Broadband analog phase shifter based on multi-stage all-pass networks

Abstract

All-pass phase shifters using ferroelectric varactors are designed, fabricated, and measured. The design equations for the all-pass phase shifter are presented. The fabrication process of the ferroelectric varactors is described. Measurement results of single-stage all-pass phase shifters show that phase shift greater than 85° can be achieved under 10-V bias. At the frequency where maximum phase shift occurs, the insertion loss is less than 2dB and the return loss is greater than 12dB. Simulations based on the measured S parameters of the single-stage phase shifters show that, by cascading four stages of individually biased single-stage phase shifters, maximum phase shift of 180° can be achieved with a phase error as low as ±3° between 2.1GHz and 3.25GHz, corresponding to a 43% bandwidth.