Synthesized Magnetic Field Focusing Using a Current-Controlled Coil Array

A novel synthesized magnetic field focusing (SMF) technology is proposed and nonradiative but focused magnetic field is experimentally demonstrated as a one-dimensional example. Contrary to common belief, a magnetic field can be focused arbitrarily by increasing the number of current-controlled transmitting coils in a manner similar to that of conventional beam-forming. Moreover, the proposed SMF is independent of frequency from dc to rf. Chronic problems associated with conventional wireless power transfer and magnetic induction tomography technologies, i.e., poor resolution and electromagnetic interference due to the extent of the magnetic field, can be resolved with the proposed SMF technology. The spatial resolution of the magnetic field of an experimental kit composed of 10 coils spaced 5 cm apart with a 90 cm long ferrite core was 12.5 cm at a distance of 10 cm, which is 4 times that of a nonfocusing coil and which may be improved if more coils are used.