基于双角度全向匹配吸收表面的成像暗室

      Imaging chamber based on dual-angle omnidirectionally matched absorbing surface

      • 摘要: 为了满足微波逆散射成像测量实验对无散射空间环境的需求,提出了一种基于双角度全向匹配吸收表面的微波成像暗室设计方案。根据电磁感应透明原理和等效媒质理论,将工作在正入射角度和某一斜入射角度的超薄电磁波吸收单元进行紧密、周期排列,通过调控其等效本构参数,实现双角度匹配吸收单元。在广泛采用的圆柱形微波成像测量架构中,根据固定位置发射天线辐射电磁波到暗室内壁的入射角度空间排布双角度吸收单元,实现直径仅6.9λ的微型微波成像暗室。仿真结果表明,在电磁波斜入射和正入射情况下,所构造成像暗室与完美匹配层之间的误差分别为4.63%和0.69%。基于成像暗室的实际实验验证了所提出方案的有效性。此微波成像暗室系统制作成本低廉,具有便携、稳定的特点,有望为地层地质勘探、岩心测量等实际工程领域的成像测量实验提供技术支撑。

         

        Abstract: To meet the demand for scattering-free environment in experiments of inverse scattering-based microwave imaging, we proposed a design scheme of an imaging chamber based on dual-angle omnidirectionally matched absorbing surface. According to the principle of electromagnetically induced transparency and the equivalent medium theory, dual-angle absorbing units were designed on the basis of the periodic arrangement of the ultra-thin absorbing units working at normal and oblique incidence of the electric fields. With a widely used cylindrical architecture, the dual-angle absorbing units were arranged spatially based on the incident angle of the electric field illuminated from the source antenna, forming a 6.9λ-diameter imaging chamber. The simulation results show that the absorbing performance of the constructed imaging chamber is comparable to that of the perfect matched layer. The errors between them are 4.63% and 0.69% when working at oblique and normal incidence conditions, respectively. Imaging experiments based on the constructed imaging chamber verified the effectiveness of the proposed scheme. With the merit of low cost, portability and stability, this imaging chamber is expected to provide technical support for imaging experiments in practical engineering fields such as geological exploration and core measurement.

         

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