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.

In this paper, a WiFi-UWB multiband monopole antenna is designed, fabricated, and tested based on the characteristic mode theory, which mainly consists of an L-shaped metal, an ``ok''-shaped metal radiator, and a T-shaped metal patch. The substrate dimensions are 40×43×1.6 mm<sup>3</sup>, featuring a rectangular ground plate at the substrate's bottom. The ``ok''-shaped metal on the upper surface is composed of a metal ring and a curved finger-shaped metal. To improve impedance matching and broaden the bandwidth, strategic modifications are implemented. Specifically, a rectangular slot is introduced at the top of the L-shaped metal, and the T-shaped metal is rotated 90° counterclockwise and positioned beneath the ``ok''-shaped metal. The microstrip feed line, constructed from metal, incorporates a feed point. Simulation results indicate that the antenna effectively covers the frequency ranges of 2.30-2.50 GHz and 3.65-9.77 GHz. At the resonance point, the maximum return loss is below -40 dB, signifying superior directional radiation characteristics. The antenna design is characterized by a wide frequency band, simple structure, and holds significant practical value for multi-frequency communication.

A tiny electromagnetic band gap (EBG) based microwave sensor with dual-band operation for dielectric characterization of Liquids is presented in this work. The suggested design uses a suspended microstrip line placed over the stack dual-band type EBG (SD-EBG) unit cell at 2.40 GHz and 2.98 GHz. To achieve the dual band characteristics, the stack type of EBG with different patch sizes and offset vias is used. To validate the sensor performance, absolute solution of butan-l-o1, methonal, and water are considered as liquid under test (LUT) and loaded in transparent polypropylene (PP) material, and the maximum sensitivity of 1.14% from the first resonance with maximum Q-factor of 137.5 from the second resonance is achieved with frequency detection resolution of 27.4 MHz. The size of proposed SD-EBG based sensor is 54.95% and 39.02% of that of planar EBG based sensor and cesaro fractals EBG based sensor.

The paper details the development of an innovative Ultra-Wideband (UWB) Circularly Polarized (CP) Multi-Input Multi-Output (MIMO) antenna. Drawing inspiration from an Electromagnetic Band-Gap Structure, the antenna incorporates two compact electromagnetic bandgap cells strategically positioned near the feedline. The result is a sophisticated triple-band notched planar antenna configuration. To enhance its performance, a slot and a stub are strategically added to the ground plane, effectively broadening the Axial Ratio Bandwidth (ARBW). This carefully designed setup achieves a wide ARBW while simultaneously rejecting interference at 3.5, 5.5, and 8.2 GHz. Notably, the MIMO antenna demonstrates an axial ratio spanning from 3 to 10.4 GHz, coupled with an impedance bandwidth ranging from 3.1 to 10.6 GHz. Diversity features of the proposed structure are quantified through three key parameters: ECC (Envelope Correlation Coefficient) greater than 0, TARC (Total Active Reflection Coefficient) surpassing 10, and DG (Diversity Gain) exceeding 9.7. These parameters collectively indicate robust diversity characteristics, underscoring the antenna's efficacy in challenging communication scenarios. Practical implementation involves the use of FR4 dielectric substrates, with precise measurements of 42.7×55×1.6 mm³. This meticulous construction ensures the realization of the proposed structure's theoretical framework, highlighting the antenna's potential applicability in advanced UWB communication systems.

A novel multiband microstrip patch antenna (Antenna-1) is introduced in this paper to target the frequencies of interest required for RF energy harvesting applications, including mobile DCS (Digital Cellular System), mobile LTE (Long Term Evolution), mobile 5G, WLAN (Wireless Local Area Network), and WIMAX (Worldwide Interoperability for Microwave Access) services. The simulated results for the proposed antenna showed outstanding performance. The antenna supports a high number of total (11) eleven operating frequencies and covers all of the frequencies of the 2.4 GHz (IEEE 802.11) band, as well as the downlink frequencies of mobile DCS 1800 and the downlink frequencies for mobile LTE/5G (Band 68). The proposed antenna has achieved a high gain for most of its resonating frequencies, with a high gain of (4.49 dBi) at the frequency of (2.4527 GHz), and a peak gain of (6.349 dBi) at the frequency of (3.95 GHz). Furthermore, the proposed antenna achieved a high bandwidth capacity of (677 MHz) at the resonating frequency of (5.2 GHz), which covers a lot of frequencies utilized by WLAN, WIMAX, and mobile LTE services, making it a suitable antenna for radio frequency energy harvesting applications. Good agreement between the measured and simulation results was observed.

In this paper, an SM-PB (Sparse Matrix Canonical Grid method-Physics Based Two Grid) acceleration algorithm is proposed which can be used to calculate electromagnetic scattering from two-dimensional rough surfaces with large dielectric constants. Firstly, a two-dimensional rough surface model is established based on the Monte Carlo method and Gaussian spectral function, and a conical incident wave with Gaussian characteristics is introduced to eliminate the error caused by artificial truncation of the rough surface. In the scattering calculation, the integral equation of the rough surface is processed by the SMCG algorithm, and then the matrix equation is further processed by applying the PBTG algorithm to decompose the matrix equation into the very near-field matrix, near-field matrix and far-field matrix. The FFT method is then used to calculate the matrix vector product during the iteration for fast computation. The proposed algorithm and the MOM algorithm were compared from the perspectives of computational accuracy and efficiency. Through comparison, it was found that the two algorithms produced highly consistent results, validating the effectiveness of the proposed algorithm. The proposed algorithm demonstrated a significant advantage in computational efficiency, with considerable efficiency also observed for large-scale rough surfaces. The electromagnetic scattering from rough surfaces with large dielectric constants was calculated, and the influence of the correlation distance r_d and dielectric constant on the electromagnetic scattering characteristics was investigated. It was found that it is important to set a reasonable value of r_d in order to balance calculation accuracy and calculation efficiency.

Magneto-acousto-electrical tomography (MAET) is an imaging method generating a source current under excitation of both static magnetic field and acoustic field, and electrodes are used to detect the electrical signal to further reconstruct conductivity image. Previous studies ignored the non-uniformity of magnetic field. However, the reconstructed image will introduce artifacts due to magnetic field inhomogeneity, which is small but cannot be neglected. We analyzed the characteristics of magneto-acousto-electrical signal under uniform and inhomogeneous magnetic fields in simulation. This paper deduces the relation of magneto-acoustic signal generated by inhomogeneous static magnetic field, and reconstructed conductivity image under non-uniform static magnetic field through synthetic aperture imaging. Furthermore, to verify the validity of the theory, an experimental platform was built to reconstruct the conductivity of phantom. In clinical applications, non-uniform static magnetic field can achieve a fully open magnetic field structure, which is much more friendly for inspection of patients with autism and even children. Permanent magnets that generate non-uniform static magnetic fields have the advantages of smaller size, lighter weight, and lower cost than magnets that generate uniform static magnetic field, which can effectively optimize equipment space.

The positive-definite stability analysis (PDSA) is presented as a technique complementary to the companion-matrix stability analysis (CMSA). The PDSA is used to analyze the stability of marching-on-in-time (MOT) schemes. The heart of the PDSA is formed by the analysis on particular linear combinations of interaction matrices from an MOT scheme, which are assumed to be real-valued. If these are all positive definite, then the PDSA guarantees the stability of the scheme. The PDSA can be of a lower complexity than the full CMSA. The construction of the PDSA is shown and applied to two numerical examples.

This paper discusses the challenges faced by existing power amplifier configurations in meeting the bandwidth requirements of modern communication technology while maintaining high efficiency due to the overlap of fundamental and harmonic frequencies. To address this issue, the paper proposes a matching method based on mode combination theory that utilizes the overlap of harmonic and fundamental impedance to simplify the design of broadband amplifiers. In this paper, a Chebyshev low-pass filter is used to control the higher harmonics instead of the conventional quarter-wavelength harmonic control network with a combination of harmonic impedances. The proposed method combines three modes of Resistive-Reactive class F^-1, class J, and class F power amplifiers, which can achieve high efficiency and octave frequency at the same time. The paper verifies the proposed method by designing and fabricating a multi-multiplier power amplifier with a drain efficiency of 61.8-73.9%, an operating bandwidth of 1.4-2.9 GHz, and a saturation output of 41.1-42.3 dBm. The amplifier also has a gain greater than 11.1-12.3 dBm, and at an output power of 36 dBm, the ACPR value is -32 to -33.1 dBc across the band.

Exact analytic solutions for the electromagnetic field due to a thin, uniform circular loop current are presented. The solutions are provided in the form of a power series with respect to wavenumber. The coefficients of the series are real functions of the spatial coordinates and loop radius and involve recursions of complete elliptic integrals or finite sums of elementary functions. Explicit expressions for the magnetic vector potential and electric and magnetic fields are provided for both cylindrical and spherical coordinate systems. The expressions are adapted for computing the electric field and axial magnetic field on the interface of two half spaces generated by a current loop lying on the half-space interface. Expressions for the self and mutual loop impedances are provided for both the free-space and interface case. Computed examples are given for specific frequency and half-space parameters and are compared to known solutions based on spherical Hankel functions or direct integration. The solutions are shown to be particularly efficient in the near field. Their derivation is motivated by recent developments of large sensors used in magnetic resonance sensing of minerals.

Flux-switching permanent magnet (FSPM) machine has wide application prospects in aerospace and automotive fields. To enhance the machine's electromagnetic performance, a novel multi-tooth flux-switching permanent magnet (MT-FSPM) machine with high-temperature superconducting (HTS) bulks is proposed. The HTS bulks are arranged in the middle of the stator teeth, aimed at diminishing flux leakage and amplifying torque output. The method of stator tooth chamfering and rotor flange is adopted to effectively suppress the torque ripple. Then based on the comprehensive sensitivity analysis, the key design parameters of the machine are layered, and the high sensitivity parameters are optimized by response surface method (RSM) and multi-objective genetic algorithm (MOGA) to obtain the optimal value. Finally, a 6/19 MT-FSPM machine model is established in 2D finite element method (FEM). Comparative analysis with the conventional model indicates a 16.4% increase in output torque and an impressive 79.6% reduction in torque ripple for the proposed model.

The armature and rail sizes of electromagnetic rail launcher vary greatly, and the refined 3D finite element computation occupies a large amount of physical memory. In order to enhance the economy of dynamic computation, this paper proposes an adaptive hexahedral mesh method based on mesh expansion, compression and translation. In addition, split nodes are used on both sides of the contact surface, and interface conditions and frictional heat sources are constrained through point penalty function method to solve non-ideal sliding electrical contact problems. Comparative calculations with the same type of software and the same model are carried out, and the results calculated in this paper are consistent with the relevant results of MEAP3D. This paper also compares the EMRL calculation results of adaptive mesh model and constant mesh model to verify the reliability of the method. In addition, the C-type EMRLs are compared and analyzed. The results show that due to the influence of velocity skin effect, the dynamic inductance gradient of the rail gradually increases over time and is greater than the static value. The maximum difference between the two is 5.65% of the dynamic inductance gradient. The steel shell generates eddy currents, causing a decrease in armature velocity of 4.7 m/s under the small caliber launcher. The maximum eddy current density waveform of the shell exhibits two peaks. In the frictionless heat, the temperature of the armature is underestimated, and under the action of frictional heat, the trailing edge of the armature is ablated and melted.

Three scenarios of high gain bow-tie based antenna array systems are introduced and investigated in this paper. The proposed designs are intended for integration as Tx/Rx antennas in C-band communication systems. Wide operating bandwidth and consistent radiation characteristics over the frequency range from 4 GHz to 5 GHz are defined for the three configurations. A two-stage Wilkinson power divider provides the feed mechanism for the proposed array. The initial structure has four radiating elements, each incorporating seven bow-tie dipoles arranged in a printed Log-Periodic Directional Array (PLPDA) configuration. The gain of the second and third designs is improved by adding resonators in front of the array elements. Furthermore, the second design features triangular-shaped resonators, while the third design employs H-shaped resonators. The designs are simulated and optimized using HFSS and CSTMWS software, and subsequently, they are fabricated using the photolithography technique. The initial design demonstrates an experimental bandwidth from 3.7 GHz to 5.1 GHz and achieves a measured gain of 13.8 dBi at 4.7 GHz. The second and third configurations operate in the frequency bands of 4.3 GHz to 5.3 GHz and 3.7 GHz to 5 GHz, respectively, exhibiting measured gains of 14.1 dBi and 15 dBi. The overall dimensions of the proposed arrays are kept within reasonable limits, with the first array being 2.51λ × 2.74λ, the second being 2.09λ × 2.82λ, and the third being 2.51λ × 2.97λ. The three array designs can be considered as good candidates for C-band communication applications.

Electromagnetic thermal performance is critical during electromagnetic launch. However, due to the harsh in-bore environment, it is difficult to obtain multi-parameter information by means of experimental measurement, which further limits our understanding of the field distribution of electromagnetic launcher. In this paper, considering the temperature dependence of material conductivity and armature solid-liquid isothermal phase transition, a bidirectional coupling model of electro-magnetic-thermal field of multi-turn electromagnetic rail launcher is established. The reliability of this model is verified by comparing the calculation results of the same model and input conditions with the numerical tool EMAP3D, as well as the related experimental comparison. In addition, the multi-turn and traditional EMRLs are compared and analyzed. The results show that compared to single-turn EMRL, the armatures have greater driving force in two multi-turn configurations, and the impulse lifting rates are about 1/2. In the multi-turn configurations, the lateral resultant forces of the two armatures are not zero, while the lateral force difference in the integrated negative rail configuration is relatively small. The ablation of the armature in the integrated negative rail configuration is less severe.

To reduce the coupling resulting from structural asymmetry and enhance the load-bearing capacity per unit area, a six-pole axial-radial active magnetic bearing (AR-AMB) has been suggested. To refine the precision of the mathematical model derived from the conventional equivalent magnetic circuit model, a modeling technique that employs the flux density and magnetic field segmentation has been proposed. Firstly, the structure and operational principle of the six-pole AR-AMB are introduced. Subsequently, an improved model based on the flux density is established by considering the internal relationship between the iron core and air gap magnetic field in a magnetic bearing with pole shoes. The model addresses issues related to the accurate calculation of fringing magnetic flux and magnetic saturation of core materials while accounting for eddy current effects on suspension force. Finally, the accuracy of the theoretical analysis results has been validated through finite element simulation and experiment, and demonstrated that the rotor based on this model exhibits robust anti-interference capabilities.