Discussion Forum

Was wondering if anybody could help give some points to a COMSOL newbie. I'm trying to simulate a parallel-plate waveguide with horn antenna-like couplers that couple the radiation in and out of the plates. The shape of the horn-like structure can be modified to increase adiabaticity, decrease it, add length, etc. I want to model several different variations of these structures and view the resulting coupling and field distribution around the couplers.

I understand that because of this, my simulation automatically becomes an open boundary problem. So far, I have tried placing a larger box (10x) around the strucutre, and tried various methods of defining the region between the plates and the surrounding region as air, making the plates copper, adding in ports, matching layers, impedance boundary conditions, etc., and have not been able to get a single successful simulation running. The most common error message I get is that I have a singular matrix and COMSOL cannot evaluate it. From what I can tell, this means that I have either over/underspecified parameters or I need different initial value conditions for the eigensolver, but I've tried modifying things to satisfy each of those theories and I've failed in that, too. I can't even make it work for just the simple parallel plates. Does anybody have any suggestions? I've uploaded a couple of files for you to see.

I'm working in COMSOL 4.0a and using a 2-D model. I am also working in the THz region, between 1-5 THz. The metal for the plates and couplers should be copper, but defining them as PECs is okay as long as a solution can be made to work.

Thanks for any help you can give...