Investigation of Mutual-Coupling Free Condition of Two RFID Tags Technology using Overlapping Study

Mutual coupling between antennas is a significant issue in telecommunication devices such as RFID tags. The coupling may degrade the overall performance. It can cause frequency detuning by altering the antenna’s overall inductance. In systems incorporating multiple antenna technologies, avoiding frequency detuning is crucial for optimal performance. Low frequency (LF) or high frequency (HF) RFID tags operating at short read range via near field magnetic resonance. Embedding multiple tags in a single card can lead to unavoidable frequency detuning due to the coupling effect, resulting in system failure and undetectable tags. This paper investigates the mutual coupling behavior of two RFID tag technologies under various overlapping conditions. The two loops antenna coupling area overlapping is varies by changing the position in x and y directions. The study examines the self-resonant frequency (SRF) of the RFID tags. Results indicate that overlapping RFID tags causes frequency detuning for both tags. However, certain overlapping conditions (around 25% overlapping area) can achieve a mutual coupling-free state.