Measures 
Post subject: Input impedance
Posted: Mon Mar 01, 2010 11:35 am


Joined: Tue Dec 15, 2009 10:22 am Posts: 10 
How can I obtain the input impedance of my circuit from the measured Sparameters?
Is the expression Zin=Zo*(1+S11)/(1S11) 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 Sparameters, not using ADS (I cannot use touchstone files).
Thank you very
much





alperuslu

Post subject: Re: Input impedance
Posted: Fri Mar 05, 2010 7:34 pm


Joined: Fri Mar 05, 2010 9:02 am Posts: 2 
They are general expressions





PeterMartin

Post subject: Re: Input impedance
Posted: Wed Apr 14, 2010 2:08 am


Joined: Sun Apr 04, 2010 7:13 pm Posts: 2 
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?


Posted 11/12/2012
