Wideband Differentially Fed Dual-Polarized Antenna for Existing and Sub-6 GHz 5G Communications

This letter proposes a differentially fed \pm45^{\circ } dual-polarized antenna with ultrawideband operation. It consists of two orthogonal stepped-dipoles backed by an inverted pyramidal cavity reflector for improvement in broadside gain. The stepped dipoles built on both sides of the substrate are constructed from small square pads and square loops for multiresonances to enhance the bandwidth. The dipoles are fed from four coaxial lines with a crossed-strip structure to accommodate the differential feed. The final design with overall size of 0.75\lambda _{\text{min}} × 0.75\lambda _{\text{min}} × 0.21\lambda _{\text{min}} (\lambda _{\text{min}} is the free-space wavelength referring to the lowest operational frequency) has been fabricated and measured. The antenna achieves a measured bandwidth of 74.2% (1.74-3.79 GHz) for return loss >15 dB and a measured isolation better than 43 dB among the differential ports. Its bandwidth can cover the frequency spectrums of the existing and new wireless communication systems such as 2G/3G/4G (1710-2690 MHz) and sub-6 GHz 5G (3100-3800 MHz). Additionally, the measured peak broadside gain is 10.5 dBi with cross-polarization level of < 20 dB within the operational bandwidth.