کنفرانس مهندسی برق ایران

صفحه اصلی / سی و چهارمین کنفرانس بین المللی مهندسی برق

Design and Characterization of Compact PCB-Based HF RFID Antennas

نویسندگان :

Alireza Halvani¹

1- دانشگاه صنعتی امیرکبیر

کلمات کلیدی :

HF RFID،PCB Antenna

چکیده :

Integrating High Frequency (HF) RFID antennas directly onto Printed Circuit Boards (PCBs) is a key enabler for miniaturized and low-cost IoT sensor motes. Within the tight geometric constraints typical of compact tags, the main design difficulty is not merely forming an inductive coil, but achieving proper resonance-frequency matching and tuning. In this work, we present an analytical and experimental study of a 13.56~MHz PCB tag antenna constrained to an annular region with inner and outer radii of 8~mm and 11~mm, respectively. To evaluate the influence of coil geometry, four prototypes were designed and fabricated on standard FR-4 PCB substrates: circular and square spiral layouts, each implemented with 12 and 14 turns. Experimental validation was performed using an ISO/IEC 14443A-compatible reader (NXP RC522), and performance was quantified in terms of maximum reliable read distance. Results reveal a non-linear dependence between the number of turns and coupling efficiency. The 12-turn circular spiral achieved the best performance, reaching a maximum read distance of 5~cm while resonating at the carrier frequency. In contrast, increasing the turns to 14 led to a substantial degradation in efficiency. The analytical evaluation shows that the higher inductance associated with additional turns, together with increased parasitic capacitance (particularly in the square configuration), shifted the self-resonant frequency significantly below the 13.56~MHz operating point, producing a severe impedance mismatch. Overall, the study empirically confirms that, for compact PCB tag antennas, maximizing the number of turns is not necessarily beneficial; instead, careful geometric tuning is crucial to maintain resonance and coupling performance. The optimized antenna design also provides a practical foundation for future integration with a wireless sensor platform.