Design of Filtering Crossover Based on 180° Filtering Couplers
Qiang Shao, Ning Yang, Rui‐Sen Chen, Guan‐Long Huang, Fu‐Chang Chen, Yi Wang
Abstract
This paper presents a novel crossover with an embedded bandpass filter function. The crossover is derived from the traditional crossover based on a tandem connection of two 3-dB 90° couplers by substituting them with 180° filtering couplers and introducing a filter function. In addition, a 180° phase shift realized by coupled resonators is added to keep the two cross paths in phase. The equivalent circuit of the crossover between the two diagonal ports have been treated as bandpass filters with coupled resonators. The design equations are derived to assist with the synthesis process for the filtering crossover. For verification, a filtering crossover with fifth-order filter characteristics, operating at 2.4 GHz, is designed, fabricated, and tested. The measured results match very well with the simulation, which verifies the proposed circuit concept.