The aim of this work is to provide a miniaturπized antenna pair, which has a smallest size of 5 mm × 25 mm (about 0.04λ × 0.20λ at 2.4 GHz) among the recent laptop antennas and yet is capable of 2.4/5/6 GHz Wi-Fi 6E operation with acceptable isolation. The antenna pair comprises two small and symmetrical antenna units. Each unit is identical in geometry and has a coupling strip and a parasitic strip with an in-series inductor. The back-to-back unit arrangement helps better isolation in the 2.4 GHz band. A decoupling coupled strip is introduced between the units with a 5 mm spacing. This floating strip of a half wavelength at about 5.36 GHz attracts the surface currents of one unit excited in the 5/6 GHz bands, which in turn helps much decreased currents entering the port of the other unit. As a result, enhanced isolation can also be achieved in the upper bands.

Flat band systems have attracted considerable interest in different branches of physics, providing a flexible platform for exploring the fundamental properties of flat bands. Flat band states in the continuum (FBICs) can be derived from a one-dimensional lattice loaded with electromagnetically induced transparency (EIT) medium. The appearance of the strong slow light phenomena has been found under the conditions of EIT and flat band. Flat bands provide a key ingredient in designing dispersionless wave excitations. Different from the conventional flat band states, the FBIC is delocalized state and has robustness, providing us an efficient way to achieve large delay slow light. These results may provide inspiration for exploring fundamental phenomena arising from FBICs.

In this paper, we present a planar array for near-field shaped focusing. A near-field synthesis method for forming a special pattern on the focal plane is investigated. The phase and amplitude of the array are adjusted by digital phase shifters and attenuators. Prototypes are fabricated and measured to verify the effectiveness of this method. Near-field shaped focusing performances with square and triangular patterns are realized respectively. The experimental results show that the method can focus the electric field to a designated area clearly. Our work can provide a reference for applications such as microwave hyperthermia and wireless power transfer.

Magnetic gears (MGs) have many advantages over mechanical gears, including high efficiency, no contact, no lubrication, and low noise. Even though MGs are energy-efficient, cogging torque and torque ripple are always challenging, especially at low-speed applications. Generally, the cancellation of cogging torque enhances the performance of the operation of PM machines. This article proposes an approach based on slicing technique through which reduced cogging torque and improved torque density can be achieved in MGs. The two-dimensional finite element method (2D FEM) has been used to analyze the models using Simcenter and MATLAB software packages. The results show that the elimination of cogging torque of the proposed models compared to the base model is 97.53% on the inner rotor, and that of the outer rotor is 42.23%. Also, the torque density is slightly improved by 0.05% on the inner rotor while 0.1% improvement on the outer rotor is obtained.

The linear sampling method (LSM) is a very popular method for determining the boundary of an object from the scattered field. However, there are instances where LSM provides the convex hull of the boundary rather than the true boundary. There are two common generalizations to LSM: the Generalized Linear Sampling Method (GLSM) and the Multipoles-based Linear Sampling Method (MLSM). In this paper, the ability of GLSM and MLSM to overcome some of the deficiencies of LSM are investigated. It is found that GLSM may be ideal for imaging thin features of scatterers and that MLSM can provide an improvement over LSM in a more general sense. GLSM may also require user input to adjust the indicator function whereas MLSM does not appear to rely as much on indicator function adjustments for adequate results.

Uncertainty analysis is one of the hot research issues in the field of computational electromagnetics in the past five years. The Method of Moments is a non-embedded uncertainty analysis method with relatively high computational efficiency, and has the unique advantage of not being affected by the ``curse of dimensionality''. However, when the nonlinearity between the simulation input and output is large, the accuracy of the Method of Moments is not ideal, which severely limits its application in the field of computational electromagnetics. In this paper, an improved strategy based on the central clustering algorithm is proposed to improve the expected value prediction results of the Method of Moments, thereby improving the accuracy of the overall uncertainty analysis. At the same time, the co-simulation technology of MATLAB software and COMSOL software is completed, then the accuracy and computational efficiency of the proposed algorithm in this paper are quantitatively verified. In this case, the clustering Method of Moments is effectively popularized in commercial electromagnetic simulation software.

Power-absorbing layers on a microstrip line prepared by 3D printing are investigated in this study. Polylactic acid (PLA) with added carbon is used in the 3D printing process for the preparation of the power-absorbing layers. The S-parameters of the 3D-printed layers are measured using a vector network analyzer. The effect of the layer thicknesses on the power absorption, which enables high-frequency devices to function correctly, is discussed. As the layer thickness increases, the magnitude of S₁₁ increases, while the magnitude of S₂₁ decreases accordingly. The experimental results show that the power absorption is within 80-95% (sheet resistance: 75.1 Ω/□-823.76 Ω/□), in the frequency range of 2-6 GHz. In addition, simulated S-parameter analysis was performed using a high-frequency structure simulator. The simulation results are in good agreement with the experimental results.

This paper presents a low-cost antenna integrable to a large set of indoor common building materials. Employing the printing technology on thin transparent polyethylene terephthalate material and using available building materials not only leads to a low-cost environmentally friendly solution for the expected massive sensor deployment but also eliminates the dispersive behavior of the materials that are interacting with them. A coplanar-strips fed fractal folded antenna element was designed and validated experimentally with four different materials including gypsum, plywood, and plexiglass. The aesthetically viable ground-free antenna achieves wideband performance and radiates in the broadside plane perpendicularly to the wall. The single antenna element covers the frequency band of 2.18-3.96 GHz with a gain of 1 dBi at 2.4 GHz. To take advantage of the large available surface, a high efficiency 2.4 GHz array rectenna for powering electronic devices intended for IoE technology is proposed. The proposed array rectenna has a dimension of 384×354×6.475 mm³ and employs a single diode as the rectifier element. The measured results for the presented array rectenna reveal an AC-DC power-conversion-efficiency (PCE) of more than 20% for input powers as low as 0.025 μW/cm² with a peak PCE of 61.3% at 4.03 μW/cm².

A fundamental building block in characterizing and tackling scientific and industrial questions boils down to the ability of quickly solving mathematical equations. However, with the ever-growing volume of information and unsustainable integration growth in electronic processors, a radically new modality for solving equations is highly imminent. Here, we introduce an electromagnetic counterpart to solve multivariable complex equations, where two metamaterialkernels are connected in series to form a closed-loop electromagnetic system. Complex-valued information is carried by electromagnetic fields, and the equation solution for arbitrary input signals can be recursively attained after a number of feedbacks. As an illustration, we present the capability of such system in solving eight complex equations, and inversely design two 4 × 4 metamaterialkernels by topology optimization, whose average element error is reduced to smaller than 10^-4. Having accomplished all unknown coefficients with high fidelity, our work represents a conspicuous apparatus for a myriad of enticing applications in ultra-compact signal processing and neuromorphic computing.

In order to improve the reliability and continuous navigation of ship propulsion, a diesel-electric hybrid field modulation motor with bread-loaf eccentric magnetic poleis proposed in this paper. The permanent magnet of the inner rotor of the motor adopts a bread-loaf eccentric magnetic pole structure and is embedded and fixed on the iron yoke of the inner rotor. The structure can obtain a sinusoidal air gap magnetic field, to reduce the torque ripple of the motor. In this study, some key parameters of the motor are optimized by using the optimization strategy of the combination of genetic algorithm and finite element method. In addition, compared with the conventional magnetic field modulation motor with surface mounted permanent magnet, the motor has a stronger rotor structure. The back-EMF, torque and loss of the motor are calculated. The proposed motor has good sinusoidal back-EMF, less loss, and better stability. Finally, the working modes of the motor in the diesel-electric hybrid ship propulsion system are mainly diesel internal combustion engine driving mode, electric propulsion mode, and hybrid propulsion mode. The system can improve the reliability and continuous navigation of the ship propulsion system.

In the wireless power transfer (WPT) system of electric vehicles, low electromagnetic field (EMF) shielding will reduce transfer efficiency. How to reduce leakage EMF and obtain a high transfer efficiency is a difficult problem. In this paper, a double inverse series coil (DISC) structure is proposed to reduce the leakage EMF of WPT systems. First, a calculation method of EMF for rectangular coils is proposed, and the leakage EMF distribution characteristics of the coil structure on the target surface are analysed according to the proposed calculation method. Secondly, an optimization method with the optimal leakage EMF effect of the target surface is given. The parameters of each coil that meet the design requirements are obtained based on the proposed optimization method. Finally, according to the obtained coil parameters, a set of WPT system based on DISC structure is developed, and the correctness of the proposed structure and method is verified by simulated and measured results. The results show that with applying the DISC structure, the maximum leakage EMF in WPT system is only 9.56 μT on target surface without additional shielding, and the transfer efficiency is up to 95%.

This paper presents an efficient Taguchi-preconditioned genetic algorithm (TPGA) strategy for the design optimization of a 630-kW permanent magnet vernier motor (PMVM). In the TPGA, firstly, the Taguchi method is combined with comparative finite element analyses (FEA) to judge the influence factors of six typical structural parameters on the torque output. Secondly, four influential parameters are taken from the six typical ones and decided as the variables in the global optimization processes coupling genetic algorithm (GA) and FEA. As two variables with small influence factors are set to constants in the computationally costly optimization processes, the calculation burden can thus be effectively reduced. Thirdly, with the four influential optimization variables, FEA-assisted GA is used to maximize the output torque of the PMVM. During the global optimization processes, a preliminarily optimized structural configuration obtained from the Taguchi analyses is used as the initial values of the variables. Finally, the working performances of the machine with the optimal parameters are obtained through FEM calculations. The optimization effectiveness is validated by comparing the output torque of the GA-optimized machine with that of the initial and the Taguchi-preliminary optimized ones.

A high-performance photonic crystal fibre-based alcohol biosensor is introduced for the selective test analytes: propanol, butanol, and pentanol operating at wavelengths ranging from 0.8 to 2.0 µm. The performance of the proposed sensor with the architecture of octagonal-shaped cladding air holes in two rings surrounding a single infiltrated hexagonal core hole produces high relative sensitivities, low confinement losses, small effective areas, and high nonlinear coefficients. At the optimal 1.4 µm wavelength, propanol, butanol, and pentanol assessed relative sensitivities of 93.10%, 93.95%, and 94.70%, respectively, and confinement losses of 6.38 × 10^-10 dB/m for propanol, 2.12 × 10^-10 dB/m for butanol and 1.04 × 10^-10 dB/m for pentanol. Moreover, the nonlinear coefficients achieved results of 2446 W^-1km^-1 for propanol, 2703 W^-1km^-1 for butanol, and 2869 W^-1km^-1 for pentanol, at the optimum wavelength. These outstanding results of optical properties prove the potential and capabilities for practical sensing and optical communication applications.

As a noninvasive imaging technique for the interior of objects, Electrical Impedance Tomography (EIT) is widely used in many fields of biomedicine. Sparse reconstruction algorithms have made major breakthroughs in the field of image reconstruction in recent years. The K-SVD algorithm is an adaptive dictionary signal sparse representation algorithm, which could improve the reconstruction accuracy. However, the parameters in the K-SVD algorithm are fixed, which cannot match all the measurement data of EIT very well. Moreover, the K-SVD algorithm adopts a greedy algorithm in the sparse coding stage, which has high computational complexity. In this study, an electrical impedance sparse imaging method based on DK-SVD (deep k-singular value decomposition) was designed. It provides the corresponding optimal model parameters for each set of measurement data through the method of multi-layer perceptron (MLP) network training, thereby improving the imaging quality. At the same time, the iterative soft threshold algorithm (ISTA) is used in the sparse coding stage to improve the convergence speed. The reconstruction results show that compared with the K-SVD algorithm and Total Variation (TV) algorithm, the reconstruction error of the DK-SVD method is smaller, and the irregular and sharp inclusions can be accurately reconstructed. Image artifacts are also greatly reduced.

The design procedure for UWB balun realized in the microstrip technology is proposed in the paper. The procedure applies Artificial Neural Network which corrects the dimensions of the approximate design found by appropriate scaling of the dimensions of the prototype. The scale coefficients for longitudinal and transverse dimensions of microstrip lines are determined from electromagnetic modeling based on transmission line equations. The scaling procedure of radial stubs is also proposed. The design procedure was verified experimentally for exemplary balun with radial stub.

Robust optimization design of brushless electrically excited synchronous machines (BEESMs) is a problem that has received extensive attention. The increase in finite element calculation cost due to the increase in the number of motor parameters is one of the main problems faced by optimization. In this paper, a robust multi-objective optimization design method of BEESM based on an improved hill-climbing algorithm is proposed. All design parameters are divided into three subspaces according to the sensitivity by the sensitivity analysis method combined with Kendall's rank coefficient, thereby reducing the consumption required for FEM calculation. The screening problem of Pareto frontier solutions is solved by an improved hill-climbing algorithm. The candidate points to be optimized are screened through the improved climbing algorithm, and only the candidate points located on the Pareto frontier will be optimized, which ensures the high performance of the candidate points. Based on the noise problems that may occur in actual production and processing, the candidate points are robustly analyzed, and the optimal design is screened out. The robust optimization design method proposed in this paper can reduce the computational cost and improve the robustness of the motor based on improving the performance of the motor.

The design and analysis of a dual-band two-port multiple-input-multiple-output (MIMO) antenna with high isolation suitable for fifth-generation (5G) and wireless local area network (WLAN) applications are introduced in this paper. On the top of the substrate, the proposed antenna element is mainly composed of a defected circular ring with an L-shaped strip, an F-shaped stub, and an L-shaped stub. The bottom of the substrate comprises two rectangular defected ground structures and a neutral line with two Y-shaped stubs. The antenna isolation structure is employed to minimize the coupling between antenna elements, which is larger than 15 dB. The overall dimension of the proposed two-port MIMO antenna is approximately 45 mm × 45 mm × 1.59 mm. The measured -10 dB impedance frequency bands include 3.28-3.72 GHz and 4.44-5.92 GHz, which can cover 5G (3.3-3.6 GHz and 4.8-5 GHz) and IEEE 802.11 a/ac/ax (5.15-5.35 GHz and 5.47-5.85 GHz). The measured efficiency is greater than 60% and 55% at the lower and higher frequency bands. The measured peak gain ranges from 4 dBi to 5.8 dBi in both operating frequency bands. The proposed MIMO antenna is feasible for the 5G and WLAN applications.

In this paper, a compact triangular-shaped multiband Antenna is proposed for linear as well as circular polarization. The proposed Antenna is well-suitable for Wi-Max, C-band, and X-band applications. 2.4 GHz is very well suitable for RFID applications. The antenna is excited with a feed of variable width at one corner of the main patch. The parametric analysis has been done for feed width, slot cutting on the ground, and tapering cut at both remaining corners of the main patch. Circular polarization is achieved due to a tapering cut. It achieved circular polarization at 2.4 and 9.8 GHz and linear polarization at 4.31 and 6.75 GHz. The structure shows an impedance bandwidth of 2.13-3.02 GHz and 4.01-10.00 GHz. The measured peak gain is achieved to be 3.66 dB. A good agreement is found between simulated and experimental results.

A novel quad-band bandpass filter (BPF) consisting of two deformed W-shaped microstrip Stepped-Impedance Resonators (SIRs) with different dimensions is proposed. The W-shaped SIRs are miniaturized from E-shaped SIRs, and each one of the SIRs generates two passbands, and thus four passbands centered at 3.18 GHz, 4.51 GHz, 5.46 GHz, and 8.43 GHz with fractional bandwidth of 6.7%, 9.1%, 8.4%, and 8.2% were obtained. Compared with the basic SIR structures and E-shaped structures, the effective area of the miniaturized SIR is reduced by more than 60% and 20%, respectively. The operating frequency bands can be determined by switching the diodes that are connected to the cross coupling lines of the two SIRs. The improved design can be used for 5G and other applications.

A super wideband antenna is proposed to operate in the frequency band 2.2-22 GHz. The antenna has two planar arms printed on the opposite faces of a three-layer dielectric substrate. Each arm of the antenna is capacitively coupled to a circular ring near its end to increase the impedance matching bandwidth. The dielectric substrate is customized to fit the shape of the antenna arms and the parasitic elements to reduce the dielectric loss. The substrate material is composed of three layers. The upper and lower layers are Rogers RO3003^TM of 0.13 mm thickness, and the middle layer is made of paper of 2.3 dielectric constant and 2.7 mm thickness. The antenna is fed through a wide band impedance matching balun of a novel simple design. A prototype of the proposed antenna is fabricated to validate the simulation results. The experimental measurements are in good agreement with the simulation results, and both of them show that the antenna operates efficiently over the frequency band 2.2-22 GHz with minimum radiation efficiency of 97% and maximum gain of 5.2 dBi. The antenna has a bandwidth to dimension ratio (BDR) of 1755.