4Ã\x974 Butler Matrix Beam Forming Network using Novel Reduced Size Branchline Coupler

This paper presents a reduced size quadrature branch-line coupler that has achieved size reduction by approximately up to 80% without having to compromise performance. This design is realized on a low cost substrate (FR4, 0.50mm, ¿r = 4.4), yields an excellent return loss (¿49.0dB) and coupling loss (¿3.30 ~ ¿3.50dB) characteristics at 1.8GHz. The practical application of this novel reduced size branch-line coupler has been implemented and demonstrated in a 4×4 Butler Matrix beam-forming network operating at 1.7-2.0GHz.