Beam propagation method for cylindrical waves

This paper proposes a method to calculate the propagation of cylindrical waves in inhomogeneous parallel plate waveguides. Like the beam propagation method, it consists of separating the wave into a known solution for an homogeneous waveguide and an unknown slowly envelope function. The envelope, the field, and the waveguide perturbation are expressed as Fourier series, leading to a system of first-order differential equations that can be solved numerically. The validity of the approach is verified by comparing results with those of full wave simulations.