Novel Passive Vector-Sum Amplitude-Variable Phase Shifter With Integrated Reconfigurable Filtering Function

In this article, a novel passive vector-sum amplitude-variable phase shifter with integrated reconfigurable filtering function is proposed for the first time. It is constructed using conventional trisection filtering topology, with all the couplings between adjacent resonators being implemented with controllable mixed electric-magnetic couplings. This not only achieves a reconfigurable filtering response but also forms an intrinsic I/Q signal generator inside the filter, which can be directly utilized to achieve continuous phase control based on the vector-sum mechanism. In such a manner, an integrated filtering phase shifter (FPS) without the need for an extra I/Q generation network and individual filtering device is obtained. By properly choosing the coupling types and coupling strengths between adjacent resonators, a continuous phase control from 0° to 360°, covering the full four quadrants, is successfully realized. Closed-form equations associating the circuit parameters and insertion phase at center frequency are deduced, providing a quantitative theoretical guideline for determining the parameters of the FPS. Subsequently, a novel tuning mechanism for independent Q-factor and resonant frequency control of the resonator is proposed and applied in the circuit to further exploit the amplitude control ability of the phase shifter. Measured results show that the proposed amplitude-variable FPS is capable of achieving a continuous phase control range of 360° and an amplitude control range of 10 dB within a center frequency tuning range of 0.75-0.95 GHz. The measured root-mean-square (rms) amplitude error and the rms phase error are less than 2.58 dB and 8.45°, respectively.