Miniaturised antenna design with crossed-field elements to radiate strong electromagnetic fields for near-field communications

Near-field (NF) communications require strong energy coupling between transmitting and receiving antennas. An antenna design methodology is thus proposed to design the reader antennas that radiate strong evanescent fields in the vicinity of antenna with good radiation efficiency. This concept employs a pair of radiating elements with approximately conjugated input impedances in nature that have large reactance such that the energy will reside in the NF region. In addition, the orientations of the antenna pair are adjusted to form the relationship of crossed-fields in the electric and magnetic field components such that the relationship in Poynting vector can be established in the near zone. Both numerical and experimental results based on an antenna design example for the radio frequency identifications applications are presented to validate the concept.