Research And Design Of High Power Electromagnetic Protective Surface Based On Energy Selection

With the development of high power microwave weapon(HPMW)and high power electromagnetic pulse technology,the security of electronic equipment is threatened seriously.Metasurface is a kind of artificial electromagnetic materials,and its electromagnetic characteristics can be designed according to people's expectations.In the aspect of system protection,the metasurface has gradually become a research hotspot because of its good spatial filtering characteristics.In high power electromagnetic protection,people mainly use active frequency selective surface(AFSS)and energy selective surface(ESS).In this thesis,,a dual-band ESS and ESS with the wideband protective performance are studied.The specific work is as follows:1)First,a dual-frequency ESS is proposed.By introduce four stubs on the four arms of cross patch,two independent resonant paths in the transmission mode is produced.As a result,the ESS can operate in two bands.slit arrays produced by the stubs of adjacent elements improve the bandwidth in the protection mode.The results show that the ESS can turn to protection mode under the high power electromagnetic pulse,and its protective bandwidth is 3.4 GHz and shielding effectiveness can reach to 20 d B.Under the working signal ESS is in transmission mode and have two transmission bands.The low-frequency passband is 0.8-1.3 GHz,Another one is around 5.36 GHz,and the bandwidth of 150 MHz.2)Then,A method to obtain broadband ESS by cascading switching metasurface and FSS is proposed.Its basic idea can be summarized as follows.Based on the broadband filtering characteristics of band-pass FSS,the ESS adds switch metasurface to solve the problem of insufficient protection in FSS,which has higher working frequency and protection bandwidth than normal ESS.This method reduces the layer coupling by the design of band-pass and band stop type metasurface cascade,which makes the switching characteristics of ESS and the broadband protection characteristics controlled independently.The ESS has retained the broadband protection of FSS and handle the solution of the lack of protection for in band signals at the same time.When ESS excited by the low power signal,switching metasurface does not work and the signal can pass.Also,the FSS allow the signal in band to pass and reflect the signal out of band.Under the incidence of HPM,the switch metasurface become active and will reflect the in band wave.At the same time,the FSS still reflect the out band wave.Based on this method,a ESS with wideband protective characteristic is designed,At the same time,the influence of unit parameters on the bandwidth and shielding efficiency is simulated.Finally,the proposed method is verified by experiments.The results show that the proposed ESS can transmit working signal of 4.02-4.44 GHz(relative bandwidth is 9.92 %),and the insertion loss is less than 2 d B.Also,it can reflect the high power microwave in the range of 0-8.85 GHz in the protective mode,and the shielding efficiency is better than 20 dB.