It looks like for S11, the chart plots the impedance, from which the reflection coefficient is calculated, Unless it is meant to mean the impedance from port 2 to port 1, which in that case it seems to indicate that the ports are matched, in which case I would expect maximum port transfer, which of course is not the case. It seems to me that the impedance looking back from port 2 would be the same. It looks like for S11, the chart plots the impedance, from which the reflection coefficient is calculated, that represents S11. However, I don't understand why the Smith chart would show 1 + j0 at the 5 Ghz point. So all energy from 1 goes back to 1, which the magnitude plot agrees with.įor S21, the magnitude plot makes sence, because it goes to 0, meaning no energy from port 1 is appearing at port 2. At 5Ghz on the Smith chart, the impedance, Z is at about infinity, so the reflection coefficient, Γ = 1. My question is, how do I interpret S21 on the Smith chart?
There the Smtih chart represtation of S11 and S21 next to a magnitude and phase plot of each. Below are the results of a simple band stop filter, resonant at 5Ghz.
I'm simulating some basic circuits and using the built in VNA to look at the results. I'm using Agilent, Advanced Design Simulator, to practice on the computer and to get the basic theory down and try to really get the feeling of it. I'm trying to become re-acquainted with S parameters, VNA, and transmission lines for some projects at work.
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