Wideband switched beam antenna array with circular polarization for undergound mines

A novel approach to design a wideband 4×4 Butler matrix with a circular polarization is presented. The proposed matrix has the interesting property of avoiding crossings which allows having the entire design over a single substrate layer. The proposed switched beam antenna system is composed of a Butler matrix network and four wideband circular polarization monopole antennas. The performance of the system in terms of beam switching, bandwidth and Axial Ratio (AR) has been simulated using CST Microwave Studio. The obtained results show an impedance bandwidth of 2.3 GHz spanning from 4.2 to 6.5 GHz and an axial ratio (AR) bandwidth of 1.2 GHz spanning from 5.2 to 6.4 GHz.