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(degrees) 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(degrees) STPS, a quadrature coupler, an RTPS with greater than 90 degrees PSR, a 180(degrees) PS with modified dc bias, and a continuously tunable 360(degrees) 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(degrees) PS are 1.7-2.28 GHz (29.1%), 10.5 dB, +/- 4.46(degrees) , 2.67(2) , 0.24 dB, and 0.099 lambda(2)(g) , 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(degrees) PS with compact circuit size and low in-band phase error.