ROBUST BIOTELEMETRY AND WIRELESS POWER TRANSFER IN ANTENNA SYSTEMS FOR MINIATURIZED ORGAN-SPECIFIC BIOELECTRONICS

Recording neural activities plays an important role in numerous applications ranging from brain mapping to implementation of brain-machine interfaces (BMI) to recover lost functions or to understand the mechanisms behind the neurological disorders such as essential tremor, Parkinsonâ s disease and epilepsy. It also constitutes the first step of a closed-loop therapy system which employs a stimulator and a decision mechanism additionally. Such systems are envisaged to record neural anomalies and then stimulate corresponding tissues to cease such activities. Methods for recording the neural signals have evolved to its current state since decades, and the evolution still goes on. This thesis focuses on how to eliminate all the wired connections for new generation neural recording systems: implantable wireless neural recording systems with a case study on in-vivo epilepsy monitoring. The scope of the thesis can be defined as wireless power transfer, wireless data communication, biocompatible packaging, and compulsory experiments on the way to human trials. First of all, wireless power transmission is performed using 4-coil resonant inductive link topology which exploits the magnetic coupling phenomena. In addition to power transfer, a reliable DC power supply is generated in the implant by means of a half-wave active rectifier and a low drop-out voltage regulator. The operation frequency, 8.5 MHz, has been optimized by taking tissue absorption and bandwidth limitations for data communication into account. Secondly, wireless data communication solutions have been investigated and two different solutions have been implemented for different application scenarios: First solution is to use load modulation scheme, which actually relies on varying the load according to the incoming neural data. However, there is a trade-off between data rate and power transfer efficiency for this solution, which in return leads us to implement the second solution, dedicated transmitter at a higher frequency. Consequently, a transmitter which can work at MICS (402-405 MHz), ISM (433 MHz) and several MedRadio bands has been implemented to transmit neural data to an external base station which includes a discrete receiver. Following the integration of all electronic circuits which have been fabricated using UMC 180 nm MM/RF technology, the implant has been packaged using biocompatible polymers (PDMS, medical grade epoxy, and Parylene-C). Packaging provides bidirectional diffusion barrier feature which enables in-vitro and in-vivo experiments to be conducted. Finally, three levels of experimentation have been conducted to validate the operation of the system: in air for electrical characterization, in a tissue-mimicking solution in-vitro characterization, and in a mouse brain for in-vivo characterization.

Networks of miniature bioelectronic implants would enable precise measurement and manipulation of the complex and distributed physiological systems in the body. For example, sensing and stimulation nodes throughout the heart, brain, or peripheral nervous system would more accurately track and treat disease or support prosthetic technologies with many degrees of freedom. A main challenge to creating this type of in-body bioelectronic network is the fact that wireless power and data transfer are often inefficient when communicating through biological tissues. This challenge is typically compounded as one increases the number of implants within the network. Here, we show that magnetoelectric wireless data and power transfer enable a network of millimeter-sized bioelectronic implants where the power transfer efficiency of the system improves as the number of implanted devices increases. Using this property, we demonstrate networks of wireless battery-free bioelectronics ranging from 1 to 6 implants where the wireless power transfer efficiency for the system increases from 0.2% to 1.3%, with each node in the network receiving 2.2 mW at a distance of 1 cm. We use this system for efficient and robust wireless data and power transfer to demonstrate proof-of-concept networks of miniature spinal cord stimulators and cardiac pacing devices in large animals. The scalability of this network architecture enabled by magnetoelectric wireless power transfer provides a platform for building wireless closed-loop networks of bioelectronic implants for next-generation electronic medicine.

As wireless has disrupted communications, wireless will also disrupt the delivery of energy. Future wireless networks will be equipped with (radiative) wireless power transfer (WPT) capability and exploit radio waves to carry both energy and information through a unified wireless information and power transfer (WIPT). Such networks will make the best use of the RF spectrum and radiation as well as the network infrastructure for the dual purpose of communicating and energizing. Consequently those networks will enable trillions of future low-power devices to sense, compute, connect, and energize anywhere, anytime, and on the move. In this paper, we review the foundations of such future system. We first give an overview of the fundamental theoretical building blocks of WPT and WIPT. Then we discuss some state-of-the-art experimental setups and prototypes of both WPT and WIPT and contrast theoretical and experimental results. We draw a special attention to how the integration of RF, signal and system designs in WPT and WIPT leads to new theoretical and experimental design challenges for both microwave and communication engineers and highlight some promising solutions. Topics and experimental testbeds discussed include closed-loop WPT and WIPT architectures with beamforming, waveform, channel acquisition, and single/multi-antenna energy harvester, centralized and distributed WPT, reconfigurable metasurfaces and intelligent surfaces for WPT, transmitter and receiver architecture for WIPT, modulation, rate-energy trade-off. Moreover, we highlight important theoretical and experimental research directions to be addressed for WPT and WIPT to become a foundational technology of future wireless networks.

Wireless power transfer (WPT) systems can potentially provide simultaneous power and data transfer for Internet-of-Things devices, such as smart speakers, glasses, and watches. However, due to the high quality factor of coils, the intrinsically narrow WPT channel bandwidth severely limits the data transmission capability of the system, especially for data downloading links requiring higher data rates. In addition, the channel bandwidth varies with power transfer distances, which is also undesirable for wireless communication. In this study, the channel features of a two-coil series–series matching magnetic resonance wireless power and data transfer (MWPDT) system, including the bandwidth and the roll-off slope are characterized analytically. Based on the characterization results, a receiver front-end circuit with a three-stage cascaded equalizer (EQ) is proposed and implemented to extend the bandwidth of a MWPDT system at different distances. The proposed EQ can provide a frequency response with a variable roll-up slope from 10 to 45 dB/dec to compensate for the distance-dependent channel response of an MWPDT system. A complete MWPDT system is built and tested to verify the performance of the proposed method. Experimental results demonstrate that the data rates can be extended from 650, 500, and 350 kbps to 850, 700, and 650 kbps at 0.4, 0.5, and 0.6-m distances, respectively. The highest data rate extension ratio is 85% at a transmission distance of 0.6 m, which is 2.4 times the radii of the coil employed in the system.

ABSTRACTMulti‐port wireless power transfer (WPT) technology can realize non‐contact power transmission between multiple devices, which is potentially used in the integrated system of PV, energy storage, and charging, cooperative power supply for multiple unmanned aerial vehicles, etc. The simultaneous transmission of power and information between multiple ports is crucial to the intelligence and automation of WPT systems. However, the research on simultaneous wireless power and information transfer (SWPIT) is really limited. In this paper, an on–off keying multi‐port SWPIT methodology based on high‐frequency carrier injection is proposed for magnetically coupled resonant WPT systems with multiple sources and loads. Taking the three‐port system as an example, the system architecture and specific circuit topology of power and information transfer circuits are demonstrated, and the corresponding equivalent circuit models are built to analyze the power transfer characteristic and information transfer gain. Meanwhile, key parameters to achieve the required information transfer gain are designed, and the power and information crosstalk is discussed. A prototype with three ports and the rated power of 400 W is fabricated in the laboratory, and the validity of the proposed methodology is verified by experimental results.

Wireless power transfer (WPT) offers a viable solution for facilitating efficient and sustainable communication networks serving energy-limited communication devices. WPT technology enables simultaneous wireless information and power transfer (WIPT). The existing WPT technologies can be categorized into three classes: inductive coupling, magnetic resonant coupling, and RF-based WPT. RF-based energy harvesting technology enables the possibility of simultaneous WIPT (SWIPT), wireless-powered communication (WPC), and wireless-powered backscatter communication (WPBC).This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book addresses the challenges incurred by the nature of WPT and provides a comprehensive reference for various solutions for realizing efficient WIPT in practice. It also provides some background information on WPT and discusses exciting research directions. The book helps to study the fundamental problems in WIPT networks, including communication security in WIPT systems, energy transfer efficiency, and interference management in WIPT systems.

5G-based green broadband communication system design with simultaneous wireless information and power transfer

Simultaneous wireless information and power transfer (SWIPT) has gained interest, especially due to its applicability in the world of Internet of Things. For pure wireless power transfer (WPT), multisine signals have already been shown to increase RF-to-DC power conversion efficiency (PCE) at the receiver which is key in WPT research. In a SWIPT system where the waveforms are modulated for information transfer, however, we expect the modulation scheme to impact both data transmission quality and WPT subsystem efficiency. This paper quantifies by means of an experimental study the impact of QAM and PSK modulated multisine signals, on the power and data transfer efficiency of a SWIPT system, taking into account the often neglected transmitter distortion. Error vector magnitude (EVM) is used as figure of merit for the impact of data transfer efficiency, output voltage ripple for the modulation's impact on WPT.

Simultaneous wireless power and data transfer (SWPDT) technology is usually needed in wireless power transfer (WPT) systems. In this paper, to achieve the efficient and stable SWPDT, the signal to noise rate (SNR) is first optimized through the analysis of data transmission gain and the interference of power transfer on data transfer. In order to reduce the interference of power channel to data transfer channel, the compensation topology of double-sided LCC and the band-stop networks are used. To solve the problem of SNR limitation, the coupling relationships between each circuit are taken into consideration and a matching method of resonance parameters to improve the SNR is presented. Based on the relationship between SNR and the parameters of data transfer channel, an optimization design method focused on parameters of data transfer channel for improving the SNR is presented. Finally, the feasibility and the correctness of the parameter design method proposed in this paper is verified by simulation and experiment.

Wireless information and power transfer (WIPT) enables more sustainable and resilient communications owing to the fact that it avoids frequent battery charging and replacement. However, it also suffers from possible information interception due to the open nature of wireless channels. Compared to traditional secure communications, secrecy wireless information and power transfer (SWIPT) carries several distinct characteristics. On one hand, wireless power transfer may increase the vulnerability of eavesdropping, since a power receiver, as a potential eavesdropper, usually has a shorter access distance than an information receiver. On the other hand, wireless power transfer can be exploited to enhance wireless security. This article reviews the security issues in various SWIPT scenarios, with an emphasis on revealing the corresponding challenges and opportunities for implementing SWIPT. Furthermore, we provide a survey on a variety of physical layer security techniques to improve secrecy performance. In particular, we propose to use massive multiple-input multiple-output (MIMO) techniques to enhance power transfer efficiency and secure information transmission simultaneously. Finally, we discuss several potential research directions to further enhance the security in SWIPT systems.

In this contribution, the authors perform the design and show the experimental results relative to a prototype of a combined wireless power transfer (WPT)–power line communications (PLC) system, in which the WPT channel is interfaced to a PLC environment to allow data transfer when the cabled connection is no longer available. The main rationale behind this idea stays in the fact that PLC communication is now a popular choice to enable communications, for instance, in smart grids and in home automation, while WPT devices start to be available in the market (i.e. for mobile phones) and soon they will be a reality also for higher power (i.e. vehicle battery charging). In particular, theoretical insights about the requirements of the system are given; a two coils system has been implemented and a measurement campaign, together with simulations, show that the system is of great potentiality and could be used in applications where both wireless power and data transfer are needed (such as vehicles battery charging), achieving maximum power transfer and good data rate in order to transmit high-speed signals.

Inductively coupled resonant wireless power transfer (WPT) systems can be used as a wireless power and information transfer (WPIT) system by properly adding the function of varying Rx loads. A new metric for the figure of merit for information transfer from Rx to Tx is proposed as the ratio of Tx input impedances for the Rx shorted and optimum loads to systematically assess the information transfer. While most of WPT and near-field communication (NFC) devices have been adopted for very short distances between Tx and Rx, this work shows that the WPIT systems using inductively coupled resonant structures with high Q-factor coils enable much longer working distances with the best power transfer efficiency and information transfer capability. Several design examples show that the newly proposed figure of merit for information transfer is an essential metric in the understanding and design of WPIT systems. The theory is validated with circuit and electromagnetic simulations for various system configurations.

Design of Dual Frequency Class E Resonant Converters for Simultaneous Wireless Power and Data Transfer in Low Power Applications

Neural implantable sensors require a harmless sustainable wireless power transfer technique for their lifetime operation. The capacitive-coupled (CC) power transfer method has proved to induce minimum electromagnetic interference as compared with inductive resonant power transfer. However, the CC method suffers from the limitation of low power transfer efficiency (PTE) and is suitable only for short-distance power transfer applications. In physical health-monitoring practices, the deep implants require high PTE with minimum electromagnetic interference. Similarly, the measured data need to be transmitted to the external world for remote monitoring and analysis. Nevertheless, the size and safety constraints limit the direct interfacing of the data communication module to implants. With this objective, this paper proposes a resonant capacitive-coupling (RCC) approach for wireless power transfer to brain implants. Moreover, to further improve the PTE, the proposed model is investigated with the additional intermediate plate capacitance between the transmitter (Tx) and the receiver (Rx). The analytical and experimental studies are carried out for intracranial pressure sensor (ICP) application and obtain the PTE of 24.2%, 34.14%, and 42.21% for CC, RCC, and RCC with an intermediate plate (RCCI) approaches, respectively. In addition, to eliminate the use of the antenna for data transfer, the same capacitive plates are used and tested with amplitude phase-shift keying (ASK) modulation technique for uplink communication. The proposed system is also integrated with the Internet of Things (IoT) module for the remote monitoring and analyses of patient health.

This chapter presents state-of-the-art and major developments in wireless power transfer using solar energy. The brief state-of-the-art is presented for solar photovoltaic technologies which can be combined with wireless power transfer (WPT) to interact with the ambient solar energy. The main purpose of the solar photovoltaic system is to distribute the collected electrical energy in various small-scale power applications wirelessly. These recent developments give technology based on how to transmit electrical power without any wires, with a small-scale by using solar energy. The power can also be transferred wirelessly through an inductive coupling as an antenna. With this wireless electricity we can charge and make wireless electricity as an input source to electronic equipment such as cellphone, MP3 Player etc. In harvesting energy, technologies of ambient solar radiation like solar photovoltaic, kinetic, thermal or electro-magnetic (EM) energy can be used to recharge the batteries. Radio frequency (RF) harvesting technologies are also popular as they are enormously available in the atmosphere. The energy converted to useful DC energy which can be used to charge electrical devices which need low power consumption. The chapter has also presented a parallel plate photovoltaic amplifier connected to a potentiometer as a Resistance-Capacitance (RC) circuit power amplifier. The effect of inductance and resulting power transfer has been theoretically determined in the RC amplifier circuit. The electrical and thermal properties and measurements from a parallel plate photovoltaic amplifier were collected to analyze the unbalanced power transfer and inductance in a nonlinear RC circuit amplifier using equivalent transfer functions. The concept of Wireless Information and Power Transfer using Electromagnetic and Radio Waves of Solar Energy Spectrum is also briefly outlined.