Design Of Phase Tuning Metasurfaces

Metasurfaces are 2-D planar artificial electromagnetic(EM)structures composed of periodic or aperiodic sub-wavelength unit cells.As new EM materials,metasurfaces can be applied to electronic countermeasures due to their formidable capabilities of manipulating EM waves.Metasurfaces have powerful capabilities to control the amplitude,phase and polarization of EM waves.Aiming at the phase characteristics of EM waves,this paper has carried out the research and design of phase-tuning metasurfaces from different perspectives,such as the tuning range,incident angle and polarization.The main content is summarized as follows:1.A reflective active metasurface with full phase tuning is designed,which uses a combination of active devices and passive metasurfaces.The active metasurface realizes the function of controlling the bias voltage of the varactor diodes through an external signal,thereby adjusting the reflection phase dynamically.The series dual-resonance structure breaks through the limitations of insufficient phase tuning range of traditional metasurfaces.Finally,the reflection phase tuning range is maintained above 360°,and the reflection amplitude is maintained above-3 d B in the 2.35 GHz～2.9 GHz frequency band.The design has strong potential in abnormal reflections,electromagnetic stealth,beam forming antennas,beam scanning antennas and phase shifters due to the advantages of low profile,easy processing,and flexible adjustment.2.From the perspective of engineering applications,the angle-insensitive and dual-polarization phase tuning metasurfaces are designed.First,three kinds of angle-insensitive full phase tuning active metasurfaces are designed and one of them is selected for physical processing and experimental verification.In the case of 0°,30°,45°and 60° incident angles,the amplitude and phase test curves are consistent,indicating that the angle stability of the design is good.Secondly,a dual-polarized phase tuning metasurface is researched and designed from the perspective of EM wave polarization.Compared with the single-polarization metasurface,this designed metasurface has a more stable phase tuning capability,which is less sensitive to the polarization angle of the incident wave.3.A 3-bit coding metasurface based on the full phase tuning metasurface is designed.The design principle of the coding metasurface unit and the scattering mechanism of the coding metasurface is described.Scattering beams of the matesurface are effectively controlled in real time via a FPGA module.By changing the sequences of the metasurface,the reflected beam can realize the functions of multi-beam splitting,beam diffuse scattering and single-beam scanning.Compared with 1-bit and 2-bit coding metasurfaces,this design has a smaller phase quantization error and richer functions,which has great potential in reducing the radar cross section(RCS)to achieve electromagnetic stealth.