Distributed-Antenna Energy Beamforming with One-Packet Feedback

Abstract

A transmit phase optimization scheme with only one-packet feedback of received signal strength indicators (RSSIs) is described for an antenna subset with the size of N T in a distributed wireless energy transfer system. For a subset antenna to be optimized, the RSSI values are measured at the device for three pre-set transmit phases while pausing the transmission from the other subset antennas except for a reference antenna. Thus, the measured RSSIs, of which number is only 3 × (N T –1), are fed back collectively. A non–iterative optimization formula derived by differentiation from parabolic interpolation is applied for three measured RSSI values. The optimized (N T –1) transmit phases can co-phase their corresponding receive phases to the unknown receive phase from a reference antenna. Our proposed scheme achieved almost the same received power as the perfectly optimized case.