A reactive power shielding structure working under 150 kHz for small electronic equipment was proposed to reduce the electromagnetic leakage of WPT system. First, the model of LCC-LCC compensation circuit was established. By ensuring transmission efficiency, a comprehensive analysis of nine sets of computational data results was conducted to select the scheme with the best shielding effect. The experimental results showed that the magnetic flux density attenuation was 27.82% at 41 mm transmission distance from the center under the optimal structure of 3 rings and 7 turns, inner diameter of 23 mm and outer diameter of 35 mm. The transmission efficiency can reach 76.73%, which is only 1.32% lower than the situation without shielding. The proposed reactive power shielding structure can significantly reduce the magnetic flux density in the external area of the WPT system without affecting the transmission efficiency of the system.

This paper presents a novel bandpass filter with reconfigurable bandwidth or transmission zeros. The proposed filter is based on a multiple-mode stub-loaded resonator. Three PIN diodes are utilized as switching elements to achieve four switchable operating states. The measurement results indicate that the 3 dB fractional bandwidth (FBW) of the filter can be varied from 32.3% to 70% at the centre frequency of 2.2 GHz, and the stopband attenuation is higher than 35 dB. The filter size is only about 0.28λ_g×0.19λ_g.

A circular antenna array with omnidirectional mode and 360° continuously directional beam-scanning mode operating in 5G indoor communication band is reported. The proposed circular antenna array is composed of 16 subarray elements, and each element consists of two back-to-back E-shaped patch antennas with a differential feeding network. The beam-scanning mode is achieved by controlling the exciting amplitudes and phases of consisting subarray elements, which is optimized by using the extended method of maximum power transmission efficiency, so as to guarantee the maximum possible gain value. The operating frequency of the circular array covers 3.3-3.6 GHz. The omnidirectional gain is about 4.7 dBi, while the directive gain reaches 16 dBi with 360° continuously beam-scanning performance and very slight gain fluctuation in the azimuth plane. The comparison with other state-of-the-art designs shows that the proposed circular array has both higher directional and omnidirectional gain values.

Parity-time (PT) reversal symmetry, as a representative example in the field of non-Hermitian physics, has attracted widespread research interest in the past few years due to its extraordinary wave dynamics. PT-symmetry enables unique spectral singularities, including the exceptional point (EP) degeneracy where two or more eigenvalues and eigenvectors coalesce, as well as the coherent perfect absorber-laser (CPAL) point where laser and its time-reversal counterpart (i.e., coherent perfect absorber) can coexist at the same frequency. These singular points not only give rise to new physical phenomena, but also provide new plausibility for building the next-generation sensors and detectors with unprecedented sensitivity. To date, investigations into EPs and CPAL points have unveiled their great potential in various sensing scenarios across a broad spectral range, spanning optics, photonics, electronics, and acoustics. In this review article, we will discuss on going developments of EP- and CPAL-based sensors composed of PT-synthetic structures and offer a glimpse into the future research directions in this emerging field.

A bidirectional inductive power transfer (BIPT) system of full-compensated series-series (SS) topology with full bridge converters on both primary and secondary sides is analyzed in this paper. The steady-state electrical characteristics of the BIPT system under triple-phase-shift control are obtained, based on which, the conditions for achieving the maximum transfer efficiency of the intermediate circuit and zero voltage switching of all switches are derived. Triple Phase-Shift Control (TPSC) strategy was proposed for the control of the two inner phase shifted of the primary and secondary side full bridge converters and the fundamental excitation voltage phase shift, which achieved the maximum transfer efficiency of the intermediate circuit and zero voltage switching of all switches. The proposed control method was verified through simulation. The results showed that the control strategy can realize the bidirectional energy transfer of the IPT system, the efficiency optimization of the intermediate link, and the zero-voltage turn-on of all switching devices under various load conditions.

This article proposes a versatile Multiple Input Multiple Output (MIMO) antenna designed for contemporary wireless systems spanning frequencies from 3 to 20 GHz. It serves applications such as 5G mobile, WiFi, WiFi-6E, X-band, partial Ku, and K-band. The original single-element antenna evolves into a 4 × 4 MIMO configuration with optimized ground plane modifications for enhanced performance. A decoupling structure achieves over 20 dB isolation between inter-elements. The feeding structure, featuring a gradually changing design connected to the antenna's radiating structure, achieves wide bandwidth characteristics. This is further improved by a partial ground structure and slots on the radiating element. The lower frequency band of 3 to 7 GHz is attained with a rectangle-shaped radiator, while semi-circular microstrip lines atop the radiator enable the higher frequency bands of 8 to 15.4 and 18.7 to 20 GHz. The slots and ground structure enhance impedance bandwidth, and semicircles improve the radiation pattern. The MIMO antenna demonstrates measured peak gains of 4.4 dBi at 3.5 GHz, maintaining a radiation efficiency exceeding 80%. Validation through metrics like ECC, DG, CCL, and TARC confirms strong agreement between simulated and experimental results, positioning the MIMO antenna as a robust choice for various wireless communication applications.

Usually inactive or also known as thinned elements are used to simplify the array design complexity by turning off some of the active elements in uniformly filled arrays. Consequently, the far-field radiation characteristics such as sidelobe level, beamwidth, and directivity may be negatively changed if no optimizer is used. Further, these radiation characteristics may be unavoidably deteriorated when the main beam is scanned to new directions other than the referenced broadside direction. In this paper, an efficient optimization method based on the genetic algorithm and a dynamic deactivation method is proposed to randomly deactivate a number of array elements to minimize the peak sidelobe level and at the same time maintain the array directivity undistorted, while scanning the main beam. The deactivation method chooses optimally the suitable number of elements and their locations that need to be deactivated such that the resulting radiation characteristics positively change according to the specified cost function. Also, the proposed scanned array uses binary coefficients to activate and deactivate the array elements, thus, the feeding network of the proposed array is very simple, and it can be easily implemented in practice. Through extensive simulation results, we show that the proposed optimization method has good performance under wide range of scanned main beam directions. It is also found that the number of deactivation elements (i.e., the optimization variables) increases with larger scan angle.

The generalized sidelobe cancellation (GSC) is a commonly used adaptive beamforming technology, which can be used in antenna arrays. Due to the error of the direction of arrival of the received signal and the spacing error of the received array elements, the signal received by the array antenna has a mismatch of steering vectors, which leads to that the GSC method cannot accurately aim at the expected signal and suppress the interference signal. In order to improve the robustness of GSC algorithm, a new adaptive beamforming algorithm named SGSC (Sequential Quadratic Programming-Generalized Side Lobe Cancellation) is proposed in this paper. In this method, firstly, the mismatching expected signal steering vector is corrected by the stepwise quadratic programming, so that the auxiliary antenna can effectively block the expected signal. Then, the optimal weight vector is obtained by combining the corrected steering vector with the GSC, so that the expected signal components of the auxiliary antenna and of the main antenna can be avoided from being cancelled due to mismatch errors. Finally, the simulation results based on MATLAB show that the new algorithm can point the desired signal more accurately and suppress the interference signal more obviously in the presence of mismatch error, which shows the effectiveness of the method.

This paper proposes a UHF-band microwave sensor for solid material detection based on a tweaking electric field coupled (ELC) resonator. The microwave sensor operates at a low resonant frequency of 0.82 GHz to characterize solid materials with a permittivity range of 1-9.8. The location of the sensing area is determined based on the surface of the resonator with the highest electric field. The permittivity of the sample is determined based on perturbation theory by observing the frequency shift relative to changes in the permittivity of the sample placed in the sensing area of the proposed sensor. From the measurement process, the proposed sensor has a normalized sensitivity (NS) of 1.49%, frequency detection resolution (FDR) of 0.012 GHz, and an average accuracy of 96.72%. This work has a significant contribution and can be recommended for several applications including the pharmaceutical, biomedical, and materials industries.

This paper presents the design of conformal microstrip antennas wrapped around on a rocket cylinder. These antennas should exhibit favorable S₁₁-parameter values within the desired radio frequency range and an omnidirectional radiation pattern. Given their external placement on rockets, the challenge in this context is to ensure heat resistance. Two types of conformal microstrip antennas are developed to address this issue: one features an 8x1 array of rectangular patch (RP) elements, and the other consists of a single long rectangular patch (LP) element. Each antenna is wrapped around the rocket cylinder, with the patch array elements tailored to match the cylinder circumference to achieve an omnidirectional radiation pattern. Both antennas operate at a resonant frequency of 2.44 GHz and are constructed using RT/duroid 5880, a flexible material with a low dielectric constant. The antennas designs are assessed through computer simulations, followed by fabrication and measurements to analyze their performance against simulation results. The results indicate that the conformal RP antenna displays an S₁₁ value of -24.512 dB at the center frequency of 2.445 GHz featuring a 48 MHz bandwidth, while the conformal LP antenna discloses an S₁₁ value of -16 dB at the center frequency of 2.44 GHz having a wider bandwidth of 55 MHz. Both of the conformal RP and LP antennas exhibit an omnidirectional radiation pattern with a maximum gain of 6.13 dB and 7.21 dB, respectively. Following simulation and testing results, the antennas can tolerate temperatures up to 71.8˚C during flight tests. Although temperature variations trigger slight frequency shifts, these deviations are insignificant. Finally, the measurement results agree with the simulation ones.

This paper presents an innovative high gain multiple-input-multiple-output antenna featuring a compact circular shape, enhanced by strategically positioned slots, slits, and defected grounds created by etching multiple iterations of circle inserted with triangle shape. The investigation thoroughly explores the various traits and properties exhibited by the antenna. The antenna design harmoniously incorporates two radiating elements shaped in circles, positioned 16 mm apart from their centers, and has been physically constructed using an FR4 substrate. Enhancing the antenna's bandwidth and gain requires the implementation of slots with fractal patterns on the ground with a precise edge-to-edge separation of 2.5 mm. The placement of the antenna elements at a 16 mm distance guarantees an isolation level exceeding 15 dB consistently throughout the entire wideband frequency range. The dimensions of the compact MIMO antenna are tailored to be 1.12λ × 1.8λ × 0.091λ (20 × 32 × 1.62 mm³). In this study, the circular patch MIMO antenna with a fractal DGS resonates precisely at 16.903 GHz. It showcases an impressive impedance bandwidth spanning 2.027 GHz, ranging from 15.946 GHz to 17.973 GHz. It exhibits a reflection coefficient of -43.82 dB and achieves an observed gain of 6.25 dBi. The observed results include a minimal envelope correlation coefficient (<0.025) and a substantial Diversity Gain (>9.89). The measured results mirror the simulated outcomes, affirming the effectiveness of the wideband, high-gain antenna design. Its bandwidth and gain are well-suited for Satellite Communications particularly in downlink applications, enabling faster data transmission rates.

Dividing large planar arrays into several subarrays and then turning off some of them reduces the complexity (cost) of the system significantly. In this paper, two optimization stages for the formation of planar subarrays and the removal of some of them are proposed. The first optimization stage improves the pattern of the original planar array after dividing it into a set of rotational square and rectangular subarrays. In the second optimization stage, it works to remove some of the subarrays completely or partially, depending on new fractal structures derived from the conventional Sierpinski carpet structure. The proposed fractal-thinned planar array is based on amplitude-only excitation, i.e. the phases of the elements are set to zero. To execute the optimization steps above, a genetic algorithm (GA) is used. Some determinants are included in the optimization process to maintain the properties of the desired pattern. Simulation results showed the effectiveness of the proposed optimization method in achieving almost the same performance in both stages of optimization.

As one of the most basic electric quantities in the power system, voltage plays an important role in many fields such as condition monitoring and fault diagnosis. The construction and development of the smart grid cannot be separated from the reform and progress of the advanced sensing and measurement technology. Noncontact voltage measurement technology, as one of the important technologies, has many advantages such as no electrical contact, low insulation requirements, easy installation, and great potential in improving the panoramic perception ability of the power system. In this paper, a noncontact measurement method of the power line voltage based on capacitive coupling principle is proposed, which realizes the reliable measurement of the line voltage waveform. First, the principle of the noncontact voltage measurement method is introduced, which mainly includes self-calibration and online measurement of the sensor. The high-frequency voltage signal is injected into the capacitive coupling network of the sensor to implement the self-calibration of the sensor. Then, the digital integration method is used to integrate the output signal of the sensor to measure the line voltage waveform. Second, the noncontact voltage sensor prototype and the signal processing circuit are designed. Finally, the test platform of the line voltage measurement is built, and the measurement test of 220 V/50 Hz line voltage waveform is carried out. The test results show the relative amplitude error of the voltage measured by the sensor is less than 2.5%, the maximum phase error less than 2° at 50 Hz, and the linearity better than 0.5%. The frequency response experiment shows that the system has almost constant gain in the frequency range of 50-1800 Hz, and the phase error reaches a maximum of 2.8° at a frequency of 1800 Hz.

Surface Plasmon Resonance (SPR) serves as a crucial optical technique in the realm of chemical sensing. Under specific conditions, the reflectivity of a thin metal film exhibits an exceptional sensitivity to optical changes in the medium on one side. In this investigation, we propose and simulate a plasmonic sensor incorporating a silicon nitride grating with Ag layers for the detection of solution and gas at an optical communication wavelength of 1550 nm. In both cases of the surface diffraction-grating, there is a notable enhancement in angular sensitivity compared to conventional prism-coupled configurations. Simulations, employing rigorous coupled wave analysis (RCWA), highlight that the suggested sensor, optimized in design parameters, offers notably superior sensitivity, a lower detection limit, and a higher figure of merit (FOM) than existing grating-based SPR sensors. This implies the potential realization of refractive index sensors with a high figure of merit through such streamlined and compact configurations.

In this paper, a miniaturized millimeter-wave (mm-wave) antipodal Vivaldi antenna (AVA) is proposed. The AVA structure is modeled using MWSCST2022 optimization tools. The AVA exhibits good impedance matching, high gain, and a small optimum size of 5x2.5x1.5 mm³, fabricated on an FR-4 substrate. An array of square and circular director units is modeled and loaded at the front and back of the AVA. The spacing between directors is studied and positioned at a tuned distance from the antenna for gain improvements and optimum radiation parameters. The AVA has an operating spectrum from 58 GHz up to 62 GHz. The finalized AVA, along with directors, obtained a high gain of 12.9 dBi with directors, while the AVA achieved 9.22 dBi without directors. The proposed antenna model is simulated and measured for short-range communications and imaging. The results of the modeling techniques and measurements agree well with each other.

An Improved Speed Loop (ISL) and Extended State Observer (ESO) strategy based on Model Predictive Control (MPC) of the Permanent Magnet Synchronous Motor (PMSM) is proposed in this paper. Firstly, considering the impact of load torque sudden changes on speed tracking performance, a reduced-order Luenberger observer is utilized to observe the load torque and combine with model prediction to form ISL. Secondly, the ESO is utilized to estimate the lumped disturbance and feedforward compensated to the improved speed loop, which improves the system's anti-interference performance. Then, a cost function that introduces the current tracking error at the switching point is constructed, reducing the current ripple. Finally, the experiments show that compared with the traditional PI speed control, the proposed strategy reduces the speed overshoot over a wide range of speeds, improves the speed tracking performance, and has superior dynamic performance and anti-disturbance performance under different operating conditions.

In this paper, a compact dual-polarized antenna with wide band and high isolation is proposed, which can be applied to the 5G WiFi frequency band. The antenna is composed of 2 × 2 arrayed patches and two orthogonal L-shaped probe structures with reduced middle patch width and loaded U-shaped slots. The proposed antenna achieves a compact size by eliminating the need for a complex feeding network, instead utilizing only two closely spaced L-shaped probes for feeding. The antenna's radiation modes excited by two ports are orthogonal in polarization direction, and each port can excite two linearly polarized radiation modes respectively within the operating frequency band, thereby achieving dual-linear polarization and wideband performance. The antenna is analyzed and designed using characteristic mode analysis (CMA). By reducing the patch middle width and loading U-shaped slots on the L-shaped probe of the antenna, the suppression of high-order modes, improvement of isolation, and reduction of cross-polarization levels are achieved. The size of the antenna is 0.54λ₀ × 0.54λ₀ × 0.068λ₀ (λ₀ is the free-space wavelength of central frequency). The measured bandwidth is 23.5% (4.73 GHz-5.99 GHz) with |S₁₁| < -10 dB, |S₂₁| < -27.9 dB, boresight gain of 4.8 dBi-6.2 dBi and cross-polarization levels better than -23 dB.

A broadband preconditioner based on a modified version of the sparsified nested dissection ordering (m-spaNDO) technique is proposed for the full wave discrete exterior calculus (DEC) A-Φformulation solver in electromagnetics. The matrix equation discretized by the DEC A-Φ solver is in general complex symmetric and indefinite. When conductive media and disparate mesh are involved, the DEC A-Φ matrix equation is ill-conditioned, and proper preconditioner must be utilized to accelerate iterative solver convergence. In this letter, an introduction to the DEC A-Φ solver is provided, followed by the implementation details of the m-spaNDO preconditioner. Numerical examples in this paper show that the proposed m-spaNDO preconditioner can effectively accelerate the convergence of iterative solvers in solving ill-conditioned problems. The m-spaNDO preconditioned DEC A-Φ solver has O(N logN) computational complexity and the efficiency of the preconditioner is independent of change in parameters such as frequency and conductivity in the problem, which indicates the broadband stable nature of the m-spaNDO preconditioner.

Model predictive control (MPC), as a frequently adopted control strategy for permanent magnet synchronous motors (PMSMs), exhibits favorable dynamic response capabilities. However, it necessitates an accurate mathematical model of the controlled object, and any parameter mismatch can lead to a decline in control performance. This paper proposes a model predictive current control (MPCC) method based on parameter identification, which can be extended to the parameter identification of plug-in permanent magnet synchronous motors (IPMSMs). A wide-adaptability variable step-size algorithm is designed in response to the varying effects of single variable step-size functions on parameter convergence speed and ripple when the motor experiences different parameter disturbances. This method classifies and fits various variable step-size functions based on the maximum value of the absolute value of different instantaneous errors. This allows different variable step-size functions to adapt to different parameter disturbances, resulting in rapid waveform convergence and consistent ripple size in the identification process. Additionally, a new variable step-size function type was designed with simple parameter settings and easy debugging. Finally, the effectiveness of the proposed method was verified through experiments, and the results showed that the method can achieve fast and accurate identification of multiple parameters under different parameter perturbations, ensuring stable current control.

In this paper, four different structures are proposed to optimize electromagnetic thrust for the primary and secondary pole linear induction motors. Firstly, the two-dimensional topology structure of the motor is established, and the correlation equation of electromagnetic thrust is established. Secondly, the electromagnetic thrust optimization of the primary structure of the motor is carried out by the chamfer method and trapezoidal structure method. Then, the secondary structure of the motor is slotted and mixed with different conductivity materials to optimize the electromagnetic thrust. At the same time, a motor model with high permeability under ideal conditions is proposed from the angle of relative permeability of secondary aluminum plate. Finally, the four optimized structures were simulated, and the changes of electromagnetic thrust, air gap density, and back electromotive force were analyzed. The simulation results fully verify the effectiveness of the four optimization structures proposed in this paper.