Synthesis and Design of Shunt Resonator-Based Phase Shifters With Reduced Phase Error and In-Band Magnitude Ripple

This paper presents a new design method for phase shifters that, for the first time, manipulates out-of-band transmission zeros (TZs) generated by shunt resonators to achieve the phase reconfiguration. Compared with conventional designs, the proposed out-of-band reconfiguration approach minimizes the impact on in-band performance during the reconfiguration, thereby substantially reducing in-band phase errors and magnitude ripples. With a derived closed-form phase slope formula, theoretical analysis is given to guide the unit design. Meanwhile, also based on this formula, the phase slope alignment is achieved for the entire phase shifter by utilizing the Particle Swarm Optimization (PSO) algorithm to optimize each individual resonator. To validate the proposed design method, two $C$ -band prototypes with different circuit topologies are designed, fabricated and measured. Both prototypes demonstrate a low phase error (±15.6° and ±5.0°) and magnitude ripple (0.7 dB and 0.6 dB), across a 360° phase tuning range, surpassing most existing phase shifters. This work is expected to be a good candidate for modern industrial applications including phased array radars, high precision phase modulators and other intelligent communication or sensing systems.

I. Introduction

Tunable phase shifters are essential components in various RF/microwave systems, such as phased array transceivers, phase modulation (PM) systems, and emerging smart antenna modules [1], [2], [3], [4]. Due to the rapid evolution of next-generation radar, sensing and communication systems in the past few decades, there has been a growing demand for reducing the in-band phase error of a phase shifter. On one hand, in advanced radar systems, the detection precision and accuracy are directly related to the phase error. On the other hand, in modern communication systems, the phase error will adversely affect functions including spatial multiplexing, interference suppression and channel estimation, which are crucial in multiple-input-multiple-output (MIMO) systems. As a result, the phase error will significantly impact signal quality, data transfer rate and the overall system reliability. Therefore, there is an urgent demand for the design of phase shifters with minimized phase error.