Terahertz and Millimetric Rectennas

In recent years, the energy market has witnessed increasing demand on green electromagnetic energy resources to meet the next generation devices requirements. While energy harvesting in the lower gigahertz band has witnessed many improvements leading to market-ready solutions, the terahertz harvesting is, still, in an immature state. As will be demonstrated later, the electromagnetic radiation frequency identifies the theory of operation and so the rectifiers are categorised, into lower and upper frequency bands. While the theoretical framework for the lower frequency rectifiers is more "uniform", there are many theories to explain the rectifier operation for upper frequency bands. For the latter case, Simmons and the transfer matrix method models are chosen and elaborated in more details. An optimisation framework that deploys the transfer matrix method to calculate the voltage-current relationship of a tunnelling diode and improve the relevant figures of merit will be also suggested. New and novel techniques leading to optimized wireless energy transmission will be elaborated. In this context, the time-modulated array technique will be considered and studied, for a range of frequencies extending to 28 GHz, as a possible substitution to the lossy linear phased array control circuits. The novel frequency-diverse array technique, leading to distance-dependent radiation pattern behaviour, will be also discovered. A market-ready solution for an efficient 2.4 GHz energy-harvesting device is presented and tailored to work in harsh electromagnetic environments. Starting from a simple and generic rectifier model, the design is upgraded to reach an end-product prototype together with its measurements in a real-world scenario. In the end, an efficient and fast simulation method capable to calculate the received power by wireless sensors is also presented. Thanks to the integral solver simulation, the results are more accurate than typical finite difference simulation and are obtained much faster as demonstrated in the corresponding chapter.