Low loss and high fabrication tolerant phase shifters using signal interference technique

Abstract

This article presents a new design of differential phase shifters based on signal interference technique. Two transmission line sections joined at their both ends is used as the phase shifting unit. Properties of the phase shifters are solely determined by the lengths and characteristic impedances of connecting transmission line sections. A lossless transmission line model is used to obtain design equations and design graphs for the phase shifters. It is observed that a fixed reference line can provide 0° to 90° differential phase shifts. While a varying reference line provides 0° to 360° differential phase shifts. Six differential phase shifters are fabricated to check the theoretical predictions at 5 GHz. All of them provide excellent phase and insertion loss performances. The main advantages are simple design technique and low insertion loss. Since no coupled-line or open-stub is used, the structure can accept higher fabrication tolerances compared to other popular methods.