A Compact Broadband 4x4 Butler Matrix With 360° Continuous Progressive Phase Shift

This article presents a novel compact broadband4x4 Butler matrix with 360 degrees continuous progressive phase shift.The tunable Butler matrix is composed of a typical 4x4 Butlermatrix and four wideband continuously tunable phase shifters(PSs). To realize the size miniaturization, the right-handedtransmission line (RHTL) is employed to construct the compactbranch-line couplers and crossovers, which performs well overthe operating bandwidth. The size of the proposed Butler matrixutilizing the compact coupler and crossover is reduced about 50%compared with the traditional design. A novel coupled-resonantPS is proposed to realize 135 degrees +/- 10 degrees continuous phase shift overa wide fractional bandwidth (FBW) of 33.3% (2.0-2.8 GHz).By cascading the miniaturized 4x4 Butler matrix and the 135?continuously tunable PSs, 360 degrees continuous progressive phase shiftbetween four outputs can be obtained. The measured resultsverify the feasibility of the design