Dual-Mode Dual-Band Bandpass Cavity Filters With Widely Separated Passbands

A dual-mode dual-band cavity is proposed for the integration of compact dual-band filters with widely separated passbands. The basic structure is a cavity working on two distinct dual-modes, realizing a four-pole dual-band filtering function. An intermediate structure is also designed to validate coupling between dual-band cavities. Finally, two dual-mode dual-band cavities are coupled together for implementing an eight-pole filter with two passbands at 5 and 7.5 GHz, respectively. Prototypes are fabricated and measured for validating all designs, showing the relevance of the proposed concept.