  Magnetic induction (MI) based communication and power transfer systems have
gained an increased attention in the recent years. Typical applications for
these systems lie in the area of wireless charging, near-field communication,
and wireless sensor networks. For an optimal system performance, the power
efficiency needs to be maximized. Typically, this optimization refers to the
impedance matching and tracking of the split-frequencies. However, an important
role of magnitude and phase of the input signal has been mostly overlooked.
Especially for the wireless power transfer systems with multiple transmitter
coils, the optimization of the transmit signals can dramatically improve the
power efficiency. In this work, we propose an iterative algorithm for the
optimization of the transmit signals for a transmitter with three orthogonal
coils and multiple single coil receivers. The proposed scheme significantly
outperforms the traditional baseline algorithms in terms of power efficiency.
