Research On Manipulation Of Space Electromagnetic Waves And Applied Technology Based On Frequency Selective Surface

In the field of manipulating space electromagnetic waves,whether to utilize traditional optical/electromagnetic devices or use artificial electromagnetic media such as metamaterial and photonic crystal,the essence of controlling the propagation states of electromagnetic waves is to use three-dimensional electromagnetic structure.Since these three-dimensional electromagnetic structures have some issues such as large volume,high loss,and large area processing difficulty,the development of controlling space electromagnetic waves is greatly restricted.As a kind of common artificial electromagnetic surface,frequency selective surface?FSS?not only has the characteristics of low-profile and low-loss,but also owns many advantages,such as mature processing technology,low cost and convenient attachment to a physical object.Based on the merits mentioned above,FSS has been widely used in the field of manipulating space electromagnetic wave.By using FSS,a high-efficiency manipulation of space electromagnetic wave can be realized,and the integration and practicability of devices are further improved.Therefore,the research on manipulation of electromagnetic waves and applied technology based on FSS becomes a frontier topic in the field of information technology.For achieve different application demands,such as realization of square wave filtering for space electromagnetic wave,free switching between transmission and cut-off states,and control of transmission direction,the researches on symmetric bi-planar FSS,active FSS and frequency selective metasurface derived from FSS are carried out in this dissertation and the main contents are as follows:1.To grasp the physical mechanism of manipulating space electromagnetic wave based on FSS,the working mechanism of FSS is qualitatively analyzed from the microscopic view of electron motion.By quantitative analysis of many theories and methods about FSS such as electromagnetic field theory,transmission line theory,pattern matching method,equivalent network method and equivalent circuit method,fast analysis and calculation for the frequency response of FSS can be achieved.Moreover,by exploring the propagation mode and evanescent mode in FSS structure,the stable filtering condition can be defined,namely the working wavelength of FSS is larger than the critical wavelength?_c=max??₁,?₂,?₃?.2.A common technical approach of realizing the square wave filtering for space electromagnetic wave is using symmetric bi-planar FSS structure.However,it is faced the multi-scale and multivariable problem in the optimization design process.Based on mutual admittance approach,a figure describing the ratio of mutual admittance to self-admittance(|Y^2,1|/Y_0re)with respect to the thickness d₂ and permittivity?₂ of coupling medium is shown in this dissertation by establishing the relationship between free variables of symmetric bi-planar FSS structure.Moreover,the specific criterion that the evanescent mode should be much smaller than the transmission mode is also proposed,and therefore the range of initial structural parameters of symmetric bi-planar FSS can be obtained quickly and accurately.After that,the optimal parameters of coupling medium can be further determined from the range of initial structural parameters by combining with the ratio of mutual admittance to self-admittance under variable incident angles and different polarizations.Meanwhile,to solve the problem that the optimal permittivity of coupling medium is non-existent?or difficult to obtain?,an array of dielectric cylinder is designed and fabricated for equivalent substitution according to the theory of periodic waveguide.3.There are two prominent problems in the design of active FSS.One is that the electromagnetic filtering characteristic of active FSS is usually bad at the rising edge?or falling edge?,and the other one is that the integrated design process of filtering structure and feed network can't be extended.To resolve the first problem,an element of active FSS with size of about 0.2?is designed by loading the electrically controlled PIN diode on the FSS,which can achieve the free switch between band pass and band stop responses at 2.45GHz.The transmissions at the center of passband and stopband are respectively-0.6d B and-20dB.Additionally,the proposed active FSS structure can realize the unlimited extension in a certain dimension since its feed network is designed based on Wheatstone bridge,overcoming the difficulty introduced by the second problem.4.Realizing the manipulation of transmission direction of electromagnetic wave is now confronted with many problems such as narrow bandwidth and low radiation efficiency.According to the boundary conditions of electromagnetic field,the relationships between the electromagnetic fields on both sides of metasurface and distributions of electric surface admittance as well as magnetic surface impedance are established in this dissertation,and the transmission magnitudes and phases with respect to electric surface admittance and magnetic surface impedance can be further determined.By combining the symmetric anchor shaped structure with symmetrically connected split-ring resonator,a Huygens particle with nearly full controls of transmission magnitudes?0⁰.9?and phases?-180°¹80°?is designed.Based on the Huygens particles,a frequency selective metasurface prototype,which can achieve the effect of beam bending,is designed and fabricated.The measurement results show that the main lobes almost point at the azimuth angle of-57°and are 10 dB larger than side lobes in the range of 6.9⁷.1GHz.All in all,in this dissertation,a symmetric bi-planar FSS structure which can realize the characteristic of square wave filtering is optimized and designed quickly.An active FSS structure with free switch between band-pass and band-stop responses is also shown here,of which processing technology can be extended.Moreover,a frequency selective metasurface possessing the effect of beam bending is designed based on the Huygens particles,whose working bandwidth and radiation efficiency can perform well.This dissertation not only develops the design theory of manipulating space electromagnetic waves,but also expands its implementation approach and application field,which provides important theoretical principle and experimental references for manipulation of space electromagnetic wave based on FSS.