[time-nuts] GPSDO control loops and correcting quantization error

Poul-Henning Kamp phk at phk.freebsd.dk
Sun Sep 16 06:21:05 UTC 2012


In message <1225454799-1347767280-cardhu_decombobulator_blackberry.rim.net-1901
834519- at b27.c1.bise6.blackberry>, lists at lazygranch.com writes:

>The PWM DAC should have perfect differential linearity, which I
>believe is all that matters in this application. (That and no missing
>codes.) Not so when you try to combine two DACs to make one higher
>resolution DAC.

The main problem with two staggered DAC's is actually that all OCXO's
drift and eventually you will have to step the major DAC which will give
a glitch in the lower bits, almost no matter how much you calibrate
beforehand.

The PRS10 uses a staggered DAC internally and the steps on the major
DAC are measurable in the output signal.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.




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