Thanks GOTWW,
As it turned out my discretisation was fine, it was how I was getting the eigenvalues. I was looking for the 3 eigenvalues that were largest in magnitude. This was fine when the main diagonal was positive but when xstep was reduced further it went negative, the eigenvalues I was...
When solving the eigenvalue problem [A]*E =(beta^2/k0^2)*E, where beta is the prop constant, E the electric field and k0 the free space wavenumber:
Is there a limit on how small a discretisation step size you can take?
In my matrix [A] the main diagonal for a 2-D mesh is constructed by the...
