Running multiple PAC simulations on the same PSS analysis

So why do you need 70 harmonics (and sidebands)? Surely this is a pretty pure sinusoidal output? I would expect that oversample should only be needed if you have a very sharp transition within the period (normally you don't need to set it above 2), for oscillators such as a ring oscillator or when you have a buffer which squares the output of an LC or crystal oscillator. That doesn't appear to be the case here.

Andrew.

Yes, It is almost a sine wave. But, if I take 10 PXF sidebands (see the black curve) and 20 PXF sidebands (see the red curve) the PPV  does not match the actual Spectre PPV (the green one).

If I take 50 PXF sidebands,  the calculated PPV matches exactly with the actual PPV of Spectre.

See the below snapshot:- The PPV of Spectre and the PPV of calculated one from PXF are indistinguishable.

The PPV is for the voltage source at net GATE_IN. Though, the oscillator output voltage is almost sinusoidal, the PPV for  the voltage source (unlike the PPV for the current source at net VOUT_M) is NOT.

So, we need more PXF sidebands.

Also, I think, for HB analysis we can not get 70 PXF sidebands without having 70 harmonics for PSS.

You're right that you can't get 70 PXF sidebands without 70 harmonics for PSS (if using harmonic balance). However, I don't know enough about computing PPV manually (the PPV output from Spectre is mostly for historical support of the old PLL modelling flow, although it is used internally inside the simulator) to know what the right answer is here. I've not read Demir's paper recently and don't really have the time to investigate this in more detail right now - you would probably better off contacting customer support so that somebody can spend enough time to investigate this properly.

Thanks,

Andrew.