3D-Printed transmit-array antenna for broadband backhaul 5G links at V band

The low-cost and compactness of transmit-array antennas (TAs) make them attractive for 5G backhaul links. However, the TA advantage is less obvious when considering the broadband operation requirement. Two main factors influence the bandwidth performance: i) the bandwidth of the unit cells; ii) the number of 360° phase wrapping zones in the aperture, which are designed for a specific frequency. Herein, we overcome these limitations by using all-dielectric unit cells (inherently broadband) and by developing a general method to quantify and manage the intricate relation between antenna gain, bandwidth and antenna height. Based on this framework we optimize, as an example, a TA design (focal distance, F=63 mm and aperture diameter D=80 mm) to comply with typical gain specification for 5G backhaul links (>30 dBi) in the WiGiG band (from 57 to 66 GHz). The feed is a dedicated compact horn ( $8\times 5\times 22 mm^{3}$ ) that provides a proper illumination of the aperture. Additive manufacturing is used to simplify the manufacturing process of the antenna. A very good agreement between simulations and experimental results is obtained, achieving good aperture efficiency for this type of antenna (42%), which rivals with existing solutions based on more expensive manufacturing techniques.