Multilayer independently controllable dual-band bandpass filter using dual-mode slotted-patch resonator

Presented is a novel multilayer dual-mode dual-band bandpass filter (BPF) using two identical microstrip cross-slotted patch resonators placed back-to-back. The lengths of the slots on the patch resonator are designed to be different, which can be used to control the two degenerate modes individually so as to build two passbands of the proposed BPF. Two separated coupling paths for the two modes can be realised by the etched slits on the common ground plane of the two microstrip resonators. As a result, the coupling coefficients between the two resonators in each passband can be controlled independently. Furthermore, a new source-load coupling scheme is incorporated in this design to enhance the stopband rejection and then improve the band-to-band isolation significantly.