Broadband CP crossed-stepped-dipole antenna incorporating a cross slotted square patch

A simple broadband circularly polarised (CP) crossed-dipole antenna is proposed. The antenna is composed of two crossed-strip dipoles with two stepped sections, which are connected by vacant-quarter rings to realise CP radiation, and a parasitic cross-slotted square patch (CSSP) consisting of a modified square-ring patch and a cross-slot, which surrounds the crossed dipoles. By controlling the width ratio of the two strip sections, the stepped dipole can provide proper amplitude between two orthogonal modes to achieve wide axial ratio (AR) bandwidth. The CSSP can generate two minimum AR points simultaneously: one point is from the ring-patch mode, while the other is generated based on the mode from the combination of the crossed dipole and the cross-slot, which can be equivalent to a magneto-electric dipole. An antenna prototype is fabricated and measured for design verification. The experimental results show that the proposed antenna with its simple structure has a wide -10 dB impedance bandwidth of more than 80% (3.38-7.97 GHz) and a 3 dB AR bandwidth of 59.1% (4.17-7.67 GHz). The proposed antenna also demonstrates excellent features including high gain, good stability, and symmetrical radiation pattern.