[time-nuts] quick and very dirty phase comparator

[Bob Paddock]

> Since I am well familiar with the Analog Devices DDS circuits, this has
> been my very first idea. The most simple one for that purpose would be a
> AD9851 (180 MHz, 32 Bit, built in clock multiplier). But when I used the
> DDS design tool available on the AD web pages I received a big warning
> saying that using a "clock X multiplier" frequency that is a near
> integer of the output frequency generates lots of unwanted spurs. Which
> was new to me since I do so in my GPSDO but should they not know better?
> This is why I dropped the thoughts on DDS.

Some AD DDS chips have a "SpurKiller" channel built into them.

See page 3.42:

http://www.analog.com.ru/Public/HS%20Systems%20Part%203%20Speaker%20Notes.pdf


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