

You don't need that.

All you need is an extra bit in your wave-shape memory.

Read the paper, please.

>	http://hjem.get2net.dk/jjn/quantfir.htm

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
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Never attribute to malice what can adequately be explained by incompetence.

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