[time-nuts] GPSDO control loops and correcting quantizationerror

Tom Van Baak tvb at LeapSecond.com
Sat Sep 15 02:10:02 UTC 2012


> I would expect a problem area would be filtering the PWM output.  Anything 
> you don't filter out will turn into close in spikes.  It might be fun to try 
> to measure them.
> 
> 64K/72 MHz is about 1 ms.   32bits at 72 MHz is 60 seconds.
> 
> Has anybody compared DDS style DACs with PWM?  The idea is to spread the 
> pulses out to make the filtering easier.  Instead of 1111100000, you would 
> get to work with 1010101010

Hal,

The Z3801A 16-bit DAC is dithered at 102.4 Hz and LP filtered. Details and plots:
http://leapsecond.com/pages/z3801a-efc/

/tvb




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