Lower-order compensation chain threshold-reduction technique for multi-stage voltage multipliers

This paper presents a novel threshold-compensation technique for multi-stage voltage multipliers employed in low power applications such as passive and autonomous wireless sensing nodes (WSNs) powered by energy harvesters. The proposed threshold-reduction technique enables a topological design methodology which, through an optimum control of the trade-off among transistor conductivity and leakage losses, is aimed at maximizing the voltage conversion efficiency (VCE) for a given ac input signal and physical chip area occupation. The conducted simulations positively assert the validity of the proposed design methodology, emphasizing the exploitable design space yielded by the transistor connection scheme in the voltage multiplier chain. An experimental validation and comparison of threshold-compensation techniques was performed, adopting 2N5247 N-channel junction field effect transistors (JFETs) for the realization of the voltage multiplier prototypes. The attained measurements clearly support the effectiveness of the proposed threshold-reduction approach, which can significantly reduce the chip area occupation for a given target output performance and ac input signal

RF Power Transfer, Energy Harvesting, and Power Management Strategies

Energy harvesting is the way to capture green energy. This can be thought of as a recycling process where energy is converted from one form (here, non-electrical) to another (here, electrical). This is done on the large energy scale as well as low energy scale. The former can enable sustainable operation of facilities, while the latter can have a significant impact on the problems of energy constrained portable applications. Different energy sources can be complementary to one another and combining multiple-source is of great importance. In particular, RF energy harvesting is a natural choice for the portable applications. There are many advantages, such as cordless operation and light-weight. Moreover, the needed infra-structure can possibly be incorporated with wearable and portable devices. RF energy harvesting is an enabling key player for Internet of Things technology. The RF energy harvesting systems consist of external antennas, LC matching networks, RF rectifiers for ac to dc conversion, and sometimes power management. Moreover, combining different energy harvesting sources is essential for robustness and sustainability. Wireless power transfer has recently been applied for battery charging of portable devices. This charging process impacts the daily experience of every human who uses electronic applications. Instead of having many types of cumbersome cords and many different standards while the users are responsible to connect periodically to ac outlets, the new approach is to have the transmitters ready in the near region and can transfer power wirelessly to the devices whenever needed. Wireless power transfer consists of a dc to ac conversion transmitter, coupled inductors between transmitter and receiver, and an ac to dc conversion receiver. Alternative far field operation is still tested for health issues. So, the focus in this study is on near field. The goals of this study are to investigate the possibilities of RF energy harvesting from various sources in the far field, dc energy combining, wireless power transfer in the near field, the underlying power management strategies, and the integration on silicon. This integration is the ultimate goal for cheap solutions to enable the technology for broader use. All systems were designed, implemented and tested to demonstrate proof-of concept prototypes

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

Design of low-power RF energy harvester for IoT sensors

Rapid technological advancement in CMOS technologies has resulted in increased deployment of low-power Internet-of-Things (IoT) devices. As batteries, used to power-up these devices, suffer from limited lifespan, powering up numerous devices have become a major concern. Radio frequency (RF) is ubiquitous in the surroundings from which energy can be harvested and utilized to increase battery lifetime. Even for low-power sensors, RF energy harvesters can be utilized as primary power sources. However, power density of RF signals is very low and therefore building blocks of RF energy harvester need to be designed carefully to maximize efficiency to gain suitable output power. This research is focused on the design of an RF energy harvesting system in standard CMOS technology. The main goal of this research is to design an RF energy harvesting system with high power conversion efficiency (PCE) and adequate output voltage for low input power. The proposed dynamic voltage compensated cross-coupled fully differential rectifier is capable of providing very high PCE. The synchronous DC-DC boost converter provides stable DC output voltage. Rectifier and DC-DC converter of the system have been designed by using low-power transistors to ensure operation at very low input power. In order to maximize the power transfer through the system, matching network and maximum power point tracking (MPPT) controller has been implemented. In order to cope with rapid input power variation, a machine learning (ML) based MPPT controller has been designed and implemented into FPGA. The proposed ML based MPPT controller has demonstrated fast response time. To further enhance the performance of the RF energy harvesting system, a self-compensated rectifier integrated energy harvesting system is also presented. The energy extracted by using the proposed RF energy harvesting systems can easily be stored and utilized to fully power up low-power sensors used for IoT devices. Integration of RF energy harvester with these devices will significantly reduce the maintenance cost and result in energy-effluent IoT technologies.Includes bibliographical references

Integrated cmos rectifier for rf-powered wireless sensor network nodes

This article presents a review of the CMOS rectifier for radio frequency energy harvesting application. The on-chip rectifier converts the ambient low-power radio frequency signal coming to antenna to useable DC voltage that recharges energy to wireless sensor network (WSN) nodes and radiofrequency identification (RFID) tags, therefore the rectifier is the most important part of the radio frequency energy harvesting system. The impedance matching network maximizes power transfer from antenna to rectifier. The design and comparison between the simulation results of one- and multi-stage differential drive cross connected rectifier (DDCCR) at the operating frequencies of 2.44GHz, and 28GHz show the output voltage of the multi-stage rectifier doubles at each added stage and power conversion efficiency (PCE) of rectifier at 2.44GHz was higher than 28GHz. The (DDCCR) rectifier is the most efficient rectifier topology to date and is used widely for passive WSN nodes and RFID tags

UHF Energy Harvesting and Power Management

As we are entering the era of Internet of Things (i.e. IoT), the physical devices become increasingly connected with each other than ever before. The connection between devices is achieved through wireless communication schemes, which unfortunately consume a significant amount of energy. This is undesirable for devices which are not directly connected to power. This is because these devices will essentially carry batteries to supply the needed energy for these operations and the batteries will eventually be depleted. This motivates the need to operate these devices off harvested energy. UHF energy harvesting, as an enabling technology for the UHF RFID, stands out amongst other energy harvesting approaches as it does not heavily rely on the natural surrounding environment and also offers a very good wireless operating range from its radiating energy source. Unlike the RFID, the power consumption and the operational range requirement of these IoT devices can vary significantly. Thus, the design of the RF energy harvesting front-end and the power management need to be re-thought for specific applications. To that end, in this thesis, discussions mainly evolve around the design of UHF energy harvesters and their associated power management units using lower power analog approaches. First, we present the background of the low power UHF energy harvesting, specially threshold-compensated rectifiers will be presented as a key technology in this area and this will be used as a build practical harvester for the UHF RFID application. Secondly, key issues with the threshold compensation will be identified and this is exploited either (i) to improve the dynamic power conversion efficiency of the harvester, (ii) to improve dynamic settling behaviour of the harvester. To exploit the ”left-over” harvested energy, an intelligent integrated power management solution has been proposed. Finally, the charge-burst approach is exploited to implement an energy harvester with -40 dBm input power sensitivity.Thesis (Ph.D.) -- University of Adelaide, School of Electrical & Electronic Engineering, 201

Mutual Coupling Compensated Multiband Linear Antenna Arrays for Radio Frequency Energy Harvesting/Transmitting

RF energy transmitting is an approach to deliver charging energy wirelessly, while RF energy harvesting is an approach to re-charge battery by capturing ambient RF energy. A multiband system composed of mutual coupling compensated linear antenna arrays and output LC matched RF-DC rectifier is proposed for RF energy harvesting and transmitting. The designed system operates in standard communication bands such as GSM850, GSM900, GSM1800, GSM1900, WiFi, Bluetooth, and LTE since ample RF ambient signals are present and numerous IoT sensors operates in these frequency bands. The design starts from a highly efficient double-ring monopole antenna. The proposed antenna has both wideband and multiband features to cover the target operating frequencies. According to Friis transmission equation, the captured/radiated RF power is proportional to the antenna gain, thus antenna array composed of double-ring monopoles is investigated to increase antenna gain. In the proposed four-element antenna array, a four-way RF energy combiner with optimum power combining efficiency is implemented to connect four antennas. Triple-band radiation patterns are synthesized by by mutual coupling compensation structure. The proposed output LC matched RF-DC rectifier is connected to antenna array to convert RF power to DC energy. The rectifier sensitivity and power conversion efficiency is boosted with dual frequency tones. System measurement results state that not only the antenna gain but also the radiation pattern of antenna array affects the total captured RF power. Antenna array is preferable to be installed at the transmitting side for RF energy transfer, while the single antenna is preferable to be installed at the receiving side for RF energy harvesting. If the receiving area is not limited, then the rectenna array composed of antenna arrays and RF-DC rectifiers can be applied for RF energy harvesting

Mutual Coupling Compensated Multiband Linear Antenna Arrays for Radio Frequency Energy Harvesting/Transmitting

RF energy transmitting is an approach to deliver charging energy wirelessly, while RF energy harvesting is an approach to re-charge battery by capturing ambient RF energy. A multiband system composed of mutual coupling compensated linear antenna arrays and output LC matched RF-DC rectifier is proposed for RF energy harvesting and transmitting. The designed system operates in standard communication bands such as GSM850, GSM900, GSM1800, GSM1900, WiFi, Bluetooth, and LTE since ample RF ambient signals are present and numerous IoT sensors operates in these frequency bands. The design starts from a highly efficient double-ring monopole antenna. The proposed antenna has both wideband and multiband features to cover the target operating frequencies. According to Friis transmission equation, the captured/radiated RF power is proportional to the antenna gain, thus antenna array composed of double-ring monopoles is investigated to increase antenna gain. In the proposed four-element antenna array, a four-way RF energy combiner with optimum power combining efficiency is implemented to connect four antennas. Triple-band radiation patterns are synthesized by by mutual coupling compensation structure. The proposed output LC matched RF-DC rectifier is connected to antenna array to convert RF power to DC energy. The rectifier sensitivity and power conversion efficiency is boosted with dual frequency tones. System measurement results state that not only the antenna gain but also the radiation pattern of antenna array affects the total captured RF power. Antenna array is preferable to be installed at the transmitting side for RF energy transfer, while the single antenna is preferable to be installed at the receiving side for RF energy harvesting. If the receiving area is not limited, then the rectenna array composed of antenna arrays and RF-DC rectifiers can be applied for RF energy harvesting

Rectification, amplification and switching capabilities for energy harvesting systems: power management circuit for piezoelectric energy harvester

Dissertação de mestrado em Biomedical EngineeringA new energy mechanism needs to be addressed to overcome the battery dependency, and consequently extend Wireless Sensor Nodes (WSN) lifetime effectively. Energy Harvesting is a promising technology that can fulfill that premise. This work consists of the realization of circuit components employable in a management system for a piezoelectric-based energy harvester, with low power consumption and high efficiency. The implementation of energy harvesting systems is necessary to power-up front-end applications without any battery. The input power and voltage levels generated by the piezoelectric transducer are relatively low, especially in small-scale systems, as such extra care has to be taken in power consumption and efficiency of the circuits. The main contribution of this work is a system capable of amplifying, rectifying and switching the unstable signal from an energy harvester source. The circuit components are designed based on 0.13 Complementary Metal-Oxide-Semiconductor (CMOS) technology. An analog switch, capable of driving the harvesting circuit at a frequency between 1 and 1 , with proper temperature behaviour, is designed and verified. An OFF resistance of 520.6 Ω and isolation of −111.24 , grant excellent isolation to the circuit. The designed voltage amplifier is capable of amplifying a minor signal with a gain of 42.56 , while requiring low power consumption. The output signal is satisfactorily amplified with a reduced offset voltage of 8 . A new architecture of a two-stage active rectifier is proposed. The power conversion efficiency is 40.4%, with a voltage efficiency of up to 90%. Low power consumption of 17.7 is achieved by the rectifier, with the embedded comparator consuming 113.9 . The outcomes validate the circuit’s power demands, which can be used for other similar applications in biomedical, industrial, and commercial fields.Para combater a dependência dos dispositivos eletrónicos relativamente ás baterias é necessário um novo sistema energético, que permita prolongar o tempo de vida útil dos mesmos. Energy Harvesting é uma tecnologia promissora utilizada para alimentar dispositivos sem bateria. Este trabalho consiste na realização de componentes empregáveis num circuito global para extrair energia a partir ds vibrações de um piezoelétricos com baixo consumo de energia e alta eficiência. Os níveis de potência e voltagem gerados pelo transdutor piezoelétrico são relativamente baixos, especialmente em sistemas de pequena escala, por isso requerem cuidado extra relativamente ao consumo de energia e eficiência dos circuitos. A principal contribuição deste trabalho é um sistema apropriado para amplificar, retificar e alternar o sinal instável proveniente de uma fonte de energy harvesting. Os componentes do sistema são implementados com base na tecnologia CMOS com 0.13 . Um interruptor analógico capaz de modelar a frequência do sinal entre 1 e 1 e estável perante variações de temperatura, é implementado. O circuito tem um excelente isolamento de −111.24 , devido a uma resistência OFF de 520.6 Ω. O amplificador implementado é apto a amplificar um pequeno sinal com um ganho de 42.56 e baixo consumo. O sinal de saída é satisfatoriamente amplificado com uma voltagem de offset de 8 . Um retificador ativo de dois estágios com uma nova arquitetura é proposto. A eficiência de conversão de energia atinge os 40.4%, com uma eficiência de voltagem até 90%. O retificador consome pouca energia, apenas 17.7 , incorporando um comparador de 113.9 . Os resultados validam as exigências energéticas do circuito, que pode ser usado para outras aplicações similares no campo biomédico, industrial e comercial

RF energy harvesters for wireless sensors, state of the art, future prospects and challenges: a review

The power consumption of portable gadgets, implantable medical devices (IMDs) and wireless sensor nodes (WSNs) has reduced significantly with the ongoing progression in low-power electronics and the swift advancement in nano and microfabrication. Energy harvesting techniques that extract and convert ambient energy into electrical power have been favored to operate such low-power devices as an alternative to batteries. Due to the expanded availability of radio frequency (RF) energy residue in the surroundings, radio frequency energy harvesters (RFEHs) for low-power devices have garnered notable attention in recent times. This work establishes a review study of RFEHs developed for the utilization of low-power devices. From the modest single band to the complex multiband circuitry, the work reviews state of the art of required circuitry for RFEH that contains a receiving antenna, impedance matching circuit, and an AC-DC rectifier. Furthermore, the advantages and disadvantages associated with various circuit architectures are comprehensively discussed. Moreover, the reported receiving antenna, impedance matching circuit, and an AC-DC rectifier are also compared to draw conclusions towards their implementations in RFEHs for sensors and biomedical devices applications