Efficient moment method analysis of radiating slots in a thick-walled rectangular waveguide

A narrow slot in the broad wall of a rectangular waveguide is analysed using a moment method which takes account of both the wave guide wall thickness, and the influence of side walls. In essence, the method of moments is used to solve a pair of coupled-integral equations, derived from the electromagnetic boundary conditions using Green´s function techniques, to find the tangential electric fields on the upper and lower surfaces of the slot. These fields are represented by a sinusoidal Fourier set of basis functions, and it is shown that only a few terms are required to cause the series to converge. The necessity of inverting large, full matrices, which can be a disadvantage of this method, is thus avoided. Theoretical results are presented for the scattering parameters of slots and these are compared with experiment. A computed curve showing the functional form of the tangential electric field in the slot is also included and is compared with some earlier calculated and trial slot-field distribution.