Two peak curve on S22 when measure return loss - RF Cafe Forums
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Post subject: Two peak curve on S22 when measure return loss Posted: Sun Apr 23, 2006 10:33 pm
Joined: Sun Apr 09, 2006 8:48 pm
Good day everybody,
currently, i doing PA evaluation board measurement. i just wanna to know why on the return loss of S22 have 2 peak curve occur? is it because there have 2 resonane circuit on the board? if yes, where is that 2 resonance circuit forming on the board?
(on output of this board's circuit diagram, there have 2 capacitor placed in parallel.(one is act as DC bolck and another one is short to ground.). And so have some capacitive decoupling circuit)
Post subject: Posted: Tue Jun 13, 2006 10:50 pm
Joined: Tue Mar 15, 2005 11:43 pm
I am not very sure about your question. But I assumed that it's kinda valley on yout S22 measurement. First, the S22 will go much lower at your operating frequency which means it has the best return loss in the operating frequency.
Regarding 2nd valleys appearance, I guess it most likely the resonance frequency appears. It can be caused by the capacitive coupling somewhere in the circuit. I am not very sure about this either. Please feel free to correct me if I'm wrong.
Post subject: Posted: Wed Jun 14, 2006 12:18 am
Joined: Tue Apr 11, 2006 8:13 pm
Is your PA enclosed in a metal housing? Could there be cavity modes?
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