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International Journal of Antennas and Propagation
Volume 2014, Article ID 583903, 7 pages
Research Article

Miniaturization Design for 8 × 8 Butler Matrix Based on Back-to-Back Bilayer Microstrip

1School of Electronic and Information Engineering, Beihang University, Beijing 100191, China
2Research Institute of Unmanned Aerial Vehicle, Beihang University, Beijing 100191, China

Received 27 January 2014; Accepted 23 February 2014; Published 30 March 2014

Academic Editor: Xiang Zhang

Copyright © 2014 Yu Zhai et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


A low-cost, compact 8 × 8 Butler matrix based on a novel bilayer microstrip configuration is presented and implemented for 4.3 GHz telecommunication application. A back-to-back placed bilayer microstrip structure has been proposed to avoid using crossover. To expand operational bandwidth of the Butler matrix, a three-branch line directional coupler has been employed as 3 dB/90° bridge, and a kind of improved two-order Schiffman phase shifter has been adopted as fixed phase shifter. For application of indoor wireless communication, a compact broadband 8 × 8 Butler matrix has been designed and fabricated. The measured results show that the return loss of the matrix is lower than −10 dB, the isolation is better than 17 dB, the power distribution error is less than ±2.0 dB, the phase error is less than ±15°, and the relative bandwidth is more than 23%.