Multiplexing and double band filtering with common-multimode cavities

A novel multiplexing and double band filtering (DBF) method is established. DBF refers to two-port equipment which serves two transmit frequency channels simultaneously. The methods build on frequency-independent resonance modes, excited within a common multimode cavity (CMC), which are assigned to different channel filters. The design principles are presented for cylindrical CMCs by way of example. It is shown that combining CMCs with advanced coupling methods produces a multitude of new design variants. Initial experimental results are presented for a diplexer and DBF equipment that are both realized with only two double-dual TE₁₁₂/TM₁₁₀ CMCs and a novel iris-providing four intercavity couplings-to perform two four-pole elliptic function filter responses