Design And Application Of Switchable Metasurfaces Based On Reconfigurable Technology

Electromagnetic metasurfaces are a new type of artificial electromagnetic material that can freely control the amplitude,phase,polarization and other characteristics of electromagnetic waves,and are widely used in the field of civilian wireless communication and military.In the past few decades,electromagnetic metasurfaces have made tremendous progress,and high-performance,miniaturized metasurfaces have been continuously discovered and updated.However,with the development of diversified and intelligent devices,single function,inability to dynamically modulate and narrow-band characteristics are one of the main challenges of electromagnetic metasurfaces design,which greatly limit the application of electromagnetic metasurfaces in antenna stealth design,antenna beam modulation,etc.Therefore,this thesis takes the design and application of switchable metasurfaces based on reconfigurable technology as the research topic,and proposes two functional switchable metasurfaces and a broadband switchable 1-bit transmission/reflection phase-shifting surface.The specific work is as follows:(1)In response to the development needs of metasurfaces in terms of multi-functionality,broadband,and dual polarization.Firstly,a switchable polarization conversion/in-phase reflection metasurface(PCIPR-MS)is investigated.By introducing PIN diodes active device at the diagonal end of the high-efficiency polarization conversion surface(PCM)based on the 2.5 D structure,the PCIPR-MS unit achieves switching between polarization conversion characteristic to in-phase reflection characteristic.Applying PCIPR-MS to dipole circularly polarized antenna arrays,the line-to-line polarization conversion property of the metasurface enables the antenna to reduce the single-station radar cross section(RCS)by more than 10 dB within a relative bandwidth of 35%.While the in-phase reflection property of the metasurface is used to improve the antenna gain,radiation efficiency and other radiation performance.Secondly,a switchable polarization conversion/absorbing surface(PCA-MS)is investigated.The PCA-MS unit is designed to switch between absorption characteristic to polarization conversion characteristic by introducing a switching structure in a resistorloaded 2.5 D metamaterial-based absorber and changing the current loop.The PCA-MS units are arranged in a 2×2 periodic scale as the reflective floor of the dipole antenna,and the antenna achieves circularly polarized wave radiation in the 5.06-5.23 GHz band by using the polarization conversion characteristic of the metasurface,avoiding the complex feed network structure.While the single-and dual-station RCS of the antenna is effectively reduced in the operating band by using the absorbing characteristic of the metasurface.(2)A reconfigurable broadband 1-bit transmission/reflection phase-shifting surface is studied for the needs of metasurfaces in antenna dual-beam,beam scanning and focusing.The unit achieves independent regulation of the transmitted phase characteristic and reflected phase characteristic under different polarized incident waves by designing the reflected phase shifting unit and transmitted phase shifting unit independently,using the polarization selective grid combination design,and using the metal over-hole structure and high-impedance line to design the DC bias circuit.Based on the design unit,a quasidiffraction-free beam antenna with integrated transmission/reflection function is proposed.By dynamically adjusting the phase distribution of the aperture field,the antenna achieves a scan of quasi-diffraction-free beam from 0°to 60°.The quasi-diffraction-free beam antenna has the advantages of dual-beam,independent beam modulation,etc.,and has good application prospects in the fields of near-field communication and imaging.