I am trying to simulate a long rectangular hollow waveguide with PEC surfaces.
A point source is put at the center.
Besides, a time monitor is put at the center too.
This simulation is just to get the spectrum of the point source within the waveguide.
The waveguide has two open boundaries with surfaces on x-y plane (i.e., the wave travels along z direction).
Originally, this is a very simple simulation. PML can be put on both open boundaries.
However, to save the simulation time and memories, I hope I can model a shorter waveguide with other boundary conditions thus the spectrum from the time monitor can still be the same as the original waveguide.
It seems that the periodic boundary condition is not correct.
Is it possible for a short waveguide with some special boundary condition that can achieve the same response as the long waveguide (maybe we can just think this long waveguide has infinite length) ?