Advances in microwave power transmission

Abstract

Power transmission by microwaves has a long history of technology development and key demonstrations. By 1975 the improvements in component conversion efficiencies (DC-to-RF and RF-DC) increased the end-to-end system efficiency from 13% to 54%. These early S-band wireless power transmission (WPT) demonstrations proved this concept as a viable form of power transmission to ground, air, and space platforms. Whereas they emphasized high power, low frequency, and long distance power beaming, recent applications have focused on relatively shorter distances and lower power over a wide range of frequencies. These applications include powering personal electronics and unmanned aerial vehicles along with energy harvesting from radiated RF emissions. WPT technology development, demonstrations, and studies have occurred at microwave and millimeter-wave frequencies. In all applications, high transmitter and rectenna efficiencies are required to minimize heat dissipation and maximize the end-to-end efficiency. High power, high efficiency solid-state amplifiers have been developed to allow phased array antenna transmitters to electronically steer the power beam to single or multiple rectennas. Thin and lightweight rectennas have been developed that are efficient, polarization agile, and conformable to a platform's structure. Along with these topics, the history, key demonstrations, WPT concepts, applications, and technology updates are discussed.