Moment method solutions of cylindrical waveguides by searching in a spectrum of two-dimensional solutions

Scattering from cylindrical structures can be computed numerically by a moment method formulation of the problem. We have developed a computer program called G2DMULT for analyzing cylindrical structures by the moment method with a spectrum of two-dimensional solutions (S2DS). A moment method code for general cylindrical structures can be used to find modes inside arbitrarily shaped waveguides. In our case, the modes can be found by considering when the boundary currents approach infinity for a given source. The field solution inside the waveguide for a particular mode can then be obtained from the boundary currents. We show this by calculating the modes and field solutions of a rectangular metal waveguide and a circular soft waveguide. G2DMULT can use this approach to analyze arbitrarily shaped waveguides with ideal PEC, PMC, soft, and hard boundaries; we can also include dielectric regions.