Design of Two-Layer $4\times 4$ Butler Matrix With Wideband Performance

This paper presents a 2.4GHz two-layer
$4\times 4$
Butler matrix in microstrip technology. By integrating several wideband building blocks, i.e., slot-coupled quadrature hybrids, window-shape based crossovers, and Schiffman differential phase shifters, working bandwidth of the proposed Butler matrix achieves for 40%. To validate the overall performance, a prototype of the proposed circuit is implemented and fabricated. The measured results have a good agreement with those obtained from the simulation.