ISM-Band Energy Harvesting Wireless Sensor Node

In recent years, the interest in remote wireless sensor networks has grown significantly, particularly with the rapid advancements in Internet of Things (IoT) technology. These networks find diverse applications, from inventory tracking to environmental monitoring. In remote areas where grid access is unavailable, wireless sensors are commonly powered by batteries, which imposes a constraint on their lifespan. However, with the emergence of wireless energy harvesting technologies, there is a transformative potential in addressing the power challenges faced by these sensors. By harnessing energy from the surrounding environment, such as solar, thermal, vibrational, or RF sources, these sensors can potentially operate autonomously for extended periods. This innovation not only enhances the sustainability of wireless sensor networks but also paves the way for a more energy-efficient and environmentally conscious approach to data collection and monitoring in various applications. This work explores the development of an RF-powered wireless sensor node in 22nm FDSOI technology working in the ISM band for energy harvesting and wireless data transmission. The sensor node encompasses power-efficient circuits, including an RF energy harvesting module equipped with a multi-stage RF Dickson rectifier, a robust power management unit, a DLL and XOR-based frequency synthesizer for RF carrier generation, and a class E power amplifier. To ensure the reliability of the WSN, a dedicated wireless RF source powers up the WSN. Additionally, the RF signal from this dedicated source serves as the reference frequency input signal for synthesizing the RF carrier for wireless data transmission, eliminating the need for an on-chip local oscillator. This approach achieves high integration and proves to be a cost-effective implementation of efficient wireless sensor nodes. The receiver and energy harvester operate at 915 MHz Frequency, while the transmitter functions at 2.45 GHz, employing On-Off Keying (OOK) for data modulation. The WSN utilizes an efficient RF rectifier design featuring a remarkable power conversion efficiency, reaching 55% at an input power of -14 dBm. Thus, the sensor node can operate effectively even with an extremely low RF input power of -25 dBm. The work demonstrates the integration of the wireless sensor node with an ultra-low-power temperature sensor, designed using 65 nm CMOS technology. This temperature sensor features an ultra-low power consumption of 60 nW and a Figure of Merit (FOM) of 0.022 [nJ.K-2]. The WSN demonstrated 55% power efficiency at a TX output power of -3.8 dBm utilizing a class E power amplifier

Energy harvesting methods for transmission lines: a comprehensive review

Humanity faces important challenges concerning the optimal use, security, and availability of energy systems, particularly electrical power systems and transmission lines. In this context, data-driven predictive maintenance plans make it possible to increase the safety, stability, reliability, and availability of electrical power systems. In contrast, strategies such as dynamic line rating (DLR) make it possible to optimize the use of power lines. However, these approaches require developing monitoring plans based on acquiring electrical data in real-time using different types of wireless sensors placed in strategic locations. Due to the specific conditions of the transmission lines, e.g., high electric and magnetic fields, this a challenging problem, aggravated by the harsh outdoor environments where power lines are built. Such sensors must also incorporate an energy harvesting (EH) unit that supplies the necessary electronics. Therefore, the EH unit plays a key role, so when designing such electronic systems, care must be taken to select the most suitable EH technology, which is currently evolving rapidly. This work reviews and analyzes the state-of-the-art technology for EH focused on transmission lines, as it is an area with enormous potential for expansion. In addition to recent advances, it also discusses the research needs and challenges that need to be addressed. Despite the importance of this topic, there is still much to investigate, as this area is still in its infancy. Although EH systems for transmission lines are reviewed, many other applications could potentially benefit from introducing wireless sensors with EH capabilities, such as power transformers, distribution switches, or low- and medium-voltage power lines, among others.This research was funded by Ministerio de Ciencia e Innovación de España, grant number PID2020-114240RB-I00 and by the Generalitat de Catalunya, grant number 2017 SGR 967.Peer ReviewedPostprint (author's final draft

Vibration energy harvesters for wireless sensor networks for aircraft health monitoring

Traditional power supply for wireless sensor nodes is batteries. However, the application of batteries in WSN has been limited due to their large size, low capacity, limited working life, and replacement cost. With rapid advancements in microelectronics, power consumption of WSN is getting lower and hence the energy harvested from ambient may be sufficient to power the tiny sensor nodes and eliminate batteries completely. As vibration is the widespread ambient source that exists in abundance on an aircraft, a WSN node system used for aircraft health monitoring powered by a piezoelectric energy harvester was designed and manufactured. Furthermore, simulations were performed to validate the design and evaluate the performance. In addition, the Z-Stack protocol was migrated to run on the system and initial experiments were carried out to analyse the current consumption of the system. A new approach for power management was reported, the execution of the operations were determined by the amount of the energy stored on the capacitor. A novel power saving interface was also developed to minimise the power consumption during the voltage measurement

Development of the future generation of smart high voltage connectors and related components for substations, with energy autonomy and wireless data transmission capability

The increased dependency on electricity of modern society, makes reliability of power transmission systems a key point. This goal can be achieved by continuously monitoring power grid parameters, so possible failure modes can be predicted beforehand. It can be done using existing Information and Communication Technologies (ICT) and Internet of Things (10T) technologies that include instrumentation and wireless communication systems, thus forming a wireless sensor network (WSN). Electrical connectors are among the most critical parts of any electrical system and hence, they can act as nodes of such WSN. Therefore, the fundamental objective of this thesis is the design, development and experimental validation of a self-powered IOT solution for real-time monitoring of the health status of a high-voltage substation connector and related components of the electrical substation. This new family of power connectors is called SmartConnector and incorporates a thermal energy harvesting system powering a microcontroller that controls a transmitter and several electronic sensors to measure the temperature, current and the electrical contact resistance (ECR) of the connector. These measurements are sent remotely via a Bluetooth 5 wireless communication module to a local gateway, which further transfers the measured data to a database server for storage as well as further analysis and visualization. By this way, after suitable data processing, the health status of the connector can be available in real-time, allowing different appealing functions, such as assessing the correct installation of the connector, the current health status or its remaining useful life (RUL) in real-time. The same principal can also be used for other components of substation like spacers, insulators, conductors, etc. Hence, to prove universality of this novel approach, a similar strategy is applied to a spacer which is capable of measuring uneven current distribution in three closely placed conductors. This novel IOT device is called as SmartSpacer. Care has to be taken that this technical and scientific development has to be compatible with existing substation bus bars and conductors, and especially to be compatible with the high operating voltages, i.e., from tens to hundreds of kilo-Volts (kV), and with currents in the order of some kilo-pm peres (kA). Although some electrical utilities and manufacturers have progressed in the development of such technologies, including smart meters and smart sensors, electrical device manufacturers such as of substation connectors manufacturers have not yet undertaken the technological advancement required for the development of such a new family of smart components involved in power transmission, which are designed to meet the future needs.La mayor dependencia de la electricidad de la sociedad moderna hace que la fiabilidad de los sistemas de transmisión de energía sea un punto clave. Este objetivo se puede lograr mediante la supervisión continua de los parámetros de la red eléctrica, por lo que los posibles modos de fallo se pueden predecir de antemano. Se puede hacer utilizando las tecnologías existentes de Tecnologías de la Información y la Comunicación (1CT) e Internet de las cosas (lo T) que incluyen sistemas de instrumentación y comunicación inalámbrica, formando así una red de sensores inalámbricos (WSN). Los conectores eléctricos se encuentran entre las partes más críticas de cualquier sistema eléctrico y, por lo tanto, pueden actuar como nodos de dicho VVSN. Por lo tanto, el objetivo fundamental de esta tesis es el diseño, desarrollo y validación experimental de una solución IOT autoalimentada para la supervisión en tiempo real del estado de salud de un conector de subestación de alta tensión y componentes relacionados de la subestación eléctrica. Esta nueva familia de conectores de alimentación se llama SmartConnector e incorpora un sistema de recolección de energía térmica que alimenta un microcontrolador que controla un transmisor y varios sensores electrónicos para medir la temperatura, la corriente y la resistencia del contacto eléctrico (ECR) del conector. Esta nueva familia de conectores de alimentación se llama SmartConnector e incorpora un sistema de recolección de energía térmica que alimenta un microcontrolador que controla un transmisor y varios sensores electrónicos para medir la temperatura, la corriente y la resistencia al contacto eléctrico (ECR) del conector. De esta manera, después del procesamiento de datos adecuado, el estado de salud del conector puede estar disponible en tiempo real, permitiendo diferentes funciones atractivas, como evaluar la correcta instalación del conector, el estado de salud actual o su vida útil restante (RUL) en tiempo real. El mismo principio también se puede utilizar para otros componentes de la subestación como espaciadores, aislantes, conductores, etc. Por lo tanto, para demostrar la universalidad de este enfoque novedoso, se aplica una estrategia similar a un espaciador, que es capaz de medir la distribución de corriente desigual en tres conductores estrechamente situados. Hay que tener cuidado de que este desarrollo técnico y científico tenga que sea compatible con las barras y "busbars" de subestación existentes, y sobre todo para ser compatible con las altas tensiones de funcionamiento, es decir, de decenas a cientos de kilovoltios (kV), y con corrientes en el orden de algunos kilo-Amperes (kA). Aunque algunas empresas eléctricas y fabricantes han progresado en el desarrollo de este tipo de tecnologías, incluidos medidores inteligentes y sensores inteligentes, los fabricantes de dispositivos eléctricos, como los fabricantes de conectores de subestación, aún no han emprendido el avance tecnológico necesario para el desarrollo de una nueva familia de componentes intel

ULTRA LOW POWER FSK RECEIVER AND RF ENERGY HARVESTER

This thesis focuses on low power receiver design and energy harvesting techniques as methods for intelligently managing energy usage and energy sources. The goal is to build an inexhaustibly powered communication system that can be widely applied, such as through wireless sensor networks (WSNs). Low power circuit design and smart power management are techniques that are often used to extend the lifetime of such mobile devices. Both methods are utilized here to optimize power usage and sources. RF energy is a promising ambient energy source that is widely available in urban areas and which we investigate in detail. A harvester circuit is modeled and analyzed in detail at low power input. Based on the circuit analysis, a design procedure is given for a narrowband energy harvester. The antenna and harvester co-design methodology improves RF to DC energy conversion efficiency. The strategy of co-design of the antenna and the harvester creates opportunities to optimize the system power conversion efficiency. Previous surveys have found that ambient RF energy is spread broadly over the frequency domain; however, here it is demonstrated that it is theoretically impossible to harvest RF energy over a wide frequency band if the ambient RF energy source(s) are weak, owing to the voltage requirements. It is found that most of the ambient RF energy lies in a series of narrow bands. Two different versions of harvesters have been designed, fabricated, and tested. The simulated and measured results demonstrate a dual-band energy harvester that obtains over 9% efficiency for two different bands (900MHz and 1800MHz) at an input power as low as -19dBm. The DC output voltage of this harvester is over 1V, which can be used to recharge the battery to form an inexhaustibly powered communication system. A new phase locked loop based receiver architecture is developed to avoid the significant conversion losses associated with OOK architectures. This also helps to minimize power consumption. A new low power mixer circuit has also been designed, and a detailed analysis is provided. Based on the mixer, a low power phase locked loop (PLL) based receiver has been designed, fabricated and measured. A power management circuit and a low power transceiver system have also been co-designed to provide a system on chip solution. The low power voltage regulator is designed to handle a variety of battery voltage, environmental temperature, and load conditions. The whole system can work with a battery and an application specific integrated circuit (ASIC) as a sensor node of a WSN network

Energy-aware Approaches for Energy Harvesting Powered Wireless Sensor Systems

Energy harvesting (EH) powered wireless sensor systems (WSSs) are gaining increasing popularity since they enable the system to be self-powering, long-lasting, almost maintenance-free, and environmentally friendly. However, the mismatch between energy generated by harvesters and energy demanded by WSS to perform the required tasks is always a bottleneck as the ambient environmental energy is limited, and the WSS is power hunger. Therefore, the thesis has proposed, designed, implemented, and tested the energy-aware approaches for wireless sensor motes (WSMs) and wireless sensor networks (WSNs), including hardware energy-aware interface (EAI), software EAI, sensing EAI and network energy-aware approaches to address this mismatch. The main contributions of this thesis to the research community are designing the energy-aware approaches for EH Powered WSMs and WSNs which enables a >30 times reduction in sleep power consumption of WSNs for successful EH powering WSNs without a start-up issue in the condition of mismatch between the energy generated by harvesters and energy demanded by WSSs in both mote and network systems. For EH powered WSM systems, the energy-aware approaches have (1) enabled the harvested energy to be accumulated in energy storage devices to deal with the mismatch for the operation of the WSMs without the start-up issue, (2) enabled a commercial available WSMs with a reduced sleep current from 28.3 μA to 0.95 μA for the developed WSM, (3) thus enabled the WSM operations for a long active time of about 1.15 s in every 7.79 s to sample and transmit a large number of data (e.g., 388 bytes), rather than a few ten milliseconds and a few bytes. For EH powered WSN systems, on top of energy-aware approached for EH powered WSM, the network energy-aware approaches have presented additional capabilities for network joining process for energy-saving and enabled EH powered WSNs. Once the EH powered WSM with the network energy-aware approach is powered up and began the network joining process, energy, as an example of 48.23 mJ for a tested case, has been saved in the case of the attempt to join the network unsuccessfully. Once the EH-WSM has joined the network successfully, the smart programme applications that incorporate the software EAI, sensing EAI and hardware EAI allow the EH powered WSM to achieve (4) asynchronous operation or (5) synchronised operation based on the energy available after the WSM has joined the network.Through designs, implementations, and analyses, it has been shown that the developed energy-aware approaches have provided an enabled capability for EH successfully powering WSS technologies in the condition of energy mismatch, and it has the potential to be used for wide industrial applications

Energy-Efficient Wireless Circuits and Systems for Internet of Things

As the demand of ultra-low power (ULP) systems for internet of thing (IoT) applications has been increasing, large efforts on evolving a new computing class is actively ongoing. The evolution of the new computing class, however, faced challenges due to hard constraints on the RF systems. Significant efforts on reducing power of power-hungry wireless radios have been done. The ULP radios, however, are mostly not standard compliant which poses a challenge to wide spread adoption. Being compliant with the WiFi network protocol can maximize an ULP radio’s potential of utilization, however, this standard demands excessive power consumption of over 10mW, that is hardly compatible with in ULP systems even with heavy duty-cycling. Also, lots of efforts to minimize off-chip components in ULP IoT device have been done, however, still not enough for practical usage without a clean external reference, therefore, this limits scaling on cost and form-factor of the new computer class of IoT applications. This research is motivated by those challenges on the RF systems, and each work focuses on radio designs for IoT applications in various aspects. First, the research covers several endeavors for relieving energy constraints on RF systems by utilizing existing network protocols that eventually meets both low-active power, and widespread adoption. This includes novel approaches on 802.11 communication with articulate iterations on low-power RF systems. The research presents three prototypes as power-efficient WiFi wake-up receivers, which bridges the gap between industry standard radios and ULP IoT radios. The proposed WiFi wake-up receivers operate with low power consumption and remain compatible with the WiFi protocol by using back-channel communication. Back-channel communication embeds a signal into a WiFi compliant transmission changing the firmware in the access point, or more specifically just the data in the payload of the WiFi packet. With a specific sequence of data in the packet, the transmitter can output a signal that mimics a modulation that is more conducive for ULP receivers, such as OOK and FSK. In this work, low power mixer-first receivers, and the first fully integrated ultra-low voltage receiver are presented, that are compatible with WiFi through back-channel communication. Another main contribution of this work is in relieving the integration challenge of IoT devices by removing the need for external, or off-chip crystals and antennas. This enables a small form-factor on the order of mm3-scale, useful for medical research and ubiquitous sensing applications. A crystal-less small form factor fully integrated 60GHz transceiver with on-chip 12-channel frequency reference, and good peak gain dual-mode on-chip antenna is presented.PHDElectrical and Computer EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/162975/1/jaeim_1.pd

An Input Power-Aware Maximum Efficiency Tracking Technique for Energy Harvesting in IoT Applications

The Internet of Things (IoT) enables intelligent monitoring and management in many applications such as industrial and biomedical systems as well as environmental and infrastructure monitoring. As a result, IoT requires billions of wireless sensor network (WSN) nodes equipped with a microcontroller and transceiver. As many of these WSN nodes are off-grid and small-sized, their limited-capacity batteries need periodic replacement. To mitigate the high costs and challenges of these battery replacements, energy harvesting from ambient sources is vital to achieve energy-autonomous operation. Energy harvesting for WSNs is challenging because the available energy varies significantly with ambient conditions and in many applications, energy must be harvested from ultra-low power levels. To tackle these stringent power constraints, this dissertation proposes a discontinuous charging technique for switched-capacitor converters that improves the power conversion efficiency (PCE) at low input power levels and extends the input power harvesting range at which high PCE is achievable. Discontinuous charging delivers current to energy storage only during clock non-overlap time. This enables tuning of the output current to minimize converter losses based on the available input power. Based on this fundamental result, an input power-aware, two-dimensional efficiency tracking technique for WSNs is presented. In addition to conventional switching frequency control, clock nonoverlap time control is introduced to adaptively optimize the power conversion efficiency according to the sensed ambient power levels. The proposed technique is designed and simulated in 90nm CMOS with post-layout extraction. Under the same input and output conditions, the proposed system maintains at least 45% PCE at 4μW input power, as opposed to a conventional continuous system which requires at least 18.7μW to maintain the same PCE. In this technique, the input power harvesting range is extended by 1.5x. The technique is applied to a WSN implementation utilizing the IEEE 802.15.4- compatible GreenNet communications protocol for industrial and wearable applications. This allows the node to meet specifications and achieve energy autonomy when deployed in harsher environments where the input power is 49% lower than what is required for conventional operation