Daniel Belo

Boosting the Efficiency: Unconventional Waveform Design for Efficient Wireless Power Transfer

Traditionally, wireless power is delivered through single-carrier, continuous-wave (CW) signals. Most research efforts to enhance the efficiency of wireless power transfer systems have been confined to the circuit-level design. However, in recent years, attention has been paid to the waveform design for wireless power transmission. It has been found that signals featuring a high peak-to-average power ratio (PAPR) can provide efficiency improvement when compared with CW signals. A number of approaches have been proposed, such as multisines/multicarrier orthogonal frequency division multiplex (OFDM) signals, chaotic signals, harmonicsignals, ultrawideband (UWB) signals, intermittent CW (ICW) signals, or white-noise signals. This article reviews these techniques with a focus on multisines/multicarrier signals, harmonic signals, and chaotic signals. A theoretical explanation for efficiency improvement is provided and accompanied by experimental results. Circuit design considerations are presented for the receiver side, and efficient transmission architectures are also described with an emphasis on spatial power combining.

A UHF rectifier with one octave bandwidth based on a non-uniform transmission line

Ambient RF energy especially in urban settings is suitable for scavenging and harvesting scenarios provided one is able to collect signals from a large number of frequency bands and consequently spanning a large aggregate bandwidth. In this work a broadband rectifier is designed capable of harvesting RF energy in the 400 MHz - 1 GHz range, which includes the analog and digital TV bands and the UHF ISM 900 MHz band. In order to obtain a sufficiently large rectifier bandwidth, a matching network based on a non-uniform transmission line is considered. A charge pump rectifier is used and the number of diodes in the circuit is optimized in order to facilitate impedance matching based on the Bode-Fano limit. A prototype is fabricated and characterized. The rectifier has a measured efficiency above 5% from 470 MHz to 990 MHz at -20 dBm input power, which increases above 60% at 10 dBm input power over a band from 470 MHz to 860 MHz.

A Flexible Research Testbed for C-RAN

This paper presents a laboratorial platform for the development and trial of C-RAN compliant features. As part of future mobile networks standardization, C-RAN is considered as an evolution of the current RAN, which inherent challenges represent an interesting topic of research among academic institutions and industry. The proposed testbed is intended to provide a cost-effective emulation of the high price and vendor-specific closed radio base station equipment such as BBU and RRH modules. Based on open FPGA platforms, it leads to a high level of flexibility according to user-defined configurations as well as it provides a high set of real-world deployments features, such as the optical CPRI interface, multi-mode and multi-band capabilities. Furthermore, due to its modularity it is targeted for a wide range of C-RAN applications and optimization scenarios such as CoMP, cloud processing and baseband signal compression.

Harmonic spaced multisines for efficient wireless power transmission

In recent years, multisine signals have been used to increase RF-to-DC conversion efficiency in wireless power transmission systems. These signals are characterized to have a high PAPR that allows to excite rectifier diodes more efficiently in low power environments, extending the reading range of a RFID tag with same average radiated power, for example. With this paper we propose a new kind of multisines, a harmonic spaced multisine that achieves unique and interesting time domain properties. Both analytic and experimental results are performed to show the superiority of this signal.

Europe and the Future for WPT: European Contributions to Wireless Power Transfer Technology

This article presents European-based contributions for wireless power transmission (WPT), related to applications ranging from future Internet of Things (IoT) and fifth-generation (5G) systems to high-power electric vehicle charging. The contributors are all members of a European consortium on WPT, COST Action IC1301. WPT is the driving technology that will enable the next stage in the current consumer electronics revolution, including batteryless sensors, passive RF identification (RFID), passive wireless sensors, the IoT, and machine-to-machine solutions. The article discusses the latest developments in research by some of the members of this group.This article presents recent European-based contributions for wireless power transmission (WPT), related to applications ranging from future Internet of Things (IoT) and fifth-generation (5G) systems to highpower electric vehicle charging. The contributors are all members of a European consortium on WPT, COST Action IC1301 (Table 1). WPT is the driving technology that will enable the next stage in the current consumer electronics revolution, including batteryless sensors, passive RF identification (RFID), passive wireless sensors, the IoT, and machine-to-machine solutions.

Increasing wireless powered systems efficiency by combining WPT and Electromagnetic Energy Harvesting

This paper proposes and discusses a multiband RF-to-DC converter approach that is simultaneous fed from electromagnetic energy that is available in the ambient, at different frequencies bands, and a dedicated wireless power transmission link. The work uses narrow band matching allowing easy high efficiency conversion on its main power source, which is the WPT link. Its performance is evaluated showing an experimental peak efficiency over 40% for all frequency bands with central frequencies at 791, 1570 and 2340 MHz (with 35% efficiency bandwidth of 30, 60 and 40 MHz, respectively), when fed with a -10 dBm CW signal. Moreover, it is shown that the additional electromagnetic energy harvested will boost the efficiency of the wireless power transmission link alone from 41% up to 48%, when a collectable ambient energy of 10 μWatts is available.

Europe and the future for WPT

This article presents European-based contributions for wireless power transmission (WPT), related to applications ranging from future Internet of Things (IoT) and fifth-generation (5G) systems to high-power electric vehicle charging. The contributors are all members of a European consortium on WPT, COST Action IC1301. WPT is the driving technology that will enable the next stage in the current consumer electronics revolution, including batteryless sensors, passive RF identification (RFID), passive wireless sensors, the IoT, and machine-to-machine solutions. The article discusses the latest developments in research by some of the members of this group.This article presents recent European-based contributions for wireless power transmission (WPT), related to applications ranging from future Internet of Things (IoT) and fifth-generation (5G) systems to highpower electric vehicle charging. The contributors are all members of a European consortium on WPT, COST Action IC1301 (Table 1). WPT is the driving technology that will enable the next stage in the current consumer electronics revolution, including batteryless sensors, passive RF identification (RFID), passive wireless sensors, the IoT, and machine-to-machine solutions.

A software-defined radio RFID reader design with improved wireless power transfer capabilities

We present a SDR-based RFID reader design possessing two features that allow to improve the wireless power transfer capability and thereby extend the reading range of passive transponders: 1) The reader generates optimized non-CW powering waveforms that improve the RF-DC conversion efficiency of passive transponders. The sensitivity of an RFID chip was measured using a CW and several non-CW signals, and a sensitivity gain of more than 3 dB relative to the CW was obtained for a 9-tone multi-sine signal. 2) Moreover, the reader employs a multi-polarization antenna scheme that switches between several linear polarizations to deliver 3 dB more power compared to circular polarization, while maintaining the desired orientation insensitivity.

Enabling a constant and efficient flow of wireless energy for IoT sensors

This work describes the design of an energy efficient transmitter for wireless power transfer applications. The main objective is to power up, efficiently, an IoT sensor moving on a multi-path environment. In this scenario a flexible transmitter will be operated in order to maintain a constant power delivery to the sensor, while maximizing both transmitter and receiver energy efficiency conversions. The mechanism operates on the basis of a backscatter circuit attached to the IoT sensor, creating a feedback link that feeds the transmitter with its Received Signal Strength (RSSI). Experimental results will be reported on a system working at 5.83 GHz for wireless power transfer and 3.45 GHz for the backscattering link.

Europe and the future for WPT COST action IC1301 team

This article presents European-based contributions for wireless power transmission (WPT), related to applications ranging from future Internet of Things (IoT) and fifth-generation (5G) systems to high-power electric vehicle charging. The contributors are all members of a European consortium on WPT, COST Action IC1301. WPT is the driving technology that will enable the next stage in the current consumer electronics revolution, including batteryless sensors, passive RF identification (RFID), passive wireless sensors, the IoT, and machine-to-machine solutions. The article discusses the latest developments in research by some of the members of this group.This article presents recent European-based contributions for wireless power transmission (WPT), related to applications ranging from future Internet of Things (IoT) and fifth-generation (5G) systems to highpower electric vehicle charging. The contributors are all members of a European consortium on WPT, COST Action IC1301 (Table 1). WPT is the driving technology that will enable the next stage in the current consumer electronics revolution, including batteryless sensors, passive RF identification (RFID), passive wireless sensors, the IoT, and machine-to-machine solutions.