A waveguide power balance theorem applied to a parallel plate waveguide with an iris

Abstract

We study the problem of wave propagation in a parallel plate waveguide with an iris. We use Green's function techniques to model the field behavior inside the waveguide. We formulate an integral equation whose solution will allow us to solve for the fields everywhere within the guide. We solve the integral equation by employing both the method of moments and a low-frequency approximation. We next develop a power balance theorem which relates the modal coefficients of the propagating modes in an exact relation. From the numerical solution, we can generate numerical approximations to the modal coefficients. We investigate if and when our numerical approximations to the modal coefficients satisfy the power balance theorem. Finally, we derive a generalized power balance theorem for scattering by obstacles and junctions inside a waveguide of arbitrary, uniform cross-sectional area.