Preface

Wireless Power Transfer (WPT) is an old concept with over 100 years of history, and it has been advocated and intensively investigated by notorious scientists, such as Nikola Tesla or William C. Brown. It can be defined as a set of technologies and systems with the purpose of transmitting electrical energy from a source to a certain destination, without using any physical connection. This technology can be useful, not only for applications where the usage of interconnecting wires is inconvenient or not possible, but also to reduce the toxic waste resulting from disposing of 6 billion batteries each year, used for battery operated sensors or electronic circuits.

Recently, several companies and products have been focusing and investing on wireless power transmission components and applications. In this context, the Internet of Things (IoT) and Internet of Nano Things (IoNT) concepts' massification could be achieved by significantly reducing or even eliminating the sensors' battery requirements.

Generally, there are two main techniques considered for WPT systems: the nearfield and the far-field radio-frequency (RF) methods. Near-field operation methods, such as inductive and/or capacitive coupling, are only capable of transferring power over short distances. On the other hand, WPT based on the far-field RF techniques (referred as far-field WPT), where the power is transmitted by electromagnetic radiation, allows for the transmission of electrical energy over longer distances, but at the cost of lower efficiencies. This feature makes the farfield method an attractive WPT option solution for powering the billions of connected devices that are expected to be ubiquitously deployed worldwide.

The main characteristics of the WPT methods are presented in Table 1.

Some interests have been referenced in the recent years towards the low profile, low power, energy efficient, and self-sustainable sensor networks. Many applications and devices have fulfilled these requirements, such as Radio Frequency Identification (RFID), wireless sensor networks (WSNs), wearable and implantable medical devices, structural health monitoring, and IoT/IoNT. Such applications can involve a wide range of power levels (μW to few W), depending on the target applications and the distance from the controlled source.

Since the concept of WPT is still an active demand, and every day there are new developments in this area, this book aims to promote and present some of the recent


Chapter 8 153

Chapter 9 177

Chapter 10 195

Rectenna Systems for RF Energy Harvesting and Wireless Power

Voltage-Doubler RF-to-DC Rectifiers for Ambient RF Energy

by Abdul Quddious, Marco A. Antoniades, Photos Vryonides and

by Mohamed Aboualalaa and Hala Elsadek

by Ahmed M.A. Sabaawi and Oras Ahmed Al-Ani

Harvesting and Wireless Power Transfer Systems

Solar Rectennas: Analysis and Design

Transfer

Symeon Nikolaou

II

advances in design and performance analysis of microwave and millimeter-wave systems that employ the WPT concepts.

multiband antennas, as well as rectifier circuits with respective matching networks,

Finally, the last chapter discusses the operating principles of voltage-doubler rectifiers. The most important design considerations for the implementation of such rectifying devices are also presented as standalone circuits. Moreover, several examples of the usage of voltage-doubler rectifiers are highlighted as part of a directive rectenna system and as an energy harvesting system. In those examples, a voltage-doubler rectifier was cascaded with an active DC-to-DC booster, demonstrating the successful implementation of WPT systems using voltage-doubler cir-

The editor and the authors would like to express their gratitude to the publisher for the assigned time, considering the invaluable experience, efforts and staff, that successfully contribute to enhance the book's quality in its final form. Finally, a special thanks to Carolina Gouveia and Ricardo Correia for the suggestions and the

To Carla Lourenço, Íris Pinho and Petra Pinho.

Telecommunications, and Computers Engineering,

Department in Instituto Superior de Engenharia de Lisboa (ISEL/IPL) and Senior Member of Instituto de Telecomunicações (IT) Aveiro, Portugal

Prof. Pedro Pinho

Assistant Professor in Electronics,

The ninth chapter presents the concept and operation of solar rectennas, as an efficient energy harvesting technology and as a better alternative to conventional solar cells. Nano antennas are used for receiving solar radiation, at both visible and infrared regions. The received power is then passed to a nano-diode that acts as a rectifier to convert the power from the AC to the DC form. Nano-arrays are often utilized to increase the captured energy and decrease the number of rectifiers on the

are introduced for successfully complete rectenna circuit models.

entire system.

cuits as the preferred rectifier topologies.

reading of this preface.

V

This book is organized in ten chapters. In the first chapter, application fields and metrics for NFF (Near-Field Focused) antennas are briefly summarized. The rest of the chapter is devoted to the description, classification, and critical review of the many synthesis techniques, for an assigned near-field distribution. It has been shown that the large number of available synthesis techniques can effectively solve many real-world focused problems, when different requirements on the antenna near-field are assigned.

The second chapter is dedicated to an overview of recent advances in the field of battery-less NFC sensors at 13.56 MHz and a comparison to other short-range RFID technologies is given. After reviewing power transfer techniques in NFC, recommendations for the practical design of NFC-based sensor tags and NFC readers are made. A list of commercial NFC integrated circuits with energy-harvesting capabilities is also provided.

The third chapter presents a review on design constraints for each approach (dualand single-band) and on the rectification techniques available for counteracting impediments of dual-band near-field wireless energy transfer systems. Pertinent challenges considering the link design are discussed, along with methods implemented to mitigate the detrimental impact on performance metrics.

Miniature implantable electronic devices for sensing, drug delivery, and local stimulation have been playing an increasing role in modern medicine. In order to implement these devices successfully, WPT technology is often utilized because it provides an alternative to the battery as power source, substantially reduces the size of implants, simplifies the surgical procedure, allows the implant placement in a restricted space within the body, reduces both medical cost and chances of complications, and avoids repeated surgeries for battery replacements. In this sense, the fourth chapter presents two recent studies focused on two key issues in the design of miniature electronic implants.

In the fifth chapter, the Time Reversal technique is presented as an inverse operation of time-domain signals, which uses the multipath effect to improve the efficiency and to reduce the interference due to its unique temporal-spatial focused effect.

The sixth chapter presents the performance of the non-orthogonal multiple access (NOMA) relaying network, with radio frequency (RF) power transfer. The exact closed-form expressions of outage probability and throughput for each link and whole system are derived using the statistical characteristics of signal-to-noise ratio (SNR) and signal-to-interference-plus-noise ratio (SINR) of transmission links.

The seventh chapter describes transceiver design methods for simultaneous wireless power transmission and information transmission, in two typical multiuser Multi-Input Multi-Output (MIMO) networks. The design problems are formulated to minimize the power consumption at the transmitter side, while satisfying the service's quality requirements of both information decoding and WPT for all users.

The eighth chapter presents several designs for single and multiband rectennas, with different characteristics for energy harvesting applications. Single and

multiband antennas, as well as rectifier circuits with respective matching networks, are introduced for successfully complete rectenna circuit models.

The ninth chapter presents the concept and operation of solar rectennas, as an efficient energy harvesting technology and as a better alternative to conventional solar cells. Nano antennas are used for receiving solar radiation, at both visible and infrared regions. The received power is then passed to a nano-diode that acts as a rectifier to convert the power from the AC to the DC form. Nano-arrays are often utilized to increase the captured energy and decrease the number of rectifiers on the entire system.

Finally, the last chapter discusses the operating principles of voltage-doubler rectifiers. The most important design considerations for the implementation of such rectifying devices are also presented as standalone circuits. Moreover, several examples of the usage of voltage-doubler rectifiers are highlighted as part of a directive rectenna system and as an energy harvesting system. In those examples, a voltage-doubler rectifier was cascaded with an active DC-to-DC booster, demonstrating the successful implementation of WPT systems using voltage-doubler circuits as the preferred rectifier topologies.

The editor and the authors would like to express their gratitude to the publisher for the assigned time, considering the invaluable experience, efforts and staff, that successfully contribute to enhance the book's quality in its final form. Finally, a special thanks to Carolina Gouveia and Ricardo Correia for the suggestions and the reading of this preface.

To Carla Lourenço, Íris Pinho and Petra Pinho.

Prof. Pedro Pinho Assistant Professor in Electronics, Telecommunications, and Computers Engineering, Department in Instituto Superior de Engenharia de Lisboa (ISEL/IPL) and Senior Member of Instituto de Telecomunicações (IT) Aveiro, Portugal

advances in design and performance analysis of microwave and millimeter-wave

This book is organized in ten chapters. In the first chapter, application fields and metrics for NFF (Near-Field Focused) antennas are briefly summarized. The rest of the chapter is devoted to the description, classification, and critical review of the many synthesis techniques, for an assigned near-field distribution. It has been shown that the large number of available synthesis techniques can effectively solve many real-world focused problems, when different requirements on the antenna

The second chapter is dedicated to an overview of recent advances in the field of battery-less NFC sensors at 13.56 MHz and a comparison to other short-range RFID technologies is given. After reviewing power transfer techniques in NFC, recommendations for the practical design of NFC-based sensor tags and NFC readers are made. A list of commercial NFC integrated circuits with energy-harvesting capabil-

The third chapter presents a review on design constraints for each approach (dualand single-band) and on the rectification techniques available for counteracting impediments of dual-band near-field wireless energy transfer systems. Pertinent

Miniature implantable electronic devices for sensing, drug delivery, and local stimulation have been playing an increasing role in modern medicine. In order to implement these devices successfully, WPT technology is often utilized because it provides an alternative to the battery as power source, substantially reduces the size of implants, simplifies the surgical procedure, allows the implant placement in a restricted space within the body, reduces both medical cost and chances of complications, and avoids repeated surgeries for battery replacements. In this sense, the fourth chapter presents two recent studies focused on two key issues in the design

In the fifth chapter, the Time Reversal technique is presented as an inverse operation of time-domain signals, which uses the multipath effect to improve the efficiency and to reduce the interference due to its unique temporal-spatial focused

The sixth chapter presents the performance of the non-orthogonal multiple access (NOMA) relaying network, with radio frequency (RF) power transfer. The exact closed-form expressions of outage probability and throughput for each link and whole system are derived using the statistical characteristics of signal-to-noise ratio (SNR) and signal-to-interference-plus-noise ratio (SINR) of transmission links.

The seventh chapter describes transceiver design methods for simultaneous wireless power transmission and information transmission, in two typical multiuser Multi-Input Multi-Output (MIMO) networks. The design problems are formulated to minimize the power consumption at the transmitter side, while satisfying the service's quality requirements of both information decoding and WPT for all users.

The eighth chapter presents several designs for single and multiband rectennas, with different characteristics for energy harvesting applications. Single and

challenges considering the link design are discussed, along with methods implemented to mitigate the detrimental impact on performance metrics.

systems that employ the WPT concepts.

near-field are assigned.

ities is also provided.

of miniature electronic implants.

effect.

IV

Chapter 1

Abstract

An Overview on Synthesis

Techniques for Near-Field

Marcos R. Pino, Rafael G. Ayestarán, Paolo Nepa

Keywords: near-field focusing, focused antennas, focused arrays,

cation systems, and even in consumer electronic goods.

Microwave and millimeter-wave antennas focused in their radiative near-field (NF) region, which are usually named as near-field focused (NFF) antennas, are becoming increasingly popular. Indeed, when compared to conventional far-field focused antennas, they can guarantee performance improvement at a relatively limited implementation cost, in short-range communication systems, wireless power transfer arrangements, remote nondestructive sensing setups, and radiofrequency identification apparatus, among many others. In this chapter, application fields and metrics for NFF antennas will be briefly summarized. Most of the chapter is then devoted to the description, classification, and critical review of the many synthesis techniques that go beyond the simple, yet effective and with a clear

near-field shaping, near-field synthesis, focused array synthesis, antenna focusing,

Many wireless systems require directive antennas for proper operation. These are antennas that are able to radiate most of their input power into a limited angular sector. Indeed, above feature can improve either the spatial resolution of a localization system or the sensitivity of a remote measurement system, reduce the interference level with other wireless systems, and increase either the transfer efficiency of wireless power transfer systems or the signal-to-noise ratio in radio communication links. As it is well known to antenna designers, antenna directivity can be increased at the expense of electrically larger antennas, namely antennas that are large in terms of the free-space wavelength. Indeed, electrically large antenna arrays are becoming popular in several industrial applications, indoor wireless communi-

Let us consider a specific wireless system whose frequency band is assigned, as well as the typical expected distance between the transmitting antenna and the target (transponder, receiving antenna, material sample under analysis, scatterer,

Focused Antennas

physical insight, conjugate-phase approach.

phase conjugate technique

1. Introduction

1

and Giuliano Manara
