This paper presents the configurations of U-slot cut hexagonal microstrip antennas loaded with shorting posts, which realize a reduction in the center frequency of axial ratio bandwidth as well as the total substrate thickness. Three configurations employing four, eight, and twelve shorting posts positioned around a hexagonal patch are presented. Shorting posts loading adds to the inductive component in the antenna's input impedance, which yields a reduction in total substrate thickness and frequency. Among three variations, the U-slot cut hexagonal patch employing eight shorting posts yields the optimum result. It achieves axial ratio bandwidth of 2.23%, for 0.033λ_cAR reduction in the substrate thickness and 55 MHz (4.5%) reduction in the center frequency of axial ratio bandwidth. All these results are for marginal reduction in peak broadside gain. Against the U-slot cut hexagonal patch on a reduced substrate thickness, shorting posts loaded antenna achieves higher axial ratio bandwidth with 56 MHz (4.81%) reduction in the center frequency of axial ratio bandwidth. Considering all these results, the proposed design offers a compact circular polarized solution, while employing a resonant U-slot. For the obtained antenna characteristics, the proposed designs can find applications in GPS L5 and L2 bands. Experimental validation for the proposed configurations has been carried out where the measured results show close agreement with simulated ones.

This manuscript describes the design of a scannable Cosecant² Shaped Pattern Generating Phased Array Antenna (PAA) intended for airborne synthetic aperture radar (SAR). The Cosecant² Shape avoids the requirement of sensitivity time control correction at receiver side. A C-band linear array antenna consisting of 16 elements is designed, analyzed, developed, and characterized. The array antenna is embedded with a U-slot and Defected Ground Structure (DGS) integrated microstrip elements. The introduction of a DGS provides an improvement of 6.5 dB in cross-polarization levels when scanning. Additionally, the null perturbation technique is employed to synthesize the excitation coefficients for the Cosecant²-Shaped pattern, aiming to achieve the minimum current taper ratio. These synthesized coefficients are combined with a progressive phase for beams that can scan within a ±30° angular range. The proposed linear array, along with its excitation and phasing network, has also been developed and characterized in an anechoic chamber.

Magnetic Coupled Resonant (MCR) Wireless Power Transfer (WPT) is typically used for electrical charging, offering high tolerance to misalignment and wider transmission range. However, MCR-WPT is assumed to be a two-port circuit, including transmitter (Tx) and receiver (Rx), and exhibits lower efficiency than conventional inductive power transfer. Various studies have been proposed to increase the 4-coil MCR-WPT efficiency, but further challenges remain due to the turn technology complexity. A relevant and simple design solution is developed in the present paper that enables the optimization of Power Transfer Efficiency (PTE) by minimizing implementation cost. To achieve that goal, the transfer- and resonator-distances, TD and RD, respectively were optimized through theory, both circuit and 3-D electromagnetic (EM) simulations via 3-D modeling and experimentation. The validation PTE results obtained from analytic calculation, simulation and experimentation affirm that the maximum efficiencies of 94.10, 90.15% and 69.35% were obtained at optimal positions around RD = 7.5 mm and TD = 100 mm, respectively. The slight difference of the obtained PTE among theory and simulation with experiment is due to the setup instrument imperfection. The performed study is useful for the WPT charging systems, such as electronic sensors, wearable devices, and communication systems.

To address the issue of significant fluctuations in radial electromagnetic forces in variable-leakage-flux reverse-salient-pole permanent magnet synchronous motors (VLF-RSPMs), which make stable operation at high speeds difficult, this paper combines an analysis of existing VLF-RSPMs with a novel optimization method to propose a multi-objective hierarchical optimization design method for VLF-RSPMs, which incorporates vibration and noise suppression. First, the paper analyzes the radial electromagnetic force model, natural frequencies, and electromagnetic vibration model of the VLF-RSPM. Second, based on the optimization objective of vibration and noise suppression, parameters with high sensitivity are optimized first through sensitivity analysis. Subsequently, the modal characteristics, radial electromagnetic forces, noise, and stress of the optimized VLF-RSPM are analyzed in detail. Finally, an experimental VLF-RSPM prototype and a test platform for measuring radial electromagnetic force fluctuations are designed. The results demonstrate that the multi-objective hierarchical optimization design method ensures the operational reliability of the optimized VLF-RSPM, enabling it to meet the requirements for high-speed operation.

This study addresses an issue with high-energy laser directed energy weapon performance assessment when applied to the problem of countering swarms of uncrewed aerial systems (UAS). Queueing theory provides a suitable modelling framework for the performance assessment of such systems, as a single server queue can process only one threat at a time, based on the order in which threats arrive at the theatre of operation. Consequently, this introduces delays into the processing of sequences of threats. Delays in such queues typically have time-dependent service times, due to the target's movement. This results in considerable complexity in terms of producing performance predictions through stochastic models. In recent applications of queueing theory to directed energy systems an ad hoc approximation has been used to estimate the delays that threats experience while waiting for service. This approach involves approximating the processing delay of a given threat by a constant value. In particular, it has been estimated by measuring the delay as a product of the expected service time and the number of threats present less one. Such an approximation can result in severely reduced and inaccurate performance predictions. In the current study, the mean delay will be used instead, and improvement on the aforementioned approximation will be demonstrated through explicit examples of swarm UAS defeat.

Wireless power transfer systems suffer from frequency splitting and drift due to horizontal coil offset, which degrade both efficiency and output power. This paper derives a sixth-order equation to calculate resonant frequencies at the maximum efficiency point (Freq-MEP). The frequencies at the maximum power point (Freq-MPP) are determined by differentiating the output power with respect to the operating frequency. Both Freq-MEP and Freq-MPP are shown to vary with horizontal offset. Based on this analysis, a segmented frequency-tracking method is proposed to achieve simultaneous high efficiency and high output power under varying offset conditions. The effectiveness of the developed magnetic resonant WPT system is validated through numerical simulations and experiments.

For small, low-power wireless power transfer (WPT) devices, maintaining constant output power and high transmission efficiency over a wide range of coupling variations remains a significant challenge. The double semicircular coplanar (DSC) coils, featuring unique magnetic field distribution, provide a potential solution for enhancing misalignment tolerance. This paper analyzes the transmission characteristics of a WPT system employing DSC coils. A circuit model for the WPT system with DSC coils is first developed, and its fundamental transmission characteristics are studied. The tolerance of output power and transmission efficiency to positional offsets (X, Y, Z) over various frequency bands is then evaluated. Finally, an experimental DSC coil system that features a stable frequency bandwidth and is largely insensitive to frequency shifts is built. Its misalignment tolerance forms a cuboid spatial zone. Within this zone, namely when the offset of the receiver in X and Y is under half its diameter, the output power and transmission efficiency remain constant, supported by a uniform magnetic field. When the receiver offset is greater than half its diameter, the magnetic field uniformity and mutual inductance change abruptly, leading to a sudden variation in output power and transmission efficiency.

To address the trade-off between torque density and power factor in conventional permanent magnet vernier rim-driven motors under material cost constraints, this study proposes a novel permanent magnet fault-tolerant vernier rim-driven motor with an inclined modulation tooth (PMFTVRDM-IMT). Unlike the conventional straight-tooth configuration, the proposed design introduces an inclination angle to the modulation teeth, thereby altering the air-gap permeance distribution pathway while preserving both the permanent magnet volume and overall motor envelope. Through magnetic field harmonic analysis, the underlying mechanism for the synchronous improvement in the torque and power factor was revealed: the inclined modulation tooth structure enhances the effective working harmonics while suppressing the ineffective harmonic components. To further optimize the motor performance, a combined approach of single-parameter scanning and multi-objective optimization was adopted, and the resulting performance metrics, such as the output torque and power factor, were systematically validated using the finite element analysis (FEA). The results indicate that, with modifications only to the modulation tooth structure, the proposed motor design achieves an approximately 15% improvement in the power factor and a 2.5% increase in the torque density, thereby substantiating the feasibility and engineering value of the inclined modulation-tooth topology in mitigating the low power factor issue inherent to vernier machines.

In this study, a high-performance wideband I-type rectangular waveguide rotary joint (RJ) has been meticulously designed, simulated, and experimentally verified for deployment in X-band radar systems operating within the 9-10 GHz frequency range. The proposed RJ achieves superior radio frequency (RF) characteristics, including an insertion loss of less than 0.1 dB and a return loss exceeding -30 dB, making it highly suitable for critical applications that require minimal signal degradation. Unlike conventional rigid waveguide systems that restrict mechanical movement, the developed RJ enables full 360° rotation with negligible variation in both amplitude and phase, thereby ensuring continuous, stable operation in dynamic environments such as mechanically rotating radar platforms. Notably, the design achieves an amplitude and phase wobble (WoW) of only 0.005 dB and a phase fluctuation within ±3.2°, meeting the stringent performance requirements of modern radar and satellite tracking systems. In addition to RF characterization, the rotary joint has been subjected to high-power RF breakdown analysis using particle-in-cell (PIC) simulations to evaluate its resilience under extreme operational stress. High-power robustness was numerically assessed using PIC simulations, indicating stable operation up to 2 kW CW and 30 kW pulsed under the simulated conditions, without breakdown signatures. This performance is further supported by optimized choke structures that minimize discontinuity-related mismatch at the mechanical interface between stationary and rotating sections. The results confirm that the developed rotary joint is not only electrically efficient and mechanically reliable but also capable of sustaining stable RF performance under high-power and rotational conditions, making it a promising candidate for next-generation radar front-ends and high-power satellite communication terminals.

Aiming to meet the contactless power supply requirements of rotary equipment, this study investigates the coil design and performance of a small resonator for magnetically coupled resonant wireless power transfer (MCR-WPT) systems operating in the MHz band. Based on the series-series (S-S) WPT circuit topology, the influence of coil inductance on the transmission characteristics of the system was analyzed. By combining the inductance calculation formula for planar spiral coils, the geometric parameters of the coil were designed with the objectives of load power (P_RL) > 40 W and transmission efficiency (η_T) > 90%. The rationality of the designed parameters was verified by field-circuit coupled simulation, and the influence laws of the driving frequency and transmission distance on transmission characteristics were also analyzed. The coils were wound according to the designed parameters, and both static and rotary dynamic power transfer experiments were conducted. The simulation results show that the designed coil achieves a transmission efficiency of 94.783% at a transmission distance of 50 mm in the 1 MHz, which meets the preset design objectives. The results of the static experiment and the dynamic rotation experiment show that the overall operating efficiency of the system (η_dc-dc) is 84%. This study demonstrates the feasibility of the proposed coil design method, and the designed small coil can realize high-efficiency and stable wireless power transfer under rotary working conditions. The research findings provide a reference for the coil design and engineering application of rotary MCR-WPT systems in the MHz band and possess practical value for the contactless power supply of sensors in rotary electrical equipment operating in confined spaces.

To address issues such as reduced motor output performance and diminished load capacity caused by permanent magnet demagnetization in Permanent Magnet Synchronous Motor (PMSM), a super-twisting algorithm-based fault-tolerant predictive control strategy for demagnetization faults in PMSM is proposed. First, the improved super-twisting non-singular fast terminal sliding mode observer (IST-NFTSMO) is constructed to accurately observe the flux linkage and predict the current at the next moment. Based on the observed values, a deadbeat fault-tolerant predictive control (DFTPC) algorithm is built to compensate for the torque loss due to permanent magnet demagnetization, thereby achieving fault-tolerant control of the system. Second, a sliding mode controller based on a novel reaching law is designed, thereby overcoming the shortcomings of traditional control strategies in PMSM vector control systems, such as poor anti-interference capability and slow response speed. Finally, experimental results demonstrate that after a demagnetization fault occurs in the PMSM, the proposed method effectively improves the fault tolerance capability of the PMSM system while ensuring the dynamic response speed of the control system, thereby endowing the system with enhanced stability and robustness.

This paper presents a useful design optimization methodology for a permanent-magnet-biased fault current limiter (PMFCL), aiming to achieve good fault current limiting performance with small magnetic materials and their losses. A physics-based magnetic circuit modelling approach is developed to update the nonlinear core saturation and permanent magnet biasing, enabling fast and reliable analysis of candidate designs. Additionally, a weighted multi-objective formulation is adopted to balance fault current mitigation, material volume, and loss minimization. The resulting optimization problem is solved by means of a deterministic pattern search approach, which enables efficient design space exploration without access to gradient information. The optimized configurations are validated using the finite-element simulations, and the robustness of the configurations under practical operating conditions is analyzed. The obtained results show a significant reduction of the magnetic material volume with the optimized PMFCL without compromising and, in certain cases, with an improvement of the function of fault current limiting against a baseline design. The research identifies technical configurations of design that are practical for real-world deployment. The combination of reduced material usage, passive operation, and better energy efficiency means the proposed PMFCL represents a reliable and sustainable solution for better protection of modern power systems, especially in areas where power systems are cost-sensitive and infrastructure-limited.

To meet the stringent space constraints and diverse connectivity requirements of modern intelligent connected vehicles, a compact MIMO antenna system designed for microwave and millimeter-wave (mm-wave) vehicle-to-everything (V2X) communications is presented. The proposed antenna features a compact footprint adaptable for integration into space-limited automotive modules, such as shark fin antenna housings. By employing a structure reuse technique, the system integrates a four-element microwave MIMO array and two orthogonal mm-wave phased arrays within a size of 30 mm × 30 mm × 2 mm. In the microwave band, a parasitic patch is introduced to achieve dual-mode resonance, ensuring a wide bandwidth for reliable control signaling. Two orthogonal rows of metallized cavities serve a dual purpose: acting as decoupling structures for the microwave MIMO system and functioning as mm-wave arrays to enable two-dimensional beam scanning. This capability is crucial for overcoming blockage effects in dynamic vehicular environments. Experimental results demonstrate that the proposed antenna achieves wide coverage in the microwave band (4.62-5.11 GHz) and high-gain beam scanning (±40°) in the mm-wave band (25.8-30.4 GHz). The measured isolation exceeds 17 dB with an envelope correlation coefficient below 0.11, validating its suitability for next-generation vehicle terminals.

This paper presents a compact four-port ultra-wideband (UWB) MIMO antenna with triple-band-notched characteristics. By introducing two types of resonators with distinct structures on both sides of the feed lines of the radiating elements, the proposed antenna achieves triple-band-notched functionality, thereby suppressing potential interference from WiMAX, C-band, and X-band. Notably, the spiral-shaped resonator simultaneously generates notch bands for both WiMAX and X-band, enabling a single structure to achieve multi-band-notched functionality and thereby enhancing the compactness and notch efficiency of the antenna design. Good agreement is observed between the simulated and measured results, validating the effectiveness and reliability of the proposed design. Across the entire operating band from 2.57 to 11.81 GHz (excluding the notch bands), the antenna exhibits a return loss below -10 dB, inter-port isolation greater than 20 dB, an envelope correlation coefficient (ECC) of less than 0.0095, and a diversity gain (DG) exceeding 9.9995 dB, fully satisfying the requirements of high-performance MIMO systems in terms of channel independence and transmission efficiency. The synergistic integration of multi-notch characteristics and high-performance metrics provides a novel technical approach for UWB-MIMO system design in complex electromagnetic environments.

This study presents the design and analysis of a compact dual-band crescent-shaped microstrip antenna that utilizes edge slots and mutual coupling enhancement techniques for Wi-Fi 2.4/5.8 GHz and agricultural communication technologies. A mutual coupling enhancement structure was added to stabilize the impedance and strengthen the dual-band performance. The antenna wass implemented on an FR-4 substrate with a thickness of 1.6 mm and a dielectric constant of 4.3. We compared four antenna elements i.e., circular patch with circular hole (CwCh), circular crescent patch (CC), circular crescent peripheral slit patch (CCPS) and circular crescent peripheral slit with ring patch (CCPSR). The simulation results show that the CwCh antenna element produced the most number of resonance frequencies, and the CCPSR antenna element produces the best minimum S₁₁ of -40.49 dB at 3.56 GHz. We compared six types of MIMO 2×1 CCPSR antenna. CCPSR-5 produced minimum S₁₁ of -30.36 dB (at 2.45 GHz) and -28.08 dB (at 5.8 dB). By adding a rectangular slot between the two antenna elements on the ground and adding three rectangular split ring resonators between the two antenna elements, the CCPSR improved the mutual coupling performance by 15.32 dB. The combination of peripheral slots and mutual coupling enhancement effectively improved the resonance frequency, resulting multiband frequency, and mutual coupling performance. Both the modeling and measurement data indicated that the antenna performed similarly. The antenna's performance was assessed for soil pH and moisture data transmission, ensuring reliable device enrollment within the smart agricultural infrastructure. These results demonstrate that the proposed crescent-shaped antenna provides an efficient and versatile solution for compact Wi-Fi infrastructure, effectively fostering innovation in next-generation communication systems.

Free-space electromagnetic waves can be coupled into on-chip propagating surface waves (SWs), a process that holds great promise for receiver front-ends in wireless communication systems. However, it has traditionally faced challenges in coupling efficiency and in controlling the on-chip wavefront of SWs. To address these challenges, we design and experimentally demonstrate SW couplers operating in the terahertz regime based on metal-insulator-metal resonators. Our devices achieve not only broadband and highly efficient coupling, with an efficiency exceeding 60% over a 20 GHz bandwidth, but also enable directional steering of the excited SWs to designated on-chip ports. In this way, mode conversion and onchip routing functionalities are seamlessly integrated into a single compact component. Based on this design, we fabricated devices and implemented corresponding terahertz wireless communication links, successfully demonstrating 16-QAM data transmission in both single-link and dual-link configurations.

This paper reviews recent advances in acoustic computation and modeling, specifically bridging effective medium theory (EMT) and biomedical ultrasound imaging. To achieve this, we examine how EMT provides the physical foundation for wave-based imaging through homogenized parameters, focusing on image reconstruction across diverse systems ranging from single pulse-receivers to multi-input and multi-output (MIMO) tomography. Furthermore, we highlight cross-disciplinary insights from computational optics, such as the transport of intensity equation and ptychography, while addressing acoustic-specific challenges like aberration correction and wave interference. In light of these challenges, emerging solutions are discussed, including ultrasound matrix imaging (UMI) via transfer matrix methods, inverse-designed matching layers, and hardware-accelerated approaches like the Krimholtz-Leedom-Matthaei (KLM) electro-acoustic model for ultrafast imaging. Ultimately, by integrating physical understanding of effective media with advanced computational algorithms, these developments provide a robust framework for the future of high-resolution 3D ultrasonography and acoustic holography.

Nowadays, a planar antenna for engineering and scientific fields is necessary for state-of-the-art energy harvesting applications. In this study, we present an ultra-wideband (UWB) microstrip antenna for different radio frequency (RF) applications, besides an energy harvesting rectifier section to charge operational low-power devices at 2.45 GHz. This antenna is used as a broadband antenna starting from 2.1 up to 7 GHz for worldwide interoperability of microwave access (WiMAX), wireless local area networks (WLAN), and ISM applications. It also covers frequency bands of 3.3-3.8 and 4.8-5 GHz for 5G mobile systems' upper and lower frequency bands, respectively. The engineered antenna comprises an octagon-shaped radiator patch, circular slots backed with a defected ground structure (DGS), and finally, a copper-reflected layer at a distance of 26 mm from the radiator patch. It is fabricated on an FR4 dielectric substrate with overall dimensions of 47 × 47 × 1.6 mm³. The antenna is engineered using the Microwave Studio Computer Simulation Technology (CST) electromagnetic (EM) simulator. It was tested using the ZVA 67 Rohde & Schwarz vector network analyzer (VNA). The measurement results demonstrate that the designed antenna fulfills a broad bandwidth with input reflection coefficient values (S₁₁) ≤ -10 dB from 2.1 to 7 GHz, besides three frequency resonances at 2.45, 3.8, and 5.88 GHz, respectively. A rectifier circuit modeling for the proposed design has been executed using the Advanced System (ADS) toolbox to implement an equivalent circuit for the manufactured antenna at the ISM band (2.45 GHz). The peak conversion efficiency for the designed rectenna is 98.5% at -10 dBm and 95.8% at 0 dBm under the load resistance of 50 kΩ. The fabricated prototype achieves omnidirectional and/or bidirectional measured radiation patterns in both E and H planes with stable high peak gain values of nearly 8 dB within the entire bandwidth. A comparison between the proposed antenna's prototype and the other presented in recent literature is reported to validate the design consistency.

Addressing the challenge of suppressing common-mode (CM) and differential-mode (DM) electromagnetic interference (EMI) in interior permanent magnet synchronous motor (IPMSM) drive systems, as well as the shortcomings of traditional methods in dynamic response and harmonic suppression, this paper proposes a comprehensive suppression strategy that integrates an active common-mode filter (ACF) with a modified harmonic suppression reaching law (M-RL). By establishing the CM/DM equivalent circuits of the inverter-motor system, the mechanism through which high-frequency parasitic parameters affect interference propagation is elucidated. Based on this, an ACF structure with adaptive impedance matching capability is designed, effectively suppressing the peak common-mode voltage and broadening the filtering bandwidth. Furthermore, the M-RL algorithm, which incorporates a saturation function and harmonic weighting factors, is proposed. This algorithm significantly suppresses differential-mode voltage harmonics by dynamically adjusting the sliding mode convergence speed and harmonic gain. Simulated and experimental results demonstrate that, compared to traditional passive filters and fixed-gain sliding mode control, the proposed strategy reduces the peak common-mode voltage spectrum by 25.74 dBμV and the peak differential-mode voltage spectrum by 30.39 dBμV. The proposed M-RL itself reduces the current total harmonic distortion (THD) by 55.79% and shortens the system dynamic response time to 0.01 seconds. This research provides effective theoretical and technical support for the electromagnetic compatibility (EMC) design of high-performance motor drive systems.

To achieve synchronous and uniform amplification of dense multi-carrier signals, this paper proposes a multi-frequency nondegenerate parametric amplifier (PA) based on a nonlinear spoof surface plasmon polariton (SSPP) waveguide. By engineering the dispersion characteristics of a varactor-diode-loaded waveguide, we realize an SSPP platform that exhibits minimized phase mismatch for three distinct signal-idler pairs under a constant pump frequency (13.348 GHz) and a fixed bias voltage. Experimental results show that the amplifier delivers highly uniform gains exceeding 20 dB for three closely spaced carriers at 6.363, 6.489, and 6.549 GHz, effectively emulating a three-frequency-shift keying (3FSK) signal. This work demonstrates a fixed-condition amplification scheme that requires no dynamic tuning, offering a promising solution for amplifying densely spaced carriers in integrated communication systems.