Efficient wireless power transfer and precise control
of power delivery and leakage field strength can be achieved using
a phased array wireless power transfer system. This has particular importance for charging multiple devices simultaneously, or
charging devices in environments where humans or foreign objects
will be in close proximity. The phased array wireless power system consists of two or more phase-synchronized power amplifiers
each driving a respective transmit coil. The system can maximize
power delivery to an intended receiver in one location while simultaneously minimizing power delivery and leakage fields in other
locations. These functions are possible by varying the amplitude
and phase of each transmitter. This paper provides an analysis of a
phased array wireless power transfer system using near-field magnetically coupled resonators, and derives parameters that can be
used to automatically determine the optimal magnitude and phase
of each transmitter to deliver power to one or more receivers. Experimental results verify the theoretical analysis and additional
features of the full system are demonstrated.