Emerging wireless IoT applications increasingly venture beyond over-the-air communication, such as deep-tissue networking for implantable sensors, air-water communication for ocean monitoring, and soil sensing. These applications face the fundamental challenge of significant power loss due to reflection at media interfaces. We present RF-Mediator, a programmable metasurface system placed at media interfaces to virtually mask the presence of the physical boundary. It is designed as a single-layer metasurface comprising arrays of varactor-based elements. By tuning the bias voltage element-wise, the surface mediates between media on both sides dynamically and beamforms towards the endpoint to boost transmission through the interface, as if no media interface existed. The control algorithm determines the surface configuration by probing the search space efficiently. We fabricate the surface on a thin, flexible substrate, and experiment with several cross-media setups. Extensive evaluation shows that RF-Mediator provides a median power gain of 8 dB for air-to-tissue links and up to 30 dB for cross-media backscatter links.

翻译：新兴的无线物联网应用越来越多地超越空中通信，例如用于植入式传感器的深部组织网络、用于海洋监测的空气-水通信以及土壤传感。这些应用面临的一个根本挑战是，由于在介质接口处的反射而导致的显著功率损耗。我们提出了RF-Mediator，这是一种可编程的超表面系统，放置在介质接口处，以虚拟掩盖物理边界的存在。它被设计为单层超表面，包含基于变容二极管的阵列单元。通过逐单元调谐偏置电压，该表面动态地介导两侧介质，并向端点形成波束，以增强通过接口的传输，仿佛不存在介质接口一样。控制算法通过高效探索搜索空间来确定表面配置。我们在薄而柔性的基底上制作了该表面，并在几种跨介质设置下进行了实验。大量评估表明，RF-Mediator为空气到组织链路提供8 dB的中位功率增益，为跨介质反向散射链路提供高达30 dB的增益。