Efficient prediction of radiation from printed transmission-line discontinuities

An efficient full-wave space domain Galerkin method of moments (MoM) is developed to compute the current distribution and the radiation associated with arbitrarily shaped microstrip (or printed transmission line) discontinuities. Several techniques are used to increase the efficiency of the MoM algorithm so that a circuit of moderate electrical size can be analyzed in reasonable time. These include the utilization of quasi-dynamic and far-field approximations of the microstrip Green´s functions where applicable, as well as the various symmetries in the problem formulation. The influence of asymmetrical currents on the radiation from some representative microstrip discontinuities is examined. Sample computational results are presented to show that the current distribution and the radiation associated with resonant size structures can be significantly higher than the regulatory limits. The MoM algorithm is validated by comparing the computed current distribution and resonant frequencies of a microstrip transmission line with analytical results derived from quasi-TEM transmission line theory.