基于集总元件的低频宽带超材料吸波体设计与实验研究

提出一种基于集总元件的超材料吸波体结构设计, 并进行了理论分析和实验验证. 仿真结果表明, 该吸波体在2.5 GHz到4.46 GHz的低频带内具有吸收率超过95%、半高宽达到70.4%的良好吸收特性. 反演计算得到的等效输入阻抗表明集总元件的加入可以使该结构在较宽的频率范围内有较好的阻抗匹配特性, 介质表面能量损耗分布的模拟计算结果说明能量主要损耗在了集总电阻中, 从而实现低频宽带的吸收特性. 制备了实验样品并用自由空间法进行测试, 测试结果与模拟结果符合得较好. 进一步的实验测试结果表明FR4基板的厚度对该吸波体的吸收特性有明显的调控作用, 且对于固定参数的结构存在最佳匹配厚度.关键词：集总元件超材料吸波体低频宽带

Design and experiments of low-frequency broadband metamaterial absorber based on lumped elements

A structure of matematerial absorber constructed based on lumped elements is proposed, analyzed theoretically and verified experimentally. The simulated results indicate that the absorption of the proposed absorber is over 95% in the frequency range of 2.5 to 4.46 GHz, and the FWHM is 70.4%. The designed structure has a better impedance matching characteristic to the free space in a wider frequency range when loaded with lumped elements by scattering parameter retrieval calculation. It also can be found that the large loss occurs in lumped resistance, which contributes much to the low-frequency broadband absorption properties obtained by simulating the energy loss distribution of the dielectric surface. Results measured by means of the free space method agree well with the simulation. Further measured results also show that the thickness of FR4 substrate obviously has controllable effects on absorption properties of the absorber, the absorption wide band will move to lower frequency with the increase of thickness, and the optimal thickness for the structure of certain parameters also can be obtained.