In this paper, a coplanar waveguide-to-rectangular waveguide TE₂₀ mode transition using an antisymmetric tapered probe is proposed. The transmission coefficient of the TE₂₀ mode is nearly 0 dB, and the reflection coefficient of the coplanar waveguide mode is smaller than -10 dB from 13.48 GHz to 14.7 GHz. In this frequency range, the transmission coefficient of the TE₁₀ mode is smaller than -20 dB while the reflection coefficient of the coupled slotline mode is smaller than -19 dB. Besides, a microstrip line-to-rectangular waveguide TE₂₀ mode transition using an antisymmetric fork is proposed. The transmission coefficient of the TE₂₀ mode is nearly 0 dB, and the reflection coefficient of the microstrip line mode is smaller than -10 dB from 13.34 GHz to 15 GHz. In this frequency range, the transmission coefficient of the TE₁₀ mode is smaller than -20 dB. To verify the simulation results, the coplanar waveguide-to-rectangular waveguide TE₂₀ transition and the microstrip line-to-rectangular waveguide TE₂₀ mode transition are back-to-back fabricated and measured, with the measurement results agreeing well with the simulation ones.

Temporal metasurfaces offer a promising platform for new-architecture wireless communications by enabling fast modulation of both electromagnetic waves and digital information. Optical control of these metasurfaces is particularly attractive as it establishes a direct physical bridge between optical and microwave signals, forming the foundation for optoelectronic hybrid communication systems. However, existing schemes are confined to static pre-alignment of the laser beam with the metasurface, lacking real-time spatial alignment capability essential for real-world mobile applications. Here, we propose and realize a mobile hybrid wireless communication system based on the designed laser-tracking-modulated microwave temporal metasurface. This communication system is constructed by integrating a photodiode-based microwave temporal metasurface, a vision-assisted laser-tracking transmitter, and a microwave receiver, enabling direct laser-to-microwave signal conversion sustained by dynamic alignment. Experimental results demonstrate that the system maintains successfully a stable hybrid communication link while the laser transmitter is in motion. This work provides a viable strategy for establishing stable hybrid wireless links for moving platforms and drones in high-mobility scenarios.

Conventional permanent magnet synchronous motors (PMSMs) suffer from limitations in speed regulation range, poor fault tolerance, and restricted torque output in electric vehicle drive applications. To address these limitations, this paper proposes a six-phase, 12-slot/10-pole hybrid-excited reverse-salient fault-tolerant motor (FT-HE-RSPM). To achieve reverse-salient characteristics and regulate the air-gap magnetic field, the rotor adopts segmented permanent magnets and a q-axis magnetic barrier. This design increases the d-axis inductance while reducing the q-axis inductance, achieving the reverse-salient characteristic L_d > L_q under rated conditions. Additionally, both the stator and rotor adopt segmented structures, forming axial magnetic paths via magnetic bridges. The excitation windings are embedded in the stator using non-magnetic materials, and the air-gap magnetic field is regulated by controlling the excitation current. The motor's magnetic field regulation mechanism was analyzed using the equivalent magnetic circuit method. Combined with three-dimensional finite element analysis (3D-FEA), the motor's electromagnetic performance and fault-tolerant characteristics were investigated, leading to the design of a current reconstruction fault-tolerant control strategy for single-phase open-circuit faults. Results demonstrate that this motor exhibits high torque output capability, excellent flux regulation characteristics, high efficiency, and outstanding fault tolerance, meeting the demands of complex operating conditions in electric vehicles.

This study proposes an extended design methodology for sequential load-modulated balanced amplifiers (SLMBAs), centered on regulating the impedance characteristics of balanced amplifiers (BAs) through continuous F^-1 class control amplifiers (CA). By expanding the load operating range of CAs at the second harmonic, the flexibility of high-efficiency designs is effectively enhanced. Theoretical analysis demonstrates that this load modulation mechanism overcomes the structural limitations of conventional LMBA, enabling high-efficiency power amplification across a wide frequency range and under conditions of large output power back-off (OPBO). Based on this architecture, an SLMBA prototype operating from 2.0 to 3.7 GHz was developed. Test results indicate that in saturated and 8 dB OPBO conditions, the drain efficiency (DE) reached 55.2%-68.7% and 46.8%-59.0%, respectively. When fed with an LTE signal featuring a 100 MHz bandwidth and 8 dB PAPR, the average DE across the entire bandwidth ranged from 49.2% to 58.3%, with an adjacent channel leakage power ratio (ACPR) exceeding -35 dBc.

Serendipity has long shaped transformative scientific discoveries, from penicillin and microwave oven to cosmic microwave background. These advances were not accidents but arose when prepared minds encountered unexpected phenomena in environments that enabled recognition and follow-up. In today's research climate, which often emphasizes narrowly defined goals and short-term deliverables, the role of serendipity is undervalued and frequently left to chance. This review introduces the concept of serendipity engineering: the intentional design of technologies, analytical frameworks, and research cultures that enhance the probability of meaningful chance discoveries. We outline four core principles - (i) expanding the observable space with advanced measurement tools, (ii) preserving anomalies through unbiased data stewardship, (iii) applying analytical methods that surface rare or emergent patterns, and (iv) fostering openness to unexpected results. Emphasis is placed on applications in biology and medicine empowered by advanced photonics and electromagnetism, where system complexity and disease heterogeneity make serendipitous findings particularly impactful. We propose a roadmap for embedding serendipity as a strategic component of 21st-century science, transforming it from a passive hope into an active driver of discovery.

Photonic crystals (PhCs) play a crucial role in describing the quantized collective behavior of wave functions. However, the existing investigations into their eigenstates primarily rely on classical computational methods. Variational quantum algorithm (VQA) represents a promising quantum computing technology that can be implemented on noisy intermediate-scale quantum (NISQ) devices, potentially surpassing the classical computational capabilities. Here, we propose a method to analyze the band and eigenstate properties of PhCs based on variational quantum eigensolver (VQE). We firstly reformulate the Maxwell's equations into a Hermitian generalized eigenvalue problem. By appropriately selecting a loss function and employing the proposed quantum eigenvalue solver, we successfully obtain the generalized eigenvalues using a quantum gradient descent algorithm. To validate our approach, we perform simulations on two prototypical PhCs in square and hexagonal lattices. The results demonstrate that a complex Ansatz can effectively capture the optimal solution, successfully yielding the generalized eigenvalues, but a simpler Ansatz exhibits significant limitations. Our findings provide new insights into the application of VQAs in PhCs and other quantum topological systems.

This paper proposes a Hybrid Multi-Strategy Enhanced Enzyme Action Optimizer (HSEAO) for designing multilayer broadband microwave absorbers under vertical irradiation conditions. The optimization objective is to minimize the absorber's reflection coefficient within a specified frequency range by selecting suitable material layers from a literature database. The performance of the Enzyme Action Optimizer (EAO) has been improved by introducing three enhancement strategies including Quasi-Opposition Based Learning (QOBL), adaptive coefficient, and leader follower. The effectiveness of these enhancement strategies is validated through simulation examples of five-layer and seven-layer microwave absorbers, achieving maximum reflection losses of -25.7975 dB and -18.1965 dB, respectively. Results demonstrate that HSEAO outperforms other heuristic algorithms in minimizing reflection coefficients for microwave absorber design. CST simulations further demonstrate that microwave absorbers designed by HSEAO achieve lower reflection losses.

With the advancement of wireless communication, Radio Frequency (RF) energy harvesting has gained significant attention over the past decade. RF energy harvesting is emerging as a sustainable alternative to conventional batteries, enabling self-powered operation in wireless sensor networks and Internet-of-Things (IoT) devices. This work presents a single band fractal based rectenna (Antenna with Rectifier) system for efficient RF energy harvesting. Here a single-diode shunt rectifier converts RF signals into usable DC power which will be usable to many self-powered wireless devices applications. The results show that the proposed antenna (41.03×37.24×1.6 mm³) features a bandwidth of 45.64% ranging from 2.08 GHz to 3.31 GHz and reflection coefficient of -60 dB at 2.45 GHz. The proposed antenna obtained maximum gain of 6.02 dBi with maximum radiation efficiency of 71.4% at 2.45 GHz. A diode rectifier with single stub matching network is used in which a HSMS2860 Schottky diode is connected in shunt for the rectification. The proposed rectifier obtains PCE of 70.07% and DC output voltage of 1.664 V at 5 dBm input power (P_in).

The Synthetic Aperture Interferometric Radiometer (SAIR) has demonstrated significant potential in Earth remote sensing and radio astronomy. However, most existing imaging methods rely on single-scale visibility function, while SAIR systems typically employ sparse arrays with insufficient sampling, which results in unsatisfactory imaging quality. In this paper, we propose a novel deep learning-based imaging method that addresses this limitation by leveraging multi-scale visibility function. The multi-scale visibility fusion network (MS-VFNet) introduces cross-attention mechanisms in the visibility domain for feature fusion across different scales, fully exploiting the implicit structural information, and subsequently reconstructs the brightness temperature images through a dedicated reconstruction module. The simulation results demonstrate that the proposed MS-VFNet achieves superior reconstruction accuracy and image quality compared to state-of-the-art methods, further validating the feasibility of multi-scale fusion in SAIR super-resolution imaging.

A compact four-element MIMO antenna with dimensions 40 × 32 × 1.2 mm³ is presented. The design employs stylized C-shaped radiators with slanted edges and a shared defected ground plane integrated with folded stubs to enhance impedance matching and bandwidth. Fabricated on an RT5880 substrate (ε_r = 2.2, tanδ = 0.0009), the antenna achieves an ultra-wide operating range of 4.24-19.70 GHz with inter-element isolation above 20 dB. Diversity metrics, including envelope correlation coefficient (< 0.02), diversity gain (≈10 dB), channel capacity loss (<0.0325 bits/s/Hz), and total active reflection coefficient (-12 to -24 dB), are verified through simulation and measurement, confirming robust MIMO characteristics. Owing to its wideband operation and high isolation, the antenna is suitable for sub-6 GHz 5G NR (n79: 4.4-5.0 GHz), WLAN/Wi-Fi (5.15-5.825 GHz), X-band navigation and radar (8-12 GHz), and Ku-band satellite communication (12-14.5 GHz).

To effectively suppress parameter perturbations, external disturbances, and ensure the stability of the PMSM system under uncertain conditions, this paper proposes a novel fast integral terminal sliding mode composite controller (NFITSMC) for speed-loop of PMSM based on super-twisting integral terminal sliding mode disturbance observer (STITSMO). Firstly, the mathematical model of the PMSM with parameter perturbations and external disturbances is analyzed. Then, the NFITSMC speed-loop controller is designed, where the NFIT sliding mode surface combines proportional, integral, and nonlinear terms, enabling effective suppression of parameter perturbations and external disturbances to ensure system stability under uncertainties. Meanwhile, the adaptive exponential switching reaching law adjusts the convergence speed according to the distance between the system state and the sliding surface, thereby mitigating system chattering. Next, the STITSMO disturbance observer is designed, in which the IT sliding mode surface is combined with a second-order super-twisting control law, allowing dynamic gain adjustment based on error magnitude to achieve global fast convergence of the adaptive nonlinear system. Finally, simulations and experiments validate that the NFITSMC-STITSMO composite controller demonstrates superior performance in finite-time convergence, robustness, chattering suppression, and disturbance rejection, making it suitable for high-performance and high-order PMSM control systems.

This paper investigates, by means of finite-element simulations, how the position of an aperture affects the electrostatic shielding effectiveness of a rectangular metallic enclosure. First, we compute the electric-field distribution on the surface of a completely closed enclosure placed in an external electric field. The results show that, for every wall, the field is weakest at the center, and that the field on walls parallel to the external field is far lower than that on walls perpendicular to it. Next, we determine the electric field that leaks into the enclosure after an aperture is introduced. We find that the field strength decreases with the distance from the aperture, that the field near the aperture is proportional to the surface field at the aperture's location when the aperture is covered. Also, its magnitude can be predicted by the classical model of the small aperture coupling. Finally, we investigate the coexistence effect and formulate guidelines for choosing the aperture position to achieve optimum shielding performance.

This study addresses multi-physics coupling challenges in high-speed sliding electrical contacts for Electromagnetic Launch Systems. A three-dimensional transient finite element model integrating electromagnetic-thermal interactions is established. By combining modified adhesion theory with Holm's contact resistance theory, we derive an analytical expression for dynamic contact resistance (DCR) that incorporates electromagnetic contact pressure, tangential friction, and temperature-dependent conductivity. The proposed localized modeling strategy with rail reverse motion technique efficiently resolves armature motion through coordinate transformation. Governing equations are discretized via the Galerkin method, with interfacial current continuity constraints and thermal partition coefficients enabling precise separation of Joule heating and frictional heat. Numerical results demonstrate robust current continuity compliance and reveal that DCR reaches its minimum during current peaks, exhibiting strong negative correlation with electromagnetic thrust. Tangential friction suppresses resistance rise by expanding the actual contact area, while electromagnetically dominated skin effects generate localized hotspots at contact trailing edges, armature limbs, and throat regions. This work elucidates the coupled frictional-Joule heating mechanisms governing multi-physics interactions, providing critical foundations for thermal management optimization in Electromagnetic Launch Systems.

In this paper, a wideband design of a conformal metasurface for RCS reduction in the range of 6.3~8.3 GHz is introduced. The proposed unit cell has a reflection amplitude less than -0.5 dB. The methodology for reducing the radar cross section using metamaterial is introduced along with the evolution of the design of the proposed unit cell. The conformal array is modeled using this unit, and the performance of a metasurface when being attached to a conformal metallic object is investigated. When the proposed metasurface is attached to a 3D object, it can achieve more diffused scattering patterns and wide scattering angles, regardless of the polarization of the incident waves and across a wide range of incident angles. It can achieve more than 10 dB reduction RCS. The sheet operates well for incident wave angles up to 60°. Both simulated and measured results demonstrate that the conformal metasurface effectively achieves diffuse reflection and RCS reduction which holds significant potential for applications in the field of advanced stealth technology, and the sheet size is scalable to larger sizes.

This paper presents an adaptive Direct Torque Control with Space Vector Modulation (DTC-SVM) strategy for a five-phase induction machine fed by a two-level inverter, designed to tolerate single open-phase faults. Under such fault conditions, the five-phase inverter generates only 16 voltage vectors distributed across 8 sectors, requiring a reconfiguration of the DTC-SVM control scheme. The proposed method introduces a modified vector selection and sector allocation approach tailored to faulted operation, enabling reliable performance without extensive controller redesign. Simulation studies in MATLAB/Simulink and experimental validation on a 3.5 kW five-phase induction motor confirm the effectiveness of the proposed approach. The results show that the adaptive DTC-SVM reduces torque ripple, maintains stable flux and current waveforms, and preserves fast dynamic response during sudden load changes. In addition, the method remains straightforward to implement, combining the simplicity of DTC with the improved voltage utilization of SVM.

A novel compact four-element MIMO antenna system is developed, featuring a rectangular Microstrip patch structure integrated with dual vertical grooves. The projected antenna design incorporate slits, triangular slot, and DGS to realize dual-band resonance with simultaneously multiband response and mitigating mutual coupling effects. The antenna operates effectively at 0.9 GHz and 2.4-2.6 GHz bands, supporting multiple IoT and wireless communication standards such as GSM (0.9 GHz), Lora (2.4 to 2.5 GHz), Wi-Fi (2.4 GHz), Bluetooth (2.4 GHz), LTE (Band 8 , Band 7, Band 41 and Band 53), and 5G (n8, n41). The antenna demonstrates satisfactory impedance matching, achieving return losses of -16.16 dB at 0.94 GHz and -31.19 dB at 2.496 GHz, with isolation levels exceeding -15 dB. The antenna delivers stable far-field radiation with 2.8-3.6 dBi gain, and prototype validation demonstrates strong agreement with simulations, confirming its suitability for compact, high-performance IoT (2.4 GHz) and 5G Sub-6 GHz devices.

This paper presents a broadband MIMO antenna for miniaturized satellites and a novel metamaterial for decoupling. The proposed metamaterial exhibits single-negative characteristics (with only permittivity ε being negative) in the 4.66-6 GHz and 6.5-9 GHz frequency bands, and double-negative characteristics (with both permittivity ε and permeability μ being negative) in the 6-6.5 GHz and 9-15.97 GHz frequency bands. In MIMO antenna applications, it significantly improves isolation between antenna elements. Finally, we develop a 4-port ultra-wideband (UWB) MIMO array antenna operating from 4.66 to 15.97 GHz, covering C-band, X-band, and Ku-band. It achieves S₁₁ < -10 dB with an operating bandwidth of 11.31 GHz. With the integrated metamaterial suppressing inter-unit coupling, the antenna demonstrates low-coupling performance (S₁₂, S₁₃, S₁₄ < −20 dB and ECC < 0.035) across the entire operating band. The maximum gain reaches 7.83 dBi, providing both high-gain performance and ultra-wideband decoupling capabilities. This MIMO antenna measures 55 mm × 55 mm × 1.6 mm and uses an FR4 substrate.

This paper proposes a composite control strategy integrating Adaptive Non-singular Terminal Sliding Mode Control (ANTSMC) with a Non-singular Fast Terminal Double-Power Sliding Mode Observer (NFTDPSMO) to achieve high-precision control of PMSM system. The strategy combines an adaptive non-singular terminal sliding mode controller with a novel sliding mode disturbance observer. The ANTSMC adaptively adjusts the convergence speed according to the distance between the system state and the sliding surface to suppress chattering, while the NFTDPSMO employs a triple-composite term with denominator modification to achieve singularity-free operation and global fast convergence. Simulated and experimental results demonstrate that under complex operating conditions including parameter perturbations, load variations, and external disturbances, the proposed composite controller achieves faster dynamic response, reduced current and torque pulsations, lower harmonic distortion (THD of only 7.1%), and significantly enhanced robustness and steady-state performance.

This paper proposes a novel microstrip patch antenna element and MIMO design based on quarter-mode substrate integrated waveguide (QMSIW). This design not only achieves antenna miniaturization but also effectively reduces the mutual coupling between antenna elements. The antenna element employs a triangular patch as the main radiator, with its long side grounded via two metal cavities. For bandwidth enhancement, a T-shaped strip is positioned at the center of the triangular patch's long side, and a new mode is introduced. A pair of slots is etched at the junction between the strip and the patch; adjusting the slot size enables dual-mode operation and control coupling. Building on this element, a 2 × 2 MIMO system is developed, featuring a compact size and requiring only one dielectric substrate, thereby achieving high integration and low cost. The patch occupies an area of (0.22 × 0.22λ₀²)/2, while the strip occupies 0.066 × 0.068λ₀² with high integration. The antenna achieves N78 band coverage with a total area of 0.0287λ₀². Experimental results demonstrate an 8.9% -10 dB impedance bandwidth (3.30-3.61 GHz) and -16 dB isolation, ensuring excellent overall performance. The antenna offers an effective solution for future 5G wireless communication systems.

Although Transformer models have made significant progress in the field of hyperspectral image denoising, their original architecture still has limitations in processing the spatial and spectral correlations of images. It often results in the loss of details in spatial features and insufficient exploration of the uniqueness of different spectral bands. To overcome these challenges, this paper proposes a Transformer based spatial spectral attention network aimed at enhancing the utilization efficiency of spatial spectral correlations. In response to the common problem of over smoothing in spatial feature processing, a dual channel spatial feature fusion module is introduced, which effectively enhances the capture of spatial details and ensures clear reproduction of image textures and edges. Meanwhile, in the spectral dimension, a multi-scale spectral feature extraction with self-attention mechanism is applied, which can sensitively identify and utilize the differences between spectral bands, thereby achieving more accurate feature extraction at the spectral level. By integrating residual connections in the spatial spectral feature extraction layer, the model can efficiently fuse spatial and spectral information, ultimately achieving high-quality denoising. The experimental results have verified the excellent performance of this method on both the ICVL dataset and the Urban real dataset, achieving good denoising results and demonstrating significant advantages in maintaining image details and spectral fidelity.