Compact multiplexer formed by coupled resonators with distributed coupling

Conventionally, the design of microwave multiplexer networks is performed in two steps: first, the filters for each channel are independently synthesized. Second, a power divider or manifold network is designed so that the responses of the isolated filters are minimally affected when integrated into the whole device. Usually this network is formed by lengths of transmission lines that introduce phase shifts to each channel. An additional optimization step of the complete network is carried out in order to further improve the response of each channel. We have followed a different approach. The complete network is formed exclusively by coupled microwave resonators, just like filters but with an arbitrary number of ports. The network is described by means of a generalized coupling matrix, suitable for the increased number of ports. The signal combination is obtained through distributed couplings between the resonators of each channel. As a result, the placement of the non-complete transmission zeros due to the interaction between channels can be controlled and used to increase the selectivity of the multiplexer.