An Experimental Multi-Antenna RF Wireless Power Transfer and Energy Harvesting System

Wireless networks are experiencing an unprecedented surge in data traffic due to the widespread adoption of mobile devices and connected terminals. Effective energy management and efficiency are critical for ensuring sustainable green communication. Energy harvesting (EH) plays a vital role in achieving low carbon emissions and net-zero goals. However, many studies in the literature rely on idealized mathematical models without experimental validation, thereby overlooking potential discrepancies with real-world applications. This paper presents an experimental multi-antenna radio frequency (RF) wireless power transfer (WPT) and EH system. The system comprises a software-defined radio as a digital transmitter, a wireless receiver with an RF energy harvester, and a power splitter/combiner unit to enable multi-antenna functionality. Comprehensive measurements are conducted to investigate the power splitter/combiner unit, transmission and conversion efficiencies, line of sight and non-line of sight propagation scenarios, and linear and nonlinear energy harvesting models. The results are presented in terms of received power, harvested power, and charging time. The findings show that, although the power splitter/combiner unit introduces losses to the system, employing multiple antennas, particularly on the transmitter side, enhances system performance. Modulation schemes with constant envelopes prove more advantageous for EH, with frequency shift keying and phase shift keying achieving, on average, up to 30% more harvested power than quadrature amplitude modulation. Nonlinear three-piecewise and heuristic models are shown to be well-suited for the multi-antenna WPT-EH system.