I made freq source for weather radar. When I tested, the input source is Agilent Source generator, it's phase noise as following: -132dBc/Hz@1KHz, -137dBc/Hz@100KHz... The tested output phase noise is -109dBc/Hz@1KHz, -114dBc/Hz@100KHz...
23dB loss for 14 multiplier.
In radar system, the OCXO I used should have -155dBc/Hz@1Khz. So the output should have -132dBc/Hz@1KHz. And the target phase noise should be better than -140 dBc/Hz @1MHz or 10MHz. But the noise floor raised, so I am afraid that the phase noise can't reach the target. Because I have no chance to install my module tested in radar, I don't know what will happen in the real system. BTW, the system chain NF is about 22dB from OCXO to my output.
Is the noise floor raised by AM noise? When I simulated with ADS, I met several times that AM noise worse than phase noise, but I modified the setting, and ADS simulated result show the AM noise should better than -140dBc/Hz @ >1KHz. In my new design, I change the amplifier to higher P1dB, the AM noise simulated result improved more than 10dB.
Anyone have any ideas?