Packaged Filtering Power Divider With High Selectivity, Extended Stopband and Wideband Isolation

A packaged filtering power divider (FPD) is presented, investigated and synthesized. The radiation loss and electromagnetic interference are reduced since the FPD is insulated in a completely enclosed substrate-integrated cavity. The isolation performance and transmission property of the proposed FPD are determined by the odd- and even-mode equivalent circuit, respectively. A 3rd-order quasi-elliptic filtering response is attained by the multi-mode filtering sections composed of doubly-stub-loaded parallel-coupled lines. Five extra TZs are generated by both the central-loading (CL) T-shaped stub and side-loading (SL) short-circuited 180° and open-circuited 90° branches, which further improves the selectivity of the passband and suppresses the higher-order harmonics. Two isolation resistors are elaborately placed between the two power-division paths, which significantly improves the isolation level over the whole passband and stopband. The design equations including the position of the TPs and TZs, and the values of the isolation resistors are derived in the synthesis procedure. For verification, an FPD prototype is designed, simulated, and measured. It exhibits advantages in terms of low loss, sharp band-edge skirts as well as wideband rejection and isolation, which is suitable for IoT (Internet of Things) applications and antenna-array feeding networks.