I have simulated phase noise of an LC VCO with spectreRF and eldoRF. The steady state oscillation freuency from both simulators (SST and PSS) are quite close(4346.7MHz and 4346.8MHz). However, phase noise results are quite different;

sim\offset freq  10KHz   100KHz  1MHz
----------------------------------------------------------------
spectreRF          -75.8     -99.5      -120.2   (dBc/Hz)
eldoRF                               -70.4         -96         -117.2  (dBc/Hz)

I have  designed VCOs with eldoRF (4 VCOs) before,
and simulated and measured phase noise reults matched within 1-2 dB and also 1/f noise corner were
matching quite close.

Device models are from the same design kit, and I have
checked accuracy of spectreRF phase noise simuation by changing parameters suggested by spectreRF documentation.

Can anybody help me with this discrepency between PN simulation results? Thanks,

Hi Paul,

thanks for reply; there is more discrepence in 1/f3 region
(@10KHz offsett -75.8 versus -70.4 dBc/Hz), and
there is less discerpency in 1/f2 region
(@1MHz offsett -120.2 versus -177.2 dBc/Hz).

So there are problems in both 1/f3 and 1/f3 regions.

Hi Andrew,

Thanks for kind reply. I have set maxsidebands to 7 initially, and then also set to 15, 30 to see any difference.
 

Hi Paul,

Thanks for comments and suggestions.

I have investigated little bit more since my last posting.
I totally agree with your findings. There are two
possible suspects to cause to difference between
simulators phase noise results i) noise transfer functions
ii) noise sources

Noise transfer functions seem to agree in both simulators.

Noise sources for devices do not seem to match.
I am still investigating though. I need to figure out
Spectre flicker and channel thermal noise settings; what
is default, and why etc. Once I get around Spectre
settings, then I will check longer length bias devices and sub-u channel length amplifer RF devices thermal noise difference in both simulators.