Tip of the Week: Guidelines for simulating oscillators - phase noise simulations

When simulating oscillators, it is important to choose the correct simulator engine (shooting Newton vs. harmonic balance.)  In general, we suggest that you use the HB (harmonic balance) engine as your first choice.  In addition, there are situations where you may need to use the augmented=yes pnoise option. 

 For LC type oscillators (mildly nonlinear), we strongly suggest using the HB engine.  For ring oscillators (or circuits that contain digital elements such as dividers), the HB engine may have trouble converging - and then should you use the shooting engine.

Below is the pnoise strategy that we suggest you use when simulating oscillators with SpectreRF:

1) Run PSS with the harmonic balance (HB) engine.  If it converges,

--goto step 2),

--else, goto step 3).
 
2) Run "normal" HB pnoise (i.e. do not use augmented=yes pnoise option).

--If the results are as expected, then you are done.

--If the results are not good (or you get "WARNING: Abnormal PPV value found, fix it" or other messages indicating your solution may have problems), try "augmented" HB pnoise.

--If that fails, goto step 3).
 
3) Try PSS using the shooting engine.  

--If it doesn't converge, contact Cadence Customer Support (http://sourcelink.cadence.com).  We will likely need to file a CCR, and if so we'll also need a testcase. 

--If shooting PSS converges, goto step 4).
 
4) Try "normal" shooting pnoise (i.e. do not use augmented=yes pnoise option).

--If the results are as expected, then you are done.

--If the results are not good (e.g. you get Floquet warnings or other warnings indicating that your solution may have problems), try "augmented" shooting pnoise.
 
5) If "augmented" pnoise fails in 2) and 4), contact Cadence Customer Support (http://sourcelink.cadence.com).  We will likely need to file a CCR, and if so we'll need a testcase.

For more information on augmented pnoise, see the http://sourcelink.cadence.com solutions:

11459288 Shooting PSS+Pnoise phase noise results
differ significantly from HB PSS+Pnoise results.
11459258 Warning:  Abnormal PPV value found, fix it.