RF Energy Harvesting Research Articles

High-efficiency quad-band RF energy harvesting system with improved cross-coupled differential-drive rectifier

Abstract RF energy harvesting technology has garnered significant attention from researchers in recent years. This paper presents a high-efficiency quad-band RF energy harvesting (RFEH) system. It introduces an improved cross-coupled differential-drive rectifier designed for ambient wireless powering, capable of harnessing power from four distinct ambient RF sources: FM-100, DTV-600, GSM-1800, and WiFi-2400 frequency bands. The proposed RFEH system demonstrates notable advancements, achieving a high RF to DC conversion efficiency of over 80 % within an input power range of −5 dB m to +13 dB m, with a 5 kΩ resistance load. This power output is deemed sufficient for energizing low-power micro-devices autonomously, without reliance on external power sources. Notably, the DC output voltage of the proposed RFEH system exhibits a high level of stability against variations in input power, a characteristic not adequately addressed in existing systems.

Modeling and Analyzing of CMOS Cross-Coupled Differential-Drive Rectifier for Ultra-Low-Power Ambient RF Energy Harvesting

This paper models and analyzes the Complementary Metal Oxide Semiconductor (CMOS) cross-coupled differential-drive (CCDD) rectifier for Ultra-Low-Power ambient radio-frequency energy harvesters (RFEHs) working in the subthreshold region. In this paper, two closed-form equations of CCDD rectifier output voltage and input resistance in the subthreshold region were derived based on BSIM4 models of NMOS and PMOS. The model give insight to specify circuit parameters according to different inputs, transistor sizes, threshold voltages, numbers of stages, load conditions and compensation voltages, which can be used to optimize the rectifier circuit. There is a good agreement between the simulation results and these models, and these models have a maximum deviation of 10% in comparison with the simulation results in the subthreshold region. The measurement results of a single-stage CCDD rectifier reported in a previous paper were adopted to verify the model. The output voltage and input resistance predicted by these models provide excellent consistency with corresponding measurement results. The model can be employed to optimize the CCDD rectifier without expensive calculation in the design stage.

Advancements and Challenges in Antenna Design and Rectifying Circuits for Radio Frequency Energy Harvesting

The proliferation of smart devices increases the demand for energy-efficient, battery-free technologies essential for sustaining IoT devices in Industry 4.0 and 5G networks, which require zero maintenance and sustainable operation. Integrating radio frequency (RF) energy harvesting with IoT and 5G technologies enables real-time data acquisition, reduces maintenance costs, and enhances productivity, supporting a carbon-free future. This survey reviews the challenges and advancements in RF energy harvesting, focusing on far-field wireless power transfer and powering low-energy devices. It examines miniaturization, circular polarization, fabrication challenges, and efficiency using the metamaterial-inspired antenna, concentrating on improving diode nonlinearity design. This study analyzes key components such as rectifiers, impedance matching networks, and antennas, and evaluates their applications in biomedical and IoT devices. The review concludes with future directions to increase bandwidth, improve power conversion efficiency, and optimize RF energy harvesting system designs.

Measurement and performance evaluation of triple band differential integrated extraoral rectifying antenna for data transfer and RF energy harvesting for tongue drive system

Wearable assistive devices are vitally important for tetraplegic individuals to provide valuable insights into their intended directives tailored to tongue motions in wireless healthcare industries. The flexible differentially driven extraoral antenna and rectenna measurement system are developed to enable differential sensing and monitoring of the set of unique tongue gestures for extraoral tongue drive system (eTDS) applications in three frequency bands of Industrial, Scientific, and Medical (ISM) (915.0 MHz, 2400 MHz, and 5800 MHz). The performance analysis is carried out using the heterogeneous human head model. The differential rectifier is coplanarly integrated with the differential extraoral antenna on the same 0.254 mm thin and 9.5 mm wider Rogers RT/ Duroid 6010 LM substrate. The footprint of the fabricated differential rectenna is 0.135 \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:{\\varvec{\\lambda\\:}}_{\\varvec{g}}\ imes\\:$$\\end{document} 0.082 \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:{\\varvec{\\lambda\\:}}_{\\varvec{g}}$$\\end{document}\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:\ imes\\:$$\\end{document} 0.002 \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:{\\varvec{\\lambda\\:}}_{\\varvec{g}}$$\\end{document} where the planar size of differential rectifier is 15.75\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:\\:\ imes\\:$$\\end{document} 2.5 mm2. The fabricated systems are situated closely to an artificial head model. The maximum conversion efficiency achieved at 2400 MHz and 5800 MHz is 83.45% and 74.8%, respectively, for 11 dBm of RF input power. Further, the link analysis, including interfacing circuit losses, was carried out theoretically at 915 MHz. Thus, the proposed differential extraoral systems can be employed to acquire and transmit the user intentions in eTDS inspired healthcare applications.

A highly efficient adaptive body bias CMOS rectifier with double-side feedback at a tone of 2.4 GHz

ABSTRACT In this paper, a highly efficient adaptive body bias CMOS rectifier employed with double side feedback, operating with 2.4 GHz frequency, is proposed for radio frequency energy harvesting. The proposed circuit is built with 45 nm TSMC CMOS technology. In the suggested architecture, the double side feedback along with body bias is used to regulate threshold voltage. The use of PMOS transistors as a diode in reverse bias configuration has restricted the reverse current without compromising the forward current. This design has gained a maximum PCE of 82.25% and 77.29% at an input power of −23.90dBm and −23.74dBm and 500K and 100K load, respectively. The circuit has maintained a wide dynamic range of 30dbm at PCE >30% and registered an input sensitivity of −10.07dBm for attaining a DC output voltage of 1 V as compared to the previous works.

Comparative Analysis of an 8 – Stage Cockcroft Walton Voltage Multiplier and A Dickson Voltage Multiplier in The Context of Radio Frequency Energy Harvesting

Purpose: This study seeks to enhance voltage multipliers for Radio Frequency (RF) energy harvesting, with an emphasis on increasing the efficiency of harvested energy. This improvement is vital for sustainable energy applications and reducing environmental pollution caused by fossil fuels. Theoretical reference: RF energy harvesting technology is gaining recognition as a viable sustainable method for capturing ambient energy, with earlier research primarily focused on antenna and circuit design. Nonetheless, the effectiveness of energy harvesting is still constrained by inadequate power output. This study expands on prior research by directly comparing two commonly utilized voltage multipliers, the Cockcroft Walton and Dickson multipliers, in the context of RF energy harvesting. Method: The Cockcroft Walton and Dickson voltage multipliers were optimally designed using Multisim and their performance was analysed using MATLAB. The comparison was conducted at an input voltage of 1V within two frequency ranges: 85 MHz – 110 MHz (FM band) and 1.8 GHz – 3.0 GHz (4G band). Output voltages for both multipliers were recorded and compared across these frequency bands. Results and Conclusion: At an input voltage of 1V within the FM band (85 MHz – 110 MHz), the Dickson voltage multiplier outperformed the Cockcroft Walton multiplier, delivering an output voltage of 11.1V compared to 6.6V. However, in the 4G band (1.8 GHz – 3.0 GHz), the Cockcroft Walton multiplier was more effective, providing a maximum output voltage of 5.2V against Dickson's 4.1V. The study concludes that the Dickson multiplier is more suitable for harvesting RF energy from the FM band, while the Cockcroft Walton multiplier is better for 4G band energy harvesting. Implications of research: The findings suggest that different RF energy harvesting applications may benefit from distinct voltage multipliers, depending on the frequency band in question. This could guide the design of more efficient RF energy harvesting circuits in future technologies aimed at sustainable energy solutions. Originality/value: This study offers a direct comparison of two voltage multipliers under different RF frequency conditions, providing valuable insights into optimizing energy harvesting technologies for green energy applications. The results help advance the understanding of efficient circuit design for specific RF frequency bands, contributing to the development of more effective energy harvesting systems.

Quad-Band Rectifier Circuit Design for IoT Applications

In this work, a novel quad-band rectifier circuit is introduced for RF energy harvesting and Internet of Things (IoT) applications. The proposed rectifier operates in the Wi-Fi frequency band and can supply low-power sensors and systems used in IoT services. The circuit operates at 2.4, 3.5, 5, and 5.8 GHz. The proposed RF-to-DC rectifier is designed based on Delon theory and Greinacher topology on an RT/Duroid 5880 substrate. The results show that our proposed circuit can harvest RF energy from the environment, providing maximum power conversion efficiency (PCE) greater than 81% when the output load is 0.511 kΩ and the input power is 12 dBm. In this work, we provide a comprehensive design framework for an affordable RF-to-DC rectifier. Our circuit performs better than similar designs in the literature. This rectifier could be integrated into an IoT node to harvest RF energy, thereby proving a green energy source. The IoT node can operate at various frequencies.

Efficient multichannel energy harvesting with dedicated energy transmitters in CR-IoT networks

Radio Frequency (RF) energy harvesting is strongly believed to be a sustainable solution to the power depletion problem in battery powered IoT devices. In addition to harvesting energy from ambient RF signals, the use of dedicated energy transmitters (ETs) that transmit energy to nearby IoT devices via RF signals has recently been proposed. In this paper, we study the problem of designing an energy harvesting policy for a group of cognitive radio-enabled IoT (CR-IoT) devices served by a number of ETs to maximize the minimum of their charging rates. With the help of cognitive radios, a CR-IoT node is capable of changing its frequency channel of operation allowing for multi-channel energy harvesting. Frequency channels are assumed to be opportunistically accessible depending on the activity of wireless users that are licensed to use those channels. The problem entails the design of the ET’s transmission policy (to what CR-IoT device, and over what channel) and the design of an ambient harvesting policy for every CR-IoT device (when it is not served by ETs). The problem is formulated as a mixed integer linear program (MILP). The objective is to maximize a lower bound on the total harvested energy in a given time frame per CR-IoT node. This optimization is subject to scheduling, total energy budget, and maximum transmit power constraints. Given the intractability of MILP formulations, a sub-optimal algorithm is proposed. Extensive experimentation is carried out to assess the effectiveness of the proposed sub-optimal algorithm by comparing it to the MILP’s solution obtained using IBM CPLEX solver with a limit on the execution time. We also combine our sub-optimal algorithm withe the CPLEX solver to produce a new two-stages algorithm that improves the original one by around 47%. Finally, we investigate the effect of multiple parameters including number of ETs, number of channels, and channel availability probability on the minimum charging rate.

Wide Power Range RF Energy Harvester for Powering Ultralow-Power Devices

Wide Power Range RF Energy Harvester for Powering Ultralow-Power Devices

Design of 2.45 GHz rectifier for low-power RF energy harvesting applications

Design of 2.45 GHz rectifier for low-power RF energy harvesting applications

Simultaneously Transmitting and Reflecting Reconfigurable Intelligent Surfaces (STAR-RIS) with Hybrid Solar, RF and Wind Energy Harvesting

Simultaneously Transmitting and Reflecting Reconfigurable Intelligent Surfaces (STAR-RIS) with Hybrid Solar, RF and Wind Energy Harvesting

A High-Gain Microstrip RF Energy Harvester for IoT Sensors in 5G Network

A High-Gain Microstrip RF Energy Harvester for IoT Sensors in 5G Network

Powering the future of farming: RF energy harvesting for environmental sustainability

Powering the future of farming: RF energy harvesting for environmental sustainability

Physical layer security in SWIPT-based cooperative vehicular relaying networks

The future of autonomous transportation systems depends on energy sustainability and secure information exchange from low-power vehicular sensors, hence the increased interest in vehicular sensor charging using simultaneous wireless information and power transfer (SWIPT). This study investigates the physical layer security of a SWIPT-based radio frequency energy harvesting cooperative vehicular relaying network subjected to cascade Nakagami-m and double Nakagami-m (DN) fading channels. In the considered system model, a stationary source communicates with a mobile destination through a power-splitting-based decode-and-forward relay in the presence of a mobile passive eavesdropper. Based on the Gamma-distributed first term of the Laguerre series, new statistical probability density function (PDF) and cumulative distribution function (CDF) expressions for the DN are derived to accurately model the complex cascaded fading scenario. The secrecy performance metrics analyzed are the secrecy outage probability (SOP), the probability of non-zero secrecy capacity (PNZSC), and the intercept probability (IP). In addition, the asymptotic SOP (ASOP) is investigated in the high signal-to-noise ratio (SNR) to enhance the comprehension of the secrecy performance. Based on the derived ASOP, the secrecy diversity order (SDO) of the proposed system is determined and examined. Particularly, we present analytical closed-form expressions for the secrecy performance metrics and provide a detailed understanding of the impact of the system parameters under the cascade fading scenario. Then, a power splitting (PS) optimization problem is formulated to minimize the SOP. The results demonstrate a reduction in the SOP with the proposed PS scheme compared to the equal PS scheme. The obtained analytical findings are validated using Monte Carlo simulations.

An automatic matching high-sensitivity RF energy harvesting system with tuning power consumption of 2.4nW

An automatic matching high-sensitivity RF energy harvesting system with tuning power consumption of 2.4nW

Efficient rectifier with wide input power range for 5G applications

This article presents three efficient rectifiers for radio frequency energy harvest-ing (RFEH) systems operating at the fifth generation (5G) band (3.5 GHz). Eachrectifier operates at various input power levels (high, low, and across a widepower range). The high and low-power rectifiers feature a single serial topologyusing HSMS-2860 and SMS-7630 Schottky diodes, respectively, along with mi-crostrip lines to implement the input and output filters and the impedance match-ing network. At an radio frequency (RF) power level of 15 dBm, the high-powerrectifier harvests 67.4% to direct current (DC) power with a 300Ωload resistorand an output voltage of 2.5V. The low-power rectifier achieves its maximumpower conversion efficiency (PCE) at -2 dBm, reaching 45% efficiency with a1200Ωload. The rectifier with a extended input power range comprises twobranches of subrectifiers functioning at both high and low power levels. De-pending on the power level, the considered subrectifier harvests radio frequencypower into DC power, while the other subrectifier is deactivated. Across a powerspan of 32.5 dB (ranging from -13 to 19.5 dBm), the rectifier maintains an effi-ciency above 30%. The proposed rectifiers are efficient and suitable for imple-mentation in 5G-enabled RFEH systems.

Stabilizing Schottky junction in conjugated polymer diodes enables long-term reliable radio-frequency energy harvesting on plastic

Due to their inherent flexibility, solution-processable conjugated polymers are increasingly being considered for the cost-effective production of thin-film semiconductor devices used in Internet of Everything (IoE) applications. With considerable improvements in charge carrier mobilities, the final challenge impeding the commercialization of conjugated polymers may be improving their environmental and electrical stabilities. Recent studies have improved the stability of computing devices (i.e., transistors) by eliminating interface traps and water molecules within conjugated polymers. However, the stability issue of Schottky diodes, which play a crucial role in configuring thin-film IoE devices used in wireless communication and energy harvesting, has been largely overlooked. This study reveals that aluminum, which is commonly used as a cathode metal in polymer Schottky diodes, creates a nonstoichiometric effect when deposited on conjugated polymers, thereby leading to the formation of charge traps over time, which reduces the rectification ratio of the Schottky diodes and induces a significant bias stress effect during operation. To address this issue, we introduce a zinc-oxide sacrificial interlayer between the conjugated polymer and cathode. This interlayer effectively eliminates the penetrated Al metal or ionized Al-induced nonstoichiometric effect without reducing the charge injection efficiency, achieving exceptional environmental and operational stability. The printed polymer Schottky diodes demonstrate consistent rectifying operation at 13.56 MHz for several months with negligible changes in electrical characteristics.

A metasurface antenna with beam steering capabilities for radio frequency energy harvesting

Limited control over parameters within the realm of design complexity, it is noted that there are incomplete unit cells displaying slightly lower transmittance in transmissive metasurface antennas. However, traditional methods require time-consuming iterative processes to select unit cells with multiple variables. Therefore, a novel approach is proposed for designing metasurface superstrates on patch antennas operating at 12.5 GHz, focusing on achieving beam steering capabilities and Radio Frequency (RF) energy harvesting functionality. It utilizes a Skeleton-based Attentions Neural Network (SANN) to aid in the complex metasurface unit cell design, enhancing the antenna's flexibility and potential applications. This network is trained to generate patterns for the metasurface unit cell, facilitating accurate and efficient design. The key feature of this antenna is beam steering in multiple directions. Steering is achieved by rotating the metasurface plane in an anti-clockwise direction. Experimental results show that by rotating the metasurface plane at different angles, the beam is directed towards specific directions, such as 10°, 15°, 18°, 21°, and 23°. A load resistance of 8kᾨ and a full wave rectifier with a Positive-Intrinsic-Negative (PIN) diode are utilized to obtain a Direct Current (DC) output voltage of 1.1 V in the proposed rectifier. Copper material is used for the metasurface plane, and the antenna is measured using RT duriod.

Left Handed Metamaterials in Microstrip Patch Antenna Design: Miniaturization, Multiband Operation, and Improved Performance

The exotic electromagnetic properties of metamaterials (MTM) can be utilized to meet the increasing demand for smaller, lighter, and more compact multiband antennas. As the resonant frequency is dependent on the aperture parameters of the antenna, metamaterials allow for the miniaturization and performance enhancement of antennas. In this paper, two novel designs of metamaterial loaded microstrip patch antennas are proposed. The first structure emphasizes the miniaturization of patch antennas with performance improvements. The second one deals with the multiband operation of metamaterial loaded antennas with wider bandwidth and improved performance. Compared to the conventional microstrip patch antenna (MPA), the proposed metamaterial loaded antenna has reduced the size by 75%, and antenna characteristics have also improved significantly. The proposed metamaterial antenna resonates at 2.45 GHz, the return loss is -26 dB, and a gain of 5.28 dB is achieved. The multiband antenna can be realized by etching different numbers of complementary split ring resonators in the ground plane. The model proposed with three split ring resonators (SRR) at the ground plane shows quad band operations and can be used in S-band and C-band simultaneously. The quad-band antenna resonates at 3.04 GHz, 3.42 GHz, 5.35 GHz, and 6.08 GHz with bandwidths of 78 MHz, 93 MHz, 167 MHz, and 185 MHz, respectively. The antennas are designed on an FR-4 substrate with a permittivity of 4.3. Nicolson-Ross-Weir (NRW) method has been employed for the extraction and verification of the metamaterial properties of the unit cells. Due to its ability to capture more energy, the reported antenna can be used as a wireless device as well as an RF energy harvesting device. DUJASE Vol. 8 (1) 1-12, 2023 (January)

Invasive weed optimization based compact hybridized fractal antenna design for RF energy harvesting and multifunctional wireless applications

This paper describes the optimal design and analysis of compact multiband Hybrid Fractal Antenna using Invasive Weed Optimization (HFAIWO). The configured structure involves the fusion of Minkowski, Sierpinski carpet and Giuseppe Peano in a coherent manner. The two-iterative conglomerated fractal antenna is realized physically by considering FR4 epoxy material (dielectric constant, εr = 4.4 and mass density = 1,900 kg/m3). The volumetric dimensions of the fabricated prototype are 36 x 36 x 1.6 mm3. In the designing process, the geometrical descriptors, namely, feedline width ‘WF’ and ground plane dimension ‘LG’ are optimized specifically using Invasive Weed Optimization (IWO) and Harmony Search Algorithm (HSA) strategies. The optimal solution is searched by changing the descriptor values under a set of practical constraints. The examined values of ‘WF’ and ‘LG’ using IWO and HSA are 3 and 31 mm, and 2.6 and 28.7 mm, respectively. Comparative results reveal that IWO offers superior solution quality and convergence than HSA. Afterwards, experimentation of the Projected HFAIWO is done to justify the recommended fractal hybridization approach. Measurements reveal that for VSWR ≤ 2, the fabricated structure produces nine resonance points (1.84, 3.99, 5.15, 5.55, 6.30, 6.58, 8.00, 9.29, and 12.01 GHz) with appreciable gain values. At the respective resonance points, the −10 dB impedance bandwidth is 3.9 %, 3.1 %, 2.1 %, 2.2 %, 1.4 %, 1.2 %, 6.9 %, 1.2 %, and 12.23 %. The provided radiation patterns are arbitrary bidirectional/omnidirectional. By applying the above-said approaches, the radiator size is reduced by 54 %. Importantly, the constructed structure covers two important bands i.e. 1.84 GHz (GSM 1800 band, downlink) and 5.55 GHz (WLAN (Lower) 5.150–5.725 GHz) associated with energy harvesting applications. The practical outcomes suggest that the introduced prototype is a proficient candidate for energy harvesting systems, Satellite communication for downlink, Long range tracking, Battlefield surveillance, Digital broadcast satellite service, Weather Radar, and Maritime navigation radar.