Radio frequency (RF) energy harvesting and wireless power transmission (WPT) technologies —both near-field and far-field—have attracted significant interest for wireless applications and RFID systems. We already utilize near-field WPT products in our life and it is expected that RF EH and far-field WPT systems can drive the future low-power wireless systems. In this article, we initially present a brief historical overview of these technologies. The main technical challenges of rectennas and WPT transmitters are discussed. Furthermore, this paper presents the recent advances on the development of these technologies, including the possibility of powering RFID systems through the millimeter wave power from 5G networks, the trends in flexible rectennas design and the technological developments on the simultaneous wireless information and power transfer (SWIPT).

In this letter, the authors present the first millimeter-wave (mm-wave) high-order backscatter modulator, based on a BiCMOS technology for 5G/Internet of Things (IoT) applications. The design and implementation of the proposed system are described, followed by the considered characterization measurement setup. This work presents a chip that performs different orders of backscatter modulation, M-quadratic-amplitude modulation (QAM), for a wide range of operation both in frequency (20-28 GHz) as well as with multiple values of input power. Besides that, the modulator presents the lowest power consumption compared with the state of the art. An extensive estimation of error vector magnitude (EVM) values for different frequencies and modulations (16, 32, and 64-QAM) is presented. These results show that it will be possible, in a future implementation, to establish low power consumption communication links with a multigigabit data rate in a wide range of frequencies.

This paper presents a mm-wave hybrid RF-DC converter based on a Gallium Arsenide (GaAs) chip for Wireless Power Transmission (WPT) applications. Both chip and external low-pass networks are described, and different scenarios are considered and measured. This work presents a very versatile system capable of operating at several frequencies, loads, and scenarios. The system proposed was evaluated considering an on-chip measurement approach and a fully assembled circuit. In both scenarios, the circuit presents results very close to the simulated, where efficiency of 54% is achieved for 13 dBm of input power for the fully assembled case and efficiency of 51% with 15 dBm of input power for on-chip measurement. Lastly, the output voltage can achieve up to 8V with a load of 1.96 k.

Applications on wireless sensing and internet of things (IoT) require communication systems based on low power with high data rates. Thus, backscatter communication plays an important role in the new emerging IoT communications. In the literature, several works have been reported about backscatter modulators with high-order modulation formats. However, only the square quadrature amplitude modulation (S-QAM) scheme is considered, although it is not optimal in the sense of power efficiency. In this letter, the performance of two dimensional (2-D) signal constellations is evaluated, namely rectangular QAM, star QAM, and hexagonal QAM, in terms of the symbol error rate, in backscatter systems context. A power consumption analysis is presented for these modulation schemes. To provide the symbols of the aforementioned constellations, a practical high-order backscatter modulator, corroborated by measurement campaigns, is implemented. Several SER curves are also presented in this work.

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 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.