Review and Comparison of Feedback-Based Dynamic Beam Focusing Techniques for Long-Ranged Wireless Power Transfer

Due to the rise of gigascale antenna arrays considered to implement long-range wireless power transfer (WPT), there is a need for a scalable high-efficiency adaptive dynamic beam focusing method. Several methods have been proposed ranging from methods requiring position information of the receiver, use of pilot signals or channel sounding, and feedback-based approaches. The latter has the potential to achieve maximum WPT efficiency due to use of feedback between the rectenna target and the transmitter array. In this paper, we present an overview of the different feedback-based long-ranged WPT methods that have been proposed. We also evaluate them in terms of convergence time, complexity of implementation, and steady-state efficiency through a simulation. The results show that methods that measure channel state information (CSI) and the both-sides retrodirective system can achieve high efficiency with less convergence time, but with added implementation complexity.