A 180 degree Tunable Analog Phase Shifter Based on a Single All-Pass Unit Cell

This article describes an analog phase shifter able to provide a continuously tunable phase shift up to 180 degree by using a single all-pass unit cell. The proposed topology is compact and easy to implement, and brings an interesting compromise between phase variation, insertion and return losses. Indeed, for a 7.5:1 tuning ratio of varactor capacitance, a phase shift variation of more than 186 degree is obtained from 6 to 7 GHz with a maximum insertion loss of 1.8 dB. The 105 degree /dB resulting Figure-of-Merit is thus among the best in distributed approaches with varactors. [copy 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2915-2918, 2013