Hi I am trying to simulate a VCO's PSRR. I used two methods to get the result. The first one is to run the pxf analysis and choose the VCO output nodes as output. Here is my setting: The second one is to follow the instruction of the application note "PSRR Characterization Using SpectreRF Autonomous Circuits". The only difference is "modulated" selected among "Special Analyses". I run the simulation and compare the results of pxf and pxf modulated. The simulation results are quite different. Here is the simulation result: The green line is the result of pxf modulated (SSB to PM) while the purple one is the result of pxf. I do not understand why the two results have so large difference (>200 dB)? and which one should be used to simulate VCO PSRR? regards, YCY
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