Ricardo Dias Fernandes

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.

Increasing the range of wireless passive sensor nodes using multisines

Wireless Sensor Networks (WSNs) usually consist of battery-powered nodes. Therefore, once the batteries deplete, the networks collapse. Passive sensor nodes are immune to this kind of problem because they do not have batteries, but on the other hand, their range is significantly shorter. This paper shows that this range can be enhanced (in a noticeable manner) if the Radio Frequency (RF) source that powers the nodes is set up to radiate a multisine waveform instead of a pure sinusoid, considering the same average power. The passive sensor used to demonstrate the usefulness of combining multiple sinusoidal waveforms is based on a low-power 16-bit microcontroller, and includes circuits for bi-directional wireless binary communication (envelope detection for downlink, backscatter for uplink). The sensor also features a 50Ω antenna port and an interface for debugging and expansion composed of 26 pins. Considering a power source of 2Werp, the maximum range of the wireless sensor (together with a half-wave dipole antenna) is 5.3 meters.

Design of a battery-free wireless sensor node

In this paper, a battery-free wireless sensor designed to harvest energy from electromagnetic waves at 866.6MHz and its detachable antenna system are described, with an emphasis on high frequency front-end design. In addition to having no local power source, the proposed sensor node is programmable, since it integrates a general-purpose microcontroller. Other features of the device are a standard 50Ω port and an interface for debugging and expansion, with of a total of 26 pins. In practice, the proposed system is capable of carrying out communication and processing tasks at up to a distance of 4.1 meters away from a transmitter antenna operating within the limits imposed by local regulatory entities, with respect to radiated power. Uplink communication is achieved using modulated backscattering. The proposed antenna system consists of a printed dipole-based antenna, with an overall efficiency in the order of 96%.

Resonant Electrical Coupling: Circuit Model and First Experimental Results

In this paper, the feasibility of resonant electrical coupling as a wireless power transfer technique is studied. A detailed comparison between this technique and the more popular resonant magnetic coupling based on circuit theory is provided. In this comparison, the strong duality that exists between the two techniques is demonstrated. The analytical results obtained are compared with the results measured with a proof-of-concept prototype.

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.

Behavior of resonant electrical coupling in terms of range and relative orientation

The subjects addressed in this document fall under the topic of wireless power transmission (WPT). Power is transferred using a novel coupling technique based on electrical coupling and resonance across a distance of 5 meters with 40% efficiency. The experimental results obtained so far suggest that the efficiency of the proposed system remains stable when the relative orientation between the transmitter and the receiver is altered. The prototypes used in the experiments measure 16 by 16 cm by 3.7 cm at most. The ratio between the range of the system and the maximum dimension of each prototype is therefore around 30.

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.

Constructive combination of resonant magnetic coupling and resonant electrical coupling

In this paper the possibility of combining resonant magnetic coupling and resonant electrical coupling is proposed and discussed. Equivalent circuit models are used to demonstrate that efficiency can be improved quite significantly using a hybrid approach. A comparison between resonant magnetic coupling only, resonant electrical coupling only and several hybrid combinations is provided.

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.

Green RFID Systems: Unconventional RFID systems

Introduction Non-conventional RFID systems include those that are not exclusively designed for identification purposes, but which also implement other advanced tasks such as location or sensing. The most widespread, yet simple, RFID system is the one-bit EAS (electronic article surveillance) system whose only purpose is to detect the presence/absence of a tagged object in the vicinity of a reader. On the other hand, current state-of-the-art N -bit RFID systems serve a broader range of purposes, and the technology is experiencing tremendous advances. RFID readers are more robust, effective, and energy-efficient. Tags can now be made thinner, cheaper, often physically flexible, and more energy-efficient. Sensors, only used in wireless sensor nodes before, are currently making their way towards RFID tags. Some examples of these sensor-enabled tags can readily be found in the literature [1]. Multi-sensor tags including processing capabilities can also be found [2]. In order to be more autonomous and effective, beyond the energy harvesting subsystem, advanced tags also incorporate energy storage and power management units (Figure 5.1). Moreover, some tags integrate more than one method to harvest and store energy, as in Figure 5.1. As the complexity of passive tags increases (due to sensor, analog-to-digital data conversion, and processing needs) the energy demand also increases, and consequently the system coverage range and the overall energy efficiency become a major concern. Some interesting approaches have been proposed, among them the use of specific signal shapes to improve the RF-DC efficiency of the harvester receivers. One of these examples unconventionally uses multi-sine signals with high PAPR (peak to average power ratio) waveforms (Figure 5.2) that benefit the rectification process on the harvester side [3]. Other kinds of power optimized waveforms, such as chaotic signals, are now being used to improve the RF-DC conversion efficiency [4].