Input impedance of a probe excited semi-infinite rectangular waveguide with a tuning post

The input impedance and surface current of a probe-excited, shortcircuited, semi-infinite rectangular waveguide are determined, in the absence and in the presence of a tuning post, by the method of moments. Expressions are given for the Green´s function in the semi-infinite rectangular waveguide and for the free space impressed electric field. The method of moments analysis is based on the assumption that the probe (and the post) consists of multifilament sources that have some surface current density components with unknown coefficients. The solution for these coefficients is found by applying the boundary conditions at some suitable points. Computer simulation for this problem is performed, and the input impedance and surface current are determined for different probe lengths, lateral positions, and distances from the short-circuited end of the waveguide and also for different values of post length, position, and radius. The case in which the post is not short-circuited by the upper wall of the waveguide is also studied