What is meant by S-parameter?
Scattering parameters or S-parameters (the elements of a scattering matrix or S-matrix) describe the electrical behavior of linear electrical networks when undergoing various steady state stimuli by electrical signals.
What is the significance of defining S-parameters over the Z parameters?
S-parameters describe the response of an N-port network to signal(s) incident to any or all of the ports. The first number in the subscript refers to the responding port, while the second number refers to the incident port. Thus S21 means the response at port 2 due to a signal at port 1.
How to interpret S parameters including S21 on Smith chart?
S11 makes sense to me. At 5Ghz on the Smith chart, the impedance, Z is at about infinity, so the reflection coefficient, Γ = 1. So all energy from 1 goes back to 1, which the magnitude plot agrees with. For S21, the magnitude plot makes sence, because it goes to 0, meaning no energy from port 1 is appearing at port 2.
What are the scattering parameters of a Smith?
In the Smith chart below, at resonance, 5GHz, it shows S11 as being ( 1 + i0 ). This doesn’t seem to make sense to me. Looking at the other graphs of S11 and S21, they seem to makes sense, where at 5GHz S21 goes to 0 dB and S11 goes to very low, meaning %100 of the signal from port 1 goes to port 2 as you would expect.
What should the input impedance be on a Smith?
In the Smith chart below, at resonance, 5GHz, it shows S11 as being ( 1 + i0 ). This doesn’t seem to make sense to me. The smith chart is showing the input impedance (not the reflection coefficient) to be Z 0 ( 1 + 0 i). This should be what you expect.
How to read S 11 off a Smith chart?
To read S 11, you need to imagine an ordinary set of polar coordinates overlayed on top of the Smith chart, with the origin at the center of the chart and magnitude 1 corresponding to the outer edge of the chart. If you want to read S 11 off the chart instead of Z i n in ADS, you should use a polar plot instead of a Smith chart.