Article ID: 2019GCL0027
The miniaturization of conventional near field communication (NFC) antennas is required to improve the flexibility of placement of the constituent electrical and electronic components. A small-sized magnetic material loaded solenoid has been proposed. However, the transmission efficiency of this design decreases as the size of the antenna decreases.
This study focuses on a linearly aligned, two-solenoid array and numerically investigates the dependency of the magnetic field distribution radiated from the solenoid array in relation to the excitation direction. The influences of the magnetic material loaded into the solenoids on the magnetic field distribution are also analyzed. Based on the results, the out-of-phase excitation can yield larger magnetic field strengths near the center of the solenoid array compared to the in-phase excitation because the total magnetic field produced by the two solenoids in the former case is the summation of the magnetic fields of the constituent fields generated within the tested area. When the observation point is far from the solenoid, the in-phase excitation can generate a larger magnetic field strength than the out-of-phase excitation because the magnetic field parallel to the solenoid becomes dominant. In addition, it is found that the excitation of the linearly aligned, two-solenoid array suitable for NFC depends on the permeability of the magnetic material and the target distance between the solenoid array and the receiving antenna.
