![]() ![]() ![]() 6 Metasurface, as a new kinds of ultra-thin metamaterials that consist of a monolayer of planar metallic structure, provides an unique way of manipulating the EM waves and achieves the excellent RCS reduction of metallic targets. Metamaterials are artificial structures which capability of manipulating the electromagnetic waves to obtain unusual properties, such as negative refraction, 4 subwavelength focusing, 5 and electromagnetic invisibility cloaking. Another technique is altering the appearance of the target (Shaping) to redirect the scattered field to more directions, but that increases the complexity of the design. Different techniques have been proposed in the previous literatures to reduce the RCS, such as applying radar absorbing materials (RAM) which transforms the electromagnetic energy into heat, 2 however the RAM often operate in the vicinity of the resonance frequency. To reduce the RCS effectively of the target is a challenging objective for the electromagnetic researchers. Radar cross section (RCS) as an important physical quantity is used to characteristic the electromagnetic scattering properties of the target. 1 There are many researches focus on the achievement of electromagnetic (EM) transparency or invisibility of the target in recent years. With the rapid development of the contemporary radio technology and the military electronic technology, the ability of the combat defence systems search and track the target have been enhanced at a great extent. Both the simulation and the measurement results are consistent to verify this excellent RCS reduction performance of the proposed metasurface. This metasurface can achieve -10dB RCS reduction in an ultra-wide frequency range from 6.6 to 23.9 GHz with a ratio bandwidth ( f H/ f L) of 3.62:1 under normal incidences for both x- and y-polarized waves. The diffuse scattering of electromagnetic (EM) waves is caused by the randomized phase distribution, leading to a low monostatic and bistatic RCS simultaneously. Ultra-wideband RCS reduction results from the phase cancellation between two local waves produced by these two unit cells. The reflection phase difference of 180° (☓7°) between two unit cells covers an ultra-wide frequency range. The proposed metasurface consists of two fractal subwavelength elements with different layer thickness. A novel metasurface based on uneven layered fractal elements is designed and fabricated for ultra-wideband radar cross section (RCS) reduction in this paper.
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