[time-nuts] fast switching quiet synthesizer
SAIDJACK at aol.com
SAIDJACK at aol.com
Tue Oct 7 21:18:19 UTC 2014
Hi Anders,
in the absence of a true phase noise analyzer the next best thing is to use
one of the Agilent 856x analyzers with the phase noise measurement
software plug-in.
By chance I had looked at Ebay over the weekend and those two can be had
for around $3500 these days (with an 8561E). Still a lot of $$, but it will
give you a nice improvement over the Rigol spectrum analyzer and still be
5x cheaper than the lowest cost commercial PN analyzer.. Its really cool to
have a good SA of course, so the PN option just comes as a bonus in my
opinion.
Attached is a sample plot of what that PN output would look like at 100MHz
from a reasonable DDS output. The noise floor is about -135dBc/Hz.
bye,
Said
In a message dated 10/7/2014 13:44:31 Pacific Daylight Time,
anders.e.e.wallin at gmail.com writes:
The spurs improve when using the DDS with an external 1GHz sample-clock
(internal PLL+VCO on the DDS-chip disabled). We produced it from 10MHz with
an ADF4350 eval-board:
http://www.anderswallin.net/wp-content/uploads/2014/03/100MHz_AD9912_interna
l_vs_external_PLL.jpg
AD must use some nice&expensive spectrum-analyzer to produce that figure
with a -100 dBm noise floor! :)
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