Single-Layer Broadband Phase Shifter Using Multimode Resonator and Shunt $\lambda $ /4 Stubs

This paper presents a new method for single-layer broadband phase shifter without needing any coupling structure. The phase shifter consists of a multimode resonator and two shunt λ/4 stubs. Meanwhile, the bandwidth of proposed phase shifters can be achieved more than 100%. For prescribed return loss, phase shift value, and phase error, this paper develops a synthesis approach to determine all parameters of designed phase shifter. In addition, both the return-loss bandwidth and phase-error bandwidths can be considered simultaneously so as to determine the return loss and phase error for a desired bandwidth. The 45°, 90°, 135°, and 180° phase shifter are theoretically designed and presented. To validate the design method, a broadband 90° phase shifter is designed, fabricated, and measured. The synthesized, simulated, and measured results are found in good agreement with each other, and the experimental results show that the phase shifter achieves 90° ± 5°, |S11| <; -14 dB, and insertion loss <; 0.7 dB over the bandwidth from 1.43 to 4.45 GHz (102.7%).