Spatial Power Combining of Multi-Sine Signals for Wireless Power Transmission Applications

This paper presents two transmitter architectures for wireless power transmission (WPT) applications. These architectures aim at transmitting high peak-to-average power ratio (PAPR) multi-sine signals, which have demonstrated to improve the RF-dc conversion efficiency of rectifier circuits, such as the ones in the receiving end of a WPT system. In order to overcome the challenges associated to the amplification of high PAPR signals, the proposed schemes make use of the spatial power combining concept, in which the individual signal components are amplified, radiated, and then combined in free space. In order to achieve the high PAPR signals, proper synchronization of the individual tones is required. Two architectures are proposed. The first one is based on the transmission of single-tone signals that are externally locked to a common reference signal that establishes the necessary phase reference. The second architecture is based on a mode-locked oscillator scheme that requires no external reference signal. Instead, this scheme takes advantage of the synchronization phenomena in oscillator circuits to establish the phase reference. Measurements are presented to validate both schemes and to show their effectiveness in improving the RF-dc conversion efficiency in rectifier circuits.