Efficient Methods to Enhance the Bandwidths of Transmitarray Antennas

This paper introduces two efficient methods to enhance the bandwidths of transmitarray antennas. For the transmitarray antenna based on resonant unit cells, two unit cells based on polarization-rotation structures are proposed to offer a 2-bit transmission phase, where the resizing unit cell is avoided to widen the bandwidth. For the lens antenna based on dielectric stubs, four unit cells are selected to offer a 2-bit transmission phase as well, to broaden the bandwidth, the effects of the oblique incidences are considered and eliminated. For the first transmitarray antenna using the proposed method, the measured 1- and 3-dB gain bandwidth is 28.0 - 37.5 GHz (29.5%) and 25.1 - 39.1 GHz (43.7%), respectively. For the second lens antenna using the corresponding proposed method, the measured 1-dB gain bandwidth is 24.8 – 30 GHz (18.9%). The proposed two methods are generalized and is also feasible for reflectarray antennas and reconfigurable intelligent surfaces.