Design of a perfect and multi-resonant metamaterial absorber for electromagnetic energy harvesting applications

In this work, a perfect absorber based on a split ring resonator structure is proposed and numerically analyzed. The software CST STUDIO was employed to carry out the numerical analysis and the optimization of the proposed structure. The electromagnetic properties of the proposed metamaterial cell were analyzed in the first phase of this study demonstrating that such structure resonates at 2.4 GHz and 4.2 GHz simultaneously. In fact, this structure has negative permittivity and permeability in these two bands. The optimization process has led us to obtain a compact resonator, which has a total size of 15 mm × 15 mm. Subsequently, the capacity of this structure as an absorber of electromagnetic energy is analyzed. The obtained results reveal that this structure has absorption efficiencies of 98.2% and 99.7% for the first and second bands respectively. Also, other characteristic parameters were evaluated. This shows that the proposed structure has a high electrical performance and can be used for the collection of electromagnetic energy, which can be used to power wireless sensor networks.

Compact and Simple High-Efficient Dual-Band RF-DC Rectifier for Wireless Electromagnetic Energy Harvesting

(1) Background: This work presents a high-efficiency, high sensitivity, compact rectifier based on a dual-band impedance matching network that employs a simple and straightforward T-matching circuit, for sub-1 GHz license-free applications. The development of a low-cost RF energy harvester dedicated to the ISM bands is introduced. The proposed rectifier design is optimized to operate at the sub-GHz frequency bands (0.9 to 2.4 GHz), specifically those at the ISM 900 and 2400 MHz. The motivation for this band is due to the low attenuation, well-known fundamental electromagnetic theories and background, and several wireless communications are emitting at those bands, such as RFID (2). Methods: The rectifier design is based on a simple, balanced single-series diode connected with a T-matching circuit. The dual-band performance is achieved by deploying reactive elements in each branch. The full mathematical analysis and simulation results are discussed in the manuscript. (3) Results: The rectifier can achieve a 80 MHz bandwidth around 920 MHz frequency and 200 MHz around the higher band 2.4 GHz. The resultant conversion efficiency level is maintained above 45% at both bands with a peak efficiency reaches up to 70% at the higher band. The optimum terminal load attached to the circuit at which the peak efficiency is achieved, is given as 4.7 kΩ. (4) Conclusion: Due to the compactness and small footprint, simple design, and simple integration with microwave circuits, the proposed rectifier architecture might find several potential applications in wireless RF energy harvesting.

Electromagnetic Energy Harvester for Transportation Infrastructure Using Vehicle-Tread Force

We propose a novel electromagnetic energy-harvesting device (EHD) for structural health monitoring systems of transportation infrastructures. The EHD is embedded in the road surface and uses the tread force of cars as the input force when tires of cars pass over it. Because the input force is very fast, the proposed EHD can generate a large amount of energy. The footprint of the device is 20 × 20 mm, its height is 7.5 mm, and its volume is 2.4 cm3. We measured the energy generated when a bicycle passed over the EHD 34 times at various speeds between 5 and 15 km/h. Subsequently, we obtained the regression curve from the results, which showed the relationship between the bicycle speed and generated energy, and estimated the electric energy generated by car at higher speeds. The results showed that, even though the size of the EHD was small, electric energies of 100 μJ, and 1.0 mJ could be generated at car speeds of 17 km/h, and 52 km/h, respectively.