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Poor phase noise performance at 10Hz offset

Question asked by GuyV on Apr 23, 2017
Latest reply on Sep 8, 2017 by sripad


I've measured the TX phase noise performance at 2600MHz ( LO 2570MHz , 3dBFS SSB CW 30MHz ) ,

and i seem to begetting poor results at close in offset (10Hz to be exact).

At 10Hz , my reference is -109dBC/Hz. For the 2570MHz LO , the phase noise should be -109+20log10(2570/30) ~ -70dBC/Hz. 

I'm getting a phase noise of about -45dBC/Hz. This is a big difference from the theoretical calculation. Could you explain this?


My reference is  a  5dBm 30.72MHz clock, generated using a signal generator.

Below is the reference phase noise performence - 


Reference phase noise


This is the phase noise measured at 2600MHz:



The profile i was using:



Thanks in advance,