A 180° tunable analog phase shifter based on a single all-pass unit cell

Abstract : This article describes an analog phase shifter able to provide a continuously tunable phase shift up to 180 by using a single allpass 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 is obtained from 6 to 7GHz with a maximum insertion loss of 1.8 dB. The 105 /dB resulting Figure-of-Merit is thus among the best in distributed approaches with varactors.