A new structure for reflection-type phase shifter with 360/spl deg/ phase control range

A novel 360deg reflection type phase shifter is proposed. It comprises a 3-dB coupler, resonant circuits, transistors and PIN diodes. The control of phase is enabled by controlling the capacitance of the varactor (transistor). The new structure provides a full 360deg phase shift and it is believed that it can be extended to phase shifts even beyond 360deg. Equations are derived to precisely describe the behaviour of the reflective load, the range of obtainable phase shifts as well as the limitations imposed by such a structure. In one case it is shown that with a careful choice of the varactor the transmission losses can be kept to lower than 2.6 dB. Also, in another case the phase control of 360deg is obtained using a bipolar transistor with a capacitance ratio (C_max/C_min) of only 1.28