Zhaoyang Hu

High-Impedance Surface-Based Broadband Absorbers With Interference Theory

A broadband and polarization-insensitive high-impedance surface (HIS) metamaterial absorber (MA) based on octagonal ring-shaped resistive patches is presented. The absorber is investigated theoretically, experimentally, and by simulation. The simulated results indicate that this structure obtains 10.28 GHz wide absorption from 3.65 to 13.93 GHz with absorptivity larger than 90% at the normal incidence. Experimental results are in accordance with those of the simulation results. The electromagnetic (EM) field distributions and the plots of surface power loss density have been illustrated to analyze the absorption mechanism of the structure. Further simulations of the absorptivity of the proposed absorber with different surface resistances and substrate thicknesses indicate that there exist optimal values for the design. The polarization-insensitive feature and the properties under oblique incidence are also investigated. Finally, the interference theory is introduced to analyze and interpret the broadband absorption mechanism at both normal and oblique incidences. The calculated absorption rates of the proposed absorber coincide well with the simulated results. Therefore, the simulated and experimental results verify the validity of the theoretically analytical method for this type of broadband absorber.

Study on series-parallel mixed-resonance model of wireless power transfer via magnetic resonance coupling

Wireless power transfer system via magnetic resonance coupling (WPT/MRC) displays its superiority in its higher efficiency, longer range and greater power output. Up to now, diverse circuit architectures are widely utilized in WPT system. This paper conducts research on series-parallel mixed-resonance (SPMR) model, by analyzing the equivalent circuit model using circuit theory, the effects that the coupling coefficient between the coils, compensation capacitance ratio and load resistance may have on the efficiency and the output power are elaborated, and the general expressions for symmetry and asymmetric SPMR WPT systems of efficiency and power were obtained. Furthermore, the general expressions can be used in the analysis for the four basic topologies (series-series, series-parallel, parallel-series and parallel-parallel) by setting the compensation capacitance ratio as 1 or 0. Numerical calculated by the Matlab software and circuit simulated by Advanced Design System (ADS), the results show that the compensation capacitance ratio of SPMR topology plays a crucial role in WPT system. Compared with common series-series model, by optimizing the compensation capacitance ratios, the efficiency of SPMR WPT system can not only be improved effectively, but also the output power can be enlarged when the coil distance is far. Additionally, optimum loads of the best efficiency point and maximum power point are changeable under the condition of changing distance. Consequently, the SPMR circuit has great practicability and transfer performance. A wireless power transfer system with series-parallel mixed-resonance structure via magnetic resonance coupling is designed and created in this paper and the correctness of the aforementioned theoretical analyses and calculation simulation is verified through the experimental results.

Application of Ultra-Thin Assembled Planar Metamaterial for Wireless Power Transfer System

Magnetically coupled resonant wireless power transfer (WPT) has been employed in many applications, including wireless charging of portable electronic devices, electric vehicles, etc. However, the power transfer efficiency (PTE) decreases sharply due to divergence of magnetic field. Electromagnetic (EM) metamaterial (MM) can control the direction of magnetic fields due to its nega- tive effective permeability. In this paper, MMs with negative effective permeability at radio frequencies (RF) are applied to a WPT system operating at around 16.30 MHz for improvement of PTE. This ul- tra-thin and assembled planar MM structure consists of a single-sided periodic array of the capaci-tively loaded split ring resonators (CLSRRs). Both simulation and experiment are performed to cha-racterize the WPT system with and without MMs. The results indicate that the contribution of high PTE is due to the property of negative effective permeability. By integrating MM in the WPT system, the experimental results verify that the measured PTE with one and two MM slabs have respectively 10% and 17% improvement compared to the case without MM. The measured PTEs of the system at different transmission distances are also investigated. Finally, the proposed MM slabs are applied in a more practical WPT system (with a light bulb load) to reveal its effects. The results verify the efficiency improvement by the realized power being transferred to the load.

Metamaterial-Based High-Efficiency Wireless Power Transfer System at 13.56 MHz for Low Power Applications

Magnetically coupled resonant wireless power transfer (WPT) has been employed in many applications, including wireless charging of portable electronic devices, electric vehicles and powering of implanted biomedical devices. However, transmission efficiency decreases sharply due to divergence of magnetic field, especially in under coupled region. Electromagnetic (EM) metamaterial (MM) can manipulate the direction of EM fields due to its abnormal effective permittivity or permeability. In this paper, an ultra-thin and extremely sub-wavelength magnetic MM is designed for a 13.56 MHz WPT system to enhance magnetic field and its power transfer efficiency (PTE). The WPT systems are investigated theoretically, experimentally and by simulation. A relatively high maximum efficiency improvement of 41.7% is obtained, and the range of efficient power transfer can be greatly extended. The proposed MM structure is very compact and ultra-thin in size compared with early publications for some miniaturized applications. In addition, large area, homogeneous magnetic field is obtained and discussed using the proposed MM. Finally, the proposed MM is applied in a more practical WPT system (with a low power light bulb load) to reveal its effects. The bulb brightness intuitively verifies the efficiency improvement in the WPT system with the MM.

Investigation of the Arrayed Dielectric Barrier Discharge Reactor for PM2.5 Removal in Air

Low-temperature plasma treatment is a promising technology for particulate matter (PM). In this paper, the arrayed dielectric barrier discharge (DBD) plasma reactor for PM2.5 removal is investigated at atmospheric pressure. In order to reveal the interaction between experimental findings and simulation results, the equivalent electrical circuit is used. The electrical model is implemented on the PSIM software. To calculate the capacitance of the arrayed DBD reactor, the capacitor expressions are developed. Considering the experimental elements, such as plasma-generated configuration and the power source, a topological equivalent circuit is given. Finally, the simulation results are compared with the experimental ones, and they agree well. In addition, the designed DBD reactor was used to investigate PM2.5 removal. PM2.5 removal after 4 min of plasma treatment found to be about 53.8%.