Oscillator hb vs transient simulation

[VERI]

Hi,
I am performing both transient and HB analysis for an oscillator. The operating frequency of the oscillator is supposed to be 20GHz. This is verified by HB analysis but transient analysis with a running time of 100ns settles to 18.8GHz frequency. Which could be the possible problem? Could it be something wrong with transient analysis? I have tried to change the options of transient but still, I can't figure out which is the problem.

Thank you all!

 

[vfone]

If you have access to IEEE papers, this document will give the answer:

Comparison of Spice Vs. Harmonic Balance Simulations

Two primary nonlinear circuit simulator methodologies are currently available for RF circuit development. These two methodologies approach the circuit simulation in two different methods. The first method, SPICE transient, operates in the time domain. The second method, harmonic balance...

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