Improvement of coupling coefficient by designing a spiral pattern formed on a printed circuit board

In recent times, the wireless power transfer (WPT) technology is attracting attention because of the expanding use of portable devices. In particular, extensive studies on the WPT technology using magnetic resonance are being conducted because this technology offers various advantages such as the achievement of a transmission efficiency of 90% or more from a distance of 1 m, as compared with traditional electromagnetic induction systems. However, studies on thin coils, as well as those on the improvement of the coupling coefficient, have hitherto been inadequate. Consequently, we have formed a spiral pattern on a printed circuit board and devised spiral patterns to improve the coupling coefficient, which was calculated by carrying out an electromagnetic field analysis. As a result, we found that the coupling coefficient improved by adjusting the inner radius and pitch of the spiral coil and by designing the geometry of the spiral coil.