In dynamic wireless charging systems for electric vehicles (EVs), the coupling mechanism is difficult to align, which leads to high output voltage fluctuations and low transmission efficiency of the system. A reverse series double-layer symmetrical coil (RSDSC) structure with magnetic core is proposed. First, the mutual inductance characteristics of this structure are analyzed based on its coupling structure. Secondly, a mutual inductance optimization method is proposed to obtain the optimal values of each parameter of the coil and the optimal values of the magnetic core parameters. Finally, a wireless power transfer system is built based on the obtained coil and magnetic core parameters, and the correctness of the structure is verified through simulation and experimentation. The results show that the maximum mutual inductance fluctuation of the structure of RSDSC with magnetic core is only 4.88%, and the efficiency is up to 97.86% when the receiving coil is offset within 50% (20.8 cm) of the outer length of the transmitting coil.

A novel design of a dumbbell shape quad elliptical slotted (DSQES) antenna for directive ultra-wideband (UWB) integrated with WCDMA, WLAN, and mid-band of 5G applications is presented. Initially, a circular patch is designed by inserting four elliptical slots in radiator with a rectangular slotted ground plane. To realize ultra-wide impedance bandwidth, three symmetrical stepped rectangular slots are inserted in ground below a stepped-quarter-wave transformer feed line. The proposed antenna achieves fractional bandwidth (FBW) of 104% (S₁₁ < -10 dB) which covers UWB frequency range of 5.4-17.3 GHz at resonant frequencies 5.8/7.4/10.3/12/15.7 GHz. Further, a ground structure is customized by loading two asymmetrical meander strip resonators (MSRs), which provides extra lower frequency bands 2.1 GHz (1.96-2.21 GHz) and 3.5 GHz (3.22-4.07 GHz) for WCDMA, WLAN, and 5G mid-band applications, respectively. Furthermore, the measured gain and half-power-beam-width (HPBW) are 1.7-6.4 dBi and 75°-20° in 5.4-17.3 GHz UWB, respectively. The optimized dimension of proposed antenna is 30×30 mm² which is simulated on Computer Simulation Technology (CST) electromagnetic simulator using an FR-4 substrate of thickness 1.6 mm and dielectric constant 4.3. The simulated structure is computed by ADS simulator, and simulated results are validated with measured ones.

A dual-band dual-sense (DBDS) circularly polarized (CP) filtering dielectric resonator antenna (FDRA) with a quasi-elliptic band-pass response is proposed in this paper. The proposed antenna consists of a rectangular dielectric resonator (DR) with a Z-shaped strip at the top, a ground plane with a rectangular slot, and a microstrip feedline etched with a section of the spur line. By using the microstrip coupled slot line structure to excite DR with a Z-shaped strip, different senses of circular polarization are achieved in the two bands. The results show that the lower and upper bands are independently controlled by the strip and the DR, respectively. In addition, three radiation nulls are generated at the passband's edge by elaborately designing a half-wavelength open stub and etching the spur line. For demonstration, a prototype DBDS CPFDRA is fabricated and measured. The measurements illustrate that the antenna achieves a wide impedance bandwidth of 38.2%, as well as a dual axial ratio (AR) bandwidth of 2.2% for the left-hand circular polarization (LHCP) and 4% for the right-hand circular polarization (RHCP). The realized gain exhibits a decline of 25 dB at the passband edge, indicating high selectivity.

When demagnetization occurs, direct-drive permanent magnet synchronous wind generator exhibits problems of poor dynamic performance, weak immunity to disturbances and speed fluctuations. Aiming at these problems, this paper proposes a cascaded linear active disturbance rejection control method. First, the mathematical models of the generator during normal operation and demagnetization are described. Second, the linear active disturbance rejection controller (LADRC) for the speed and current loops is designed. The compensation for demagnetization disturbances at the speed loop's input is enabled by the control approach. The current output of the speed loop is imported as a rated value into the LADRC of the current loop. At the same time, the current is compensated at the input. Compensated speed and current accurately track the given values, and the goal of achieving demagnetization fault tolerance is met. Finally, this method is compared with dual-loop Proportional Integral (PI) control. The experimental results affirm that, under this control method, when demagnetization occurs, the speed fluctuation is reduced by 95.7%, the current response time decreased from 0.01 seconds to 0.001 seconds, and the electromagnetic torque ripple amplitude reduced by 50%. These experimental results fully validate the heightened fault tolerance and resistance to interference exhibited by the method advocated in this paper.

A Sierpinski Gasket Fractal Structure embedded in an Octagonal Microstrip Printed Monopole Antenna is proposed. The prototype is mathematically developed in a miniaturized cross-sectional area with ultra-wide resonance. A fractal design resembling a third-order Sierpinski gasket is applied to the octagonal radiator in a mutually proportional manner, increases the radiation across the entire surface area by extending the effective length of the dielectric. Additionally, the partial ground alters the resonant modes of TM11 and TM21 to a second-order iterative response via two contactless slots. Also, the driven radiator exhibits Fractional Bandwidth (FBW) of 156% spanning at 2.65 GHz-21.6 GHz, along with a peak gain 6.23 dB. The fabricated prototype demonstrates excellent agreement during testing and measurement using a microwave analyzer and an anechoic chamber, respectively. The proposed antenna covers resonance for applications at the S, C, X, and Ku bands. Also, it completely envelopes the Ultra-Wideband (UWB) and Sub-6 GHz 5G spectrum.

In the wireless power transfer (WPT) system of electric vehicles, the system leakage magnetic field and transmission efficiency depend on the coil structure, and the traditional unipolar coil has high transmission efficiency but generates high leakage magnetic field. In order to maintain the transmission efficiency while reducing the magnetic leakage and improve the safety index of the WPT system, this paper proposes a bidirectional inverse series coil of four meshes structure (FBISC), which maintains the high transmission efficiency of the WPT system only by the advantages of the coil structure without applying any metal materials and shielding coils. At the same time, the leakage field produced by the coil structure of the target area is less than the safety limit value, which makes the traditional shielding coils no longer necessary, and is light, clean, and highly efficient. First, the leakage magnetic field generated by the coil in the target region after energization is analytically calculated using a vector potential-based method for calculating the magnetic induction strength of rectangular coils. Secondly, a coil parameter assignment optimization method that weighs two structural performance indexes, namely, transmission efficiency and leakage magnetic field, is given to obtain the coil parameters that satisfy the given conditions. Furthermore, the proposed coil structure is compared with the conventional coil structure. Compared with the conventional unipolar coil, the bidirectional inverse series coil of four meshes reduces the leakage magnetic field by 56.4% and sacrifices only 2.38% of the transmission efficiency. Compared with the reverse double D coil (DD coil), the bidirectional inverse series coils of four meshes reduces the leakage magnetic field in the target region by 48.5% and sacrifices only 1.3% of the transmission efficiency. Finally, an electric vehicle WPT system with shielding is built to verify the correctness of the proposed structure. The results show that the leakage magnetic field of the FBISC coil structure in the target region is only 5.22 μT, and the transmission efficiency is more than 95% at an output power of 4 kW.

A compact spoof surface plasmon polariton (SSPP) low-pass filter is proposed. By adopting a novel fishbone structure, the effective depth of the groove is increased, reducing the filter width by 24.84%. The length of the filter is reduced by 22.23% with a new transmission structure. To intuitively display this structure, the filter is designed and fabricated. The area of the filter is 47.44 mm × 8 mm. The results demonstrate that the insertion and return losses are less than 3 dB and greater than 13 dB, respectively, in a wideband range of 0-10.00 GHz.

This article aims to exploit Ricci tensor with certain geometric properties which are used for feature representation and ship detection in synthetic aperture radar (SAR) image. The proposed method is composed of the following key points. Firstly, Riemannian metrics on the Gamma manifold are constructed based on the family of Gamma density functions. Secondly, direct calculation gives the Ricci tensor of Gamma manifold, where the curvature tensor resorts to the torsion-free affine connection. Thirdly, a general scheme for Zermelo navigation problem on the Riemannian manifold is addressed, and the solution of the navigation problem is proposed. Fourthly, feature representation problems are formulated as certain forms of Finsler metric of Randers type, indicating a joint framework for extracting low-dimensional features with closed-form solutions. Comprehensive experiments on real SAR image data sets demonstrate the effectiveness of the proposed method against compared state-of-the-art detection approaches.

A low-profile ultra-high frequency (UHF) radio frequency identification (RFID) tag antenna for double-sided anti-metal applications is proposed. The antenna comprises a middle layer of radiation patch, which is sandwiched between two layers of foam substrates, each with a thickness of 0.5 mm, and flanked by two layers of ground plane. A rectangular loop is designed on the radiation patch to expand the frequency band and optimize impedance matching. Particularly, one side of the radiation patch is shorted to the ground through a slotted stub to reduce the antenna size. The tag antenna is compact with a dimension of 38 mm × 20 mm × 1.15 mm (0.1159λ × 0.061λ × 0.0035λ at 915 MHz). When the two ground planes are individually mounted on metallic objects, the read distances are 5.4 m and 5.2 m, respectively. The proposed tag antenna demonstrates double-sided metal resistance, making it highly suitable for use in the industrial internet of things field.

A broadband circular arc-shaped slot antenna is proposed in this paper which operates from 25.1 GHz to 31.5 GHz. The antenna is based on a substrate-integrated waveguide (SIW) and fed through a grounded coplanar waveguide (GCPW). A circular arc-shaped slot is presented instead of a conventional narrow rectangular slot to extend bandwidth performance. The slot antenna generates six closely resonant frequencies by exciting high-order modes, which help get a broadband response. Antenna's prototype is fabricated using the standard Printed Circuit Board (PCB) process. The results of its measurement show that the antenna achieves an impedance bandwidth of 22.6% at 28 GHz and a peak gain of 11.5 dBi. The efficiency in the operating bandwidth is more than 85%. The antenna shows the merits of low-profile, high-gain, and broadband characteristics, which are very suitable for mm-wave wireless communication systems.

In the context of 6G communication technology, Reconfigurable Intelligent Surfaces (RIS) can effectively reconfigure signal propagation paths through the adjustment of their passive metamaterial reflector units. This capability mitigates the issue of radio wave attenuation in the complex environments of mine tunnels by optimizing signal paths, thereby reducing energy loss and minimizing coverage dead zones. By utilizing RIS-assisted multi-antenna terrestrial mobile communication channels and ray tracing techniques, researchers have established a wireless channel fading model specifically for rectangular coal mine tunnels. The results suggest that under comparable conditions, RIS technology enhances low-frequency signals (e.g., 2.4 GHz) more effectively than high-frequency signals (e.g., 30 GHz). Furthermore, these improvements are more pronounced as the size of the RIS increases.

In this study, an optimal multi-band microstrip fed metasurface antenna is designed. Three by three non-uniform circular radiating cross slotted elements make up the antenna's metasurface. The metasurface is analyzed using characteristic mode analysis (CMA), and the Modal Significance (MS), Characteristic angle (CA), and Eigen Value (EV) curves are utilized to optimize the antenna's performance. In addition, surface currents are examined for the metasurface and patch using CMA, and the design incorporates microstrip feeding to excite the targeted frequency bands. With its resonance frequencies of 5.4 GHz, 8.9 GHz, 12.8 GHz, 15.9 GHz, and 19.8-31.58 GHz, the developed antenna has potential uses in 5G and wireless communications. The suggested antenna achieves a gain of 10.05 on average. The prototyped model conformability analysis of the antenna is also performed, and good matching with simulation results is found.

A design of compact planar SIW filter with notch band characteristics is proposed. Double split square complementary split ring resonators are used to realize the ultra-wide band (UWB) characteristics. Proposed UWB filter contributes a passband from 2.9 GHz to 10.3 GHz with minimum insertion loss 0.7 dB at 3.7 GHz and maximum of 1.84 dB at 7 GHz. By employing complementary split ring resonator in the ground plane, a narrow band characteristic is obtained to reject the undesired wireless local area network (WLAN) signals. The notch band frequency ranges from 5 GHz to 5.7 GHz with insertion loss of 14 dB at center frequency. The 3 dB fractional bandwidth in the notch band is 12.9%. The variation of group delay less than 0.5 ns in the passband range. Overall size of the proposed filter is 0.35λ_g × 1.06λ_g. Because of these salient features, the proposed filter can be used for space applications.

Simultaneous realization of load-independent dual-type output, namely constant current output (CCO) and constant voltage output (CVO), is necessary in some wireless power transmission (WPT) application fields. Therefore, an S-CL compensated WPT system with dual-type output function is proposed in this paper. This proposed system consists of a two-coil loosely coupled transformer（LCT）which can avoid cross-coupling phenomena, a transmitter-side compensation capacitor, a receiver-side compensation capacitor and a receiver-side compensation inductor. Meanwhile, the proposed system can achieve near zero-phase-angle (ZPA) and zero-voltage-switching (ZVS) operations, avoiding power losses caused by reactive circulation. In addition, the theoretical analysis of the system's constant voltage and constant current outputs are further elaborated in this paper, and a test prototype is fabricated to verify the rationality and implementability of the proposed WPT system.

To solve the issue of chattering that occurs during the estimation of the rotor position in the permanent magnet-assisted synchronous reluctance motor using the conventional sliding mode observer (SMO), the saturation function is used in this paper instead of the original sign function to reduce its jittering effect; to solve the problem of phase delay caused by the low-pass filter (LPF), the adaptive law is implemented as a substitute for the LPF. This allows for a smoother back electromotive force and eliminates the need for position compensation caused by phase delay; finally, the phase-locked-loop (PLL) technique is used to extract more accurate rotor position information. A 3 kW permanent magnet-assisted synchronous reluctance motor is taken as the control object, and a simulation model of the control system is established. The results show that the improved saturation function adaptive SMO has higher level of accuracy in estimating rotor position information than the conventional SMO.

Wafer-level three-dimensional stacked integration technology is demonstrated in this paper, employing three gallium arsenide (GaAs) monolithic integrated circuits (MMICs) and gold (Au) bumps, and specifically designed for high-density and low-profile applications operating at millimeter-wave frequencies. A ground coplanar waveguide to ground coplanar waveguide (GCPW to GCPW) hot via interconnect has been developed to facilitate vertical transitions within a multi-stacked electromagnetic (EM) environment. Electrical connection between the upper and lower layers is achieved through 70 μm-height Au bumps. Compared to 2.5D packaging, this innovative structure exhibits an increased integration capability of more than three times within the same area, with a thickness of 0.451 mm. Ultra-wideband transmission between RF chips is achieved within a compact area of 0.16 square millimeters, enabling extremely short-distance interconnect for system-in-package configurations. Appropriate utilization of ground metal within the package ensures strict electromagnetic field confinement, preventing interference from adjacent circuits. The designed transitions were fabricated and characterized. The measured result has an insertion loss of less than 0.65 dB and return loss of better than 20 dB up to 40 GHz for a back-to-back structure. This integration technology can further enhance integration capability, reduce transmission loss, and improve electromagnetic isolation. The presented approach holds significant potential for applications requiring high-density integration and reliable performance in the millimeter-wave regime.

The magnetic field produced by overhead high voltage transmission lines has received extensive attention owing to its possible biological effects on humanity. The scientific community as well as general public are interested in the possible threats that living things may pose from the magnetic field. This research proposes a magnetic field mitigation approach near an overhead transmission line to avoid negative impact on the population around these lines. Apart from altering human brain activity and heart rate, magnetic fields can also lead to diseases like cancer. As a result, many techniques are employed to lessen that magnetic field. To reduce this magnetic field, scientists are looking for transmission line schemes. The suggested study investigates the influence of mechanical rearranging power conductors on magnetic field mitigation using genetic algorithm (GA) which is one of the evolutionary optimization techniques. The proposed GA has the objective to minimize the magnetic field as a fitness function and the location of conductors as genes considering their symmetry. The proposed method is tested using two published study cases of actual overhead transmission lines resulting in 48.4% and 57% reduction in magnetic field for case1 and case2, respectively. The contribution of the proposed method is to provide higher mitigation level of the mechanical rearrangement method depending on different sub-conductors spacing for one phase. The proposed mechanical rearrangement increases the geometric mean radius of the inner phase by optimizing its sub-conductors spacing within allowable critical ranges, thus the practical implementation of the proposed method requires a special design of the inner insulators string to support its sub-conductors.

In this paper, a very small 4-port MIMO antenna is designed, based on a metamaterial structure composed of embedded octagonal Split-Ring Resonators (SSRs). The antenna array shows an axial symmetry configuration with dimensions of 32 × 32 mm², corresponding to 0.157λ², approximately, related to a center frequency of 3.5 GHz, with a high electromagnetic isolation despite the radiators' closeness, reaching values bigger than 26 dB for adjacent antennas, and more than 28 dB for opposite antennas. The antenna is built on a substrate with dielectric permittivity of 2.2 and 1.27 mm thick. The Total Active Reflection Coefficient (TARC) presents a steady behavior for different random phases at the incoming signals, keeping a system bandwidth of 0.9 GHz for a -10 dB value. On the other hand, the Envelope Correlations Coefficient (ECC) reports values lower than 0.001 in all the antenna relationships, achieving a very uncorrelated performance of the electric fields in each element. The radiation pattern is quasi-omnidirectional, obtaining a low gain around -2 dBi, a trade-off that is considering the size reduction of the MIMO antenna.

Future 6G networks are anticipated to use reconfigurable intelligent surfaces (RISs) because of their capability to expand coverage, provide a customizable wireless environment, increase localization accuracy, etc. In this paper, RIS-aided localization is considered with orthogonal frequency division multiplexing (OFDM) and single-input single-output (SISO) downlink system in millimeter-wave (mmWave). An efficient beam sweeping (EBS) scheme is proposed accomplished by an RIS to scan the area of interest and estimate the direction of the user equipment (UE), i.e., the signal's angle of departure (AoD). The AoD with the measured signal time of arrival (ToA), from the RIS to the UE, is used to estimate the UE position. The ToA measurements can be obtained by exploiting the OFDM signal, while the beam sweeping can be obtained by carefully designing the RIS phase profile. The first step of the proposed EBS scheme is to scan the whole area of interest with equally spaced beam angles for coarse estimation of AoD. Then, based on this estimation, the RIS is reconfigured to sweep a slight angle's range by narrow beams to refine the AoD estimation. Besides, a multi-RIS scenario is proposed, and leveraging the EBS and the consensus fusion method is used to obtain accurate position estimation. Simulation results demonstrate that the proposed EBS in single and multi-RIS scenarios enhances positioning accuracy compared to linear beam sweeping (LBS) methods. Also, the impact of increasing the number of RIS elements and number of sweeping beams, as well as the number of RISs, is investigated thoroughly via numerical simulations. Furthermore, the achievable localization accuracy is assessed using the positioning error bound (PEB).

Aiming at the operational stability of DC-biased transformer, a multi-parameter correlation method based on electromagnetic coupling is presented in this paper. The mode-state analysis scheme is designed, and the feature parameters of electromagnetic, mechanical, and acoustic fields in internal components are simulated and analyzed. The electromagnetic properties under DC bias are simulated by the electromagnetic model, thus the winding current and magnetic flux density are extracted as the feature parameters. Then the vibration and stress distribution can be solved by the mechanical model, which are treated as the feature parametersof the mechanical field. By utilizing the computed mechanical information as excitation, the spatial-temporal distribution of sound pressure can be obtained in the acoustic model. Taking three-phase three-limb transformer and three-phase group transformer as examples, the electromagnetic, mechanical, and acoustic parameters of components are analyzed under different conditions. The variations of feature parameters are summarized and contrasted. Furthermore, actual vibration and noise parameters are measured through dynamic experimental platforms. The effectiveness of the multi-parameter correlation method is verified by the consistency between simulation and experiments, and the unobservable abnormal physical features can be represented by observable electrical information.