Recent advances in broadband rectennas for wireless power transfer and ambient RF energy harvesting

Wireless energy harvesting (WEH) from ambient electromagnetic fields is becoming an emerging technology that can be exploited as a power source for many low power electronic devices. A number of key challenges are identified but the optimum design of rectennas for ambient WEH is very challenging. This paper presents a review on recent progress in multiband and broadband rectennas for WEH and wireless power transfer applications, and introduces the latest research on this topic at the University of Liverpool, UK. In addition to the existing technologies, we have developed a number of novel techniques to develop rectennas with a simple structure, a very broad bandwidth and an improved RF-DC conversion efficiency. Moreover, our rectennas can achieve consistent performance for a dynamic input power level or a wide load impedance range. The state-of-the-art technologies presented in this paper could have a great impact on the future development of rectennas for many related applications.