Non-Uniformly Distributed-Turns Coil Antenna for Enhanced H-Field in HF-RFID

A design study of coil antennas aimed to be used as Interrogators in high-frequency (HF) radio frequency identification (RFID) is presented. The magnetic field (H-field) of the coil is enhanced by defining optimally the number of turns of the antenna, and optimizing and exploiting the internal area of an initial coil. The distributed turns coil antennas are designed for highest possible H-field without compromising the Q-factor of the antenna with respect to an initial design. To achieve best solution, a non-uniformly distributed turns design is proposed and whose radiating elements are formulated accordingly. The analytical and simulated results show reasonable agreement to validate the designs. The enhanced H-field of the antenna shows an unconstrained Q-factor, indicates a potential rise to the interrogating coverage and as a result a higher efficient antenna.