Research On The Design Of Millimeter Wave Frequency Selective Surface And Its Ultrafast Laser Processing

Frequency selective surface(FSS)is a surface structure composed of dielectric layer and metal layer,which can reflect or transmit specific electromagnetic waves.With the rapid development of modern communication,stealth technology,anti-missile technology and photoelectric interference technology,the demand for electromagnetic wave frequency band is becoming increasingly higher,and the research of FSS is gradually developing to sub-millimeter wave,millimeter wave or other high frequency band.However,for millimeter wave FSS with short wavelength,the traditional processing has great difficulty.Therefore,this paper simulates the design of millimeter wave FSS unit structure with emulation software,and combines ultra-fast laser processing technology to realize the exploration of millimeter wave FSS processing technology.The main research contents of this paper can be summarized as follows:(1)The millimeter wave FSS structure for U-band is proposed.The U-band millimeter wave FSS is composed of three layers of metal structure,and its middle layer of metal structure is composed of hexagonal patch ring and hexagonal patch arranged according to the triangle.The upper and lower layers have the same metal structure and are composed of complementary structures of the middle layer.Firstly,the working bandwidths of six-sided gap FSS and square gap FSS are compared,and the six-sided gap FSS with larger bandwidths is selected.Then,based on the principle of the multi-layer structure is used to form multi-resonant element to realize multi-frequency design,the complementary structure is added to the other side of the dielectric layer,therefore,a double-layer complementary hexagonal FSS with dual-frequency characteristics is proposed.Based on the resonance points of different layers are fused with each other,a three-layer complementary hexagonal FSS is designed by adding layers of metal structure and dielectric substrate,which can transmit electromagnetic waves in 24.16 ～ 27.69 GHz and U-band.The FSS can be used as a secondary reflector in multi-frequency common reflector antenna.(2)A double-layer large-spacing millimeter-wave FSS structure working in E-band is proposed,in which dielectric substrate was loaded on and below each layer of metal structure.The metal structure consisted of square ring gap and six-side ring gap,which are separated by foam.The Eband FSS transmits electromagnetic waves in 60.03 ～ 89.33 GHz,covering the whole E-band.At the same time,it also has good flatness,good out-ofband suppression ability,and small insertion loss.And it has good angle stability at oblique incidence of 60° and is not sensitive to TE /TM polarization.It can be used as waveguide filter in millimeter wave field,such as high broadband and short range mobile communication,autonomous driving and target detection of 77 GHz automotive radar,etc.(3)The ultra-fast laser lens processing system is built to explore the relationship between surface topography and scanning mode,scanning speed,scanning interval and laser power.After experimental study,a good combination of processing parameters is optimized: laser power is 250 m W,scanning speed is 1.5mm/s,scanning interval is 10μm,which verifies the feasibility of ultra-fast laser processing millimeter-wave FSS,providing a solid experimental basis for millimeter-wave FSS processing.(4)Millimeter-wave FSS samples are prepared by combining the established ultrafast laser lens processing system and appropriate process parameters,and the electromagnetic characteristics of E-band FSS samples are tested by waveguide method.The results show that there is some error between the test results and the simulation results in the frequency range of 26.5 ～ 33 GHz,but the test results are basically consistent with the simulation results in the frequency range of 33 ～ 40 GHz.It is proved that the ultra-fast laser lens processing system is suitable for the preparation of millimeter-wave FSS.