Compact Analog Phase Shifters using Thin-Film (Ba,Sr)TiO3 Varactors

This paper describes the realization of compact 360 degree phase-shifter MMICs using thin-film BST varactors in a series cascade of all-pass networks. Unlike conventional delay-line structures, all-pass networks provide constant phase shift with small variation of insertion loss. In similar fashion, very broadband phase-shifters can be implemented by cascading all-pass networks with staggered center-frequencies. Using a thin-film BST technology for the varactors, extremely compact and low-cost phase-shifter structures have been developed. Selected results are shown in the 1-30GHz range.