A Hybrid Architecture 360° Phase Shifter With Continuously Tunable Phase Shift and Low In-Band Phase Error

This article presents a design method for a hybrid architecture 360° phase shifter (PS) using a cascade of switched-type phase shifter (STPS) and reflection-type phase shifter (RTPS). A phase-shifted structure that switches between slot line and microstrip is proposed for STPS design, and a 3-dB quadrature coupler based on a capacitively loaded coupled line and parallel transmission line structure is proposed for RTPS design. Equivalent models and closed-form equations are presented for both structures. From the theoretical analysis, it can be found that the proposed phase-shifted structure can achieve a wider matching bandwidth and a lower in-band phase error as the phase-shift range (PSR) increases, which is contrary to the conventional STPS. For the quadrature coupler, a design method to reduce the amplitude difference and phase difference is obtained by theoretical analysis. To validate the proposed concept, a 90° STPS, a quadrature coupler, an RTPS with greater than 90° PSR, a 180° PS with modified dc bias, and a continuously tunable 360° PS were designed, fabricated, and measured. From measurement, the operating bandwidth, return loss (RL), in-band phase error, maximum rms phase error, maximum rms amplitude error, and circuit size of the proposed hybrid architecture 360° PS are 1.7-2.28 GHz (29.1%), 10.5 dB, ±4.46°, 2.67°, 0.24 dB, and 0.099\lambda _{\text {g}}^{2} , respectively. The average insertion loss at the center frequency is 1.9 dB. The measured results demonstrate the validity of the proposed design method for continuously tunable 360° PS with compact circuit size and low in-band phase error.