Coaxial probe modeling in waveguides and cavities

Extraction of the two-port scattering matrix of a probe-excited semiinfinite waveguide based on moment method solutions of three short-circuited guides is presented. Results show that this solution (1) provides an easy way to determine the two-port scattering matrix of probe-excited waveguide problems, and (2) enables the accurate determination of the loading effects of the probe on the resonant frequencies of unperturbed cavities. Both of these provide a key to the design of input/output cavities of waveguide filters. Agreement with experimental data is excellent for loose-coupled probe-excited semiinfinite waveguide problems.<>