Spectral Domain Analysis of Microstrip GAP Discontinuities and GAP-Coupled Resonators

A fullwave analysis of microstrip gap discontinuities in an open environment is presented. The analysis is general and includes gaps between lines of differing width. The analysis is extended to coupled resonators in order to study the coupling between two gap discontinuities. It is shown that the coupling between the two gaps is not negligible when surface waves are strongly excited. The analysis includes the effects of both longitudinal and transverse current on the strip and mode conversion. The effects of space wave and surface wave radiation are included by making use of the exact spectral domain Green´s function. The analysis of the gap-coupled resonator is new and numerical calculations of the complex two-port scattering matrices of several gap-coupled resonators are presented.