Millimeter-Wave Dual-Circularly Polarized Wide-Angle Scanning Antenna Array for Vehicular Communication Systems

This manuscript presents a millimeter-wave wideband and wide-angle scanning dual-circularly polarized (CP) antenna array based on traveling-wave sequential feeding metasurface (TSF-MS) for vehicular communication systems. The antenna element consists of a dual-layer rectangle metasurface structures fed by a simple two-port traveling-wave sequential stripline through four non-uniform crossed slots. Each crossed slot will be excited twice by the ring strip line, which means the slots are reused. By adjusting the length and width of the crossed slots and strip line, two orthogonal electric fields with equal amplitudes and 90° phase difference can be achieved, thereby realizing good right- and left-handed circular polarizations (RHCP, LHCP). The antenna element can achieve a wide impedance bandwidth of 25.8% and axial ratio (AR) bandwidth of 31%, with a compact size of 0.38 $\lambda_{\text{mid}}$, which is far smaller than the other reported CP antenna. Then, based on the newly designed dual-CP antenna element, a 4 × 4 array is constructed by 2 × 2 sequentially rotated subarrays. This layout can improve the scanning performance, suppress the cross polarization, and realize modular wiring to simplify the feed network. Benefited from the layout, the array can achieve a wide scanning angle of ±60° over the whole bandwidth with the gain variation and AR less than 3 dB. For demonstration, one prototype is fabricated and the measured results show a good agreement with the simulated results. The dual-CP wide-angle scanning phased array can fully meet the communication needs of vehicular communication systems, indicating a good application prospect.