Transversal directional filters for channel combining

A new concept for the design of power combiners based on matched directional filters is presented. The directional filters consist of individual balanced sections composed of hybrids and single resonators. Each of the sections corresponds to a pole of an all-pass function composed of the sum of S₁₁ and S₁₂ of the desired filter transfer function. A simple synthesis method is presented. The filter combiner has the advantage of ease of tunability because each pole is associated with a single resonator. Furthermore, no cross-couplings are required to realise finite frequency transmission zeros. Experimental results for a prototype device are presented.