Synthesis and Design of a Fourth Order Differential Filtering Phase Shifter

This paper proposes a fourth-order differential filtering phase shifter which is consisting of a main filter path and a reference filter path. By properly adjusting the passband bandwidth of the main filter, a stable phase function of the proposed phase filtering shifter is achieved. The main filter is a fourth-order generalized Chebyshev filter with two transmission zeros which is consist of microstrip lines and coupled microstrip lines. The key parameters of the proposed filtering phase shifter are determined by the derived formulas. A prototype is designed with a central frequency of 2.4 GHz, a phase shift of 90°, and a fraction bandwidth of 30%. Good agreement is obtained between the circuit simulation results and the full-wave simulation results.