Wireless power transfer promises to revolutionize the way in which we use and power mobile devices. However, low transfer efficiencies prevent this technology from seeing wide scale real-world adoption. The aim of this work is to use quasioptics to develop a system composed of a dielectric lens fed by a phased array to reduce spillover losses, increasing the beam efficiency, while working on the antenna system’s Fresnel zone. The DC-RF electronics, digital beamforming and beam-steering by an FPGA, and radiating 4 × 4 microstrip patch phased array have been developed and experimented upon, while the lens has been designed and simulated. This paper details these preliminary results, where the phased array radiation pattern was measured, showing that the beam is being generated and steered as expected, prompting the lens construction for the complete system experimentation.

Wireless Power Transfer (WPT) promises to revolutionize energy distribution, being especially important in space exploration. By enabling previously impossible mission designs while avoiding interference concerns with living beings, the first widescale implementation of high-power WPT may happen here. To achieve long-distances, energy is transferred via electromagnetic waves, whose efficiency can be increased by focusing into a beam. In this paper we discuss various aspects, from the theory of quasioptics, usage of focusing components, the promise of time-modulated arrays, the importance of transparency in space and finalize with energy rectification back into DC. We hope to cover here the most important points required to make radiative WPT a reality in space applications.

ZeroPower devices are the next generation of Internet of Things. Typically taping from ambient energy, or activated by a remote reader, their first and foremost challenge is the operation distance from the nearest RF source. Unfortunately, these systems can only be activated within a range of a few tens of meters due to their minimum activation power (also named reading sensitivity). This work reduces the harvesting power to a new threshold of -28dBm (1.5 μW). We demonstrate a wireless motion sensor operating in burst mode with as low as 120 mV of DC voltage and 0.72 μJ of stored energy. This efficient operation is achieved without any DC/DC conversion thanks to a four-stages rectifier biasing a tunnel diode Voltage-controlled oscillator (VCO).

The Internet of Things has transformed modern technology relying on sensors powered by batteries. However, the environmental impact of batteries is a significant concern. This paper explores wireless power transfer as a viable solution to this problem. This study focuses on optimizing the antenna impedance to maximize the performance of the diode on the WPT receiver. The study was made with a numerical and theoretical analysis, simulations, and experimental validations. Moreover, it was demonstrated that the optimum input impedance is high impedance, approaching an open circuit. The paper concludes that designing RF-DC converters with high source impedance leads to an improvement on the rectifying efficiency.

Wireless power transfer (WPT) promises to revolutionize the way we use electrical devices. When considering indoor applications, these devices may be moving inside a certain area while the transmitter is fixed, like an electrical appliance. In these scenarios, beam forming and beam steering capabilities are required for achieving high efficiency. By implementing the quasioptical approach, we can focus energy at specific positions on the radiative near-field region to reduce the spillover losses, which, when coupled to electronically configured phased arrays, allows coverage for moving targets in terms of attitude and range. Here, we present a system capable of doing that to transfer power wirelessly for indoor applications. It consists of a 4x4 phased array transmitter at 5.8 GHz, whose radiating elements are rectangular microstrip patch antennas. Dielectric lenses were implemented, to focus the energy and reduce the spillover losses. This paper presents the design procedure to achieve the system requirements, as well as experimental results of two system configurations, one with an optimized lens and another using two dielectric lenses, up to a maximum transfer distance of 2 m. Finally, an RF-dc converter was used, enabling dc-dc WPT, while a feedback channel closes the loop for automatic optimization.