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Ambiguity in results with PLL phase noise application

Question asked by gkrf on Jan 22, 2016
Latest reply on Jan 28, 2016 by DonY

Dear Hittite Support,

 

   I noticed that in your phase noise tool, the close in PLL phase noise changes quite substantially depending on whether or not I append the crystal input phase noise at the 10 MHz, 100 MHz offsets. This is not a reasonable outcome as the PLL phase noise close in (1Hz and 10Hz) should not be affected by the crystal’s 10 MHz and 100 MHz phase noise. See below:

 

CASE1)                                                                           CASE2)

                                                                                       

Why the phase noise bump just because I included               I just removed the crystal noise numbers at

values for 1e7 and 1e8 crystal oscillator noise offsets?          1e7 and 1e8 offsets. Data not available.

 

 

Capture.JPG

 

Also in case 2, why does the phase noise go up so steeply at 10 MHz?

 

In short, how do I set the tool so that I get trustworthy results and not ambiguous ones? Thanks,

 

Gerald Wong (User HMC703LP4E Synthesizer evaluation board)

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