Spiral Inductor Q calculation

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GSarris

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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
 

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).
 

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