neoflash wrote on Mar 30th, 2008, 3:57am:
Thanks for the replies.
I understand that inductance will seek minimum "impedance" path, and reduces its inductance in higher frequency. But, how people could extract the real inductance from measured S-parameters?
From point of view of electrical magnetic wave, there are no separate inductance and capacitance for solid object.
Just there exists electrical and magnetic energy arround it.
From Foster's reactance theorem, a derivative of reactance of lossless object regarding frequency is always positive.
So if we map reactance X to only L like 2*pi*freq*L, L must be propotional to freq^n, here n>-1.
-1 < n <0 ----->> L decrease with frequency.
0 < n ----->> L increase with frequency.
If there exists loss, a derivative could be negative. For example, assume second resonance point of simple dipole antenna.
Extraction's issue results in what lumped model you apply for a target solid object around frequency you are considering.