Modeling of narrow-gap couplings to a patch filter

A high unloaded Q of a patch microstrip resonator can be achieved with a superconductor. To ensure that the loaded Q remains high, instead of direct connections, couplings by a narrow gap are frequently used to link the patch to other parts of the circuit. Because of the high Q, high accuracies are required to model both the patch itself and the gap coupling without sacrificing the speed of computation. High accuracy in patches has in fact been obtained, this paper therefore concentrates on the accuracy in the modeling of gap coupling. For fast computation of a narrow gap, a novel transmission line model is presented.