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Why does my S11 parameter change when adding a 2nd inactive port?

Posted 14.01.2014, 12:08 GMT-5 RF & Microwave Engineering, Results & Visualization Version 4.3b 2 Replies

Bryan Adomanis
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When looking at off-normal reflection from a periodic structure, my S11 results change when I add a second, unexcited periodic port (S2x). My first periodic port is sending a TM mode in Hy, with amplitude H0 = E0/377[1/S], and thus ewfd.S11 represents the reflected TM response. My results look as expected.

I then added a 2nd inactive port to get results of a single field component (E = Ex, with amplitude E0), expecting ewfd.S21 to consist of just the results along Ex. However, this changes the S11 results! Why?

My only guess is if port 2 is absorbing the Ex component, thus port 1 collects only the remainder? (in this case, the remainder would be mostly Ez components, and possibly a small amount of Ey from chirality)

Thanks for your time and consideration on the matter!

-Bryan
2 Replies Last Post 27.06.2014, 07:33 GMT-4
Robert Koslover Certified Consultant
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Posted: 1 decade ago 17.01.2014, 12:11 GMT-5
In most cases, any change to any boundary condition that intercepts any of the wave power from your port#1 could be expected to change S11.
In most cases, any change to any boundary condition that intercepts any of the wave power from your port#1 could be expected to change S11.
Affar Karimullah
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Posted: 1 decade ago 27.06.2014, 07:33 GMT-4
Hi,
I was curious reading about your problem and how you manage to seperate the Ex and Ey components using definitions in the port. Hence I wanted to ask, does specifying Ex=1 in port 2 tell comsol to measure only the Ex component when the input from port 1 is Ey=1 (turned on) . Secondly can this be used to measure Ex and Ey components from diffraction orders?
Hi, I was curious reading about your problem and how you manage to seperate the Ex and Ey components using definitions in the port. Hence I wanted to ask, does specifying Ex=1 in port 2 tell comsol to measure only the Ex component when the input from port 1 is Ey=1 (turned on) . Secondly can this be used to measure Ex and Ey components from diffraction orders?

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