1-bit Terahertz beam-scanning space-time-coding metasurfaces based on PB phase principle

The beam scanning range and precision are limited by the low quantization accuracy of traditional space-coding metasurfaces. Aiming at this problem, we first propose a 1-bit reflective time-coding metasurface based on the Pancharatnam-Berry (PB) phase principle, with an accurate phase difference of 180° and a phase shift error of less than 0.5° in the operating band of 95GHz-115GHz. The insertion loss of the unit cell is less than 5.6 dB, with a bandwidth of 19.4%. In this paper, the equivalent 4-bit phase distribution is optimized by fractional time-coding to compensate for quantization errors. Finally, quasi-continuous beam scanning with a large field of view greater than ±70° is achieved with a minimum step size of 0.5°. The proposed terahertz space-time-coding metasurface offers a low-cost, low-profile, and reconfigurable approach for potential applications in future 6G communication and radar imaging.