Synthesis and design of miniaturized poly-phase differential phase shifters with filtering function

Abstract

In this paper, a class of miniaturized poly-phase differential phase shifters with filtering function is proposed, synthesized and developed. The proposed design is constructed by using parallel-coupled microstrip lines as the phase-shifting element in all branches. Operational mechanisms for these parallel-coupled microstrip lines are given. Closed-form formulas of insertion phase and phase slope are derived to guide a practical design procedure for phase shifters with arbitrary shifted phases and minimized phase errors. Benefitting from the compact size of those parallel-coupled microstrip lines, the proposed design is much smaller when compared with state-of-the-art works. To validate the proposed concept and synthesis method, a class of five-way poly-phase (ΔΦ = 45°, 90°, 135°, and 180°) differential phase shifter centered at 3 GHz is designed, fabricated, and measured. Measured results indicate that, achieved relative phase shifts are 45° ± 2.7°, 91° ± 2.9°, 135° ± 3.2°, and 181° ± 3.9° within a 33 % fractional bandwidth, with amplitude imbalances smaller than 0.2 dB among different ways.