Design and Implementation of a 1 × 4 Bow-Tie Antenna Array Integrated with a Butler Matrix for Switched-Beam ISM-Band Applications

Abstract

Wireless communication systems based on beamforming antennas encounter many design issues, including limited directional precision, complexity of implementation, and poor performance in regard to gain at small form factors. This paper presents an integrated 1 × 4 bowtie antenna array (AA) and a 4 × 4 Butler matrix (BM) to achieve effective beamswitching capabilities at the 2.45-GHz ISM frequency band. This integrated design enables four different beams to be generated corresponding to phase shifts of -135°, -45°, +45°, and +135°. The design of the 1 × 4 AA and matched 4 × 4 BM was initially validated using simulation and then further validated by prototyping and measuring the performance of the same configuration. When comparing the results from simulation and measurement, a strong similarity was realised between the two. In addition, the antenna array provided approximately 150 MHz of impedance bandwidth and a voltage standing wave ratio (VSWR) of ≤ 2 and a 23 dB reflection coefficient at the centre frequency of 27. The results of the comparative analysis of the antenna arrays constructed from FR4, PTFE, RT5880, and RO4350B showed the impact of the dielectric properties and thickness on gain performance. The antenna array fabricated with FR4 (1.60 mm) produced a measured gain of 8.71 dBi and a theoretical gain of 9.07 dBi and an elevation and azimuth beam width of 25.5° and 250°, respectively. These experimental results conclusively demonstrate that this integrated system provides stable, low-cost, and effective beam-switching performance that can be utilised in current wireless communications systems.