| Frequency selective surface（FSS）is a two-dimensional surface structure which is composed of periodic metal patch units or aperture units arranged on the surface of the medium.In the military field,it is often used in radar radome to reduce the Radar Cross Section（RCS）of scattering sources and greatly improve the stealth performance of electronic countermeasure weapon equipment.It is widely used due to its efficient electromagnetic control advantages.In order to solve the problem that the single-band communication system cannot meet the high communication capacity,broadband transmission and multi-frequency transmission FSS are mostly used to increase the channel capacity of the microwave communication system and improve transmission efficiency.This paper revolves around a series of bottleneck problems that urgently need to be solved,such as limited frequency bandwidth and low transmission efficiency.A variety of new multifunctional FSSs with excellent performance are designed and applied to radome to achieve RCS reduction.The main research contents are as follows:1.For various complex typical environments,a variety of new frequency selective surfaces with typical performance（broadband,multi-frequency,miniaturization,coding）are designed.1)Aiming at the application requirements of large-capacity broadband signal transmission,a four-corner notched ring structure FSS is designed,which performs ultra-wideband transmission in the C-band to X-band,and can flexibly adjust the working frequency band by changing the value of the notch radius.2)Aiming at the application requirements of multi-frequency signal transmission in modern communication equipment,a single-notch special-shaped structure multi-frequency FSS with the advantages of flat out-of-band and strong cut-off characteristics is proposed.Utilizing its asymmetry,the rotation angle of the FSS is controlled by the servo motor and the reconfigurable function across the passband is realized.3)Aiming at the problem that the traditional FSS cannot meet the requirements of high-integration and lightweight devices,a miniaturized FSS is designed based on cell curling and metal via technology,and the cell size is only 0.04λ0×0.04λ0.4)For the comparison of single-layer FSS,it is difficult to optimize complex electromagnetic properties such as broadband and steep cut-off.A digital coding FSS is proposed,and the coding matrix is optimized by the SA algorithm to obtain the topology of the target electromagnetic characteristics.2.Based on two typical bandpass FSSs,the electromagnetic characteristics of finite FSSs with different array numbers are studied.By comparing and analyzing the electromagnetic characteristics of finite/infinite FSSs,the influence of unit arrays on electromagnetic characteristics and modulation laws are extracted and analyzed.The study investigated the influence of FSS radome loading on the radiation performance and radar scattering cross-section characteristics of microstrip patch antennas.The results showed that the loading of FSS radome had a small impact on the antenna’s working performance,and the radar scattering cross-section was significantly reduced,verifying the radar stealth performance of the designed FSS.3.Finally,varactor diodes and PIN diodes are respectively loaded in the FSS structure,and the passive FSS is expanded into an active reconfigurable FSS,so that it can realize the tunable function of narrowband transmission and broadband transmission within the frequency range.When the varactor diode is loaded,the passband can be continuously reconfigured by controlling the working voltage of the varactor diode;when the PIN diode is loaded,it can achieve electromagnetic reconfigurable characteristics of low-frequency transmission,high-frequency cutoff,and low-frequency transmission in the on and off states,respectively,and can be used for electromagnetic switching. |
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