High/low-impedance transmission-line and coupledline filter networks for differential phase shifters

摘要

Two compact and simple to design differential phase shifter topologies, based on high/low-impedance transmissionline sections and open-ended coupled-line sections, are presented for the first time. The basic circuit theory for single section topologies is reviewed, leading to design equations and graphs for direct circuit synthesis. Balanced topologies and multiple section designs are also proposed improving the performance and feasibility of the phase shifters. Two planar microstrip single section differential phase shifter hybrids, at a centre frequency of 12 GHz and a 45 and 1358 phase difference have been designed and manufactured. The designs have a simulated 0.5 dB amplitude and 18 phase imbalance over more than 25 and 40% bandwidth, respectively. Experimental results verify the circuit performance and feasibility of the proposed differential phase shifters.