Dual-Band Single-Pole Double-Throw Filtering Switch Using Multimode Cavity Resonators

A dual-band single-pole double-throw (SPDT) filtering switch using hybrid microstrip-cavity structure is proposed in this brief. Two rectangular cavities act as the multimode resonators, and the cross-shaped microstrip lines (MLs) are adopted to feed them. Then two filtering channels are constructed, while only one channel is supposed to be turned on in each operating state. For this purpose, PIN diodes are integrated into the two output MLs to switch the two channels arbitrarily. The channel using reversely biased PIN diodes is turned on with dual-band filtering response. On the contrary, the other channel using forward biased PIN diodes is switched off with high OFF-state suppression and channel isolation. The measurements indicate a dual-band filtering response along with below 0.75 dB insertion loss in the switched-on channel. And 38 dB suppression as well as 33.3 dB channel isolation is obtained in the switched-off channel. Benefitting from the hybrid microstrip-cavity structure, the bandwidths of the two bands could be adjusted independently. And meanwhile the two multimode cavities are shared by the two channels to compact the size. In this way, the proposed microstrip-cavity structure possesses a dual-band SPDT filtering switch response, flexible passbands and miniaturization.