Optically transparent compact 4 × 4 Butler matrix for Wi-Fi applications

Abstract

In this paper, an optically transparent (OT) compact 4 × 4 Butler matrix (BM) operating at 2.4GHz for Wi-Fi applications is proposed. The device has structured grids refined in quadrilateral cell shapes. The dimensions of cells are chosen based on a simple formula which guarantees a minimum required transparency level in conjunction with a limited rounds of optimizations. A theoretical optical transparency value of 76.2% has been obtained without affecting the excellent electrical performance of the BM. Moreover, complimentary square split ring resonators (CS-SRRs) are patterned in the ground plane of each transparent transmission line in the BM. This loading technique provides a relative size reduction of 16.6% compared to a conventional structure. Simulated and measured results of the proposed design agree well with conventional BM’s results. The proposed technique and its related features can be expanded to other microwave devices.