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Changing S parameters
Posted May 17, 2013, 11:49 a.m. EDT RF & Microwave Engineering Version 4.3b 1 Reply
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I am calculating and then plotting the reflection and transmission coefficients [abs(S11)^2 and abs(S21)^2] for a plasmonic wire grating structure using the RF module. Initially I set the ports at a distance of 1.5 times the maximum wavelength from the grating. In second simulation I then moved the ports further away to a distance of 2.5 times the maximum wavelength from the grating. The 1D reflection and transmission coefficients plot changes substantially.
Are there standing wave effects coming into play between the grating and ports? Is there some type of isolator that I should be using to make sure the radiation travels in only one direction?
v/r
John
Are there standing wave effects coming into play between the grating and ports? Is there some type of isolator that I should be using to make sure the radiation travels in only one direction?
v/r
John
1 Reply Last Post May 17, 2013, 4:19 p.m. EDT
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Posted:
1 decade ago
Never mind.
I found the answer in Pozar's Microwave Engineering. The S-parameters will change when the reference plane is shifted. Therefore, since the reflection and transmission coefficients depend on S11 and S21 respectively, they will change when the port to element distance is changed.
So, this begs the next question. Is there a "right" distance between a port and a periodic structure for the calculation of reflection and transmission coefficients? If so, what is that distance?
v/r
John
I found the answer in Pozar's Microwave Engineering. The S-parameters will change when the reference plane is shifted. Therefore, since the reflection and transmission coefficients depend on S11 and S21 respectively, they will change when the port to element distance is changed.
So, this begs the next question. Is there a "right" distance between a port and a periodic structure for the calculation of reflection and transmission coefficients? If so, what is that distance?
v/r
John