Study On RCS Reduction Of Hign-Gain Antenna Based On Metasurfaces

With the continuous development of radio technology,military detection technology and stealth technology have been developed rapidly.Radar Cross Section(RCS)is the most critical concept in radar stealth technology.Traditional RCS reduction methods such as changing the shape of the target and loading radar absorbing materials can effectively reduce the RCS of the aircraft target.However,the antenna system,as a special scatterer,has a serious impact on the stealth performance of the entire platform.Therefore,the antenna RCS reduction is particularly important.Thus,how to better balance the radiation performance and scattering performance of the antenna is regarded as research focus.Aiming at this subject,this paper proposed three methods to achieve high gain and low RCS antennas,and verified the effectiveness of these methods through simulation and measurement.1.A circularly polarized(CP)holographic antenna(HA)with high gain and low RCS based on holographic metasurface and frequency selective absorber(FSA)has been designed.First,based on the HA theory,a high-gain CP HA is designed.The CP HA is composed of a source antenna and a holographic metasurface.The source antenna is a monopole antenna which has an omnidirectional radiation pattern in the azimuth plane.Due to the phase and impedance modulation technology,the holographic metasurface can convert the linearly polarized(LP)omnidirectional wave radiated by the monopole antenna into a directional CP wave.On the basis of the CP HA,a FSA superstrate designed and loaded above the CP HA.The FSA realizes good transmission characteristic in the working frequency band of the CP HA,and obtains absorbing effect at the lower frequency band and the higher band.Thus,the RCS reduction band of the CP HA is effectively expanded.The proposed HA loaded with the FSA has an impedance matching frequency band from 10.5 to 15 GHz,and 3 d B axial ratio(AR)frequency band is 10.4-13 GHz.The proposed antenna has a maximum gain of 18.8 d Bi at 11.4 GHz.At the same time,The RCS reduction band is from 4 to 18 GHz,with a largest RCS reduction value of 16 d B.2.A circularly polarized(CP)antenna with high gain and low RCS based on holographic metasurface and hybrid metasurface has been designed.In order to further broaden the RCS reduction frequency band of the above-mentioned CP HA,an improved hybrid metamaterial superstrate is designed and loaded above the CP HA.The hybrid superstrate is composed of two kinds of FSAs,marked as FSA I and FSA II,respectively.The proposed superstrate realizes excellent transmission characteristics in the working band of CP HA.Thus,good radiation performance is maintained.Moreover,the superstrate exhibits absorbing characteristics in the lower frequency band from 3 to 10 GHz under incident plane wave.Thus,the proposed antenna has low RCS characteristics in this band.In the higher frequency band 17-24 GHz,the two kinds of reflective FSA(RFSAs)have a phase difference of 180±37°.Therefore,the RCS reduction is achieved in this band by reflective wave cancellation.In the final design,the impedance matching frequency band of the proposed antenna covers the band from 9 to 15 GHz,and 3 d B AR frequency band is 9.5-13.7 GHz.The maximum gain reaches 18.7 d Bi at 11.4 GHz.In addition,the proposed CP antenna has low RCS characteristics in the frequency band from 3 to 24GHz,and the maximum RCS reduction is up to 20 d B.3.A low RCS phased array antenna working in the frequency range of f_L-f_H(f_H(28)1.8f_L)has been designed.Based on the theory of the array antenna,a short dipole patch is used as the antenna radiator,and multiple impedance transformations transform the input impedance of 400Ωto 50Ω,which is convenient for impedance matching with the 50Ωof the antenna port.Then,the common mode resonant current on the antenna unit cell is eliminated by loading the short-circuit via,which broadens the antenna working bandwidth.In addition,the superstrate is loaded to improve the scanning characteristics of the array antenna.When the beams of designed array scans to E-plane60°and H-plane 60°,the active VSWR is lower than 2.5.The radiation efficiency of the array unit is higher than 80%in the working band.At the same time,the array achieves low RCS characteristics based on absorbing metamaterial.Finally,the radiation and scattering characteristics of the finite 8×8 array are analyzed through measurement.