For assessing Geomagnetically Induced Currents (GICs) risks in mid-latitude coastal power grids, this study developed a three-dimensional Earth conductivity model that incorporates coastal effects. The model was constructed using geological cross-sectional data from the China Earthquake Administration and measured terrestrial conductivity data. Focusing on the strong geomagnetic storm of February 27, 2023, the spatiotemporal characteristics of GICs in Shandong Peninsula across 34 substations and 46 transmission lines were accurately computed. The GICs peak of the substation appears at Muping , and the GICs peak of the transmission line appears at Zouxian-Luzhou Line. Notably, two coastal substations exceeded the safety limit for GICs. Areas of highest risk are concentrated in the southeastern coastal region of Shandong, underscoring the significant impact of coastal effects and changes in Geological Structure. This method and its findings provide a global reference for predicting and issuing early warnings regarding GICs in long-distance mid-latitude coastal power grids.

Coarse discretization introduces significant errors in the solution of scattering problems, in part due to discretization errors in the contrast operator. We present a procedure for the automatic construction of a modified contrast operator for electromagnetic scattering problems by using trainable neural networks to represent a modified contrast operator. We achieve a higher accuracy on a coarse discretization while still keeping computation time down compared to a fine discretization. By using synthetic data from a full-wave Maxwell solver to train the network for one-dimensional slab scatterers and two-dimensional polygonal scatterers, we are able to use the techniques found in deep learning to improve accuracy in coarse-grid forward scattering problems.

An original computational framework is developed to simulate the propagation of ultrashort laser pulses with arbitrary temporal and spectral profiles through uniform linear dielectric materials. The study investigates how spectral phase sampling during propagation affects computational efficiency and accuracy. The proposed approach enables a comprehensive analysis of ultrashort pulse evolution in both the time and frequency domains. To demonstrate its effectiveness, the algorithm is applied to various propagation phenomena, such as temporal and spectral shifts, pulse broadening, asymmetric distortions, and chirping in dispersive media, using a wavelet-based time-frequency decomposition.

In this paper, a broadband circularly polarized (CP) magneto-electric (ME) dipole antenna based on microstrip line aperture-coupled feeding structure is proposed. The antenna is fed by the microstrip line, which is utilized to couple the energy to the antenna through the slot etched on the ground plane. Based on a linearly polarized (LP) ME dipole antenna, two centrosymmetric L-shaped strips are loaded to the patches located at the +45° diagonal position and the patches located at the -45° diagonal position are truncated. As a result, the current direction is changed to be parallel to the equivalent magnetic current to radiate CP wave. To improve the axial-ratio (AR) bandwidth of the antenna, the rectangular slot initially etched on the ground plane is modified to an asymmetric cross slot, which can generate a minimum AR point at high frequency. In this way, the AR bandwidth is increased from 32.4% to 51.7%. On this basis, to further extend the AR bandwidth, the metal columns are introduced at both ends of the antenna, and another additional AR minimum point is generated at the low frequency. The measured results indicate that the impedance bandwidth (|S₁₁| ≤ -10 dB) is 57% (2.40-4.33 GHz) and the 3 dB AR bandwidth is 63% (2.39-4.57 GHz). Moreover, the proposed antenna exhibits flat gain and stable unidirectional radiation pattern across the operational frequency region.

This paper introduces a compact, circularly polarized (CP) truncated-corners patch antenna with a highly stable phase center for Global Positioning System (GPS) L1 applications. The antenna is excited by a central coaxial feed and features two corner truncations and a square-shaped slot with an integrated tab to generate CP. Designed for the GPS L1 band (1.563-1.587 GHz), the antenna achieves a -10 dB impedance matching bandwidth of 100 MHz (1.52-1.62 GHz), covering the target frequency range. Key performance metrics include a wide 3-dB axial ratio (AR) beamwidth of 190° and a fractional AR bandwidth of 1.5%. A prototype was fabricated and tested, and the measured results show reasonable agreement with simulations, confirming the design's effectiveness.

This paper presents a single-layered dual-band microstrip patch antenna with periodic sinusoidal slots. The antenna operates within 860-930 MHz and 2400-2500 MHz. The first band encompasses both the European as well as North American UHF-RFID bands while the second band covers the 2.45 GHz Microwave-RFID/WLAN band. Moreover, the presence of the sinusoidal slots helps the antenna exhibit frequency-dependent beam scanning within the 2.45 GHz band. Four such antenna units are placed close to each other with different orientations to create a 2 × 2 antenna system. This system can detect UHF-RFID tags using both horizontal and vertical polarizations. It can also perform frequency-dependent beam scanning with horizontal polarization in the yz-plane and vertical polarization in the xz-plane. The beam maximum scans from -300 to 310 in the yz-plane and -320 to 290 in the xz-plane.

The article presents the geometry and optimization of a small-sized dual-band F-shaped monopole antenna for medical applications in the 2.45/5.8 GHz ISM bands. The antenna is printed on a partial ground FR4 substrate, and its geometrical parameters are optimized by a hybrid procedure based on Artificial Neural Networks (ANNs) and Particle Swarm Optimization (PSO).Two ANN architectures, Feedforward Backpropagation Neural Network (FFBPN) and Generalized Regression Neural Network (GRNN), are trained on a dataset of 121 samples generated using varying patch sizes. The FFBPN model is better with a mean squared error of 3.9506 × 10^-5 at epoch 21. The optimized antenna has resonances at 2.448 GHz and 5.8 GHz with S₁₁ < -10 dB, bandwidths of 610 MHz (2.21-2.82 GHz) and 400 MHz (5.61-6.01 GHz), and peak gains of 2.262 dBi and 3.861 dBi, respectively. Measurements on a prototype are in agreement with simulations to confirm the appropriateness of the design for wireless medical devices, such as wearable sensors and telemedicine systems.

This paper presents a compact dual-band RF energy harvesting rectifier designed for operation at 2.45 GHz and 5.2 GHz Industrial, Scientific, and Medical (ISM) bands. The rectifier employs a voltage-doubler topology integrated with a dual-band impedance matching network (MN) composed of a coupled-line section and a microstrip transmission line. The analytical design of the MN is established using the ABCD-matrix formulation to determine the initial modal impedances and electrical lengths, which are subsequently refined through full-wave electromagnetic optimization in ADS. The proposed approach achieves accurate dual-frequency impedance transformation using only two matching segments, significantly simplifying the structure compared with conventional multi-section designs. The prototype, fabricated on a low-cost FR-4 substrate, occupies a compact area of 34×25 mm². Measurements show high power conversion efficiencies of 75% and 55% at 2.45 GHz and 5.2 GHz, respectively, under a 0 dBm input power and a 1 kΩ load, in close agreement with simulations. The results confirm that the proposed design provides an effective and low-cost solution for ambient RF energy harvesting and low-power IoT applications.

Cables are the main coupling path of electromagnetic interference, and the electromagnetic interference generated by cable conduction and radiation can interfere with the motor position encoder signal. Cable grounding can reduce the impact of this interference on the encoder signal. Therefore, this article first obtains the shielding mechanism of single end grounding and double end grounding of cables through theoretical analysis. Then, under two interference modes of plane wave radiation and adjacent cable radiation, the voltage frequency response and interference voltage peak and amplitude of single end grounding and double end grounding of the cable were compared. The results showed that the double end grounding of the cable shielding layer had better anti-electromagnetic interference effect. In addition, based on the double end grounding, comparing the interference voltages of different grounding resistances, cable lengths, shield thicknesses, and load conditions, some conclusions about the changes in interference voltage have been obtained.

Underwater electromagnetic communication is severely limited by the high permittivity and conductivity of water, which cause strong attenuation at higher frequencies. To overcome this challenge, a compact dual-polarized hexagonal loop antenna is proposed and experimentally validated for low-frequency underwater communication at 40-45 MHz. The antenna, fabricated on FR-4 and sealed with epoxy resin, eliminates bulky waterproof housings while ensuring stable impedance performance with a measured return loss better than -10 dB. Experiments conducted in freshwater confirm the effectiveness of polarization diversity, achieving an average received-power improvement of 4.59 dB under maximal-ratio combining. These results demonstrate, for the first time, the feasibility of a practical dual-polarized hexagonal loop design for robust, low-frequency underwater communication systems and future MIMO-like implementations.

In this paper, we present a dual-mode, dual-polarized orbital angular momentum (OAM) antenna, implemented as a four-element uniform circular array (UCA) with a series-fed network on a single-layer substrate. The novelty of the antenna lies in its ability to generate four orthogonal states simultaneously in a single transmission channel - two from l = ±1 OAM states and two from vertical/horizontal polarizations - without requiring multilayer feeds or complex phase-shifting networks. Full-wave simulations and experimental measurements have been used to validate the antenna's performance within the 5.85-6.1 GHz band. Far-field radiation patterns exhibit the characteristic vortex-beam profile, featuring a conical shape with a central null, while phase distributions reconstructed via FFT-based holography confirm the generation of distinct OAM modes. The antenna has four feed ports; of these, activating Ports 1 and 4 yields the highest OAM modal purity at 6 and 6.1 GHz, while Ports 2 and 3 peak in purity at 6.1 GHz. Owing to its compact, reconfigurable architecture, the designed and tested antenna is well-suited for integration into space- and power-constrained platforms such as UAVs, IoT devices, and full-duplex MIMO systems.

With the increasing demand for high-capacity communication systems, vortex beams endowed with orbital angular momentum (OAM) have emerged as a promising candidate for enhancing channel capacity of communication systems. Persistent limitations of conventional OAM generators, such as narrow bandwidth, single-mode constraints, and decreased purity in high-order OAM modes are addressed. In this work, by combining Pancharatnam-Berry (PB) phase theory and equivalent circuit, we design a metasurface unit with gradient phase compensation. The metasurface unit overcomes the bandwidth limits of the resonant structures, achieving 360˚ linear phase modulation over 8-20 GHz (85.7% relative bandwidth) and allowing vortex waves with multiple OAM modes and high order mode purity. Quantitative assessment of modal purity via OAM spectral decomposition demonstrates exceptional agreement between experimental measurements and full-wave simulations, thereby corroborating the theoretical framework and underscoring the methodology's potential for practical implementation.

To mitigate unbalanced vibration caused by rotor eccentricity in composite cage rotor bearingless induction motors (CCR-BIM), this paper proposes an enhanced hybrid control strategy integrating a rotor-speed adaptive second-order generalized integrator (RA-SOGI) harmonic observer with dual-channel compensation. A variable step-size adaptive LMS (VSS-ALMS) algorithm is introduced to optimize RA-SOGI, enabling real-time extraction of fundamental vibration components with reduced computational burden and improved convergence. In the feedback channel, an adaptive PID controller with variable learning rates and residual feedforward correction is designed, achieving a superior balance between transient response and steady-state precision. Lyapunov-based analysis establishes the global asymptotic stability of the proposed scheme under practical step-size constraints. Experimental validations demonstrate that the proposed method significantly outperforms conventional PID and feedforward control, achieving faster convergence, higher vibration attenuation, and enhanced trajectory stability in high-speed CCR-BIM operation.

A wide band, high gain 1 × 2 array Vivaldi shaped slot Substrate Integrated Waveguide (SIW) Multiple Input Multiple Output (MIMO) antenna with square shaped periodic Artificial Magnetic Conductor (AMC) placed beneath the antenna for applications in X band is presented. A two-port MIMO antenna backed by AMC patches is designed and realized for enhanced gain and bandwidth. The single antenna 1 × 2 array has electrical dimensions of 1.57λ_r × 1.13λ_r × 0.027λ_r. The designed antenna structure has bandwidth of 1.39 GHz (8.79 GHz-10.18 GHz) with a percentage bandwidth of 14.65% and Gain of 11.67 dBi. The edge to edge distance between the MIMO antenna elements is 5 mm (λ_r/4). The periodic AMC patches improve vital MIMO antenna performance metrics like Isolation, Envelope Correlation Coefficient (ECC), Diversity Gain (DG), Channel Capacity Loss (CCL) and radiation pattern. The unit cell analysis of periodic square AMC patch and a polynomial regression model to find the best goodness of fit for Gain-Bandwidth product versus square AMC patch size is studied. Antenna gain variation seen over the complete bandwidth is < 1 dBi which makes it a flat gain response antenna. The proposed high-gain, wide-band 1 × 2 Vivaldi-slot SIW MIMO antenna with AMC is suitable for X-band radar, point-to-point high-throughput wireless links, and compact platform communication systems requiring robust diversity performance.

In this paper, a new method is proposed for failure diagnosis of programmable metasurfaces, which jointly uses the single-point measurement strategy and Bernoulli-Gaussian (BG) prior. Specifically, leveraging the dynamic tuning property of programmable metasurfaces, the radiated fields is measured with a single fixed probe, therefore reducing the time and error of the measurement process. Moreover, the BG prior inherent in the programmable metasurface under test is exploited during the reconstruction process in order to perform the diagnosis with a small number of measurements without resorting to prior knowledge of the radiation pattern of the failure-free programmable metasurface. The accuracy, efficiency and robustness of the proposed method are verified through a set of representative numerical experiments, where the results are compared with those from existing diagnostic methods.

This paper presents a medical ethanol concentration sensor based on the principles of liquid-coupling loss, which enables rapid and accurate measurement and classification of medical ethanol concentrations. The sensor system consists of integrated circuits for liquid-coupling loss, amplitude detection, signal processing, and visualization. It utilizes variations in RF signal amplitude to determine the concentration. Theoretical analysis, grounded in the Bruggeman model, quantitatively correlates the dielectric constant of medical ethanol with its concentration, thereby establishing a robust theoretical foundation for the sensor design. Experimental validation demonstrates the sensor's ability to precisely differentiate among medical ethanol concentrations of 95%, 75%, and 50% at test frequencies of 1 GHz, 2 GHz, and 3 GHz. The agreement between empirical data and theoretical predictions confirms the sensor's efficacy and reliability. Key advantages include user-friendly operation, cost efficiency, and intuitively presented results, rendering the sensor highly suitable for broad medical applications.

This paper presents a 2.45 GHz/5.8 GHz circularly polarized RFID reader antenna based on an Artificial Magnetic Conductor (AMC) for detecting tagged objects in IoT applications. An efficient reader antenna is proposed to increase the interrogation distance and reduce the uncertainty in tag detection. The antenna consists of two dipole pairs printed on both sides of the substrate to operate at 2.45 GHz and 5.8 GHz, connected via feed delay lines in a cross-dipole configuration. The read range is further enhanced by a 5×5 AMC surface placed 0.042λ₀ below the printed antenna, where λ₀ is the wavelength at the lower resonant frequency. The AMC backing results in a gain of 7.1 dBi at 2.45 GHz and 9.41 dBi at 5.8 GHz, improving the read range of the reader. Impedance bandwidth is also enhanced to 2.25-2.91 GHz for the 2.45 GHz band and 5.1-6.3 GHz for the 5.8 GHz band, reducing tag detection errors. The axial ratio bandwidth of the antenna is 2.18-2.99 GHz at 2.45 GHz and 5.27-5.88 GHz at 5.8 GHz, ensuring circular polarization over the operating bands.

To enable accurate online observation of permanent-magnet (PM) flux linkage in permanent-magnet synchronous motors (PMSMs), this paper proposes an improved adaptive higher-order square-root cubature kalman filter (IAHSRCKF) flux-linkage observer. Firstly, a nonlinear PMSM model is established to capture complex operating conditions. Secondly, fifth-order cubature integration and an adaptive estimator are embedded into a square-root cubature Kalman framework, yielding an adaptive fifth-order SRCKF observer that tracks PM flux-linkage variations under parameter drift and disturbances. Then, experimental scenarios are created by perturbing key electromagnetic and mechanical parameters and injecting external time-varying disturbances. Finally, simulation and hardware tests benchmark the proposed IAHSRCKF against UKF, CKF, and SRCKF. Results demonstrate that IAHSRCKF achieves the highest flux-estimation accuracy, exhibits low sensitivity to parameter uncertainties, and maintains strong robustness across complex operating conditions, thereby enabling reliable online monitoring of PM flux linkage.

A compact Ultra-Wideband (UWB) Multiple-Input Multiple-Output (MIMO) antenna with a culturally inspired radiating structure is developed in this study. The radiating element is inspired by the traditional gonjong shape of Minangkabau architecture, which resembles upward-curving buffalo horns, forming a distinctive roof-like patch that enhances the impedance characteristics. A 50-ohm microstrip line is used to excite the patch, with a partial ground plane placed beneath the patch. To improve bandwidth and support low-frequency operation, an L-shaped strip is introduced on the ground plane, and the patch is optimized through edge modification and parametric analysis. The antenna achieves a wide measured impedance bandwidth of 2.2-20 GHz (S₁₁ < -10 dB), fully covering and extending beyond the Federal Communications Commission (FCC)-defined UWB range. High isolation is achieved with S₁₂ consistently below -20 dB across the band. Excellent MIMO performance is demonstrated with an envelope correlation coefficient (ECC) below 0.01, diversity gain (DG) above 9.95 dB, channel capacity loss (CCL) lower than 0.4 bit/s/Hz, and Total Active Reflection Coefficient (TARC) below -10 dB. The antenna also exhibits stable radiation patterns and maintains high efficiency throughout the operating band. With overall dimensions of just 30 × 30 mm², the developed antenna is more compact than most recent UWB MIMO designs, making it highly suitable for modern wireless communication systems requiring wide bandwidth and reliable multi-antenna performance.

High frequency communication systems are critical for 5G networks, particularly in the millimeter-wave bands, where ultra-wideband (5G-UWB) performance is essential for high data rates and low latency. In this work, we propose, for the first time to the best of our knowledge, an ultra-wideband 5G MIMO beamforming module covering both the 28 and 60 GHz bands. The proposed design is based on a low-cost, low-profile Rotman Lens (RL) implemented on an FR4 substrate with a thickness of 1.6 mm and a dielectric constant of 4.3. The RL features five beam ports and seven array ports, with additional dummy ports introduced to minimize reflections and enhance adjacent beam port isolation across the full 5G-UWB range. Simulation results demonstrate excellent performance, with isolation and mutual coupling maintained below -25 dB between input beam ports and below -15 dB between array ports across the entire bandwidth. The VSWR remains below 2 for all ports. Although this work presents a single RL-based beamformer, it is envisioned as a building block within a larger hybrid MIMO architecture, where multiple lenses can be interconnected to support parallel data streams and spatial multiplexing. This modular approach enables flexible scaling to full MIMO operation while maintaining low cost and compactness. The proposed design is a strong candidate for 5G and mmWave applications, including hybrid beamforming systems, MIMO architectures, radar, and satellite communications. Comparative analysis with recent literature demonstrates its superior bandwidth and isolation performance.