Circular ports in parallel-plate waveguide analysis with isotropic excitations

Exact and consistent modeling of circularly shaped ports in the power/ground plane analysis under the assumption of isotropic excitations is addressed in this paper. Novel expressions are first derived for accurate calculation of the parallel-plate impedance of circular ports in the cavity resonator method. These ports are usually approximated as either rectangular or linear ones, leading to inaccurate results at high frequencies. The second part of this paper develops a novel semianalytical approach, derived from the contour integral equation, for modeling of circular ports assuming infinitely large reference planes. It will be shown that the radial waveguide method is a low frequency approximation of our approach and neglects the scattering among the open ports. The analytical solutions for infinite planes are then combined with the contour integral method to model finite-sized power planes. This improves the computational efficiency since a discretization of circular ports is avoided, especially for problems with a large number of circular ports.