Near- and far-field wireless power transfer

This paper presents and overview of near and far-field wireless power transfer at RF and microwave frequencies for a variety of applications, ranging from near-field capacitive kW-level powering for cars in motion at MHz frequencies, to harvesting very low statistically-varying power densities across the microwave range and a study of directive beaming for space applications. In all applications, the primary consideration is both transmit and receive power efficiency, but at higher power levels, other factors such as safety regulations, become relevant and require new approaches. Specific examples are given for a near-field phased array at 6.78 MHz for vehicle powering, an airborn 4.3GHz harvester and a study for a microwave large array lunar directive beaming scenario.