Dual-Beam Power Allocation Transmitarray Antenna Based on Independently Regulated Copolarized Amplitude/Phase Metasurface

In this letter, a transmissive metasurface (MS) with independently regulated co-polarized amplitude and phase is proposed. The unit of MS is composed of four metal layers printed on two substrates. The co-polarized transmission phase and amplitude are adjusted by double-split ring resonator (DSRR1) and DSRR2 surrounding the circular patch, respectively. By adjusting the opening angle of DSRR1, a wide phase coverage range of 333° is achieved. Additionally, by rotating DSRR2, continuous amplitude control is attained while maintaining a constant transmission phase. The DSRR1 and DSRR2 are placed on same metal layers and circular patches are placed in each metal layer to decouple the amplitude and phase modulation. Besides, the proposed MS manipulate the co-polarized wave without the need for polarized gratings. Thus, the number of substrate layer is reduced compared to other reported multi-layer co-polarized transmissive units. To demonstrate its characteristics, we design a transmitarray antenna for power allocation that can generate dual beams with power ratios of 2:1 or 1:1. Finally, a prototype with 2:1 power ratio is fabricated and measured. Its beams are directed at (θ = 10°, ϕ = 0°) and (θ = 25°, ϕ = 90°). The measured results are consistent with the designed goals and the aperture efficiency (AE) can reach 25.13%.