Loop antenna design for lateral H-field uniformity in misaligned HF-RFID links

The performance of High-Frequency Radio Frequency Identification (HF-RFID) links depends on the alignment of the magnetically coupled interrogator and transponder antenna pairs. In this paper, we propose a design method to achieve lateral uniformity in the H-field of circular interrogator loop antennas to reduce the effect of lateral antenna misalignment. This is achieved by parametrically adjusting the radii of antenna turns to minimize the range of H-field variation at a given read-out distance. This design approach results in an enhancement of the axial H-field, while achieving minimal variation in the lateral H-field profile.