Implementation and Characterization of Butler Matrix Integrated with Array Antenna in Two-Layer Structure

This paper presents the development of a compact beam-steerable antenna by integrating a Butler matrix with an array antenna. The configuration comprises a 4 × 4 Butler matrix as a feeding network and four square patch antennas as radiating elements. For achieving a compact configuration, the Butler matrix is miniaturized using meandering techniques, while radiating elements are arranged in a linear array. The Butler matrix and array antenna are constructed in a two-layer structure and connected one each other using a microstrip line feeding method through 50–Ω coaxial cables. Therefore, a compact BSA with the dimensions of $1.82\lambda_{0}\times 0.58\lambda_{0}$ can be achieved. The designed configuration is then fabricated, and the corresponding prototype is experimentally measured. The results of measurement indicate good reflection coefficient response and radiation pattern characteristics of proposed configuration. The −10 dB reflection coefficient bandwidth is 12.5%, and the beams can be steered at the elevation angles of ±5° and ±40°.