A Compact Broadband 4#x00D7;4 Butler Matrix With 360#x00B0; Continuous Progressive Phase Shift

摘要

This article presents a novel compact broadband $4times 4$ Butler matrix with 360#x00B0; continuous progressive phase shift. The tunable Butler matrix is composed of a typical $4times 4$ Butler matrix and four wideband continuously tunable phase shifters (PSs). To realize the size miniaturization, the right-handed transmission line (RHTL) is employed to construct the compact branch-line couplers and crossovers, which performs well over the operating bandwidth. The size of the proposed Butler matrix utilizing the compact coupler and crossover is reduced about 50#x0025; compared with the traditional design. A novel coupled-resonant PS is proposed to realize $135^{circ }pm 10^{circ }$ continuous phase shift over a wide fractional bandwidth (FBW) of 33.3#x0025; (2.0#x2013;2.8 GHz). By cascading the miniaturized $4times 4$ Butler matrix and the 135#x00B0; continuously tunable PSs, 360#x00B0; continuous progressive phase shift between four outputs can be obtained. The measured results verify the feasibility of the design.