Single-Beam-Scanning 1-bit Metasurface With Dual Circular Polarization Based on Hybrid Coding Mechanism

In this article, a single-beam-scanning metasurface with dual circular polarization (CP) using hybrid coding mechanism is presented, which can steer the scattered wave in a large range of angles under the planar incident wave. In order to suppress the grating lobes generated by periodic 1-bit phase quantization errors, elaborately designed 2-D fixed phase delays (FPDs) are introduced. The 1-bit active coding is designed based on the current reversal method, which realizes two states with 180° phase difference over the frequency range of 8.5–11 GHz by switching two p-i-n diodes for both left-handed CP (LHCP) and right-handed CP (RHCP) incidence. The passive coding is realized by rotating the metasurface unit cell based on the Pancharatnam-Berry (P-B) phase principle to introduce the 2-D FPD. The proposed design mechanism is theoretically analyzed, full-wave simulated, and demonstrated by experiment. An $8\times 8$ metasurface prototype is fabricated and measured. The experimental results show that steered beams from −30° to +30° without grating lobes in both $xo\textit {z}$ and $yo\textit {z}$ planes can be obtained around 9.5 GHz. The sidelobe level (SLL) can be minimized to −8.87 dB, and the beam pointing deviation is within 3°.