Hyperspectral images often suffer from various types of noise pollution during acquisition and processing, which can significantly affect their application. However, existing denoising methods have limitation in fully utilizing the spatial and spectral correlation of hyperspectral image. In order to take full advantage of the multiscale spatial features and global spectral correlation of hyperspectral image, a hyperspectral image denoising method based on multiscale spatial-spectral feature fusion in frequency domain is proposed in this paper. The proposed method utilizes the structural decomposition of multiscale wavelet transform to transfer the denoising of hyperspectral image to the frequency domain, not only minimizing information loss, but also decomposing noise into small scales, making it easier to remove in the frequency domain. Moreover, a cross-multiscale fusion attention is designed to improve the model performance by considering multiscale information and cross-space learning. A spectral position-aware self-attention module is proposed to more fully exploit the spectral correlation in hyperspectral image. And a multiscale fusion of spatial-spectral feature module is introduced to merge the different spatial and spectral features, thereby enhancing the denoising performance of the model. The experimental results demonstrate that the proposed method outperforms mainstream denoising methods in terms of performance. In addition, it exhibits better visual quality in texture details and edge protection.

In the field of drilling engineering, innovations in drilling communication(also known as hole-ground communication while drilling) technology are crucial for enhancing exploration efficiency, ensuring operational safety, and optimizing data collection. Extremely Low Frequency electromagnetic (ELF-EM) wave communication transmission technology, with its exceptional penetration capability in formations and low attenuation characteristics, is emerging as a key technology in drilling communications. However, this technology faces challenges such as complex transmission model calculations and difficulty in extracting weak signals from the ground, which hinder its further development. Addressing issues like the inability of conventional models to accurately describe non-uniform media, low frequencies, and near-field open-space conditions in ELF-EM transmission under drilling conditions, as well as numerical dispersion, this paper innovatively conducts a comprehensive and systematic analysis of electromagnetic distribution in extended-reach horizontal wells using the finite element modeling and analysis method. Through software simulations and field tests, the following conclusions are drawn: The induced current on the drill pipe plays a major role in the ground field distribution and the signal received by the system terminal; the horizontal drill pipe in a horizontal well has a certain impact on the ground-received signal, mainly manifesting in that the orientation of the ground-receiving electrode should align with the direction of the horizontal well, and the larger the azimuth difference is from the drilling direction, the smaller the signal reception is; at the surface of the drilling platform, not only can multiple electrodes be used to receive signals, but magnetic sensors can also be employed to receive magnetic component signals. Addressing the issue of extracting communication signals in complex electromagnetic environments during electromagnetic measurement-while-drilling (EM-MWD) operations, a multi-channel intelligent signal extraction method has been designed. This method can improve the in-band signal-to-noise ratio (SNR) by more than 3 to 5 dB and further extend the communication transmission distance compared to single-channel models.

This paper presents the design and implementation of a microstrip patch sensor based on a single complementary split ring resonator (SC−SRR), operating at a resonant frequency of 2.44 GHz for salinity detection. The sensor evaluates liquid under test (LUT) by monitoring variations in resonant frequency, reflection coefficient, and quality factor to extract the complex permittivity. The proposed design was simulated using High Frequency Structure Simulator (HFSS) and fabricated on an FR−4 substrate, incorporating a Teflon container to prevent direct contact with the sensing surface. Simulated and measured results exhibit a significant agreement, validating the sensor's performance. A frequency shift of 104.4 MHz was observed as the salinity concentration varied from 0 to 100 parts per thousand, attributed to dielectric perturbation effects. The proposed sensor demonstrates several advantages, including non-contact and non-destructive measurement, reusability, cost-effectiveness, high sensitivity, minimal fluid volume requirement, and reliable accuracy. These features highlight its potential for applications requiring precise and efficient.

This article presents a dipole antenna with added U- and L-shaped stubs designed with copper plates to support frequencies according to the Digital Video Broadcasting (DVB) standard in the 510-790 MHz range. The dipole antenna was placed on a polyester mylar film substrate with a thickness of 0.3 mm and a dielectric constant of 3.2. The CST program was used for simulating the optimization parameters with a size of 270 × 15.5 × 0.59 mm for the use with a flat-screen television. This research uses the technique of reducing signal wave reflection with a 1 × 41 units I-shaped electromagnetic band gap (EBG) strip, which is made from copper plates, placed beneath the antenna with foam sheets as an intermediary. The distance between the EBG plate and the antenna is appropriately 2 mm, with an impedance bandwidth of 46.01% (502-802 MHz) and a unidirectional pattern, resulting in an average gain of 3.62 dBi. For applications with television structures, installing the antenna and EBG plate at the top position can cover the most suitable frequency range, which is 44.32% (504-791 MHz).

The unbalanced rotor mass of permanent magnet assisted bearingless synchronous reluctance motor (PMa-BSynRM) will cause rotor vibration at the same frequency, which has a great influence on its operating performance at high speed. To solve this problem, a control method of unbalance vibration suppression based on variable step size and variable angle search algorithm is proposed in this paper. Firstly, the causes of rotor vibration are analyzed, and the equations of motion of the rotor in the vibratory state are derived. Secondly, the improved Sigmoid function is used to change the step size and angle of the search algorithm, and a fuzzy inference machine is used to adjust the Sigmoid function weights. The vibration suppression control system is constructed, and vibration suppression simulation is performed. The vibration suppression control of the PMa-BSynRM is realized. Finally, the PMa-BSynRM experimental platform is established, and vibration suppression experiments are carried out under the conditions of equal speed and external interference. Experimental results show that the control algorithm can effectively suppress rotor vibration. The unbalanced vibration suppression control proposed in this paper can achieve stable levitation operation of the PMa-BSynRM.

To address the problems of difficulty in adjusting weight coefficients in model predictive torque control of permanent magnet synchronous motors and the large influence of parameters on the motor control performance, a no weighing factor model predictive torque control based on a composite sliding mode disturbance observer is proposed. Firstly, the parallel structure of torque and magnetic chain is designed. The weighting factors are eliminated by choosing a common optimal voltage vector. Secondly, a composite sliding mode perturbation observer is designed to reduce the dependence on an accurate model of the motor. An improved variable gain approximation rate is introduced to eliminate observer jitter. A power exponential term is added to improve the exponential approximation term and to increase the convergence speed of the system state. Finally, the experimental results show that the proposed strategy not only eliminates the cumbersome tuning work of the weight coefficients but also improves the control performance of the motor under parameter mismatch.

This paper proposes a compact stepped-impedance low-pass filter using coplanar open-circuited stubs. The coplanar open-circuited stubs, which are used to compensate for the capacitive effect of the stepped-impedance low-pass filter, are implemented underneath the stepped-impedance low-pass filter. Consequently, the size of the stepped-impedance low-pass filter can be significantly reduced from 11.1 mm × 23.4 mm to 5.6 mm × 9.4 mm without altering its performance, amounting to a reduction rate of 79.83%. In addition, The transmission coefficient is attenuated below -30 dB, which is less than -20 dB attenuation of the conventional stepped-impedance low-pass filter. To verify the simulation result, the conventional stepped-impedance low-pass filter and the compact stepped-impedance low-pass filter using coplanar open-circuited stubs are fabricated and measured where the measurement results agree well with the simulation ones.

Adaptive control techniques are crucial in optimizing the performance of 2.45 GHz microwave transceivers amidst varying electrical parameters. These transceivers, integral to modern wireless communication systems, often encounter fluctuations in operating conditions that can impact signal quality and reliability. Adaptive control mechanisms enable real-time adjustment of transceiver parameters, ensuring consistent and efficient operation across diverse environments. This study addresses the adaptive control of a 2.45 GHz microwave transceiver in the presence of electrical parameter fluctuations, complemented by a multi-band antenna design aimed at minimizing losses. Electrical parameter fluctuations in transceivers can significantly affect performance and reliability, particularly in dynamic environments. The proposed approach integrates adaptive control algorithms to dynamically adjust transceiver parameters in response to fluctuations, ensuring optimal operational conditions. The integrated approach for adaptive control of a 2.45 GHz microwave transceiver, coupled with a multi-band antenna system optimized to reduce total harmonic distortion (THD). The study addresses the challenges posed by electrical parameter fluctuations in transceiver performance by employing adaptive control algorithms that dynamically adjust operational parameters. The multi-band antenna design, optimized through advanced modeling techniques, achieves a THD reduction of up to 20% across different frequency bands. Experimental validation demonstrates significant improvements in signal purity and transmission efficiency, showcasing the efficacy of this integrated approach in enhancing the reliability and performance of microwave communication systems in dynamic environments.

This article presents the design and analysis of a Compact Planar Antenna with Multi-Resonant Geometry for Broadband CubeSat Applications. The antenna features a dual-layer architecture comprising a front semi-circular radiator with strategically positioned circular and rectangular slots, and a complex ground plane etched with complementary geometries to enhance performance. The optimized geometry, with key dimensions such as an overall size of 15 mm × 15 mm × 1.5 mm, enables a wide impedance bandwidth ranging from 2.9 GHz to 11.6 GHz. The impedance bandwidth of the radiator is 120%, with an electrical size of 0.14λ × 0.14λ × 0.014λ. Confirmed through both simulation and measurement using a VNA in an anechoic chamber, the gain performance increases steadily with frequency, reaching a peak of 4.2 dBi at 9.2 GHz, while maintaining a stable gain above 3 dBi between 3.8 GHz and 10.1 GHz. Radiation efficiency peaks at 87% around 5.6 GHz and remains above 75% within the mid-band range (4-8 GHz), indicating highly effective power radiation and minimal losses. Surface current and 3D radiation pattern analysis show efficient and focused radiation behavior at 6 and 9 GHz, supporting its suitability for wideband radar and secure communication applications.

This work presents a compact single-band patch antenna designed for Near-Field Communication (NFC) based skin implant applications. The antenna features an inset-fed patch structure on FR-4 substrate and resonates at 2450 MHz. Three techniques are employed to miniaturize the antenna: a shorting pin between the patch and ground, defected ground structure (DGS), and utilization of tissue electrical properties. A polyamide insulator is used to cover the antenna for biocompatibility. Thus, the optimized antenna volume is found to be 6 × 6 × 0.46 mm³, with near-perfect impedance matching of 51.14 + j4.6 Ω. The antenna also offers enhanced impedance bandwidths of 52.24%. Compared to state-of-the-art designs, the proposed antenna exhibits significantly reduced specific absorption rate (SAR) values of 1.32 W/kg and 0.152 W/kg averaged over 1 g and 10 g of tissue, respectively, in compliance with international safety guidelines. The proposed antenna is effectively free from gain limitations due to the inherently short communication range of NFC technology. Finally, the antenna is measured for its return loss ex vivo, and it is found to be in close agreement with the simulation results. Thus, the balanced performance among the compact size, large bandwidth, and very low SAR makes the antenna a strong candidate for NFC based healthcare systems.

To address the challenge of balancing sidelobe suppression and computational efficiency in phased array random phase feeding optimization, this paper proposes a multi-objective collaborative optimization scheme based on the Dynamic Shuffled Frog Leaping Algorithm (DSFLA). By establishing a hardware-compatible binary encoding model for phase quantization errors and introducing sidelobe variance constraints, the method achieves joint optimization of peak sidelobe level (PSLL) and beam pattern flatness. Simulation results demonstrate: For 32-element Taylor-weighted arrays, optimized PSLL reaches -28.6 dB (8.8 dB improvement vs. initial) with sidelobe variance reduced from 3.5 dB² to 1.2 dB²; For Chebyshev-weighted arrays, PSLL achieves -31.2 dB. The algorithm maintains robust performance under practical imperfections including element spacing perturbations (0.02λ RMS error) where PSLL stabilizes at -27.3 dB (σ=0.9 dB), and phase quantization errors (5° RMS) yielding -27.9 dB PSLL. DSFLA significantly outperforms conventional methods - reducing convergence generations from 276 to 28 and computation time by 29.2% (85 s) versus ant colony optimization while demonstrating O(N^1.5) scalability to 128-element arrays (PSLL=-32.1 dB in 218 sec). Real-time operation is feasible with PSLL=-27 dB achievable in ≤40 ms, meeting 50 ms radar beam-switching deadlines. This approach provides a practical solution for real-time beam control in high-precision phased array radar systems.

In this paper, a novel miniaturized broadband dielectric waveguide (DW) bandpass filter (BPF) with wide stopband response is proposed. The proposed BPF is composed of two square DW resonators operating in TM₁₀₁ mode. By etching a coplanar waveguide (CPW) resonator on a silver-plated metal surface in the middle of the two DW resonators, an additional resonant mode is introduced, thereby broadening the bandwidth of the filter while retaining the inherent advantages of the DW structure. Simultaneously, the CPW resonator creates a new coupling path that enables cross-coupling and introduces a controlled transmission zero (TZ). The position of the TZ can be adjusted to suppress the second harmonic of the filter, ensuring effective stopband performance. For verification, a DW BPF with center frequency of 5 GHz and a fractional bandwidth of 11.4% was designed, fabricated, and measured. The measured results are in excellent agreement with the simulated ones. Specifically, the upper stopband of the filter extends to twice of the center frequency (10 GHz), demonstrating the wide stopband characteristics of the filter.

Aiming at the crosstalk problem between multiple coupled transmission lines in high-speed interconnection, a crosstalk cancellation method based on the inverse matrix of the Coupled Transmission Lines-Transfer Function Matrix (CTL-TFM) is proposed. The method first constructs the transfer function matrix of multiple coupled microstrip lines, and then designs the corresponding circuit for the inverse matrix of the transfer function matrix at the output ports. This ensures that the transfer function matrix of the entire system is reduced to a unit matrix, effectively reducing the crosstalk between transmission lines. Simulation results show that the quality of the signal eye diagrams at the outputs of all three coupled microstrip lines is significantly improved after using this method, and the crosstalk amplitude and jitter are substantially reduced.

A 2D flat, 2D curved, and 3D finite element method (FEM) implementation of the spatially-variant lattice (SVL) algorithm is presented. This powerful algorithm is used in electromagnetics to preserve the electromagnetic properties and geometry of periodic structures that are bent, twisted, conformed, or otherwise spatially varied. Applications of the SVL algorithm include photonic crystals, metamaterials, conformal frequency selective surfaces, cloaking devices, and volumetric circuits over complex geometries. The present work shows examples of SVLs over a planar surface lattice, a doubly-curved surface lattice, and a volumetric lattice.

This paper presents the design and development of a miniaturized Multiple-Input Multiple-Output (MIMO) antenna for sub-6 GHz 5G applications, featuring reduced cross polarization and enhanced isolation between antenna elements. Utilizing characteristics mode analysis, slots are introduced in the patch to achieve orthogonal mode separation, effectively minimizing cross polarization. Further bandwidth enhancement is achieved by incorporating slot loading in the ground plane. To improve isolation between antenna elements, spiral decoupling (SD) and aperture spiral decoupling (ASD) structures are employed. The proposed MIMO antenna, with dimensions 0.32λ_o*0.32λ_o*0.01λ_o where λ_o is the wavelength at the lower band frequency of 3.5 GHz, was fabricated and experimentally tested to validate its performance. Measurement results indicate significant compactness, low envelope correlation coefficient (ECC), high gain, minimal channel capacity loss, and very low mutual coupling between elements. The measured results are in good agreement with simulated results, confirming that the proposed antenna is a promising candidate for advanced MIMO applications in next-generation wireless communication systems.

To address internal parameter ingress and external load perturbations in the speed loop of a permanent magnet synchronous motor (PMSM) and enhance the dynamic performance and robustness of its speed control system, this study proposes a novel adaptive sliding mode reaching law-based controller integrated with a global non-singular fast terminal sliding mode observer (GNFTSMO). The proposed reaching law incorporates system state variables as power functions, thereby minimizing steady-state errors and resolving the inherent trade-off between chatter suppression and rapid response. To further enhance the dynamic and steady-state performance of the PMSM control system, a GNFTSMO is designed. This observer reduces the switching gain of the convergence law while incorporating feed-forward compensation for perturbations, thereby improving the system's anti-disturbance capability. The feasibility and effectiveness of the proposed sliding mode control method are empirically validated through both simulation and experimental studies.

This paper investigates a new, simple, fast, and broadband procedure to extract the material intrinsic parameters through new mathematical modeling. It only uses the transmission coefficient of two identical lines. The method is based on the mathematical reformulation of the two transmission lines, taking into account the effects of discontinuities at the interface connecting the trapper and the connector, as well as the included S-parameters. These test cells have different lengths, so the sample under test (SUT) complex relative permittivity is determined after fixing the vacuum structure's electric length. At the same time, the mathematical formulation of the telecommunications equation, which links transmission and reflection coefficients, was used to determine the loss tangent parameter by combining the attenuation and phase coefficients. The correction of the electric length difference of the transmission coefficients resulting from the measurement of the vacuum-filled test cells is done using an affine function. The frequency is the variable parameter, and the slope (rate of variation) and the initial value (ordered at the origin) are computed according to the test cell used. On the one hand, the suggested principle has the advantage of extracting the relative permittivity of the sample under test beyond the limit set by the appearance of higher-order modes (propagated by considering the test fixture's transverse dimensions). On the other hand, the use of the reflection coefficient, although it improves the attenuation coefficient extraction, limits the characterization band of the loss tangent. A circular coaxial test fixture has been used in the 1-20 GHz frequency range to validate the proposed method with samples of various materials, including semolina, polenta, Q-Cell 5020 (ceramic powder), aquarium stone, distilled water, and phantom gel. The results are compared with those from the two transmission lines technique, as defined in its popular form.

The lightning channel is a rapidly evolving transient plasma that radiates intense electromagnetic (EM) fields and emits broadband optical radiation. This paper presents a theoretical and experimental investigation into the correlation between electromagnetic fields generated during lightning events and the corresponding optical spectra observed during various phases of the discharge. Using advanced EM field modelling and high-speed optical spectroscopy, we demonstrate that key plasma parameters such as temperature, electron density, and ionization state can be inferred from combined electromagnetic-optical datasets. This multidisciplinary analysis not only reveals the underlying physical characteristics of the lightning channel but also provides insights for future atmospheric diagnostics, lightning modelling, and protective technologies.

In this paper, a novel multiple-input multiple-output (MIMO) antenna for 5G applications in n77, n78, n79 and 6 GHz bands is proposed. The antenna structure is compact, measuring 30×50×1.5 mm³. The antenna is composed of two microstrip antenna units, which are formed of two hexagonal rings with lotus and small human, with the floor partially removed. The antenna functions in a frequency range of 3.3 to 9 GHz. The flow of coupling currents is impeded, and the isolation of the antenna is improved by the use of stepped rectangular slots and the floor of the projecting T-shaped structure, resulting in the antenna having an isolation of less than -20 dB over the entire operating bandwidth. Furthermore, the envelope correlation coefficient (ECC) is less than 0.008, the diversity gain (DG) greater than 9.95, the total active reflectance coefficient (TARC) less than -30 dB, and the channel capacity loss (CCL) less than 0.32 bit/s/Hz. The simulations and measurements of the antenna demonstrate its reliability and stability, thus indicating its potential for significant applications in 5G wireless communications.

This paper introduces a novel wideband antenna composed of fabric materials, suitable for wearable and flexible applications and a straightforward single-unit Metamaterial (MTM). The antenna design employs ShieldIT Super as the conductive fabric and Felt as the dielectric substrate, creating a lightweight and adaptable solution with dimensions of 58 mm × 34 mm × 2 mm. Operating over a frequency range of 1.88 to 6.88 GHz, the proposed antenna achieves a peak gain of 4.72 dBi and a radiation efficiency of 94%. The antenna has wide measured bandwidth from 1.2 to 3.5 GHz (97%) and 4.0 to 5.9 GHz (38%) with average measured gain of 3 dBi in the lower band and 4.6 dBi in the upper band. The MTM-inspired design features a double rectangular complementary split-ring resonator at the center of the radiating patch, which enhances bandwidth. The MTM structure exhibits epsilon-near-zero (ENZ) and Mu-negative (MNG) properties were proposed. This novel design illustrates significant advancements in wideband antenna performance and is suitable for fabric-based S band, C band, 5G, Wireless Body Area Network (WBAN), and microwave imaging applications.