Scavenging Microwave Wireless Power: A Unified Model, Rectenna Design Automation, and Cutting-Edge Techniques

While sufficient review articles exist on inductive short-range wireless power transfer (WPT), long-haul microwave WPT (MWPT) for solar power satellites, and ambient microwave wireless energy harvesting (MWEH) in urban areas, few studies focus on the fundamental modeling and related design automation of receiver systems. This article reviews the development of MWPT and MWEH receivers, with a focus on rectenna design automation. A novel rectifier model capable of accurately modeling the rectification process under both high and low input power is presented. The model reveals the theoretical boundary of radio frequency-to-direct current (dc) efficiency and, most importantly, enables an automated system design. The automated rectenna design flow is sequential, with the least possible engagement of iterative optimization. It covers the design automation of every module (i.e., rectifiers, matching circuits, antennae, and dc–dc converters). Scaling-up of the technique to large rectenna arrays is also possible, where the challenges in array partitioning and power combining are briefly discussed. In addition, several cutting-edge rectenna techniques for MWPT and MWEH are reviewed, including the dynamic range extension technique, the harmonics-based retro-directive technique, and the simultaneous wireless information and power transfer technique, which can be good complements to the presented automated design methodology.