Discussion Forum

Hi,

I am trying to simulate a 2D structure composed of Air and a substrate (n = 17/3). Bothe materials are semiinfinite. The propagation direction is y. I use scattered field formalism as solve for. My E filed is like E0*exp(-j*emw.k0*y) meaning that E field is in x direction propagating in y direction.
I am trying to lunch EM wave from air side toward the interface and calculate the reflection. The incident angle is normal to the interface. If I do this successfully, I will move to other angles, and finally I am going to simulate scatterer on substrate problem.
Because the materials are semiinfinite I need to use PML. I am surrounding the whole structure with PML.
I tried also side boundaries as periodic and the rest as PML. I also tried different kinds of mesh even extremely fine mesh.
I calculate reflection by defining a cut line in air side. Then I am integrating emw.Poavy on the line which gives me average power flow in y direcion (W/m). I also integrate (1/2)*E0^2/Z0 on that line which results in incident power (W/m). Then simply, reflected power will be the difference between incident and measured power flow in y direction. If I divide the result of that subtraction onto incident power it should give me reflection.
But I am getting fabry-prot-like results with reflection more than 1, or between 0 and 2. When the whole structure is just air or substrate without any interface this method gives 0 reflection which seems reasonable. but when I have an interface I can not get 50% fix reflection as I am supposed to get.
I attached also the mph file.
I appreciate if somebody take a look at that to see what is the problem.

Thanks,
Mohammad