RF Energy Harvesting Research Articles

Graphene-Based Materials for Energy Harvesting at Microwave Frequencies: A Comprehensive Review

Harvesting energy from microwave frequency is one of the key areas of research in the past decade to provide an alternative power source for wireless devices and sensor networks. The increase in the employment of Internet of Things (IoT) devices as well as sensors in order to support technological advancement leads to an increase in the energy demand. This in turn leads to environmental pollution due to the large amount of batteries being disposed. As such, in order to support the current demand for clean and sustainable energy that can reduce environmental pollution, various approaches to reduce the usage of conventional batteries in these systems are being researched. One of the approaches is the usage of the antenna to harvest radio frequency energy. The appearance of graphenebased material further sparked the interest of researchers due to its exciting properties. Therefore, this paper aims to provide a comprehensive review on the advancement of the usage of graphene-based material in the field of harvesting ambient radio frequency energy. Graphene material is first introduced in order to understand its characteristics and properties as a replacement for the conventional copper material. Current state-of-the-art approaches on graphene-based radio frequency energy harvesting systems were then reviewed and compared. The future prospect of graphene-based material in energy harvesting systems was also presented and discussed, shedding light on the future potential areas for research and development.

Ultra-thin flexible rectenna integrated with power management unit for wireless power harvester/charging of smartwatch/wristband

This paper proposes a circularly polarized ultra-thin flexible antenna with a flexible rectifier and power management unit (PMU) for smartwatch/wristband applications. The flexible antenna is compact (0.17λ0 × 0.20λ0 × 0.0004λ0) and has a stepped ground plane. A parasitic element is used at the substrate bottom to reduce the specific absorption rate (SAR) and enhance the gain up to 3.2 dBi, at the resonating frequency of WLAN/Wi-Fi (2.45 GHz). The SAR of the proposed design is also analysed at the resonating frequency, and it satisfies the guidelines of the International Commission on Non-Ionizing Radiation Protection (ICNIRP) and IEEE C95.1–2019 human safety standards. An impedance matching circuit is used between the antenna and the RF energy harvester to improve conversion efficiency. Polarization mismatch is avoided with the help of circular polarization, achieved by tuning stubs of size 0.02λ0 × 0.044λ0. The integration of the antenna and rectenna results in a good conversion efficiency of 78.2% at − 5 dBm of input power with a load resistance of 2 KΩ. The availability of RF signals allows the user to charge the smartwatch/wristband by connecting the PMU circuit with the RF energy harvester.

A High-Efficiency, Ultrawide-Dynamic-Range Radio Frequency Energy Harvester Using Adaptive Reconfigurable Technique

This paper presents a novel adaptive reconfigurable rectifier architecture for radio frequency energy harvesting (RFEH); in addition, a new metric for high-efficiency dynamic range (DR) is proposed. The presented rectifier architecture is based on a double-sided diode-feedback cross-coupled differential-drive rectifier (CCDR) structure incorporating self-body bias for reconfigurable operation. An adaptive structure based on a Schmitt trigger is proposed to adaptively switch the rectifier connection without auxiliary voltage (Vaux), with two rectifier stages in parallel at low power and in series at high power. The system is simulated at a 180 nm CMOS process and the results show more than 17 dB DR at 900 MHz, with efficiency higher than 50% at a 100 kΩ load.

Evolutionary algorithm for minimizing the temperature influence of low power RF Energy Harvesting circuits

The aim of this work is to analyze and optimize the design of low-power Radio Frequency (RF) Energy Harvesting rectifiers by using an Evolutionary Algorithm. Although, generally neglected in the literature, the RF rectifier operation strongly depends on the operation temperature. When it varies, the input impedance can change significantly, affecting the circuit matching and its power conversion efficiency. In this work, an evolutionary algorithm is used to identify which parameters of an RF diode are responsible for the performance degradation as a function of temperature and to optimize the rectifier circuit in order to reduce the temperature influence. This work demonstrates that the saturation current, the zero-bias junction capacitance, the load and the series resistance have an important impact in designing an optimized circuit. Results indicate that the applied algorithm can be used aiming the project of a circuit more robust to temperature variations. The obtained results have also been compared to experimental ones, corroborating the analysis.

Energy Balance-Oriented RF Energy Harvesting Schemes for Intelligent Reflecting Surface-Assisted Cognitive Radio Sensor Networks

Energy Balance-Oriented RF Energy Harvesting Schemes for Intelligent Reflecting Surface-Assisted Cognitive Radio Sensor Networks

A complete artificial intelligence pipeline for radio frequency energy prediction in cellular bands for energy harvesting systems

Radio Frequency (RF) energy harvesting has been used to power wireless and low-powered devices. However, RF energy harvesting has limitations in terms of the amount of power that can be collected based on signal availability. Hence, energy prediction is essential to improve energy harvesting circuits' performance. Previous research has mainly focused on improving power harvesting policies or theoretically estimating the harvested energy. Very few works have considered the prediction of the RF signal as time series data using real RF measurements. Moreover, challenges such as the power consumed by the circuit's harvesting decisions and the impact of outliers on the model performance haven't been addressed yet. This paper presents a complete pipeline for developing the best predictive model for RF energy in cellular frequency bands. Real-time measurements are taken in different frequency bands using software-defined radio technology. We use four artificial intelligence techniques to model the RF energy signal. Additionally, we propose an optimized model with an enhanced loss function, which makes the model more resilient to anomalies, saving computational power and time consumed in cleaning the data. The four algorithms are investigated, and their prediction accuracies are compared. The average power of a period of 5 min is accurately forecasted. Numerical results in the 1960 MHz band show that long short-term memory has the best performance, followed by the DeepAR algorithm with prediction accuracies of 95.76% and 95.02%, respectively. Moreover, the proposed optimized model showed a 32.2% lower prediction error than the traditional models.

RF Energy Harvesting

This article presents research on the usefulness of three different electric circuit simulation environments for exploring energy harvesting from electromagnetic waves using energy harvesters. The software that is compared includes KiCad EDA, LT Spice and MATLAB Simscape Electrical.Too prepare a common background for the results comparison, crucial equations that combine RF transmission with energy are presented. Commercially available harvesters are also presented. An overview of the state-of-the-art research on this topic is summarised. In order to verify software using conditions that are similar to real ones, the power available at the 868 MHZ ISM band, which is close to the LTE bands used for telecommunications, is calculated. The results obtained using different software are close to being identical for all tested simulation environments.

Modeling of Schottky diode and optimal matching circuit design for low power RF energy harvesting

This work designs and implements a single-stage rectifier-based RF energy harvesting device. This device integrates a receiving antenna and a rectifying circuit to convert ambient electromagnetic energy into useful DC power efficiently. The rectenna is carefully engineered with an optimal matching circuit, achieving high efficiency with a return loss of less than −10 dB. The design uses a practical model of the Schottky diode, where both RF and DC characteristics are derived through extensive experimental measurements. The results from both experiments and simulations confirm the effectiveness of the design, showing its proficiency in efficient RF energy harvesting under low-power conditions. The antenna produced operates in the wifi band with a gain close to 4 dBi and a bandwidth of 100 MHz. With a load resistance of 1600 Ω, the proposed device achieves an impressive RF-to-DC conversion efficiency of approximately 52% at a low incident power of −5 dBm. These findings highlight the potential and reliability of rectenna systems for practical and efficient RF energy harvesting applications. The study significantly contributes to our understanding of rectenna-based energy harvesting, providing valuable insights for future design considerations and applications in low-power RF systems.

RF Energy Harvesting Techniques for Battery-Less Wireless Sensing, Industry 4.0, and Internet of Things: A Review

RF Energy Harvesting Techniques for Battery-Less Wireless Sensing, Industry 4.0, and Internet of Things: A Review

Co-Design of an Auxiliary Self-Bias Module and a CMOS Rectifier for RF Energy Harvesting

Co-Design of an Auxiliary Self-Bias Module and a CMOS Rectifier for RF Energy Harvesting

Stealth RF energy harvesting in MRI using selective shielding.

To utilize the transmit radiofrequency (RF) field in MRI as a power source, near or within the field of view but without affecting image quality or safety. Power harvesting is performed by RF induction in a resonant coil. Resulting RF field distortion in the subject is canceled by a selective shield that couples to the harvester while being transparent to the RF transmitter. Such shielding is designed with the help of electromagnetic simulation. A shielded harvester of 3 cm diameter is implemented, assessed on the bench, and tested in a 3T MRI system, recording power yield during typical scans. The concept of selective shielding is confirmed by simulation. Bench tests show effective power harvesting in the presence of the shield. In the MRI system, it is confirmed that selective shielding virtually eliminates RF perturbation. In scans with the harvester immediately adjacent to a phantom, up to 100 mW of average power are harvested without affecting image quality. Selective shielding enables stealthy RF harvesting which can be used to supply wireless power to on-body devices during MRI.

High-efficiency rectifying circuit for 5.8GHz wireless RF energy harvesting applications

High-efficiency rectifying circuit for 5.8GHz wireless RF energy harvesting applications

Wearable All-Fabric Hybrid Energy Harvester to Simultaneously Harvest Radiofrequency and Triboelectric Energy.

Distributed micro-energy harvesting devices offer the flexibility, sustainability, and multi-scenario applicability that will be critical to wearable electronic products in the Internet of Things. The radiofrequency and triboelectric (RF-TE) hybrid energy harvester (HEH) concept and prototype is presented for the first time, to simultaneously capture the energy from ambient electromagnetic waves and biological motions. The proposed hybrid energy harvesting system consists of a wearable rectenna, a triboelectric nanogenerator (TENG), and a power management circuit (PMC). Among them, the all-fabric rectenna exhibits good impedance matching characteristics in the ISM frequency. The flexible TENG unit can generate a maximum power density of 0.024µWcm-2. The designed multifunctional fabric-based PMC can considerably enhance the controllability of harvested hybrid energy. Additionally, a normalizable fabric circuit board quasi surface mount technology (FCB-SMT) is proposed to integrate all modules on the same fabric substrate in one step, making the entire system superior mechanical robustness. The proposed wearable fabric-based RF-TE hybrid energy harvester is capable of successfully driving consumer electronics (such as sensors, watches, etc.). It provides a new energy solution strategy for self-powered wearable electronic devices and is anticipated to encourage the efficient utilization of renewable energy.

A hybrid energy supply system based on metamaterial antenna integrated solar cells for IoT nodes

In this paper, a hybrid energy supply system based on solar cells integrated metamaterial (MTM) antenna is presented for use in Internet of Things (IoT) nodes. The work develops an energy supply system having dimensions of 40×40 mm2, that is qualified for storing and releasing energy. To realize miniaturization technique and gain enhancing, the design of antenna employs complementary split-ring resonator (CSRR) and a 4×1 array. Meanwhile, this work is miniaturized by integrating solar cells on the substrate. The result is a very compact integrated antenna with overall dimensions of 82.5×33 mm2 and the ability to harvest radio frequency (RF) energy and solar energy, which covers frequency band from 5.2 to 6.2 GHz. Different antenna structures were built to analyze S11 spectra, voltage standing wave ratio (VSWR), radiation patterns and surface current distribution, respectively. For further verification, the design was fabricated and compared to the simulated one. Moreover, practical experiments were conducted with four kinds of environment setup. The fabricated antenna provides maximum voltage of 1.63 V, indicating a good applicability to RF energy harvesting. The energy supply system provides a stable output voltage with 2.9 V in different conditions. The results highlight the feasibility of energy supply system in energy harvesting and powering for various IoT nodes.

Performance Analysis for Reconfigurable Intelligent Surface-aided Communication Systems with Energy Harvesting under Imperfect Nakagami-m Channel Information

Reconfigurable intelligent surface (RIS) can serve as a passive relay to maintain communication between a transceiver in severe scenarios of no direct link between them. In addition, harvesting energy from radio frequency (RF) signals can meliorate significantly energy efficiency. In this research, we propose RIS-aided communication systems with energy harvesting (RISwEH) which combine both RIS and RF energy harvesting to improve energy efficiency as well as communication reliability. To evaluate realistically and quickly the performance of the RISwEH, we propose the explicit formulas of the system throughput and the outage probability under the realistic scenario of Nakagami-m fading and imperfect channel state information (CSI). Moreover, we propose an optimization algorithm relied upon a Golden section search to attain the optimum value of the time splitting factor of energy harvester to obtain the best system performance. Various results corroborate the theoretical derivations, confirm the efficacy of the proposed optimization algorithm, and illustrate the influence of innumerable system settings on the system performance. Particularly, the imperfect CSI deteriorates considerably the system performance. Nonetheless, the performance of the RISwEH can be enhanced by accreting the quantity of the elements of the RIS as well as with the lower fading severity. Furthermore, the time splitting factor also impacts dramatically the outage performance of the RISwEH and its optimal value mitigates significantly the outage probability.

Design and optimization of broadband CPW rectenna for RF energy harvesting

ABSTRACT Wireless sensor networks (WSNs) are widely used in a variety of sectors, including the surveillance, healthcare, and military, and so on. The high cost and short lifespan of wireless sensor networks prohibit emerging and low-income nations for using their benefits. This article proposes a compact, low cost, and broadband coplanar waveguide rectenna with a simple novel ground plane operate in band range of 4.8–5.5 GHz (700 MHz) for an effective solution to radio frequency (RF) energy harvesting applications in WSNs. A parametric study of distinct antennas is also conducted to strengthen the attributes of the proposed antenna. The defected ground structure created on the co-plane offers 105° measured half power beamwidth (HPBW) in the H-plane for wide angular coverage. As a result, design alignment does not need to be extremely perfect in order to make conversion efficiency constant. The rectifying circuit is made compact by using a two-stub impedance matching network. At load resistance of 1k Ω, the power conversion efficiency of the proposed rectenna for a low input power level of −10 dBm is 27.2% (simulated) and 20.1% (measured) while its maximum value is 52.5% (simulated) and 50.1% (measured) for input power level of 10 dBm.

A novel high-efficiency class-F voltage doubler rectifier for RF energy harvesting

A novel high-efficiency class-F voltage doubler rectifier for RF energy harvesting

A metasurface-inspired printed monopole antenna for 5G and RF energy harvesting application

In this paper, a wideband circularly polarized (CP) Y-shaped printed monopole antenna with the twin parasitic conducting strips (PCS) loaded with a circular-shaped metasurface (MS) layer is investigated. Initially, a linearly polarized (LP) Y-shaped monopole antenna is designed. Thereby, to attain a CP from LP, a metallic strip is used to short one of the parasitic conducting strips to the ground plane. Further, a circular-shaped MS of a radius of 1.25λ∘, is placed just below the radiator at a height of 0.33λ∘, which enhances the impedance and axial bandwidths, as well as the CP antenna gain, with a motive to achieve the performance trade-offs from an application perspective. So, it is fabricated on FR-4 substrate with a dimension of 1.33λ∘×0.9λ∘×0.02λ∘ (λ∘ = 5 GHz) & offers the measured impedance bandwidth of 2.58 GHz (3.27–5.85 GHz, 48.45%), axial bandwidth of 860 MHz (4.24–5.1 GHz, 19.67%), CP gain avg. of > 8.75 dBic, & antenna efficiency of > 80% in the desired frequency band (3.5/5 GHz). In addition to the fundamental analysis pursued here, CP is presented in the form of a distinctive gain-bandwidth product relationship, which has been noted as being very rare in the existing literature, especially for 5G communications (sub-6 GHz) and RF energy harvesting applications.

Dielectric Resonator Antennas for RF Energy-Harvesting/Wireless Power Transmission Applications: A state-of-the-art review

This article presents an overview of dielectric resonator (DR)-based sensing elements and their applications in RF energy-harvesting (RFEH) and wireless power transmission (WPT) systems. With increased wireless applications, the demand for electrical energy goes up, thereby enabling the development of various energy sources. RF energy is widely available and the most efficient energy source. Although DR antennas (DRAs) have been studied extensively in the last few decades, they have not been employed in RFEH and WPT applications. The intention of the proposed article is 1) to provide an overview of the DRA for RFEH and WPT applications; 2) to accommodate various performance enhancement approaches for the DRA; and 3) to highlight the research gap for developing a complete rectenna system that helps future researchers. We believe that this survey may help the DRA.

High-efficiency CMOS charge pump for ultra-low power RF energy harvesting applications

This paper explicates the design and implementation of a switch capacitor DC–DC converter system for Radio Frequency (RF) energy harvesting applications for an input voltage in the sub-150 mV range, using 180-nm CMOS triple-well BCD technology. The proposed system incorporates a charge pump architecture that employs an improvised Dynamic Gate Biasing (DGB), Forward and Reverse Body Bias technique (FRBB), along with a time axis symmetrical clocking scheme implemented using an advanced bootstrapped CMOS driver to enhance the overall drive capability of the system at low input voltages. Post-layout extracted simulations demonstrate that the proposed system achieves higher overall efficiency, delivering a peak Power Conversion Efficiency (PCE) of 85.8% at 125 mV input voltage, outperforming other state-of-the-art architectures in similar voltage ranges. Moreover, the proposed system exhibits reliable operation even at input voltages as low as 85 mV, while maintaining good overall efficiency.