[time-nuts] Frequency subtraction with D-flip flops
EWKehren at aol.com
EWKehren at aol.com
Tue Jun 25 17:48:34 EDT 2013
In the Austron 2110 is a dual D FF Mixer along with circuitry to get 100 Hz
out. I did a board using 2 XTAL Filter stages and you can get 1 E-12 using
a 100 MHz period counter. Using my previously mentioned Ping Pong counter
at 200 MHz and Offset of 1 Hz at 5 MHz you get 1 Hz out. Resolution is 1
E-15, there is some jitter and quite a bit of AV. Presently we use a PTS 40
to generate the offset but it will be replaced by an AD9913 DDS. Schmitt
trigger jitter is not a problem since the ping pong counter functions like
time stamp and with two synchronizing stages does not miss a single count. The
2 by 2.5 inch board with out any other additions allows you also to do AV
measurements as long as one of the inputs is offset by 1 or 10 Hz. The DDS
is a piggy back board and only is needed if you want to measure frequency
at high resolution. For AV the board does every thing.
We plan on using it for long term monitoring using 5/10 Hz out and average
at least 10 counts. Resolution 1 E-14. Data will be recorded on a USB
stick.
Key components are a MAX 3000 32 macro G/A two 16F633 PIC's and one 16F688
PIC output is RS 232. Basically the same board Corby now uses with a few
more functions in the G/A.
Bert Kehren
In a message dated 6/25/2013 4:07:01 P.M. Eastern Daylight Time,
timenuts at binsamp.e4ward.com writes:
(Original seems to have got lost - try again)
> More recently we are using two D FF's for mixing in A/V
> applications and very high resolution frequency measurements with
> up to 1 E-15 a second using output frequencies from 0.5 Hz to 100
> Hz.
> Do to attachment limitations if you want more info contact me off
> list and I send you some scans.
> Bert Kehren
Bert,
This is very interesting. Can you explain in more detail how you can
reach 1e-15 in 1 second with those offset frequencies?
Can you give the input frequencies, the IC type, and how you measure
the output?
Thanks
Mike M
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