This lecture in the Wireless Without Batteries Series discusses the fundamentals of Power Optimized Waveforms (POWs), which can be used to extend the range of wireless energy-harvesting links.
WWB05: Power-Optimized Waveforms
Paper: M.S. Trotter, J.D. Griffin, and G.D. Durgin. “Power-Optimized Waveforms for Improving the Range and Reliability of RFID Systems.”IEEE International Conference on RFID 09, Orlando, FL. April 2009. 8 pages.