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Error on PSS in VCO simulation

Ruixin

Hi, all. 

I am simulating a VCO and there is a switched capacitor driven by a vpulse source in the schematic. 

When I use PSS analysis , it shows the error like this:  

`V10' is a periodic input signal, which is inconsistent with autonomous circuits.

Could someone help me with this problem since it bothers me for a long time. 

Thanks a lot. 

  • This is not possible. You cannot simulate in PSS a circuit that has both a driven signal input and an autonomous (e.g. oscillator) at the same time. Since PSS needs to run over the common frequency, that common frequency would have a highly nonlinear (chaotic) relationship with the two frequencies - a tiny change in the oscillator frequency could mean that the beat frequency changes from 100MHz to a fraction of a Hz - and it just can't be simulated.

    The hb analysis does have a "semi-autonomous" mode where  you can have an oscillator and driven tone(s) at the same time - although if there's a switch cap circuit you'd probably need lots of harmonics to accurately simulate the response for this part. Shooting would probably be the best choice - but since that's technically infeasible, you may have no choice here. You can't use multi-tone QPSS (the mixed-frequency time shooting method) because that does not support oscillators (again, it's not really feasible from the technology perspective).

    Kind Regards,

    Andrew.

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