Research On The Theory And Design Method Of Electromagnetic Stealth Metamaterials Applied To Antenna Radomes

Frequency Selective Surface(FSS)is a periodic electromagnetic metamaterial with the ability to manipulate spatial electromagnetic waves,and it is mainly used in antenna covers,reflectors,and polarizers.When used as an antenna cover,FSS is considered a spatial filter,mainly achieving the characteristics of a bandpass filter.With frequent mili-tary conflicts in recent years,the importance of electromagnetic control in modern warfare has been increasingly emphasized.To significantly reduce radar cross-section and achieve unexpected military purposes by obtaining good stealth effects for aircraft and ships,high-selectivity FSS can fulfill this important task.However,traditional FSS can only achieve better selectivity by coupling multiple layers of dielectric substrates with metal gap layers,which can lead to risks such as a high overall profile and difficult processing.To address these issues,this paper summarizes the main research contents as follows:1.Designed a single-layer,dual-polarization,dual-band,and high-selectivity FSS based on Substrate Integrated Waveguide(SIW).The coupling mechanism between SIW resonant cavities and bandpass-type FSS was explored first.Then,by inserting a zero point using the SIW resonant cavity at any transition band of the traditional first-order FSS,the single-sideband suppression was achieved.On this basis,a new SIW resonant cavity was added to couple with FSS to achieve high-selectivity dual-band FSS by inserting a zero point at another transition band.This structure has only one layer of dielectric substrate and maintains a stable angle of 40° under dual polarization.2.Designed two multi-band FSS based on SIW.First,on the basis of the single-layer,dual-polarization,dual-band,and high-selectivity FSS based on SIW,a dual-band FSS with good high-selectivity on one band was designed by coupling two traditional band-pass FSS structures with cross-shaped and rectangular gaps with two resonant cavities that do not strictly conform to the SIW structure standards.This structure maintains a stable angle of 40° under dual polarization.Then,by dividing the SIW resonant cavity into four identical small cavities and coupling the same-sized square ring FSS in symmetrical cav-ities with adjacent square ring FSS sizes close to each other,a three-band FSS with good high-selectivity in the middle band and dual-polarization stability of 40° was achieved by using two sets of SIW resonant cavities coupled with FSS in a staggered manner for the passband(working frequency band is close).3.Designed a liquid crystal tunable FSS.To overcome the drawbacks of varactor diodes with high insertion loss and inability to continuously tune in the Ku band,SIW was used to design FSS units that are filled with liquid crystal in the SIW resonant cavity.By adjusting the external bias voltage to change the liquid crystal and achieve the purpose of changing the dielectric constant,liquid crystal tunable FSS was realized.