Generating Arbitrary Shaped Near-Field With Arbitrary Polarization by Combining Tensor Holographic Impedance Metasurface and Phase Conjugation Techniques

This letter innovatively proposes combining the favorable features of tensor holographic impedance metasurface (THIMS) (flexible polarization) and phase conjugation (arbitrary shaping and polarization) to flexibly design THIMS, which has the ability to generate arbitrary shaped near-field with arbitrary polarization without increasing cost, structural, and calculating complexity. The THIMS unit cell is modulated by two degrees of freedom: geometry parameters θ_t (metal patch rotation angle) and g, which solely determine the current direction and the unit cell impedance, respectively. The design scheme of continuous surface impedance value and two direction unit cells (θ_t = 0° or 90°) is used to design high-efficiency THIMS. Two examples are designed: A right-hand circular polarization square “▪”-shaped near-field with size 32 mm × 32 mm at 18 GHz. A linearly polarized “I”-shaped near-field with size 20 mm × 56 mm at 18 GHz. The designed shaped near-field has the following advantages: high focusing efficiency of up to 63.3% (measured), high circular polarization conversion efficiency of 95.3% and sidelobe as low as −15 dB. The calculated, simulated, and measured results agree well, and validate the proposed technique.