A broadband dual-polarized single-layer 1-bit unit cell is proposed for achieving the independently controllable dual-beam reflectarray antenna. The unit cell independently provides two-state phase compensation for two orthogonally linearly-polarized waves. The 180-degree reflective phase difference between the two states is achieved by tuning the magnetic resonance of State 0 and the electrical resonance of State 1. With its two resonances close to each other, the unit cell has a reflective phase difference of 180±20 degrees between two states over a broad bandwidth of 27.2-51.1 GHz. The cross-polarization levels of below -30 dB ensure the high isolation between two polarizations. Using the proposed dual-polarized unit cells, a 1-bit dual-beam reflectarray antenna is designed and excited by a dual-polarized horn to show the ability of independently controlling two orthogonally linearly-polarized waves. At 33 GHz, the beams direct to -15 degrees and 20 degrees for the feeding of horizontally and vertically polarized port, respectively. The 1.5-dB gain bandwidth is greater than 20% for both polarizations. The proposed dual-polarized reflectarray antenna with independently controllable 1-bit dual beams provides an alternative design for the multiuser multiple-input multiple-output applications.

A single-beam pre-phased 1-bit reflective metasurface is proposed to achieve single-beam patterns under normally incident plane waves. Theoretical analysis and numerical simulations are presented to show that, under normally incident waves, single-beam patterns can be achieved by introducing a fixed pre-phase distribution with two values in the 1-bit metasurface. Compared with conventional 1-bit reflective metasurfaces, the proposed scheme alleviates the inherent limitation of single-beam patterns on 1-bit reflective metasurfaces under normally incident plane waves. To verify the proposed scheme, a 1-bit unit cell is designed with a 180º ± 25º phase difference between the two states for frequencies ranging from 34.3 to 49.9 GHz, and a layer-stacking method is proposed to achieve two pre-phases with a 90-degree phase difference. As an example, three 1-bit reflective metasurfaces comprising 20×20 unit cells with single beams pointing separately at 0, 15 and 30 degrees are designed and measured over frequencies of 37.0 to 41.0 GHz; the measured sidelobe levels are less than -7.8 dB. Simulated and measured results show that the proposed pre-phased 1-bit metasurface can achieve single-beam patterns under normally incident plane waves.