A hybrid moment‐ray‐mode method for wave scattering from an aperture coupled system

Wave scattering from an aperture coupled system is studied using a new method which combines the hybrid ray‐mode method and method of moments. The latter is used to formulate the coupling process and the former to provide the Green's function of a parallel plate waveguide. Following standard procedures of the method of moments, we first formulate a system equation for field distributions across the aperture. By expressing these unknown distributions in terms of appropriate basis functions and choosing appropriate weighting functions, the system equation is then reduced to a matrix equation which is solved numerically. In the system of equations, one needs to compute the Green's function of the waveguide for various arrangements of locations of source and receiver. The hybrid ray‐mode formulation is best suited for this purpose because it combines rays and modes self‐consistently to optimize the advantages of each. The efficiency of the ray‐mode Green's function makes use of the moment method practical in waveguides, and the flexibility of the moment method permits application of the Green's function considered to arbitrarily shaped and placed apertures. Numerical implementation illustrates these aspects.