Research On Controllable Electromagnetic Focusing Based On Metasurface

Frequency Select Surface(FSS)is a periodic array element that uses the same periodic metal structure(or slightly different)to be uniformly arranged on a certain substrate.It is often used in frequency selectors and spatial in the application of filters and radar cross-section reduction,the periodic arrangement of units can realize the adjustment and reconstruction of phase and frequency information.In some specific cases,it can achieve the same functions as the Phased array antenna.Compared with the phased array antenna which needs complicated power divider and feed network as well as large number of amplifiers and phase shifters,FSS has a clear price advantageIn this paper,the resonant structure of a single FSS surface unit is changed by reconfiguring the FSS,changing the on-off state and voltage of the diode,and reconstructing the working state of the metasurface so that it can work in different states,which realize the frequency selection function for the incident electromagnetic wave and change the frequency of the reflected electromagnetic wave.On this basis,we further realize the digital control of the unit.This technology includes,but is not limited to,high-performance Field-Programmable Gate Array(FPGA).Using this type of technology,reconfigurable reflective antenna arrays and digital programmable logic gate arrays can be linked together,So as to achieve precise and rapid adjustment of the electromagnetic wave amplitude and phase through the precise control of the digital circuit.In the research on the controllable electromagnetic wave focusing of metasurfaces,Firstly,the principle simulation of the surface elements loaded with diodes is carried out based on the research of metasurface reflector antenna principle.After that,After that,a metasurface structure that can reconstruct the resonant frequency of the surface through the on-off of the diode was designed and processed.Later,on the basis of the two states of diode on-off reconstruction,it is further expanded,using varactor diodes to linearly control the phase characteristics of the metasurface,and generate multiple resonance states(muti-bit).Through this adjustment,the phase characteristics of a single metasurface unit are changed to realize the functions of focusing and wave shaping.This kind of phase control combined with focusing theory and pattern shaping theory can focus or generate multiple beams at a specific position,thereby achieving beam focusing and phase deflection of the reflective array.Finally,we studied the phase distribution algorithm for approach focusing and far-field beam deflection,and optimized the focusing effect and beam deflection effect.