Design Of Several Broadband Artificial Electromagnetic Surfaces With Low RCS

With the continued progress and development of electromagnetic detection technology in recent years,low RCS artificial electromagnetic materials have received more and more researchers' attention.By adjusting the geometric parameters,we can realize the flexible control of the electromagnetic wave.Artificial electromagnetic surfaces which consist of artificial electromagnetic absorbing materials or artificial magnetic conductors gradually become one of the research hotspot due to their low profile and good conformal shape.Broadband artificial electromagnetic surfaces with low RCS have greater theoretical research value and potential application prospect in electromagnetic stealth field.In this thesis,several broadband artificial electromagnetic surfaces with low RCS based on an artificial electromagnetic absorbing material unit cell or an artificial magnetic conductor unit cell are proposed.The main contributions of this thesis listed as follows:1.Design of broadband artificial electromagnetic absorbing surface with low RCS.Firstly,we propose a new artificial electromagnetic absorbing material unit cell.The unit cell has a good performance of broad band,high absorption,wide incident angle,and polarization-insensitive by introducing lumped resistances and an air gap.Then a broadband artificial electromagnetic absorbing surface with low RCS is designed.Full-wave electromagnetic simulations show that,compared to the same aperture metal plate,from 7.5GHz to 20 GHz,it can obtain at least 10 d B monostatic RCS reduction,the relative bandwidth is about 90.9%;and at 9.4GHz,it obtains its peak reduction: 29.5d B.At oblique incident wave,the surface can still obtain monostatic RCS reduction,but with the oblique incidence increasing,the magnitude is decreased.At last,we fabricated the artificial electromagnetic absorbing surface and measured it.The measured and simulated results are in good agreement.2.Design of broadband artificial electromagnetic surface with low backward RCS in a chessboard structure.Firstly,a novel artificial magnetic conductor unit cell is proposed.By changing the geometric parameters of the unit cell,two elements with the phase difference about 180 degree in a broad band are designed,resulting in phase cancellation of the reflected electromagnetic waves.On the base of these,a broadband artificial electromagnetic surface with low backward RCS is designed in a chessboard structure. Full-wave electromagnetic simulations show that,compared to the same aperture metal plate,at normal incident wave,from 11 GHz to 22 GHz,it can obtain at least 10 d B monostatic RCS reduction,at 11 GHz and 20.5GHz,it obtains its peaks of reduction that are 20.8d B and 24.5d B.At last,we fabricated the artificial electromagnetic surface and measured it.The measured and simulated results are in good agreement.3.Design of coding broadband artificial electromagnetic surface with directed low-RCS.Firstly,according to the array antenna theory,the scattering field's calculation formula of the artificial electromagnetic surface which consist of artificial magnetic conductor units is derived.The surface is made of two kinds of artificial magnetic conductor sub-array: 0 element and 1 element,the phase difference of them is about 180 degree in a broad band.By designing the coding sequences of the artificial electromagnetic surface in the particle swarm optimization,a coding broadband artificial electromagnetic surface with directed low-RCS can be achieved.At last,take the surface which designed when the angle of incidence is (?=45°,?=0°) as an example,we have simulated it.The results show that,compared to the same aperture metal plate,the designed surface can reduce RCS at the directed angle(?=45°,?=0°) from 8GHz to 23 GHz,and from 11 GHz to 20.5GHz,it can obtain almost 10 d B monostatic RCS reduction,at 12 GHz and 19.5GHz,it obtains its peaks of reduction that are 22.2 d B and 28.2d B.