This study introduces and evaluates a smaller rectangular antenna featuring parasitic mushroom patches to achieve enhanced gain and wide impedance bandwidth (WIBW) for 5G millimeter-wave (mm-wave) applications (28 GHz/38 GHz). The antenna structure consists of a simple rectangular patch fed by an inset feed microstrip line operating at 50 Ω. To improve the antenna gain and impedance bandwidth, a parasitic mushroom structure is introduced around the edges of the main patch. Additionally, to further enhance operating bandwidth and matching, two rectangular Defected Ground Structures (DGSs) are incorporated in the bottom side. The antenna is fabricated on a low-cost substrate specifically FR4 (ε_r = 4.4 , tangδ = 0.02), with dimensions of (12 × 13 × 0.8) mm³. The results demonstrate a wide impedance bandwidth of 14.2 GHz (50.71% FBW) covering frequencies of 25.98 GHz to 40.18 GHz, and the antenna achieves a maximum gain of 7.20 dB at 28 GHz and maintains an efficiency more than 80% across the entire bandwidth. These outcomes make the antenna a good choice for 5G applications at 28 GHz and 38 GHz.

This paper presents a compact four-port ultra-wideband (UWB) multiple-input multiple-output (MIMO) antenna with exceptional isolation characteristics, specifically designed for high-frequency band communications. The antenna features a sunflower-shaped radiating patch and an irregularly stepped rectangular ground structure, which are optimized to achieve broadband impedance matching and low coupling. With dimensions of 1.26λ₀ × 1.26λ₀ × 0.025λ₀, the antenna operates across 5.4-20 GHz, covering C-band (4-8 GHz), X-band (8-12 GHz), and Ku-band (12-18 GHz), while supporting multi-band communication compatibility. Simulation and measurement results show a return loss (|S₁₁|) below -10 dB over the entire frequency range, with a fractional bandwidth of 109.5%. The inter-port isolation (S₁₂) exceeds -20 dB across the band and reaches -30 dB in the high-frequency range (10-20 GHz). The antenna exhibits a radiation efficiency exceeding 80%, a peak gain of 9.3 dBi, an envelope correlation coefficient (ECC) below 0.008, a total active reflection coefficient (TARC) below -30 dB, and a group delay less than 2.3 ns, thereby meeting the stringent requirements for MIMO systems. This design offers a high-performance solution for applications in 5G, satellite, and radar communications, which combines wide bandwidth, high isolation, and low coupling in a compact form factor. The 5.4-20 GHz antenna bandwidth supplements 5G/6G applications which caters to multi-scenarios of Wi-Fi and satellite communications and facilitates signal reception and preprocessing in LEO satellite systems.

A high-impedance ground plane has been proposed that enables the reflection of magnetic fields within a frequency range of interest. When being combined with loop coil antennas or H-field-oriented structures, it can boost transmission efficiency by up to 3 dB. Although several approaches, such as mushroom-shaped protuberant surfaces paired with capacitive loading, have been described to suppress surface waves at certain frequency ranges, the shift to a desired frequency range (e.g., from 5 GHz to 1 GHz) is marginal, and their form factors make these methods less ideal for applications in power and data communication. Here, we describe new strategies for a low-profile high-impedance ground plane. The insertion of a metal ground plane between the top and bottom mushroom-shaped surfaces reinforces capacitive couplings between adjacent unit cells. When coupled with extended spiral paths, this configuration leads to an apparent change in the resonant frequency of the structure. Fabrication of the proposed structure demonstrates that the sandwiched metal ground plane, paired with extended spiral paths, leads to a noticeable shift in the resonant frequency toward lower sub-GHz ranges at given dimensions. Measurements are in good agreement with the results from the analytical model.

In order to reduce the use of rare-earth materials and solve the problem of rising manufacturing costs of permanent magnet motors due to higher rare-earth prices, this paper proposes an asymmetric segmented less-rare-earth permanent magnet motor (ASLREPMM), which combines NdFeB permanent magnets with ferrite permanent magnets to form a common excitation source. In order to efficiently design the parameters of this motor, an optimization strategy of sensitivity stratification and multi-objective optimization is proposed, with output torque, torque pulsation, cogging torque and peak air-gap magnet density as the optimization objectives, and multi-objective optimization is carried out on the optimization variables with high sensitivity. Compared with the V-type permanent magnet motor (V-type PMM), the cogging torque of the optimized ASLREPMM is decreased by 49.67%, torque pulsation decreased by 10.77%, peak air-gap magnetic density increased by 0.051 T, and the total amount of NdFeB material decreased by 2184 mm³. The reasonableness of the structural design and the effectiveness of the optimization of the ASLREPMM are verified through experiments.

This paper addresses the challenge of inter-band interference suppression in Dual-Band Power Amplifier (DBPA) by proposing a high-isolation dual-band power amplifier design integrated with a Ring-Coupled Bandstop Filter (RCBSF). Through a ring-coupled structure of main transmission lines and coupled branches, combined with the collaborative tuning of λ/4 open stubs and coupling capacitor, the design achieves low-loss transmission in the dual-frequency passbands of 1.5 GHz and 2.1 GHz, forms a suppression band of ≥ 20 dB in the 1.6-2.0 GHz range, and realizes deep suppression of > 40 dB for second/third harmonics. The RCBSF is embedded into the output matching network of the power amplifier to form a dual-band power amplifier. Measured results show that the power-added efficiencies (PAEs) of the amplifier at 1.5 GHz and 2.1 GHz are 58% and 60%, respectively, with output powers of 38 dBm and 37 dBm, and gains of 15 dB and 14 dB, respectively. In non-target frequency bands, the PAE approaches 0%, and a suppression greater than 40 dB is achieved, verifying that the filter's high selectivity and compact layout enhance the performance of the dual-band power amplifier. This design achieves efficient power transmission and strong interference isolation, providing a cost-effective solution for multi-band communication systems.

This article addresses the challenges associated with poor tunability and the single absorption function in absorbers. To address these challenges, we designed a dual-band switchable tunable absorber utilizing graphene and vanadium dioxide.The proposed absorber exploits the phase transition characteristics of vanadium dioxide to achieve absorption in the low-frequency band when it is in the dielectric state and absorption switching in the high-frequency band after phase transition. Furthermore, the Fermi level is altered by applying a bias voltage to the graphene, resulting in reduced square resistance. This mechanism allows tuning of the absorption frequency when the vanadium dioxide is in the dielectric state and adjustment of the absorption bandwidth when it is in the metallic state. Simulation results reveal that when the vanadium dioxide is in the dielectric state, the absorption rate exceeds 90% within the 20.0-27.7 GHz range. At this time, increasing the Fermi level of the graphene alters the absorption frequencies to 11 GHz and 42 GHz, respectively. Conversely, when the vanadium dioxide is in the metallic state, the absorption rate exceeds 90% within the 31.1-48.7 GHz range. Thus, elevating the Fermi level of the graphene leads to absorption band tuning at higher frequencies. This absorber demonstrates strong tunability and multifunctional absorption capabilities, offering outstanding practical application value.

In this study, we present a Y-shaped electromagnetic waveguide switch with integrated resonators designed to control wave propagation within a specific frequency range. The switch comprises two input lines and one output line, with each input line connected to a resonator of height d₁ and d₃ that can either allow or block transmission of the signal. Using the Transfer Matrix Method (TMM), we determined transmission and reflection properties to analyze the device's performance in ON (transmission) and OFF (blocking) states. Our results indicate that, depending on the choice of geometric and structural parameters, the resonators enable a transmission of more than 99% (T₁₃) from the first input line to the output line in the ON state, while reducing the transmission from the second input line to less than 1% (T₂₃) in the OFF state .These findings show the importance of resonator tuning for achieving precise electromagnetic wave control, offering a practical approach for enhancing signal management in advanced optical communication systems.

This paper presents a single-layer reflective metasurface for generating dual-linearly polarized orbital angular momentum (OAM) beams with mode number l=-1 at X-band. Phase modulation is achieved by adjusting the unit cell dimensions, which efficiently converts linearly polarized waves into vortex waves with the desired OAM mode. The proposed unit cell integrates a compact `米'-shaped inner patch with a square frame, with a compact size of 0.4λ₀ × 0.4λ₀, enabling independent control of both x-polarized and y-polarized waves. By varying the unit size,a broad phase shift range of 374° is achieved at 8-12 GHz. Based on phase compensation principles, the designed metasurface array is successfully generates dual-polarized vortex waves at X-band. The proposed metasurface exhibits high gain, narrow divergence angle, bandwidth, and dual-polarization capability, demonstrating significant potential for OAM wave multiplexing in wireless communication systems.

This paper presents a broadband circularly polarized (CP) implantable antenna for biomedical applications operating in the 2.45 GHz Industrial, Scientific, and Medical (ISM) band. Its key innovation is an annular ground plane structure with a square open slot, which simultaneously broadens both impedance and axial ratio (AR) bandwidths. This achieves a wide effective bandwidth of 30.8% (2.17-2.96 GHz), demonstrating superior bandwidth compared to existing implantable CP antennas. The antenna employs an inverted S-shaped radiating patch, and by adjusting the position of the radiating branches, it can switch between left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP). The simulated and measured results of the antenna show good agreement, and the SAR meets IEEE standards.

This paper presents the design of a four-element conformal Multi-Input Multi-Output (MIMO) antenna system for Ultra-Wideband (UWB) applications. It is implemented on a flexible RT Duroid 5880 substrate with a relative permittivity of 2.2, a loss tangent of 0.0009, and a thickness of 0.25 mm. It employs a stepped microstrip line-fed guitar-shaped antenna as a single antenna element. The single antenna element is then arranged orthogonally around the four edges of a 63 × 63 mm² substrate to create a 4-element MIMO system. The four antennas, designated as Ant-1 to Ant-4, have their ground planes connected through L-shaped stubs. The prototypes of single antenna element and 4-element MIMO are built to compare the simulation and measurement findings. The single antenna element is tested under flat, X-bend, and Y-bend cases. It achieves -10 dB impedance bandwidth from 3.14 GHz to over 10.6 GHz, a maximum group delay deviation of 2 ns, and a system fidelity factor greater than 80% in all cases. The 4-element MIMO system was also tested in flat and conformal configurations. It covers a minimum -10 dB impedance bandwidth from 3.5 to 10.8 GHz and exhibits mutual coupling below -18 dB. Its equivalent circuit model is also realized. Its diversity analysis shows an envelope correlation coefficient (ECC) below 0.01, diversity gain (DG) near 10 dB, channel capacity loss (CCL) under 0.4 bits/s/Hz, total active reflection coefficient (TARC) below -10 dB, and mean effective gain (MEG) between -3 dB and -12 dB across the operating band.

A novel dual compressive sensing (DCS) method is presented to resolve the limitations in computational accuracy and efficiency encountered by conventional DCS approaches during monostatic electromagnetic scattering analysis. Based on the connection between adaptive cross approximation (ACA) and generalized orthogonal matching pursuit (gOMP) in DCS, the integration of ACA and gOMP into the DCS framework is implemented. Specifically, ACA is employed to construct a deterministic measurement matrix by extracting row indexes containing critical information from the impedance matrix. This method reduces column correlation in the measurement matrix, enabling fewer rows to achieve comparable accuracy. Furthermore, the gOMP algorithm is adopted for signal recovery, leveraging its multi-column selection mechanism to better utilize the optimized information from ACA, thereby enhancing reconstruction accuracy and efficiency. Numerical analysis demonstrates that the proposed method achieves a significant enhancement in both accuracy and efficiency.

DBIM is a deterministic iterative method which exhibits second-order convergence indicating that the reconstruction error decreases quadratically with successive iterations. Existing regularization techniques when applied with DBIM often face challenges in determining the optimal regularization parameter (λ), leading to inconsistent convergence across various problems. To address this, a quantitative imaging algorithm is proposed in this paper by combining the Distorted Born Iterative Method (DBIM) and Hybrid LSQR method for solving Inverse Scattering Problems (ISP). This enhances the accuracy of the reconstructed object profiles and optimizes the regularization level to prevent both under- and over-regularization. For a fair comparison with the results in the literature, simulation studies are conducted using a breast profile that has two tumor inclusions, each with a radius of 6 mm, and two fibro-glandular tissue inclusions, each with a radius of 10 mm. The proposed method achieves a Root Mean Square Error (RMSE) of 0.75, indicating a better level of accuracy. The experimental validation is performed using a phantom made of Delrin material. The Delrin phantom, with a diameter of 10 cm, contains three inclusions made of PVC material with diameters of 10 mm, 6 mm and 3 mm. These inclusions have been successfully reconstructed with errors 0.085, 0.128 and 0.165 respectively. These results demonstrate the effectiveness of this algorithm in reconstructing both high and low-dielectric profiles, making it suitable for microwave imaging applications.

This paper presents the design and performance evaluation of a planar ultra-wideband (UWB) antenna employing an elliptical dipole structure, targeting comprehensive omnidirectional coverage within the 1-10 GHz frequency band for 5G Internet of Things (IoT) applications. The antenna, constructed on a cost-effective FR4 substrate, exhibits an impressive impedance bandwidth of 10:1 (S₁₁ ≤ -10 dB) and frequency-dependent gain ranging from 3 to 8 dBi. Its design features ensure minimal side lobe levels below -20 dB, contributing to enhanced signal integrity and reduced interference. Notably, the azimuthal plane radiation pattern maintains a remarkable 1 dB out-of-roundness, facilitating robust communication in diverse IoT environments. Extensive 3D radiation pattern measurements affirm the antenna's effectiveness in optimizing signal propagation and reliability across varying deployment scenarios. This study underscores the significance of the elliptical dipole configuration in advancing UWB technology, highlighting its potential for seamless integration into future 5G IoT networks.

This paper introduces an intelligent Maximum Power Point Tracking (MPPT) framework for photovoltaic systems that achieves significant performance gains through two primary innovations: a dynamic search space optimization that intelligently constrains the search region to approximately 2% of the conventional area, and a sophisticated Q-learning algorithm operating within this optimized region. The framework establishes a real-time relationship between environmental conditions and maximum power point parameters for this aggressive search space reduction. For complex partial shading conditions, an adaptive switching mechanism dynamically activates an enhanced meta-heuristic optimization component with improved convergence properties, ensuring appropriate algorithm selection based on detected operating conditions. Experimental results demonstrate that under uniform irradiance, the framework achieves 99.12% tracking efficiency (a 3.34% improvement over P&O). Under rapidly changing conditions, it maintains 97.83% efficiency (compared to P&O's 90.12%), and under partial shading, it achieves 95.89% global MPPT efficiency (versus 76.25% for P&O). The proposed method significantly reduces steady-state oscillations to 0.41% (from 1.87% for P&O) and offers 42.3% faster convergence. While requiring moderately higher computational resources, the approach is implementable on medium-range microcontrollers, balancing performance with practical deployment.

Breast cancer is considered one of the major cancers among women. Early identification of breast cancer is essential for improving treatment outcomes, necessitating the application of accurate, non-invasive imaging methods. This paper presents a comparative evaluation of Electrical Impedance Tomography (EIT) and Ultrasound Tomography (UST) for breast tumour diagnosis, employing a simulated multilayer breast model. The forward problem, which entails the determination of electrical conductivity and acoustic pressure distribution, was addressed through finite element analysis utilizing COMSOL Multiphysics software. The inverse problem of EIT was solved using Total Variation regularization with Primal-Dual Interior Point Method (TV-PDIPM) and that of ultrasound by employing attenuation-weighted bilinear interpolation to effectively resolve propagation losses through tissue layers, subsequently leading to segmentation. The images reconstructed and segmented from both modalities were subjected to quantitative evaluation employing metrics such as accuracy, Dice coefficient, sensitivity, specificity, and correlation coefficient (CC). The findings indicate that both approaches offers complimentary information regarding tumor, with each approach presenting distinct advantages based on tissue characteristics and image clarity.

In order to enhance the detection capability of small targets, long-term coherent integration (LTCI) is commonly employed. The core idea of LTCI is to accumulate target energy over an extended observation period, thereby enhancing the signal-to-noise ratio (SNR) of the target signal. However, for maneuvering targets, defocusing may occur due to range migration (RM) and Doppler frequency migration (DFM). In this study, a novel method based on the keystone transform and improved 3-D coherent integration (KT-ITDCI) for maneuvering target detection is proposed. KT-ITDCI not only eliminates the RM induced by unambiguous velocity through KT, but also compensates for residual RM and DFM in the KT-processed echoes via ITDCI, ultimately achieving coherent integration. Simulation results show that, compared with the TDCI method, KT-ITDCI significantly reduces computational complexity while maintaining comparable noise resistance. Furthermore, the effectiveness of the proposed method is further validated through processing and analyzing real measured radar data.

In this paper, a novel differential tri-band bandpass filter with a low-loss characteristic and high selectivity is proposed. The low-loss feature is attributed to the non-coupled structure, which circumvents the additional radiation losses from coupling slots. Furthermore, the excellent isolation and significantly enhanced selectivity between passbands are achieved via the inherent transmission zeros among them. Three desirable differential operating passbands can be conveniently allocated by adjusting the impedance ratios of the tri-section stepped impedance resonators. Consequently, the proposed filter design demonstrates a straightforward and efficient design methodology. To validate the feasibility of this approach, a differential tri-band bandpass with passbands at 1.35 GHz, 4.5 GHz, and 7.6 GHz was constructed and experimentally verified. The measured minimum insertion losses were 0.15 dB, 0.5 dB, and 1.2 dB respectively, indicating high performance. Specifically, the roll-off rates of the lower and upper edges of the three passbands are as follows: for the first passband, 30 dB/GHz and 23 dB/GHz; for the second passband, 27 dB/GHz and 25 dB/GHz; and for the third passband, 24 dB/GHz and 29 dB/GHz. The achieved concordance between simulated and measured results confirms the practicality and viability of this design for advanced communication systems.

This article presents an innovative UHF RFID tag sensor featuring a flexible ring resonator dipole integrated with a fluidic channel. Leveraging the unique characteristics of the resonator dipole, the sensor demonstrates high sensitivity in detecting the dielectric properties of various liquids. The RFID integration facilitates wireless communication and remote monitoring, enabling real-time, continuous measurement of sensor data. The sensor's flexible design allows for easy attachment on the PLA fluid channel, enhancing its practical utility. Experimental results show a strong correlation with reference measurements obtained using traditional laboratory methods using VNA. The sensor achieves effective impedance matching up to 1 GHz, even without the presence of a liquid in the channel. Moreover, confining liquids with high dielectric constants within the channel broadens the operational range across the UHF RFID band, spanning 865 MHz to 928 MHz, and the wireless RFID tag sensor is well suited for applications requiring real-time analysis and continuous monitoring. The proposed flexible ring resonator dipole UHF RFID tag sensor, coupled with fluidic channel-based tuning, offers significant potential for applications such as chemical analysis of liquids. Its unique blend of flexibility, wireless data communication, and accurate dielectric characterization opens new avenues for noninvasive and remote sensing in liquid-based system.

This study presents a compact four-port antenna optimized for sub-6 GHz 5G MIMO systems. The design incorporates a crescent-shaped radiating element paired with a defected ground structure (DGS) to improve both bandwidth and port-to-port isolation. Operating within the 3.2-3.8 GHz frequency band, the antenna maintains a VSWR below 2. The orthogonal arrangement of the radiators effectively suppresses mutual coupling, ensuring that isolation levels exceed -15 dB. Simulated and measured results validate the design, demonstrating a maximum gain of 5 dBi and radiation efficiency reaching up to 80%. Key MIMO performance indicators - such as envelope correlation coefficient (ECC), total active reflection coefficient (TARC), channel capacity loss (CCL), and diversity gain (DG) - confirm the antenna's suitability for robust 5G communication.

In this paper, a novel hybrid-excitation external-rotor switched reluctance motor is presented to solve the problem of low output torque of traditional switched reluctance motors (SRMs). The hybrid-excitation SRM, serving as an effective alternative to electric excitation SRMs, achieves comparable torque output with reduced excitation currents and lower power consumption within a certain range. First, the structural configuration and operational principles of the proposed SRM are presented and investigated. Then, key electromagnetic properties based on three-dimensional finite element analysis are analyzed in detail, such as the distribution of magnetic density, torque, and flux linkage. Furthermore, the validation is subsequently conducted through simulation data and performance comparisons with conventional outer-rotor 6/4 SRMs, conclusively confirming the theoretical framework's practical feasibility. Finally, the direct torque control with variable flux linkage based on the HESRM is executed, and the good control performance is verified under different conditions.