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, [email protected] 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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