360° reflection-type analogue phase shifter implemented with a single 90° branch-line coupler

A small reflection-type 360/spl deg/ analogue phase shifter is realised with four varactors and a 90/spl deg/ branch-line coupler. New design formulas for the phase shift and the insertion loss are derived and applied to the circuit optimisation. The phase shifter shows a total phase shift of 380/spl deg/ and an insertion loss of 4.5/spl plusmn/0.8 dB at 10 GHz. The variation of the phase is <4/spl deg/ over the whole range of temperature from 0 to 50/spl deg/C.