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This study investigates the counterintuitive behaviors of a microwave‐induced atmospheric pressure plasma jet (APPJ) under the influence of an external electrostatic field applied by one or a pair of parallel electrode plates subjected to DC voltages. The findings demonstrate that the plasma jet consistently deflects toward the electrode plate with an electrostatic potential, irrespective of the direction of the applied field. The deflection becomes more pronounced with increasing voltage on the electrode plate until the ionic wind generated by the high voltage significantly affects the jet's behavior. Remarkably, a negative voltage induces a greater deflection compared to a positive voltage. To further investigate this discovery, the dielectric properties and the non‐neutral characteristics of the APPJ are analyzed, and the simulations of the electric field distribution reveal a non‐uniform distribution, which plays a crucial role in understanding the mechanism behind the observed behaviors of the plasma jet. This study provides a comprehensive understanding of the underlying mechanism driving the observed phenomena and sheds light on the collective behavior of plasma jets under non‐uniform electric fields. The findings of this study offer valuable guidelines for investigating and controlling the behavior of APPJs. [ABSTRACT FROM AUTHOR]

A novel planar lens structure is proposed by using metasurfaces to convert cylindrical‐like surface wave to inclined nondiffracting wave with a deflection angle. Based on the geometric optics, the refractive index distribution of the surface wave lens is derived. A square metal ring‐shaped metasurface cell is used for realizing small refractive index whilst two opposite E‐shaped metal patches are used to form the meta‐cell with large refractive index. By adjusting the size of meta‐cells, the desired refractive index distribution is obtained after optimization. Measured results show that the inclined nondiffractive surface wave can be achieved with the maximum propagation distance of 99.72 mm at the tilted angle of 26.8°, which are consistent with the full‐wave simulation and numerical calculation results. The proposed meta‐lens achieves compact size, large titled angle, and long nondiffraction propagation distance, therefore could be well utilized in surface wave communication and nondestructive detection of surface defects. [ABSTRACT FROM AUTHOR]

A microwave atmospheric pressure plasma jet (MW‐APPJ) generator based on a substrate‐integrated waveguide (SIW) resonator is proposed. A thin, straight plasma needle with a length of 9 cm could be obtained. Higher than 90% of microwave feeding efficiency is obtained under a wide range of gas flow rates without a microwave matching network. As the gas flow increased from 1 to 14 L/min, a transition from laminar to turbulent mode is observed in the plasma jet's morphology. Furthermore, a preliminary surface treatment was tested for the device. The polyimide film became super hydrophilic after a 5‐min treatment with the developed SIW‐based plasma generator. Generally, the SIW‐based MW‐APPJ is low‐cost, electrodeless, and low‐profile along the plasma jet length direction. [ABSTRACT FROM AUTHOR]

In this letter, an efficient broadband microwave rectifier with compact size for wireless power transfer is presented. It is proven that the proposed voltage doubler is easier to be matched than the series diode rectifier to achieve a wide bandwidth. In our analysis, the voltage doubler itself is already matched without the input matching network at the lower frequency band. For higher frequency band matching, a short section of microstrip line is connected to the input port of the voltage doubler. Thus, the proposed rectifier can operate over a broad bandwidth. To verify the design concept, a rectifier is fabricated, and the measurement results demonstrate that the power conversion efficiency is greater than 50% from 0.1 to 4.3 GHz at an 18 dBm input power level, and is higher than 70% within a wide bandwidth of 76.9%. In addition, when the input power is 18 dBm, the peak efficiency is 76.36% at 1.4 GHz. The results show that the proposed rectifier has the merits of compact size, broad bandwidth, and high efficiency. [ABSTRACT FROM AUTHOR]

Graphene has received intensive research interest in various areas due to its outstanding mechanical, electrical properties, high specific surface area and 2D flexible structure. Mechanical exfoliation generates defect‐free graphene, but suffers from ultra‐low yield. This drawback can be partially overcome by chemical vapor deposition method (CVD). However, conventional CVD imposes high temperature. In recent years, microwave plasma‐enhanced CVD (MPCVD) has been widely investigated as a viable strategy toward large‐area graphene synthesis. In this review, important issues during the process are summarized. Firstly, various MPCVD devices that have been explored for graphene synthesis are presented. Secondly, effect of carbon sources, nitrogen‐containing gases, and CO2 in the precursors are discussed. Thirdly, MPCVD enabled direct synthesis of graphene on metal substrates and non‐metal sustrates is discussed. Finally, the advances of MPCVD in lowering the graphene synthesis temperature are demonstrated. [ABSTRACT FROM AUTHOR]

A novel two‐dimensional atmospheric pressure plasma jet device is proposed for large‐area processing. A finite element algorithm is adopted to obtain the optimized dimensions of the designed device based on microwave power reflection coefficient |S11| and electric field intensity. The plasma parameters of electron density ne and electron temperature Te within 0.1 ms after microwave power input were analyzed. When plasma is fully excited, ne is close to 3.5 × 1018 m−3, and Te is calculated to be 2 eV. Besides, an experimental system is established, and microwave power of 70 W can process 30 L of argon per minute, which shows a high energy efficiency. Two plasma jets with a width of 10 mm and a length of 5 mm are successfully excited. In addition, reflected power measured by the power meter is only 9.5% of incident power, which is in good agreement with simulation results. [ABSTRACT FROM AUTHOR]

Graphite‐derived carbon materials have been widely used in metal‐ion batteries due to their good mechanical and electrical properties, cost effectiveness, light weight, and environmental friendliness. Though natural graphite has been commercially used in lithium‐ion batteries, the small interlayer spacing hinders its application in other metal‐ion batteries. As such, numerous works have been done to enhance the metal‐ion storage capability of graphite and its derivatives. In this review, structural engineering on graphite including expanded graphite, graphite intercalation compounds and porous graphite, and the corresponding electrolyte engineering for lithium‐ion batteries, sodium ion batteries, potassium ion batteries, and dual ion batteries are summarized, aiming to make a comparison between various strategies and give a suggestion on future work in this area. [ABSTRACT FROM AUTHOR]

In this article, a novel lens antenna with wide beamwidth using three‐dimensional printing is proposed. The proposed antenna is comprised of a concave lens by using three‐dimensional printing, a lantern shaped patch with a parasitic ring, and eight loaded monopoles around the center. The antenna operating frequency is 5.8 GHz, and the prototype is implemented. The measured half power beamwidth are 142° and 130° at the xoz and the yoz planes, respectively. Besides, the antenna is low cost, easy to fabricated, and very low cross polarization. Measured results agree well with the simulation results. [ABSTRACT FROM AUTHOR]

A K‐band (18–27 GHz) dielectric‐loaded waveguide antenna is designed as the feed for a parabolic reflector. The antenna is composed of a waveguide launcher and a dielectric load. The waveguide launcher is fabricated by selective laser melting using aluminium alloy. The dielectric load is fabricated by stereolithography using resin. The aperture field distribution of the antenna is tuned by extending the E‐ and H‐walls of the waveguide launcher to radiate a sidelobe‐reduced main beam in the boresight from −90° to + 90°. The agreement is achieved between the simulation and measurement. It has impedance bandwidth of |S11|<−10 from 18 to 27 GHz, the maximum gain of 11.8 dBi @ 19 GHz, and 3‐dB gain bandwidth from 18 to 25 GHz. For the sidelobe reduced, simple design and low cost, the proposed antenna features a good candidate as the feed for a parabolic reflector. [ABSTRACT FROM AUTHOR]

This letter presents a reconfigurable leaky‐wave antenna for near‐field beam manipulation. The proposed antenna is based on a radial waveguide and a reconfigurable capacitive sheet, which is divided into four regions. To realize the reconfigurability, PIN diodes are electrically soldered to the gap between the adjacent patches in the upper surface except for the isolation zone, where no diodes are printed. By switching the states of PIN diodes in each region by turns, wavenumbers with two different azimuths are generated, thus the near‐field beam deflection can be achieved in different regions. By using the Genetic Algorithm, the PIN diodes are optimally deployed for realizing high antenna efficiency. The simulated (measured) results show that with the implementation of the reconfigurable capacitive sheet results in a near‐field beam scanning property. The beam deflection at a tilted angle of 17.4° (16.2°) can be achieved in different regions. [ABSTRACT FROM AUTHOR]

This letter presents a new design method for a tunable bandpass filter with independently and widely tunable transmission zeros (TZs). Varactor‐loaded microstrip resonators are introduced to a fixed bandpass filter to realize the continuously tunable TZs. Although the tunable resonators have unloaded Q lower than 100, the insertion loss of the filter is not increased. The coupling matrix with the lossy resonators is synthesized and used to analyze the characteristic of the TZ‐tunable filter. A bandpass filter centered at 2 GHz with a 3‐dB bandwidth of 230 MHz is designed to validate the design concept. The measured results show good agreement with the simulated results. The fabricated filter has 2 TZs ranging from 1.4 to 1.8 GHz and from 2.28 to 3.08 GHz, respectively. The TZ‐tunable filter exhibits insertion losses ranging from 1.62 dB to 1.93 dB at the center frequency. The center frequency and bandwidth keep nearly unchanged when the TZs are tuned. [ABSTRACT FROM AUTHOR]

In this paper, the electromagnetic environment (EME) characteristics on Wangjiang campus of Sichuan University, a typical densely populated urban area, are measured and analyzed. According to the people's daily routine, the EME measurements are performed during daytime, nighttime, weekday, and weekend, respectively. By measuring the electric field (E‐field) values along the main roads on the campus, the maps of E‐field spatial distribution are obtained. Results indicate that the EME on the campus is relatively stable. The probability density functions of three orthogonal components of E‐field are all lognormal distribution and very similar to each other due to depolarization phenomenon and polarization rotation of multipath propagation. Moreover, the total E‐field is also lognormal distribution because of the high linear correlation between the components. In addition, E‐field were also measured over time on three different sites, playground, laboratory, and student dormitory, in order to get time‐varying characteristics of the EME. Results suggest how the people's activities influence on EME. All measurements on Wangjiang campus show that the maximum E‐field value is far below the regulatory exposure limits proposed by the International Commission on Non‐Ionizing Radiation Protection. Key Points: Electromagnetic environment characteristics on Wangjiang campus of Sichuan UniversityMeasurement of E‐field spatial and temporal distributionThree orthogonal components of E‐field obey lognormal distribution [ABSTRACT FROM AUTHOR]

Two‐dimensional (2D) carbon hybrids have promise in various areas such as energy storage and catalysis. Simple methods for controllable fabrication of 2D graphitic carbon hybrids in a scalable manner remains challenging. Now, a microwave‐assisted strategy for mass production of 2D carbon hybrids based on self‐boosting catalytic carbonization of a metal–agarose framework is demonstrated. Hybrids including hollow Fe3C nanoparticles, Ni/Co nanoparticles, and hollow FeOx nanoparticles uniformly embedded in 2D graphitic carbon nanosheets (GCNs) are obtained, demonstrating the generality of the approach. Metal–polymer coordination and microwave‐enabled fast catalytic decomposition of precursors play vital roles in facilitating the formation of the nanosheet structure. The resulting FeOx‐GCNs hybrid exhibits superior lithium‐storage performance (1118 mAh g−1 at 500 mA g−1 and 818 mAh g−1 at 2000 mA g−1 after 1200 cycles). Superdrying: Microwave‐enabled fast evaporation of water and decomposition of nitrate converted a metal–agarose framework into a 2D nanosheet structure. Using this approach, hybrids such as hollow Fe3C nanoparticles, Ni/Co nanoparticles, and hollow FeOx nanoparticles uniformly embedded in 2D graphitic carbon nanosheets could be obtained after annealing. [ABSTRACT FROM AUTHOR]

This Letter presents a third‐order multilayer substrate integrated waveguide (SIW) filter with broadband stopband. The filter is composed of three vertically stacked square SIW cavities. The input/output feeding structure and the coupling slot in the middle metal layer of two cavities are properly designed to just allow the fundamental resonant mode to a couple while other higher spurious resonant modes are isolated. The fabricated filter is at a centre frequency of 6.96 GHz with a stopband suppression of 24 dB up to 2.77f0. [ABSTRACT FROM AUTHOR]

Outside Front Cover: Plasma Process. B Outside Front Cover b : Microwave atmospheric pressure plasma jet generated from substrate integrated waveguide resonator by Chaoxia Zhao et al (e2200230). Polym. [Extracted from the article]

In this study, a substrate integrated waveguide (SIW) combined with complementary split‐ring resonator (CSRR) structure is proposed for high‐sensitivity measurement of complex permittivity of low loss material at 2.45 GHz. The simulated results demonstrated that the small changes can be sensed through loading the CSRR structure on both sides of SIW. Then, the experiments are performed on various dielectric samples to validate the proposed structure by measuring the particulate samples with different moisture contents and solution samples in different mixed volume ratio. The measured results show that the sensitivity of the proposed SIW with CSRR structure is always higher than the structure without CSRR. Furthermore, neural network based on actual experimental scattering parameters is used for obtaining the permittivity of samples under test. The experimental values agree well with the theoretical values, and the relative errors of ε′ and ε′′ are <5 and 10%. [ABSTRACT FROM AUTHOR]

This article proposes a novel concept for constructing a microwave (MW) rectifying circuit by using a multilayer structure, aiming at reducing physical dimensions. Specifically, an embedded via-hole with connection of conductor layers in the multilayer structure is designed. A full-wave electromagnetic analysis is carried out to study the impacts of various via-hole design parameters. Then, a C-band rectifying circuit based on HSMS-286C Schottky diode is fabricated with the proposed multilayer structure for demonstration. The maximum MW-DC conversion efficiency of 61% has been measured. In comparison with the counterpart, namely a conventional microstrip rectifying circuit, the proposed multilayer circuit shows a great reduction of physical dimensions and a very similar efficiency, which validates that the proposed circuit can reduce physical dimensions significantly without sacrificing the MW-DC conversion efficiency. [ABSTRACT FROM AUTHOR]

Microwave-assisted continuous-flow reactors (MCFRs) are a valuable alternative to conventional reactors for accelerating chemical reactions. However, despite several interesting applications, only little quantitative research has been conducted on the temperature uniformity of the heating load. With water as a common inorganic solvent, a novel MCFR type based on a special ridged waveguide for heating water is studied by optimizing some parameters of micropipes in order to achieve better temperature uniformity. Compared to the original reactor, the standard deviation of the electric field decreased significantly when using the optimized reactor under the same heating conditions while the average electric field density increased. The optimized results were verified by experiments. [ABSTRACT FROM AUTHOR]

Microwaves have been widely used in organic chemical syntheses, but the mechanism is still unclear. The aim of this paper is to study the polarization of polar molecule reactions in the liquid phase. A novel model is proposed to describe the polarization of chemical reactions. In this model, the polarization is expressed by the summation of the orientational polarization of the liquid mixture and the polarization increment due to the chemical process. On the basis of the assumption of local equilibrium, the chemical process is divided into a series of equilibrium systems. We derive the general expression for the polarization increment according to the mass balance equations. By considering a simple chemical process, we give a specific expression for the polarization. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

ABSTRACT The transparent antenna can potentially be combined with solar cells to create multifunctional compact systems. In this article, an optically transparent broadside antenna is presented. Based on a meshed patch antenna which has three horizontal lines and three vertical lines, the antenna has four more lines to increase the bandwidth. The antenna is fed by a top fed for simple structure, and the area of the feed line is much smaller than the one of a side fed. The transparency is much better because of the low ratio of metal area, which can be further reduced without destroying the performance of the antenna. The transparent broadside antenna is studied at 2.5 GHz. On the upper surface of the antenna, the ratio of metal area is 3.2%, and the measured −10 dB impedance bandwidth is close to 60 MHz. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:146-149, 2015 [ABSTRACT FROM AUTHOR]

This Letter reports a high isolation diplexer using stub‐loaded resonators (SLRs). Each SLR can generate one transmission pole and one transmission zero (TZ). By changing the length of the open stub, the frequency of the TZ can be adjusted. The upper channel filter using the capacitive coupled SLRs can have TZs above the passband, while the lower channel filter using inductive coupled SLRs can have TZs below the passband. With those TZs, the isolation of the diplexer is greatly improved. A high isolation diplexer is designed and fabricated to validate the design concept. [ABSTRACT FROM AUTHOR]

In this article, a novel microstrip grid array antenna is presented. For achieving a high gain and good impedance match, its structural parameters were optimized by a parallel genetic algorithm. A prototype antenna measures a gain of 18.3 dBi with an input return loss of -15.0 dB at its working frequency of 2.45 GHz. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2976–2978, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23856 [ABSTRACT FROM AUTHOR]