A Circularly Polarized Antenna Array with Broad Bandwidth and Flat Gain Characteristics

This paper presents an array antenna with wide bandwidth for tunnels under construction. The antenna is composed of eight sequential-fed patch antenna elements and a broadband feeding network capable of power division and phase shifting. By loading rectangular branches and arc-shaped chamfer parasitic elements, the performance of circular polarization is improved. Furthermore, to reduce the diagonal cross-polarization effectively, the eight antenna elements are rotationally laid out. The proposed antenna array achieves a simulated -10 dB impedance bandwidth of 73.3% (1.32-2.85 GHz), a 3dB AR bandwidth of 65.1%(1.45-2.85 GHz), and a peak gain of 15 dBic, which justify the applicability of the proposed antenna array for tunnels under construction.