Analysis and Design of Compact Triple-Mode Ceramic Cavity Filters Using Parallel Coupled Resonators Approach

-A novel compact triple-mode ceramic cavity filter is presented. The filter is analysed using the parallel-coupled resonators approach. The absence of intra-cavity couplings allows using a simple rectangular cuboid while the input to output coupling via a single printed circuit board interface manages three controllable transmission zeros per cuboid. To verify the proposed approach, a design operating at the DCS-1800 transmit band is presented. The design has three transmission zeros on the low side aiming to achieve maximum isolation using a single cuboid.