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Salisbury screen
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The Salisbury screen is maybe the first ever anti-radar or, to be more precise, anti-reflective concept; the so called RAM (radar absorbent material). It was first described in 1952 and was applied in ship radar cross section reduction (RCS). There have been many design refinements over the years especially because of the increasing interest for stealth planes, but the principles remain the same.
The most easy to understand salisbury screen design consists of a ground plane which is the metallic surface that needs to be concealed, a lossless dielectric of a given thickness (a quarter of the wavelength that will be absorbed) and a thin lossy screen.
The principle is this:
The incident wave (which we will consider to be made up by parallel beams) is split into two (equal in intensity) waves that have the same wavelength (λ)
The first wave is reflected by the exterior surface (the thin lossy screen) while the second beam travels through the dielectric, and it is reflected by the ground plane (which is the most inner layer of the salisbury screen)
The reflected waves interfere and cancel each other’s electric fields (radar is an electromagnetic beam-microwave and IR)
To explain the phenomenon, we need to look at the interference theory. Two waves that are coherent interact, they combine to form a single output wave and if their peaks coincide, the output intensity is the sum of the two intensities. However, if the two waves are completely out of phase the two intensities cancel each other out (that only happens when the two waves are offset by one half a wavelength).
The second wave (in step 2.) travels twice (once from and once to the exterior thin lossy screen) the distance equal to one quarter a wavelength, for a total distance of one half a wavelength. Thus the two waves cancel each other.
The incidence angle the waves that are canceled do not come from the same exact incident wave. However, they are all similar thus they are coherent and interfere.
There are a few disadvantages inherent to this model (some of which have been solved). One would be the fact that salisbury screens work well only for a very narrow portion of the radar spectrum thus making it very vulnerable to multiple radar protected areas. Another problem is the thickness of the screen itself, the radar wavelengths are between 10 cm and 1 mm, thus for a longer wavelength, the thickness gets up to 2.5 centimeters which is quite difficult to cope with (in the aerospace applications), reaserches are being made for ultrathin salisbury screens involving Sievenpiper HIGP(high impedance ground plane)(source:Wiley Periodicals, Inc. Microwave Opt Technol Lett) which shows remarkable improvements to the thickness of the screen
The most easy to understand salisbury screen design consists of a ground plane which is the metallic surface that needs to be concealed, a lossless dielectric of a given thickness (a quarter of the wavelength that will be absorbed) and a thin lossy screen.
The principle is this:
The incident wave (which we will consider to be made up by parallel beams) is split into two (equal in intensity) waves that have the same wavelength (λ)
The first wave is reflected by the exterior surface (the thin lossy screen) while the second beam travels through the dielectric, and it is reflected by the ground plane (which is the most inner layer of the salisbury screen)
The reflected waves interfere and cancel each other’s electric fields (radar is an electromagnetic beam-microwave and IR)
To explain the phenomenon, we need to look at the interference theory. Two waves that are coherent interact, they combine to form a single output wave and if their peaks coincide, the output intensity is the sum of the two intensities. However, if the two waves are completely out of phase the two intensities cancel each other out (that only happens when the two waves are offset by one half a wavelength).
The second wave (in step 2.) travels twice (once from and once to the exterior thin lossy screen) the distance equal to one quarter a wavelength, for a total distance of one half a wavelength. Thus the two waves cancel each other.
The incidence angle the waves that are canceled do not come from the same exact incident wave. However, they are all similar thus they are coherent and interfere.
There are a few disadvantages inherent to this model (some of which have been solved). One would be the fact that salisbury screens work well only for a very narrow portion of the radar spectrum thus making it very vulnerable to multiple radar protected areas. Another problem is the thickness of the screen itself, the radar wavelengths are between 10 cm and 1 mm, thus for a longer wavelength, the thickness gets up to 2.5 centimeters which is quite difficult to cope with (in the aerospace applications), reaserches are being made for ultrathin salisbury screens involving Sievenpiper HIGP(high impedance ground plane)(source:Wiley Periodicals, Inc. Microwave Opt Technol Lett) which shows remarkable improvements to the thickness of the screen
不错的东西 找到几篇相关的中文资料：
Salisbury屏的优化设计
Optimum design of a Salisbury screen
>2004年11期
王东方 , 周忠祥 , 张海丰 , 秦柏
广义匹配规律在Salisbury屏反射性质研究中的应用 Application of General Matching Law in the Research of Salisbury Screen's Reflection Nature [佳木斯大学学报（自然科学版） Journal of Jiamusi University(Natural Science Edition)] 王东方 , 张海丰 , 王志林
三维网格法在Salisbury屏优化设计中的应用 Application of Three Dimensional Lattice Method in Salisbury Screen Optimized Design [佳木斯大学学报（自然科学版） Journal of Jiamusi University(Natural Science Edition)] 张海丰 , 王东方 , 崔虹云 , 孙杨民
传统Salisbury screen中的Spacer是泡沫等没有什么损耗的材料，但是把泡沫换成有高磁损耗和电损耗的材料后，我的计算结果发现效果不明显！还请达人指点指点！
我估计做这个人不是很多，我都是第一次听说 呵呵
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