Single-Beam 1 Bit Reflective Metasurface Using Prephased Unit Cells for Normally Incident Plane Waves

A single-beam prephased 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 prephase 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 180°±25° 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 prephases with a 90° 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° 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 prephased 1 bit metasurface can achieve single-beam patterns under normally incident plane waves.