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

This letter describes an analog phase shifter (PS) able to provide a continuously tunable phase shift up to 180° 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° is obtained from 6 to 7 GHz with a maximum insertion loss of 1.8 dB. The 105 °/dB resulting Figure-of-Merit (FoM) is thus among the best in distributed approaches with