Compact Triple-Band Bandpass Filters Using Rectangular Waveguide Resonators

This paper outlines a new class triple-band bandpass filters employing cavities that resonate in three orthogonal modes. The proposed design can achieve equivalent performance with fewer cavities, thus significantly reducing the size and footprint when compared to traditional approaches. The concept is applicable to all triple-band cavities as demonstrated in this paper using rectangular waveguide cavities. The proposed triple-band filter offers increased Q and allows for independent control of each frequency and coupling parameter. A 4th order C-band triple-band filter is designed, manufactured, and tested to validate the proposed concept. To the best of authors' knowledge, this is the first triple-band filter realized with a cavity structure.