An analytical approach to synthesis of diplexers with an optimal lumped-element junction model

This paper presents an analytical approach to synthesis of a diplexer with a lumped-element junction model. The approach is based on the synthesis theory for a bandpass filter with a general complex load. Both non-resonant node type and the resonator type of junctions are considered in a uniform way. Different from existing diplexer synthesis methods, the junction model is synthesized rather than fixed at the beginning, to optimally satisfy the required overall diplexer specifications. The new scheme is suitable for designing coaxial combline type of diplexer. For each type of junction, a synthesis example is given to demonstrate the effectiveness of the proposed approach.