In this paper, a bandwidth improvement technique in SIW slotted antennas is presented. Distinct from conventional SIW antennas with multiple cavity modes, a single cavity mode (TE₂₁₀) is utilized to improve the bandwidth. When a rectangle slot is loaded at bottom surface of the cavity, the TE₂₁₀ cavity mode is perturbed. As a result, two independent modes (odd TE₂₁₀, even TE₂₁₀) are introduced and merged in close proximity. Finally, the antenna is fabricated and tested. The measured results render an impedance bandwidth of 12.8% and a maximum gain of 7.1 dBi. The cross-polar level of maximum -29 dB and -34 dB is at 9.73 GHz and 10.63 GHz, respectively. The proposed design holds many features such as easy fabrication and light weight. Besides, the proposed design is a single-layered that makes it extremely convenient to integrate with other planar configurations.

This paper presents the analysis and design of in-phase/out-of-phase power dividers with compact-size and ultra-wideband characteristics. The proposed designs are composed of a T-junction microstrip (MS)-to-slotline power divider with a shorting via and two slotline-to-MS transitions. The phase response at the outputs can be controlled by arranging the MS-line direction of the transition, i.e., the same direction results in the in-phase, whereas the opposite MS-line directions reverse the electrical field, thus resulting in the out-of-phase. Thanks to utilizing the MS-to-slotline power divider and circular slots and circular stubs at the transitions, the proposed structures achieve ultra-wide bandwidth and compact size simultaneously. The dividers are theoretically analyzed using transmission-line equivalent circuit, and then verified computationally and experimentally. Simulation and measurement indicate that the proposed power dividers yield ultra-wideband performance across 1.2-11.0 GHz (~160%) with magnitude difference ±0.5 dB and phase difference ±5° at the outputs. As an example of application, a differential-fed Vivaldi antenna fed by the proposed out-of-phase power divider is implemented. The antenna yields a 160% bandwidth (1.2-11.0 GHz) for 10-dB return loss and a stable end-fire radiation within the whole impedance bandwidth.

This paper presents a low profile and low-cost patch antenna with dual circularly polarized (CP) capability in X-band at a canter frequency of 8.3 GHz. The dual-CP antenna is divided into three layers, composed of a parasitic square patch, radiation square patch with four equal arms, and 90˚ patch coupler. Two arms of the radiation patch are connected to the 90˚ hybrid coupler using two metalized vias. right-handed circular polarization (RHCP) and Left-handed circular polarization (LHCP) is achieved by exciting two different ports. To validate the proposed design, the prototype of dual-CP antenna is fabricated and measured. Based on the measurement, the structure of proposed antenna has an excellent circular-polarization purity of less than 3-dB over the whole operational frequency bandwidth of the antenna (8 GHz-8.47 GHz) with a wide 3-dB axial ratio (AR) beamwidth of 133˚ across the angular range from -55° to +78° at 8.3 GHz.

This article presents a novel electrically small asymmetric coplanar strip (ACS) fed metamaterial inspired antenna for quad band operation. A metamaterial inspired open split ring resonator (OSRR) is the radiator which is fed using ACS to obtain four operating bands. The proposed antenna with a compact size of 18 mm × 15.5 mm × 1.6 mm is fabricated and tested. The experimental results are in good compliance with simulated ones. The proposed electrically small antenna has a radian sphere (ka) of 0.65 and achieves an average gain of 2.24 dBi with requisite radiation properties suitable for WiMAX and WLAN applications.

In this paper, novel mode switchable microwave coupled line couplers on ferrite substrates are presented. The couplers are realized in Composite Right/Left Handedcoplanar waveguide configurations. Two different types of mode switchable couplers are proposed. The first one can switch the power from the backward coupling port to the through port. The second one can switch the power from the backward coupling port to both the through and forward coupling ports. In both cases, the mode switching is achieved by varying the applied DC magnetic bias. The theoretical analysis of the switching mechanism has been carried out based on the general coupled mode approach. The analysis is then verified numerically and experimentally. The measurement results confirm the switching functionalities of the fabricated couplers with better than 10 dB isolation between the switched signals. Moreover, these novel mode switchable couplers are compact and require very low external DC magnetic bias due to their CPW configurations. These new proposed switrches can be applied in the smart microwave compoennts in different radar/communication application.

A novel compact two-side anti-metal tag antenna for radio frequency identification (RFID) applications is proposed in this paper. The proposed tag antenna is composed by three aluminum patches separated by two layers of foam substrates. Particularly, the middle patch of the antenna is designed as three nested deformable rings for the miniaturization of antenna and realizes better power transmission coefficient (PTC) between the antenna and tag microchip. The antenna operates at the center frequency of 915 MHz and maintains a compact size of 35 mm × 22 mm × 2.15 mm (0.1068λ₀ × 0.0671λ₀ × 0.0066λ₀). When the front or back side of the tag antenna is mounted on a large background metallic plate and tested with an effective-isotropic-radiated-power (EIRP) of 4 W, the antenna can achieve the maximum read distances of 6.23 m or 6.08 m. The tag antenna shows various advantages, including small size, low profile, and good antenna performance. Most importantly, the proposed tag antenna has two-side anti-metal property compared to a traditional single-side anti-metal antenna, which fulfills the emerging demands in the industrial internet of things field.

Limited endurance has become a bottleneck restricting the wide application of unmanned aerial vehicles (UAVs), and wireless power transfer (WPT) technology is expected to become an effective means to help UAVs break this bottleneck. UAV has strict restrictions on the weight of onboard system, so the lightweight design of the receiving side has become the core goal of UAV WPT systems design. In order to achieve this goal, this paper first proposes a novel magnetic coupler based on hollow copper-coated aluminum tubes, in which the receivers act as both landing gears and energy pick-up. The coupling mechanism of the magnetic coupler is analyzed. Secondly, based on the LCC-S resonant compensation network with a simple structure on the receiving-side, the system circuit is designed, and the system transmission model is established. Finally, a UAV WPT prototype is built and tested. The experimental results show that the transmission power of the designed system can reach 157 W, the overall efficiency 80%, and each receiver (also acting as landing gear) weight only 22 g. The weight power density ratio is 3.568 W/g.

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.