This chapter proposes an overview of microwave energy harvesting with focuses on the design of high efficiency low power rectifying circuits. A background survey of RF energy harvesting techniques is presented first. Then, the performances of conventional rectifier topologies are analyzed and discussed. A review of the most efficient rectenna designs, from the state of the art, is also presented. Design considerations for low power rectifier operations are detailed and new high efficient rectifying circuits are designed and evaluated in both GSM and ISM bands under low power constraints.
TopWireless Power Transmission: Background Survey
The concept of wireless power transmission ages more than 100 years and has been firstly presented by Nicolas TESLA in his United States patent No. 685,954, dated November 5, 1901, (Glenn, 1994), where he describes the process of electromagnetic waves transfer as transmitting electrical signal “disturbances” through the natural media. In the claim 11 of his patent, he stated the principles of wireless energy transmission, the storage of the energy in a capacitor and energy management over the time. Although Tesla wireless power transmission systems implementation was unsuccessful, he did transmit power from his oscillators that operated up to 100MV at 150 kHz. Research efforts continued later in the 1930s to promote wireless power transmission by the invention of magnetron and klystron.
Rectification of microwave signals for supplying dc power through wireless transmission has been proposed and researched in the context of higher power beaming since 1950s. This era witnessed also the advancement of high-power microwave tubes by Raytheon Company, Waltham, MA (Brown, 1984) and a 15-kW average power S-band cross-field amplifying tube was developed with 81% overall DC to RF efficiency by 1958. A good review of the early history of microwave converters is given in (Edwards, 1947). In the early 1960s, the first application employing microwave rectification of dc power extraction was performed. Innovative researches at Raytheon have been carried out and the term “rectenna”, referring to a receiving antenna followed by a rectifier built around balanced bridge or single semiconductor diode, has been introduced. Practical demonstrations of wireless power transmission began to appear in military and space-related research programs. The Solar Power Satellite (SPS) project, (Glaser, 1968) proposed by Peter Glaser in 1968, is considered as one of the most ambitious project dealing with high power WPT. It consists of a gigantic satellite designed as an electric power plant orbiting in the Geostationary Earth Orbit (GEO) that capture permanently the solar power and send it towards ground stations through microwave beam. An illustration is given in Figure 1, (Falkenstein, 2011). Despite the 100% efficiency that could be reached by the SPS, the project was never put into practice due to the large antenna sizes and costs. For 5GW of transmitted power, the satellite would need to be 5.2 km wide and 10.4 km long, with an emitter antenna of around 1km in diameter (Marian et al., 2012).