Broadband Phase Shifter Using Loaded Transmission Line

This letter presents a novel loaded transmission line, which has a constant phase shift over a wide bandwidth, referenced to a uniform transmission line. Compared with the conventional coupled line phase shifter, the configuration shows good performance with simplicity in both design and fabrication. The optimal design parameters for different phase shift values up to 120° are also presented to allow for a quick design process. To verify the configuration, a 90° phase shifter using a T shaped open stub loaded transmission line is designed, fabricated and measured. Excellent performance is achieved with small insertion loss and phase deviation over a bandwidth of 82%.

I. Introduction

The phase shifter plays an important role in microwave beamformers found in phase-array antenna systems, phase modulation communication systems and emerging intelligent antenna systems for broadband wireless mobile communications.