Tuned HF coil structure detecting RFID/NFC tags for medical monitoring patch

This paper presents the study, electromagnetic simulations, design and experimentation of a new antenna reader at HF frequency for detecting RFID and NFC tags on a potential biomedical patch. Semi-autonomous monitoring of patients has been fruitfully investigated for years and RFID/NFC is part of friendly technologies for avoiding battery. The challenge is to build some control areas in which the biomedical patch can monitor the patient easily. Herein, we propose a structure in a chair by means of two HF 300x300 mm² copper sub-coils included in the seat and the back of a chair. The detection ability by magnetic coupling is improved by the quadrature currents feeding of these two sub-coils (90° phase shift). After preliminary simulations for showing the interest in quadrature currents, the design is described step by step for the tuning of the two equivalent RLC resonators, modeling the structure of the proposed antenna. After tuning and matching, the antenna is used with a commercial HF reader (SIL 2125) for detecting ISO 15693 flexible tags (20x40 mm²).