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Reflection Coefficient to Impedance transformation on the Smith Chart

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fuseless

New Member
A certain RF transistor has a source - reflection coefficient with a magnitude of .105 and a phase angle of 160°. When plotted on the Smith Chart, the normalized impedance is .825 +j .06 Ω. What is the actual or unnormalized impedance? What does it depend on? Is it 50(.825 +j .06 Ω) or 41 +j 3 Ω? Is the Smith Chart automatically normalized to 50 when dealing with RF transistor reflection coefficients that were derived from S - parameters and when determining the actual impedance the transistor wants to see?
Thanks...
 

RadioRon

Well-Known Member
A Smith Chart should have its normalized impedance pre-defined and it is usually found written somewhere on a printed chart, or stated clearly somewhere on a soft chart. The usual Z is 50 ohms. Yes, in your example, it is 41+j3 ohms. Smith Charts are not automatically normalized to any specific impedance, but 50 ohms is so commonly used that it can be your assumed default.
 

fuseless

New Member
Hi RadioRon,
I hope this post gets out, I had trouble the other day trying to post on this forum. Anyway, thanks for answering my thread.
 
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