Single-Beam-Scanning 1-Bit Metasurface with Dual Circular Polarization Based on Hybrid Coding Mechanism

In this paper, a single-beam-scanning metasurface with dual circular polarization 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 two-dimensional 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 GHz - 11 GHz by switching two PIN diodes for both left-handed circular polarization (LHCP) and right-handed circular polarization (RHCP) incidence. The passive coding is realized by rotating the metasurface unit cell based on Pancharatnam-Berry (P-B) phase principle to introduce the two-dimensional FPD. The proposed design mechanism is theoretically analyzed, full-wave simulated, and demonstrated by experiment. An 8×8 metasurface prototype is fabricated and measured. The experimental results show that steered beams from -30° to +30° without grating lobes in both x-o-z plane and y-o-z plane can be obtained around 9.5 GHz. The side lobe level (SLL) can be minimized to -8.87 dB, and the beam pointing deviation is within 3°.