Design of Planar 8-by-16 Butler Matrix for 16-Element Switch-Beam Antenna Array

摘要

In this paper, a planar 8×16 Butler matrix is designed using microstrip technology to build up a 16-element switched-beam antenna array. By connecting 180° hybrid couplers with 8 output ports of the conventional 8×8 Butler matrix, each original output is split into two ports with an equal power division and a 180° phase difference. Hence, the outputs of the Butler matrix can be expanded to 16 outputs. As the developed matrix is integrated with 16 microstrip antenna elements, one can form a 16-element switch-beam antenna array with 8 switched beams pointing to 8 different azimuth angles. The measured radiation patterns of the developed antenna array demonstrate that the main-beam directions point to azimuth angles of -47°, -33°, -19°, -4°, 5°, 17°, 30°, and 46° at 9.4 GHz and agree the theoretical results very well.