Discussion Forum

Hi everyone.
I am using the RF module of COMSOL 4.4. My problem is to solve the vector wave equation in frequency domain (add physics-->radio frequency-->electromagnetic waves, frequency domain (emw)). My geometry is a simple 2D rectangular in x,y plane, where I excite the E-fields on bottom side, and put boundary condition on the upper side. The lateral boundaries are metallic. The boundary condition I want to implement on the upper side is By=0, Ez=0, where Ez is the out-of-plane component. This type of boundary conditions can be easily implemented in a more basic compile language, e.g. FORTRAN. But I didn't know how to do it directly in COSMOL.
As far as I know, COMSOL provides two ways to solve this problem. 1.using port boundary condition; 2. using a series of constraints.
I looked carefully about the description of port boundary. It seems in order to implement a port as boundary condition, one need to choose a specific eigenmode, e.g. TE10 or TE01. The boundary will then keep transparent to that mode and absorb the other modes. But in my case the wave is always a combination of a lot of eigenmodes. Only let one eignemode on the boundary is not enough. Do I miss something here?
In terms of using constraints, I am not fully understand its principle at the moment. What I know is that both pointwise constraint and weak constraint are used in the weak form of PDE. But the vector wave equation in the emw interface is not a weak form yet. Does COMSOL automatically transform it into weak form before solving it, or I need to rewrite it into weak form? The next question is how to define the constraints. I tried to combine an electric field boundary condition, which can give me Ez=0, together with a weak constraint Hy=0. But this seems not work correctly.
I hope anyone can give me some suggestion, either using port boundary conditon or constraints to do this. Thank you.