Shengming Wang

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.

A New Remote Control Microwave Plasma Jet Excited by Surface Waves

A 2.45-GHz microwave plasma jet (MPJ) is designed based on the excitation of surface plasmon polaritons located in the discharge tube. The unique structure of internal metal antenna with an adjusting screw-pitch gauge is convenient to control plasma discharge at different locations for various gases (Ar, N2, O2, and so on) MPJ can be operated at wide pressure range with low incident power. R`egulating the position of the metal antenna and the flow rate, the longest plasma jet of 23 cm is produced at 100 Pa with the operating power of 30 W. As for high pressure, a plasma jet with a length of 7.5 cm is generated 50-cm away from the hole of the waveguide when incident power reaches 50 W. Field analysis is performed using the traditional software, plasma density, electron temperature, and the discharge components are diagnosed analyzed by the Langmuir double probe and spectrograph, respectively. This kind of plasma jet can be achieved for discharge at the desired positions, so it is suitable for the special industrial applications, such as ignition and recombustion for a certain distance.

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.

Simulated and experimental studies on the array dielectric barrier discharge of water electrodes

A kind of dielectric barrier discharge (DBD) device composed of water electrodes with 3 × 3 forms can produce large-area low-temperature plasmas at atmospheric pressure. To reflect the discharge characteristics of DBD better, a dynamic simulation model, which is based on the voltage controlled current source (CCS), is established, then the established model in Matlab/Simulink is used to simulate the DBD in air. The voltage–current waves and Lissajous at a voltage of 10 kV, 11 kV and 12 kV peak value with a frequency of 15 kHz are studied. The change of the discharge power of DBD with a different amplitude and frequency of applied voltage is also analyzed. The result shows the voltage–current waves, Lissajous and discharge power of DBD under different conditions from the simulation agree well with those of the experiment. In addition, we propose a method to calculate the dielectric barrier capacitance and the gap capacitance which is valid through analyzing the variation of capacitance at different voltage amplitudes.

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%.

Effect of MgO/Fe Interface Oxidation State on Electric-Field Modulation of Interfacial Magnetic Anisotropy

The impact of the MgO/Fe interface oxidation state on the electric-field-modified magnetic anisotropy in MgO/Fe has been revealed by density functional calculations. It is shown that the influence of the interface oxidation is strong enough to dominate the effect of the electric field on the magnetic anisotropy of MgO/Fe-based films. The magnetoelectric coefficients are calculated to be positive for the ideal and overoxidized MgO/Fe interface, but an abnormal negative value emerges in the underoxidized case. By analyzing the interface states based on density of states and band structures, we demonstrate that the considerably different electronic structures of the three oxidized MgO/Fe interfaces lead to the strong discrepancy in the electric-field modulation of the interfacial magnetic anisotropy. These results are of considerable interest in the area of electric-field-controlled magnetic anisotropy and switching.

The Double-Spiral Antenna for the Production of Microwave Plasma Jets

A double-spiral surface plasmon polariton (SPP) antenna is designed to produce a long-microwave plasma jet at atmospheric pressure with low power. This new structure antenna is made by an outer-tube spiral copper wire and an inner copper wire. To explore the influence of the new structure SPP exciter, many experiments are carried out in which the longest plasma jet of 13.5 cm is produced at atmospheric pressure with a power of 50 W. From the results of experiments, theoretical analysis, and field simulation by COMSOL, it is obvious that the new SPP antenna can produce longer plasma jets at a low gas flow rate, low power, and longer distance. Therefore, it is more suitable for special industrial applications for long-distance discharge.

Fabrication of SnS Using PECVD Method With Combined Solid Sources

A flat capacitively coupled plasma enhanced chemical vapor deposition reactor is used to prepare tin sulfide thin films. In this equipment, the plasma is generated by a radio-frequency power supply with the frequency of 13.56 MHz, and there are three quartz crucibles fixed on the side of the chamber between the two electrodes, which is a novel design from general plasma enhanced chemical vapor deposition facility. The images of the plasma discharge are presented, and a fiber optic spectrometer (AvaSpec-2048) is used to monitor the different plasma discharged states. The SnS films are obtained with power ranges from 80 to 120 W and vapor of the solid sources at 50-Pa pressure. The prepared films possess the excellent photo-electricity property.