SONNET simulations_spiral inductors

Hello,

I have some questions regarding inductor simulations in SONNET.

1. If i try to simulate a ~14nH rectangular spiral inductor in sonnet, the inductance graph shows a self-resonance at ~8GHz. But i dont see this reflecting in my S21 graph. Why does this happen?
2. Can I extract a circuit model from a sonnet simulation? I want to do some post processing in ADS using the generated s-parameter file.
3. For a spiral inductor 2 port simulations, the Q curve it simulates, is it loaded or unloaded Q?

Excuse me if these kind of questions have been answered before. I am new to EM simulations, and would appreciate if someone can help me out with this.

What do you expect to see in S21 for self resonance in inductance?

There is no lumped model extraction, unfortunately. But if you wan to take the data to ADS, you need no lumped model. Just use the Touchstone file (s2p).

It is the Q factor into port 1, with all other ports shorted. Calculation is Imag{Y11}/Real{Y11}.

thanks volker!
What do you expect to see in S21 for self resonance in inductance?
i thought since it is essential a parallel LC ckt (with the parasitic), i should be able to see this resonance in the S21 as a dip. correct me if i am wrong.

It is the Q factor into port 1, with all other ports shorted. Calculation is Imag{Y11}/Real{Y11}
interestingly, the Q factor curve hits zero at the self-resonance. shouldnt it be a maximum at resonance? so, i am a bit confused as to what this SONNET Q factor is.

also, if you can help me with ADS,
i get a warning if my ports are on the same wire. for eq, a parallel RLC ckt, and port terminations all in parallel, it so happens that the ports are on the same wire. This gives me a result with a S21 showing a max at the resonance freq. But now when i change the port placement to the other node of the parallel ckt, with no grounding of the RLC network, I get a dip in S21 at resonance. What is the right way to simulate? In reality, I will have my LC ckt which is magnetically coupled to a CPW transmission line without grounding any of the terminals. so how can i simulate this? any suggestions?

No, the Q factor should not have a maximum at SRF.

For your questions on S21 and resonance, I am not sure how you connect your ports to the inductor. Maybe some screenshot can help to understand what you are doing.

Hello vadisam,

At and above self resonance frequency, an inductor ceases to behave as an inductor; since parasitic cap starts dominating....so the Q factor for the inductor goes to zero; as pointed out by volker.............Beyond SRF the capacitive nature predominates and the structure can no longer be used as an inductor......