Ultra-Wideband Dual-Circularly Polarized Crossed-Dipole Antenna With Stripline Coupler and Parasitic Elements for Vehicular Sensing and Communications

Targeting the high-quality signal and transmission robustness of sensing and communications in future intelligent vehicles, this article proposes an ultra-wideband compact antenna which can work at left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP). It consists of two cross-arranged dipoles, four parasitic elements, a feeding network, and a ground plane. The radiation arm of the dipoles is shaped in a truncated elliptical form to broaden the 3-dB axial ratio bandwidth. To stabilize the radiation pattern and improve the axial ratio at higher frequencies in the proposed cross-dipole antenna, four sequential rotating patches are strategically positioned on the two cross-arranged dipoles. The design incorporates a specialized and highly-integrated feed network, comprising a miniaturized 90° stripline coupler and two double-sided parallel lines. This feed network is meticulously engineered to excite the dipoles, resulting in the generation of dual-circularly polarized radiation. Through the implementation of this innovative approach, an ultra-wideband dual-circularly polarized antenna having stable radiation pattern is designed, manufactured, and measured. The proposed cross-dipole antenna achieves impedance bandwidth (Reflection coefficient ≤−10 dB) from 1.25 to 4.7 GHz and axial ratio bandwidth (Axial ratio ≤ 3 dB) from 1.3 to 4.7 GHz, indicating that the overlapped impedance and axial ratio bandwidth reaches 113.3%. Good radiation performance is obtained within the ultra-wide bandwidth.