RF Energy Harvesting Applications Research Articles

Design of Circularly Polarized Koch Snowflake Fractal Antenna With Schottky Band Diode Rectifiers for RF Energy Harvesting Applications

ABSTRACTRadio frequency (RF) energy harvesting has recently become an effective way of powering wireless devices, reducing the requirement of batteries along with their related storage as well as lifespan restrictions. One of the main obstacles to RF energy harvesting is the limited quantity of energy that can be obtained from wireless sources due to weak signal strength, low efficiency, and poor gain. To address these shortcomings, the proposed method is designed based on the circularly polarized Koch snowflake fractal antenna with the Jerusalem cross (JC)–based frequency‐selective surface (FSS) and Schottky diode–based rectifiers for RF energy harvesting applications at the resonance frequency of 5.8 GHz. The electromagnetic energy from the environment can effectively captured using a proposed wide band and high gain antenna designed using a Koch snowflake array based on FSSs. Flame Retardant‐4 (FR‐4) material has good dielectric qualities for electronics, and it is employed as the dielectric substrate in this model; copper serves as the ground plane. The squid game optimizer (SGO) determines the ideal outer snowflake dimensions by maximizing the resonance frequency in order to achieve high gain. The optimally selected outer snowflake length and width are 40 and 23.09 mm. The designed antenna model uses a rectifier based on Schottky diodes for RF energy harvesting applications, which involves converting electromagnetic waves into direct current. The fractal antenna model and RF energy harvesting are designed and simulated using the ANSYS HFSS and Matlab RF toolbox. The model is used to evaluate the antenna's performance by concentrating on gain radiation patterns, S11, and voltage standing wave ratio (VSWR). The Koch snowflake fractal antenna, which uses a JC–based FSS, has been measured for performance at 5.8‐GHz frequency; the values obtained for impedance bandwidth, gain, S11, and VSWR are 7.61%, 9.962 dB, −33 dB, and 1.01, respectively. The analysis of the experimental data demonstrates that the Koch snowflake fractal antenna, which is being proposed for energy harvesting applications, outperforms several other existing designs in terms of effectiveness.

Design of 2.45 GHz rectenna based on high-gain 2-element array antenna and 7-stage voltage-doubler rectifier for energy harvesting applications

Abstract This paper proposes a new design of a 2.45 GHz compact rectenna for ambient RF energy harvesting, presenting a complete energy harvesting system. The proposed rectenna design features a two-element antenna array with high gain and a novel voltage-doubler configuration. The two-element antenna array is fabricated on Rogers RT/Duroid-5880 substrate, utilizing a rectangular microstrip patch antenna fed by a symmetric 50 Ω coplanar line. The antenna’s performance is tested numerically and experimentally in terms of return loss (S11) and radiation patterns. The results show excellent matching bandwidth at 2.45 GHz with a high gain of 7.03 dBi, providing a reasonable agreement between measurement and simulation results. The rectenna design employs a 7-stage voltage doubler rectifier that generates a dynamic DC voltage and improves the circuit’s reliability and performance. The receiving antenna and the rectifier are connected via a single L-section, comprising a shunt capacitor and a series inductor, for impedance matching, resulting in size reduction. The rectifier exhibits a peak simulated power conversion efficiency (PCE) of 75% and a measured efficiency of 60% at an input power of 20 dBm. The rectenna yields a high output DC voltage of 4.9 V at an input power of 13 dBm with a resistive load of 1 kΩ. These results reveal that the proposed 2.45 GHz rectenna is a suitable candidate for RF energy harvesting applications in low-power sensors and electronic devices.

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.

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

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.

Dual-band low-power RF-to-DC signal converter circuits for energy harvesting

This article presents dual-band low-power, high-sensitive radio-frequency (RF)-to-direct current (DC) signal converter circuits, operating at 2.45 and 5.5 GHz bands, for radio frequency energy harvesting applications. In particular, it focuses on the lumped element and microstrip transmission line model circuits. The lumped element RF-to-DC converter circuit is composed of a dual-band impedance matching circuit, voltage-doubler rectifier, and DC-pass filter with a resistive load of 5 kΩ. This converter circuit gives a DC output voltage of 48 mV at 2.45 GHz and 25 mV at 5.5 GHz on −25 dBm input power. Maximum conversion efficiency is 47% at the 2.45 GHz band and 27% at the 5.5 GHz band when the input power is set to −10 dBm. Circuit design steps, matching conditions, performance parameters, and so on, are presented using Advanced Design System simulation. To validate the concept of the lumped element model, a microstrip transmission line RF-to-DC converter model is simulated and fabricated. It also composes of a dual-band matching network, voltage-doubler, and DC-pass filter with a load resistance of 5 kΩ. At a low input power of −18 dBm, it gives an output voltage of 21 mV in measurement. An appropriate match between the simulation and measurement is noted.

Enhancing RF energy harvesting in smart cities with two port MIMO-UWB antenna design using machine learning algorithms

Abstract This work presents the two port ultra-wide band MIMO antenna with novel isolation structure and dual band RF Rectifier for 3.3 GHz and 4.65 GHz frequencies for RF energy harvesting applications. The anticipated antenna is systematically examined within the ultra-wideband (UWB) range from 3.1 GHz to 10.6 GHz design frequency with four different steps: Antenna 1, Antenna 2, Antenna 3 and Antenna 4 (optimal design) are chosen for comprehensive study. A unique isolation structure was developed between two identical elements separated by 10 mm, resulting in an enhanced isolation of −23.5 dB at 3.15 GHz, −27 dB at 5.8 GHz, −28 dB at 9.26 GHz and greater than −34 dB at 7.5 GHz. The suggested antenna resonates at UWB band and have fractional bandwidth of 118.66 % and a peak gain of 4.1 dB at 3.15 GHz, 3.68 dB at 5.8 GHz, 6.4 dB at 7.5 GHz and 3.2 dB at 9.26 GHz has been obtained. Radiation efficiencies of 92.5 %, 95 %, 90 % and 84.5 % at 3.15 GHz, 5.8 GHz, 7.5 GHz and 9.26 GHz were obtained respectively. The recommended MIMO performance is simulated using HFSS in terms of ECC, DG, MEG and CCL. The results adhere to specified requirements and confirmed by experimentation. An HFSS simulated dataset of reflection coefficient is used as input for the various ML algorithms namely, Support Vector Machine (SVM), Ensemble, k-nearest neighbors’ algorithm (KNN) and Gaussian Process Regression (GPR) models are trained with 80 % of the data and testing with 20 % of the data. The test results are compared and corresponding performance values of MAE, RMSE, MSE & R 2 are 0.00029, 0.00197, 3.87e−6 and 1.0 validation results and corresponding test results are 0.00031, 0.00229, 5.20e−6 and 0.999. Finally, the proposed dual band rectifier with a shorted stub is tested for harvesting applications at 3.3 GHz and 4.65 GHz frequency and it attained RF to DC conversion efficiencies of 69 % and 55.40 % respectively.

Drone Shaped Fractal Antenna with Defected Ground Structure for RF Energy Harvesting Applications

A proposed multiband drone shaped fractal antenna (Antenna-1) is introduced in this paper that targets the most required frequencies used for radio frequency energy harvesting applications, including WLAN-2.4G, WLAN-5G, WLAN-6G, Mobile DCS1700, Mobile LTE and WIMAX services. A novel fractal shape is designed and combined with a standard square geometrical shape in order to implement the front patch of the antenna. The antenna is simulated with CST Studio Suite software and fabricated on FR-4 substrate. Different antenna stages with parametric study and optimization were implemented to get the best performance from the drone shape fractal antenna. The multiband (Antenna-1) supports six resonate frequencies (1.7155 GHz, 2.424 GHz, 3.36 GHz, 3.789 GHz, 5.843 GHz, 6.886 GHz) with peak gain of (2.83 dBi) at the frequency 2.45 GHz and a maximum bandwidth of (0.4281 GHz) at the frequency 5.8 GHz that make it a suitable antenna for radio frequency energy harvesting applications.

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.

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

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

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.

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.

High-Efficiency Multiband Rectifier for RF Energy Harvesting Applications

High-Efficiency Multiband Rectifier for RF Energy Harvesting Applications

Simulation based Comparative Review on a Metasurface based Perfect Absorber

In this paper, the different research papers are studied and comparatively analyzed to carry out the simulation based survey of various proposals for improvement to design Metarsurface based Perfect Absorber for GHz and THz frequency band for RF Energy Harvesting applications. Using a structure that can effectively absorb the most radiation is one of the biggest obstacles in reducing the impact of EM wave radiation. A perfect absorber may be created using variety of structures and materials with various specifications. Various structures are designed and simulated by different authors in variety of simulation softwares using useful parameters. Three distinct structures have been created, two of which were created using CST Microwave Studio and the third using HFFS for comparative study. A perfect absorber can be constructed for GHz and THz for dual band and multiband since the operating frequency range and band are not limited.

Double elliptical resonator based quad-band incident angle and polarization angle insensitive metamaterial absorber for wireless applications

In this article, a double elliptical split ring resonator-based quad band metamaterial absorber (MMA) is demonstrated for applications in the microwave range. The resonator is made up of four squares outside split rings and two elliptical split rings positioned in the middle of the structure. The resonating patch is placed over an FR-4 dielectric layer with a thickness of 1.6 mm. The unit cell has an electrical size of 0.103λ0 × 0.103λ0, where λ0 is the wavelength determined at 2.576 GHz. The MMA shows maximum absorption of 99.83% at 2.576 GHz, 99.98% at 5.648 GHz, 99.56% at 8.32 GHz, and 99.15% at 13.456 GHz with TE mode. For TM mode, at 2.576 GHz, 5.632 GHz, 8.304 GHz, and 13.44 GHz, corresponding absorptions are 99.21%, 99.67%, 99.5%, and 99%, respectively. The MMA is polarisation and incidence angle (0° to 90°) insensitivity for both TM and TE modes. The unit cell provides single negative characteristics including an EMR (effective medium ratio) of 9.71 and a Q factor (quality factor) over 25. The proposed MMA provides high harvesting efficiencies of 92.87%, 76.9%, 94.12%, and 90.97% for frequencies of 2.57 GHz, 5.64 GHz, 8.32 GHz, and 13.45 GHz, correspondingly. The equivalent circuit is modeled to understand the resonance behavior of the MMA and the circuit parameters are determined and validated using Advanced Design Systems (ADS) software. The performance of the MMA is examined using the prototype of the array of the unit cells in an experimental setup. The experimental outcome provides a close similarity with simulation outcomes indicating the good performance of the MMA. The metamaterial absorber's high performance makes it suitable for many applications, such as RF energy harvesting applications, image technologies, stealth technologies, and radar systems as well as minimizing electromagnetic interference in satellites.

A Co-Planar Waveguide Ultra-Wideband Antenna for Ambient Wi-Fi RF Power Transmission and Energy Harvesting Applications

This study proposes an ultra-wideband antenna for ambient radio frequency (RF) energy harvesting applications. The antenna is based on a co-planar waveguide (CPW) transmission line and incorporates a rectangular slot as an antenna harvester. The proposed antenna utilizes an evolutionary design process to achieve impedance matching of the 50 Ω CPW feeding line over the desired frequency bands. A parametric study investigates CPW elements and rectangular slot size. The harvester antenna is then connected to the primary rectifier circuit of the voltage doubler to examine the signal characteristics. The antenna covers the Industry, Science, and Medicine (ISM) Wi-Fi bands of 2.45 GHz and 5 GHz, achieving a realized gain of 3.641 dBi and 4.644 dBi at 2.45 GHz and 5 GHz, respectively. It exhibits a relatively broad frequency ranging from 2.16 GHz to 6.32 GHz, covering the ultra-wideband fractional bandwidth (FBW) of 105%.

Metasurface-Assisted Broadband Compact Dual-Polarized Dipole Antenna for RF Energy Harvesting

In this letter, a low-cost dual-polarized broadband dipole antenna is studied for RF energy harvesting applications. The 2×2 antennas are arranged with a rotational symmetry over an Artificial Magnetic Conductor (AMC) surface to capture the ambient RF energy from both the Horizontal (H) and Vertical (V) polarizations in a multiple input multiple output (MIMO) environment. The antenna is then integrated with a single-series rectifier circuit network in a series fashion. In the final step, an LED is connected as the common load to demonstrate the process of capturing the RF energy, thereby glowing the LED.

A Low-Profile Compact Broadband CP DRA for RF Energy Harvesting Applications

In this letter, a low-profile circularly polarized (CP) chamfered rectangular dielectric resonator antenna (RDRA) is designed and investigated for radio frequency energy harvesting (RFEH) applications. The proposed modified RDRA comprises of dielectric resonator (DR) made up of Alumina material (ε r = 9.9) mounted on the PEC ground plane. Dual unequal triangular-shaped vertical slits are engraved on the rectangular DR for generating the orthogonal modes with CP characteristics. The optimized antenna offers an impedance bandwidth (IBW) of 51.4% (2.25–3.81 GHz) and axial ratio bandwidth (ARBW) of 14.8% (3.25–3.77 GHz), respectively. The peak realized gain and maximum radiation efficiency are 7.18 dBi and 97.8% in desired frequency bands. Due to the wide impedance and AR bandwidths with realized gain and radiation efficiency, the optimized antenna is suitable for integration with a rectifier circuit for RF energy harvesting applications. A rectifier circuit with a single shunt diode topology is also designed for rectification purposes. The rectifier achieved 67.16% RF-DC power conversion efficiency (PCE) at 3.5 GHz and 5dBm input power. At 0dBm input power, the rectifier achieved 60.26% PCE. The effective input power range, during which the PCE maintains above 50%, is calculated to be 15.2 dBm from −3.5 to 11.7 dBm.

Machine Learning Based b-Shaped Monopole Antenna for RF Energy Harvesting Applications

In this paper, a machine learning (ML) based b-shaped multiband monopole antenna for RF energy harvesting system is presented. ML algorithms are used to optimize the antenna in order to reduce the simulation time and speed up the design process. Geometric parameters on the antenna have been determined as input in the ML model. There are two different output data: the complex and decibel magnitudes of the reflection coefficient (S11) parameters, which have been determined as output parameters. The dataset consists of 1890 samples in total. Initially, attempts were made to predict the decibel magnitude of reflection coefficient parameters using different ML algorithms, and these ML algorithms were compared with each other. Then, for the complex part of the reflection coefficientparameters, a Multi-Output regression model was applied to the real and imaginary values. The best results were obtained with the K-Nearest Neighbors algorithm for the decibel magnitude of reflection coefficient parameters, achieving a 0.14% RMSE value and a 99% R2value. The Multi-Output Regression algorithm was applied to complex (Real, Imaginary) values, achieving an R2value of 92.51% and a RMSE value of 0.10.

4-Port MIMO antenna with novel isolator conducting structure for sub-1 GHz/sub-6 GHz and RF-energy harvesting applications

A 4-port MIMO antenna with a novel isolator structure for sub-1GHz/sub-6GHz and RF-energy harvesting applications is presented in this research. The proposed antenna is investigated systematically at 2.6 GHz design frequency with four distinct stages: STEP-1, STEP-2, STEP-3 and STEP-4 and an optimal design (STEP-4: mm3) is chosen for further study. A unique isolation structure was developed between two identical elements separated by , resulting an improved isolation of greater than 14 dB at 0.9 GHz and greater than 18 dB at 2.6 GHz is obtained. The suggested antenna resonates at 900 MHz-simulated & measured and 2.6 GHz-simulated & 2.8 GHz-measured with simulated fractional bandwidth/resonating band of 24.6%/0.778–1 GHz & 20.7%/2.4–2.94 GHz and a measured fractional bandwidth/resonating band of 17.8%/0.83–0.99 GHz & 21%/2.41–3 GHz at lower and upper resonating frequencies respectively. A peak gain of 1.5 dB at 900 MHz and 4.2 dB at 2.8 GHz has been obtained. The SAR values of less than 0.5 and 1.6 W/kg and radiation efficiencies of 74.7% and 90% at 900 MHz and 2.8 GHz were obtained, respectively. The suggested antenna's MIMO performance is simulated using electromagnetic tool HFSS in terms of ECC, DG, TARC, MEG and CCL, and the obtained results are experimentally verified. Further, the proposed antenna is tested for harvesting applications wherein 9.5 mW of harvested power, 76.45% power conversion efficiency (PCE), 4V harvested voltage, current 2.4mA and 12.46 mW Friis equation output at 915 MHz and 26.98 mW of harvested power, 69.5% power conversion efficiency, 5V harvested voltage, current 5.4 mA and 38.8 mW Friis equation output at 2.5 GHz are recorded.