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How can I get only scattered field without background field in Electromagnetic Waves, Transient
Posted 2025年8月22日 GMT+8 05:53 Electromagnetics, RF & Microwave Engineering, Wave Optics 1 Reply
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Hello, everyone! I tried to reproduce a FDTD article in COMSOL. I would like to introduce the model briefly: I couple temw with general form PDE to describe the dynamic in material. I set a Gaussian incident pulse in SBC and make it illuminate on a metasurface.
I set a probe to get the output signal. There are two signals caused by the nonlinear PDE. I want to observe: (1) THz signal(2)400THz. I can get 400THz signal now, but I can't get THz signal. It may be covered by the background noise from Gauss pulse, and I want to eliminate it now.
However, TS/SF technique used in the FDTD article which can help them get scattered field directly without background field doesn't exist in COMSOL. And background/scattered field technique only exists in Electromagnetic Waves, Frequency domain. So what I can do in Electromagnetic Waves, Transient now?
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Although I may not fully understand your question, I will suggest a possible solution if you haven't considered it already: 1. With your model meshed exactly as before, set your material properties and interactions such that there is no scattering. Solve the problem and save the solution. This is your background field in time and space. (2) Now, set the material properties and interactions such that the wave scattering of interest to you occurs. Solve the problem again. This yields your combined scattered + background field in time and space. Subtract the first set of fields from the second set to reveal the "scattered" field components. This approach should work best (in terms of minimizing numerical noise) if you change only the material properties and interactions -- but not the actual geometry, mesh, time stepping, or discretization -- when setting up the two different configurations.
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