Power Transfer Optimization for HF RFID Systems Working in Metallic Environments

Abstract

Abstract In wireless systems, the power transfer efficiency is very important. Many systems are used in harsh environments and the signal transmitted can be drastically affected by these environments. HF RFID systems are widespread nowadays, in many domains, but the metallic environments are an impediment to the extension of these systems in different applications. In this paper is presented a solution in optimizing the power transferred through the RFID reader antenna in the identification area where tags are found. This solution involves using an automatic matching unit (AMU) circuit that can match the impedance of the reader antenna at 50 Ω, even if the metallic environments located nearby are constantly changing. Using the proposed solution and only 1cm between the reader antenna and a metallic plane the reading distance is increased up to 75% from the reference distance (reading distance when no perturbing environment is used around). The fast tuning process can identify the tags even if they are attached by moving objects.