Loop antenna producing uniform horizontal magnetic fields over plane for HF RFID applications

Abstract

A planar loop antenna producing uniform magnetic fields horizontal to its plane is presented. The antenna consists of a pair of two-turn spiral coils that are sequentially excited. To prevent undesirable magnetic coupling between the coils, a novel coil-switching circuit is proposed, which is automatically operated using the interrogating signal from the reader. The antenna is suitable for a high-frequency radio frequency identification reader antenna installed under a chip tray to monitor gaming chips in a casino. © The Institution of Engineering and Technology 2014.