Study of Metamaterial Configuration and its Applications for Frequency Selective Shielding Screen and Radome

讨论了作为超材料或人工设计材料的有限长金属棒阵列片的电磁性能，并以频率选择屏蔽罩和天线罩材料为主要用途。金属棒周期性地排列在薄的介质片上。杆的共振发生在特定的频率上，其波长大约等于杆长度的两倍。金属棒阵列片的介电常数ε_r=ε_r‘-jε_r“是金属棒共振时的平均介电常数，表现为频率色散。在低于谐振频率时，由于金属棒的极化作用，ε_r’变高。在f_0处，ε_r‘迅速下降，在高于谐振频率时，ε_r’变为负值。虚部ε_r”在f_0处达到最大值。作为磁性材料，考虑了磁性金属微粒的杂化材料，…在实验上，证实了它们的介电常数几乎为零，金属棒取向薄片的传输系数在f_0处达到最小值。频率选择电磁波屏蔽是由两个或多个金属棒排列的板组成的，这些板之间有间隔材料。实验证实了它们的屏蔽性能。作为该材料的另一种应用，讨论了吸波材料。作为吸波材料，金属取向薄板的关键性能之一是ε_r‘在f_0附近的迅速减小，这导致薄板输入阻抗的电抗X的频率变化相反，即dx/dw&lt；0。在传统材料中，X的频率性质总是dx/dw&gt；0，这就是福斯特电抗定理。由于金属棒定向片与传统介质片的频率变化相反，因此当这些片被层合时，可以最小化输入阻抗的频率变化。基于这一思想，实现了宽带吸波材料。目前，由棒状板制成的频率选择屏蔽屏和宽带吸波材料正在投入使用。较少

The electromagnetic properties of finite-length metal-rod array sheets are discussed as metamaterial, or artificially designed material, and as their chief uses, frequency selective shielding screen and radome materials are investigated.The metal rods are periodically aligned on a thin dielectric sheets. The resonance of the rods occurs at specific frequency whose wave-length is approximately equal to double the rod length. The metal-rod array sheet permittivity,ε_r=ε_r'-jε_r", which is a average permittivity when the sheet is supposed to be homogeneous, shows frequency dispersion by the metal rod resonance. At frequencies lower than the resonant frequency, f_0,ε_r' becomes high due to the polarizations of the metal rods. The permittivity decreases rapidly at f_0, and at frequencies higher than the resonant frequency, ε_r' becomes negative. The imaginary part, ε_r", becomes maximum at f_0. As magnetic materials, hybrid materials of fine particles of magnetic metals are considered, and … More experimentally their permittivity was confirmed to be almost zero.The transmission coefficient of the metal-rod aligned sheet becomes minimum at f_0. The frequency selective EM wave screens are made with two or more metal-rod aligned sheets with spacing materials between them. Their shielding properties are experimentally confirmed.As one of the another applications of this material, absorber is discussed. As absorbing material, one of the key properties of the metal aligned sheet is the rapid decrease of ε_r' around f_0, which leads to the opposite frequency change in reactance X of the sheet input impedance, that is, dX/dw< 0. In conventional material, the frequency property of X is always dX/dw> 0, which is known as Foster's reactance theorem. Since the frequency changes of the metal rod aligned sheet and conventional dielectric sheet are opposite each other, it is possible to minimize the frequency change of input impedance, when these sheets are laminated. Based on this idea, the wide band absorber is achieved.The frequency selective shielding screens and the wide band absorbers, both made of the rod aligned sheet, are now in process of coming into use.. Less