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Irregular grating modeling using ports or background field

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Dear all,

I am a novice at comsol and has been building my first model for some time. I want to calculate the scattered field caused by a plane wave incident upon an irregular grating (with dozens of periods). First I used port as the excitation, but found that the scattered field is reflected at the port, which appears to be a tricky problem to solve based on the discussion on the Internet.

So instead I use the background field approach. However, after setting a plane wave (like exp(-j*emw.k*y)) as the background field and solving the model, I find that the background field is present both in the air and inside the grating material (with n=1.5). So now I am very suspicious about the correctness of my model, since it is the sum of the background field and scattered field that has to satisfy the wave equation. Can anyone help me? Many thanks!

Tan Jia


1 Reply Last Post 19 set 2014, 08:07 GMT-4
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Hello Jia Tan

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Posted: 10 years ago 19 set 2014, 08:07 GMT-4
I would like to know it as well. What is the difference between the "port type" and "background wave type" attitude? It has been solved and discussed many times, but not the basics, only some pieces of the problems and the Documentation is not very helpful. Could anyone please write 5 points which are important to these attitudes and summarize with useful tips (maybe even in the relation to the far field - sizes limits etc. ... )? Please!

Thank you very much!
Katerina
I would like to know it as well. What is the difference between the "port type" and "background wave type" attitude? It has been solved and discussed many times, but not the basics, only some pieces of the problems and the Documentation is not very helpful. Could anyone please write 5 points which are important to these attitudes and summarize with useful tips (maybe even in the relation to the far field - sizes limits etc. ... )? Please! Thank you very much! Katerina

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