HF RFID Reader Antenna with Loop Switch for Avoiding Magnetic Coupling

This paper studies the magnetic coupling between two adjacent loop antennas that are parallel to each other in a plane and presents a new practical method to avoid the resulting magnetic coupling interference. The study focuses on the high frequency radio-frequency identification (RFID) system for casino applications, where several loop antennas are closely built into a game table to monitor gaming chips. In this case, neighboring loop antennas may severely interfere with each other by magnetic coupling, which leads to the malfunction of the RFID system. In this paper, we present a practical loop antenna with a new loop switch circuit for avoiding magnetic coupling. The loop switch circuit is integrated with a matching circuit and automatically operated by using an interrogating signal from a reader. We verified the validity of the proposed design by showing that an RFID reader with the proposed antenna can exactly and separately read the gaming chips placed on the different betting zones of a game table.