A circularly polarized broadband array antenna with sequentially rotated patch elements with diamond-shaped artificial ground structure

In this paper, a circularly polarized microstrip array antenna is proposed by 2 $\times$ 2 CP elements in a sequential rotation mode with relative phases 0°, 90°, 180° and 270°. The overall dimension of this array antenna is 81.7 mm $\times$ 81.7 mm $\times$ 4.8 mm, array antenna consists of sequentially positioned four microstrip patch antenna elements with DAGSs. The main purpose of this work is to show the potential of enhancement of the 3-dB axial ratio bandwidth from a single element and basic array structures with an in-phase fed. The proposed antenna achieved a wide impedance bandwidth of 74.9 % at 4.30 GHz-9.45 GHz. The overlapped bandwidth of 3-dB axial ratio with -10-dB impedance bandwidth is 74.9%. In addition, the cross-polarization is amply suppressed in the proposed antenna.