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Input impedance - RF Cafe Forums
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| Measures |
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Post subject: Input impedance
Posted: Mon Mar 01, 2010 11:35 am
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Joined: Tue Dec 15, 2009 10:22 am
Posts: 10
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How can I obtain the input impedance of my circuit from the measured S-parameters?
Is the expression Zin=Zo*(1+S11)/(1-S11) a general expression, or it is only valid
in the cases in which GammaL is zero? I don't obtain the input impedance using this
expression.
Is GammaL zero occurs only when the load impedance is equal to the impedance
of the network? Or does it occur whenever the load impedance is equal to the reference
impedance?
Does anybody know which is the expression than ADS uses to obtain
the Zin from the S11 parameter? I know this expression works perfectly, but I would
like to obtain Zin by myself from the measured S-parameters, not using ADS (I cannot
use touchstone files).
Thank you very much
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| alperuslu
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Post subject: Re: Input impedance
Posted: Fri Mar 05, 2010 7:34 pm
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Joined: Fri Mar 05, 2010 9:02 am
Posts: 2
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They are general expressions
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| PeterMartin
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Post subject: Re: Input impedance
Posted: Wed Apr 14, 2010 2:08 am
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Joined: Sun Apr 04, 2010 7:13 pm
Posts: 2
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The spread sheet program "matching network calculator" which is available for free on
this page: http://www.rfshop.co.uk/blog/downloads
can do what you need. For example, it will convert the reflection coefficient
Mag =0.35 Angle = 78 degs , in a 50 ohm system, into an impedance of : Z=44.91+j35.04
ohms Does that sound like the right answer? Incidentally, the program
uses the same equation you mention. Maybe your problem was in the manipulation of complex
numbers? |
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Posted 11/12/2012
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