Near-Field Antenna Arrays for Steerable Sub-Wavelength Magnetic-Field Beams

A two-dimensional array of resonant capacitively loaded loops for magnetic near-field focusing is presented. The array is designed to produce a narrow magnetic-field beam in the near-field with a reduced residual surrounding electric field. It is shown that the array allows subwavelength beam steering and shaping. The array operation is discussed and explained in detail using a simplified circuit model. The observations made based on the model are then utilized to devise an optimization procedure aimed at fine-tuning the array so as to eliminate the need in multiple excitation sources and maximize the achievable magnetic-field beam intensity. The proposed array may prove useful in a variety of applications including the improvement of wireless power transfer devices performance and the creation of efficient external sources for magnetically mediated therapy.