From (81), to maximize the power transfer efficiency, the quality factor of each coil must be maximized. Following (26), the quality factor is inversely proportional to the antenna resistance. As given by (93), resistance consists of four parts. The radiated resistance for typical parameters of interest is very small and could be neglected in the optimization process. The DC part can be suppressed through a series of steps: conductivity maximization, decreasing wire length and cross-sectional area magnification (well known in the case of DC).