A Novel Compact Schiffman Phase Shifter With 92% Fractional Bandwidth Enabled by Quasi-0-Degree Phase Inverter

This paper introduces a new class of Schiffman phase shifters, named as the Type G Schiffman phase shifter. For the first time, it is demonstrated that the bandwidth of Schiffman phase shifters can be significantly enhanced by inserting a phase inverter within the coupled-line structure. The proposed topology maintains the electrical lengths of both the coupled line and the reference line at 90°, while the additional phase inverter is inherently compact, resulting in almost no increase in circuit area. A prototype is designed and implemented on a printed circuit board (PCB) to validate the concept. Measured results show a phase error of less than 3°, an insertion loss below 0.5 dB, and an operating bandwidth from 1 to 2.7 GHz, corresponding to a 92% fractional bandwidth.