This letter presents, for the first time, a custom-built high frequency (HF) radio frequency identification (RFID) system that enables the communication with an RFID transponder (tag), which is attached to an object located in an enclosed metal housing. Proof-of-concept measurements of the custom-built HF RFID system show a good system performance and a favorable extension of the read range in the metal environment by 19% in comparison to the read range of the free space system. These results are realized by a novel passive repeater structure, which is included in the system (i.e., reader–repeater–tag). The passive repeater consists of an arrangement of two booster antennas and ferrite material. Next to simulation and measurement results, this letter provides an equivalent circuit model of the reader–repeater–tag system for system design.

中文翻译：

---

用于与金属外壳中的标签通信的无源 HF RFID 中继器

这封信首次介绍了一种定制的高频 (HF) 射频识别 (RFID) 系统，该系统能够与贴在封闭金属外壳中的物体上的 RFID 应答器（标签）进行通信。定制的 HF RFID 系统的概念验证测量显示出良好的系统性能，与自由空间系统的读取范围相比，金属环境中的读取范围扩大了 19%。这些结果是通过一种新颖的无源中继器结构实现的，该结构包含在系统中（即阅读器-中继器-标签）。无源中继器由两个增强天线和铁氧体材料组成。除了仿真和测量结果之外，这封信还提供了用于系统设计的阅读器-中继器-标签系统的等效电路模型。