Spiral Inductor Q calculation

[GSarris]

Hello. I have simulated a spiral inductor in RF mode Momentum and i have a question regarding Q. I use 2 definitions/methods to calculate it, the one concerning the resonant frequency and the 3 dB bandwidth and the other with the imaginary over real part of the impedance. While the 2 methods agree very well for low frequencies, for relatively high freqs the Im/Re method gives a lower Q than the f/BW method. Can you please explain why? Also what is the range of validity of these 2 expressions?
Thank you in advance,
George

 

[BigBoss]

Because of skindepth effect and Eddy currents effects are not included in calculations.

 

[N.Narayanan]

In low frequency, PCB parasitics effect will be low.
But in high frequency, PCB parasitics effect will be high.
So calculate your Q based on Reactance/Resistance (Im/Re).