This paper describes the design methodology of a compact multiband microstrip patch antenna intended for next-generation wireless communication applications. The proposed antenna operates over seven distinct frequency bands: 1.25-1.32 GHz, 2.30-2.44 GHz, 2.50-2.75 GHz, 2.92-3.25 GHz, 3.40-3.65 GHz, 3.70-4.23 GHz, and 4.70-6.0 GHz. These operating bands support a wide range of wireless services, including LTE, 5G communications, Wi-MAX, ISM applications, radar systems, and broadband wireless communications. Multiband performance is achieved through the incorporation of three strategically placed slits in the radiating patch along with a square split-ring resonator (SSRR). By adjusting the dimensions of the slits and the position of the SSRR, the operating frequency bands can be effectively tuned. The proposed antenna occupies a compact footprint of 40 × 40 mm² and consists of a radiating patch, a partial ground plane, and an SSRR structure. Simulation results demonstrate resonant frequencies at 1.3, 2.38, 2.66, 3.0, 3.5, 4.2, 4.9, and 5.7 GHz. Owing to its compact size, multiband capability, and simple structure, the proposed antenna offers advantages in terms of reduced cost, lower system complexity, and miniaturization, making it suitable for modern wireless communication systems.

Due to the high electrical conductivity, relative permittivity, and magnetic permeability of seawater, the propagation behavior of electromagnetic fields differs significantly from that in air. The conductive nature of seawater causes strong eddy current loss and magnetic field attenuation, thereby reducing the effective coupling coefficient and resulting in frequency detuning between the transmitter and receiver coils. Moreover, the marine environment introduces parasitic impedance paths and additional energy dissipation due to the conductive medium, which further decreases transmission efficiency. These unique electromagnetic characteristics make the design and optimization of wireless power transfer (WPT) systems in seawater more complex and challenging than in air, motivating this study to develop and analyze a dual-receiver WPT architecture that improves midrange transmission efficiency under underwater conditions. To address this issue, a single-transmitter dual-receiver (1TX-2RX) WPT system operating in the 300-550 kHz frequency range is designed and implemented. Experimental results demonstrate that, under midrange transmission in seawater, the efficiency of the proposed 2RX architecture improves markedly from 12% in the 1RX system to 25%, while maintaining stable output performance under various receiver coil misalignment conditions. In addition, compared with operation in air, the optimal operating frequency of the 2RX system in seawater shifts leftward from approximately 460 kHz to 410 kHz. To better characterize the impact of seawater on transmission performance, complex impedance and mutual inductance parameters are incorporated into the conventional circuit model, enabling effective representation of the additional losses and coupling attenuation induced by the conductive medium. The predicted load voltage is consistent largely with the experimental measurements, validating the accuracy and applicability of the proposed modeling approach. Overall, this study not only verifies experimentally the feasibility of improving midrange transmission efficiency through a dual-receiver architecture but also establishes theoretically a circuit modeling method suited better for seawater environments, providing useful insights for the design and optimization of marine WPT systems.

Time-modulated metasurfaces (TMMs) enable low-observable and reconfigurable radar deception, but existing approaches remain limited in synthesizing complex range-velocity (R-V) false-target clusters because of forward-designed modulation schemes and single-platform operation. This paper presents a task-oriented framework for multidimensional false-target synthesis against frequency-modulated continuous-wave (FMCW) radars. An analytical model explicitly connects TMM temporal modulation with the FMCW R-V estimation chain. Intra-frame modulation reshapes the echo spectrum to generate programmable range offsets, while inter-frame control modifies the slow-time response to generate programmable velocity offsets. The modulation-sequence design is then formulated as a combinatorial inverse-design problem and solved using Physics-Informed Initialization-Assisted Particle Swarm Optimization (PIIA-PSO), which exploits analytical R-V relations to construct a physically informative initial population, thereby reducing ineffective early-stage exploration and improving convergence efficiency toward high-quality realizable solutions. The framework is further extended to distributed multi-platform cooperation to increase spatial degrees of freedom and enable coherent energy aggregation. Results show range and velocity errors below 10% for single-platform synthesis and improve the overall SSIM by 7-10 percentage points under distributed configurations, demonstrating enhanced synthesis fidelity, flexibility, and scalability.

This paper presents a compact, low-cost, frequency-domain bistatic radar system using two identical square microstrip patch antennas fabricated on an FR-4 substrate (εr = 4.4, thickness = 1.6 mm). The antenna incorporates a suspended air-gap configuration to enhance bandwidth and radiation efficiency, and is designed to resonate near 3.3 GHz. The antenna was designed and optimised using CST Microwave Studio and experimentally validated using a Vector Network Analyser (VNA). Simulation results demonstrate a peak gain of 6.6 dBi and radiation efficiency of 83.2%. The fabricated antenna exhibits a measured peak gain of 7.0 dBi at 3.23 GHz and a |S₁₁| ≤ −10 dB bandwidth from approximately 3.0 to 3.5 GHz, with a measured resonance minimum of −14.3 dB at 3.27 GHz. The bistatic radar system operates over a swept frequency range of 2.8 to 3.8 GHz, acquiring complex S₂₁ parameters at each discrete frequency step. The received S₂₁ data is processed using background subtraction to suppress antenna coupling and background clutter, followed by an Inverse Fast Fourier Transform (IFFT) for range-domain target localisation. The proposed system is experimentally validated in single-target and multiple-target scenarios. Closely spaced targets are further characterised using a CLEAN iterative deconvolution algorithm as a post-processing step. Consistent target localisation across all scenarios is confirmed by two-dimensional radar images obtained from cross-range scanning. The results demonstrate the feasibility of a low-cost bistatic radar platform for short-range sensing applications including security scanning, remote target localisation, and multi-target detection

In this study, a coplanar waveguide (CPW)-fed half-moon monopole ultra-wideband (UWB) antenna is proposed, simulated, fabricated, and experimentally validated for ground-penetrating radar (GPR) applications. The antenna is specifically designed to provide high forward gain and stable wideband performance via integrating a full-copper metallic reflector. The proposed antenna exhibits good impedance matching and satisfactory reflection coefficient characteristics across the UWB frequency range of 3.1-10.6 GHz. By incorporating the metallic reflector, a significant radiation enhancement is achieved. The antenna attains a peak gain of 8.7 dBi at 6 GHz and maintains a gain above 6.5 dBi throughout the operating bandwidth. This gain improvement and suppression of back radiation are particularly important for GPR systems, where deep subsurface penetration and high-resolution imaging are essential. The integration of a metallic reflector provides a simple yet highly effective approach for gain enhancement without complex structures or advanced materials, as confirmed by both simulated and experimental results. These findings demonstrate the suitability of the proposed antenna for practical high-gain UWB GPR and broadband sensing applications.

Conventional methods face prohibitive computational overhead for multi-aspect monostatic scattering analysis of large-scale finite periodic arrays (LFPAs) due to repetitive preprocessing and full-matrix inversion under wide-angle multiple-incidence scenarios. To meet this challenge, this paper proposes an efficient multi-measurement vector compressive sensing framework combined with characteristic mode subdomain extraction (MMV-CS-CM-SED). It extracts excitation-independent CM-SED basis functions from a coupled subarray, forming a reusable sparse dictionary. Furthermore, we introduce a uniform spatial sampling strategy based on golden-section low-discrepancy sequences, which drastically reduces matrix filling by extracting only a small portion of impedance matrix rows. Finally, the method leverages the joint sparsity of multi-angle coefficients through an MMV model to accelerate the solution process. Numerical results demonstrate that, compared to the accurate subdomain entire-domain (ASED) and method of moments (MoM), the proposed method achieves high radar cross section (RCS) accuracy while reducing total matrix filling and computational time by over 70%, validating its efficiency and accuracy for large-scale array electromagnetic analyses.

Power line communication (PLC) channels are significantly affected by bursty and impulsive electromagnetic interference (EMI), whose temporal clustering and amplitude variability are not adequately captured by conventional statistical models. Existing approaches often treat impulse arrivals and amplitudes independently, limiting their ability to reproduce the coupled dynamics observed in practical transmission line environments. In this study, a marked self-exciting point process model is proposed for PLC noise characterization, where impulse arrival times are governed by a Hawkes-type process, and amplitudes are represented as stochastic marks. The framework incorporates mark-dependent excitation, allowing higher-amplitude impulses to influence subsequent event occurrences and thereby capture the observed bursty structure. A measurement-driven analysis shows that PLC impulsive noise exhibits short-term temporal dependence and deviation from memoryless behavior, as reflected in skewed inter-arrival distributions, nonlinear complementary cumulative distribution function (CCDF) characteristics, and non-zero autocorrelation at small lags. Parameter estimation indicates dominant baseline activity with moderate self-excitation and rapidly decaying temporal influence. Amplitude modeling revealed a skewed distribution with intermittent high-energy events, whereas extreme value analysis using a generalized Pareto distribution suggested a bounded tail behavior for threshold exceedances. A joint likelihood-based estimation framework was developed to enable practical parameter inference. Validation of measured PLC datasets demonstrated that the proposed model consistently captures both temporal and amplitude characteristics without parameter re-estimation. A comparative analysis with a Poisson model showed clear discrepancies, with a quantified CCDF error of 0.15932, highlighting the limitations of memoryless assumptions. Overall, the proposed marked self-exciting framework provides a physically interpretable and statistically consistent representation of impulsive EMI in PLC systems, offering a robust foundation for improved modeling and mitigation strategies.

This paper describes the design and analysis of a compact folded monopole antenna based on a Y-shaped meandered configuration, to operate within the 5 GHz to 6.5 GHz frequency range. TThe antenna has a compact size of 40 × 30 mm², and is fabricated on a low-cost FR4 epoxy substrate, making it suitable for easy integration into wireless systems. The main radiating configuration consists of a central vertical feedline connected symmetrically to meandered arms, forming a Y-shaped layout that enables a compact size without affecting radiation efficiency. The antenna is fed through a microstrip line, with the input signal equally distributed to both arms, each functioning as a quarter-wavelength monopole. The antenna demonstrates omnidirectional radiation patterns in both the E and H-planes and achieves a gain of 3\,dB. To ensure human safety, we also performed a specific absorption rate (SAR) analysis using a human baby phantom model. The maximum SAR is 0.128\,W/Kg at both frequencies, well below the acceptable 1.6\,W/kg limit set by the ICNIRP guidelines. The fabricated prototype was tested, and the measured results closely match simulations, validating the antenna's suitability for modern compact wireless applications.

This paper proposes a compact 8-port multiple-input multiple-output (MIMO) wideband self-decoupled antenna for 5G mobile terminal applications. Based on an orthogonal mode decoupling scheme, a combination of a loop antenna and an N-shaped antenna is utilized to achieve wideband coverage and high isolation in the N79 (4.35-5.1 GHz) band. Building on this decoupling mechanism, a 5-mm clearance is created between the ground plane and the side frame to mitigate mutual coupling between ports while optimizing impedance matching to broaden the bandwidth. Four antenna modules are symmetrically distributed on the FR4 dielectric side frames, forming a compact 8-port MIMO antenna array. The measured results show that the proposed system achieves consistent isolation better than 30 dB across the target frequency band, an envelope correlation coefficient (ECC) lower than 0.005, and a total radiation efficiency over 73% (averaging 80%). Thanks to its excellent isolation and bandwidth performance in a limited space, this scheme is a highly competitive candidate design for 5G smart terminal applications.

Conventional ferrite-based permanent magnet-assisted synchronous reluctance motors (PMaSynRMs) suffer from low torque density and are vulnerable to irreversible demagnetization under heavy-load conditions due to the reverse armature field. To address this, this paper proposes a hybrid-magnet rotor topology in which ferrite and NdFeB magnets are arranged in series along the flux path within each U-type flux barrier (NdFeB on the airgap side, ferrite on the inner side), while the three radially layered U-type branches are connected magnetically in parallel. Within each barrier, the magnetomotive forces of the two magnet types superpose to enhance the excitation flux; meanwhile, a dual synergistic mechanism - outer NdFeB shielding and flux shunting via parallel rotor bridges - suppresses the demagnetizing field. To tackle the 15-dimensional optimization problem, a Kriging-NSGA-III framework incorporating Pearson sensitivity screening is established. Finite-element results show that, compared to the benchmark all-ferrite machine, the optimized motor achieves a 20.78% increase in average torque, torque ripple reduction from 18.80% to 8.07%, and 89.49% efficiency. The benchmark exhibits local irreversible demagnetization at 3 times rated d-axis current, whereas the proposed topology shows no observable demagnetization even at 6 times rated current, validating the effectiveness of the proposed hybrid topology and optimization strategy.

Slow-light photonic crystals with group indices exceeding 100 typically require complex defect engineering - line-defect waveguides, coupled resonator optical waveguides (CROWs), or carefully designed heterostructures. These approaches, while effective, introduce fabrication complexity, optical losses, and bandwidth limitations. Recent advances achieving group indices of 50-100 in engineered structures still fall short of theoretical predictions for bulk photonic crystals operating in higher-order bands. However, a critical knowledge gap persists: most higher bands (3-8) largely unexplored. Here, we demonstrate that bulk square lattice photonic crystals operating in higher-order TM bands achieve ultra-slow light (group index 226.5) and extreme anisotropic dispersion (ratio 58.36) - performance comparable to state-of-the-art defect-engineered waveguide structures, achieved in a bulk crystal without any line defects, coupled resonators, or heterostructures, thereby maintaining fabrication simplicity. Through systematic equifrequency contour (EFC) analysis of bands 1-8 using high-density k-space sampling, we establish a quantitative framework revealing that higher bands offer superior slow-light characteristics unattainable in conventionally studied lower bands. Our GaAs/organic semiconductor system achieves this performance with moderate dielectric contrast (ε_r = 6.86), compatible with standard electron-beam lithography fabrication. A systematic parametric sweep of the rod radius (R/a = 0.30-0.50) further reveals that this slow-light performance is structurally robust and tunable by geometry: the Band 4 group index varies by less than 25% across the full sweep; Band 3 sustains a high normalized delay–bandwidth product (NDBP = 0.40-0.48) over a wide fabrication-tolerant range; Band 4 reaches an NDBP optimum of 0.403 at R/a = 0.38; Band 7 uniquely combines NDBP > 0.1 with an anisotropy ratio above 200; Band 8 exhibits extreme anisotropy (ratio up to 1369).

Owing to glass's excellent electrical properties and stability, Through-Glass Via (TGV) technology is regarded as a key technology for next-generation three-dimensional integration. Research on TGV-based transmission structures and Substrate-Integrated-Waveguide (SIW) structures has been relatively extensive. However, the investigated frequency range remains limited, rarely exceeding 100 GHz, and studies focusing on the intrinsic characteristics of the vias are still lacking. To address this issue, this study designs a set of TGV calibration standards operating in the D-band to extract the S-parameters and electrical parameters of the vias and to analyze their performance, thereby providing useful insights for the subsequent design of TGV devices in the terahertz band.

Devices such as drones and low Earth orbit satellites demand antennas that are lightweight, thin, and sufficiently flexible to conform to curved surfaces. At millimetre wave frequencies, however, closely placing multiple antennas inevitably introduces mutual coupling, which degrades communication quality. This paper presents a four element antenna array fabricated on a flexible polyethylene ter-ephthalate (PET) substrate, operating in the 26.21-29.64 GHz band. Unlike conventional approaches that rely on additional decoupling components, our design eliminates interference solely through a centrosymmetric four quadrant layout of the radiating elements, without any auxiliary structures. Measurements show that isolation among all four ports exceeds 46.95 dB; the envelope correlation coefficient (ECC) reaches as low as 0.0000312; and the diversity gain approaches the theoretical limit of 10 dB. The antenna maintains a radiation efficiency above 90% and a gain of 2.40-3.20 dBi, with stable coverage patterns across the entire band. With a thickness of only 0.12 mm, this flexible antenna offers a simple, low cost, high performance solution for conformal ap-plications. The work demonstrates that careful layout design can replace complex decoupling networks, providing a new pathway for lightweight, flexible, large scale antenna arrays in future 5G/6G communication systems.

Rotor mass eccentricity in an outer-rotor coreless bearingless permanent magnet synchronous motor (ORC-BPMSM) causes synchronous unbalance vibration, which degrades suspension stability and limits high-speed operation. To suppress this vibration, an optimized secondary-path estimation variable-step-size filtered-x least mean square (OSPE-VSS-FxLMS) feedforward compensation method is proposed. First, the rotor unbalance vibration mechanism is derived from the suspension force model. Then, a hyperbolic tangent-exponential (tanh-exp) function is introduced to adaptively regulate the FxLMS step size, improving the trade-off between convergence speed and steady-state error. Meanwhile, a normalized least mean square (NLMS)-based online secondary-path estimation strategy is developed to reduce gradient deviation caused by secondary-path mismatch. Simulations and experiments are conducted under constant-speed and acceleration conditions. Compared with the uncompensated condition at 3000 r/min, the displacement vibration amplitudes in the x- and y-direction are both reduced to 11 μm, corresponding to a reduction of about 69.4%. The effectiveness of the proposed unbalance vibration compensation method is confirmed by both simulated and experimental results.

This manuscript presents a novel compact reflective frequency selective surface (FSS) for wideband polarization conversion, enabling efficient polarization manipulation over the frequency range of 8.2 GHz to 9.5 GHz, which is the X-band spectrum for electromagnetic applications. The proposed FSS consists of a metallic pattern printed on an FR4 substrate with a relative permittivity of ε_r = 4.4, loss tangent of tanδ = 0.02, and thickness of 1.6 mm, backed by a ground plane. This configuration enables reflective-mode operation with a tunable frequency range typically spanning X-band, achieved by optimizing the unit cell's geometrical parameters. The proposed structure provides efficient linear-to-orthogonal polarization conversion over 8.2-9.5 GHz (1.3 GHz bandwidth, center frequency of 8.85 GHz), with a polarization conversion ratio (PCR) exceeding 98%. This frequency range lies within the X-band and provides a fractional bandwidth of approximately 14.69. Under oblique incidence, the proposed FSS maintains a PCR above 90% up to 40°, with only a slight bandwidth reduction, and shows good agreement between simulated and measured results. Owing to its compact nature, excellent angular stability and wide operating bandwidth, the proposed FSS is suitable for radar and wireless communication applications.

Electromagnetic harvesters based on magnetic levitation have emerged as particularly attractive systems owing to their contactless suspension, low mechanical damping, and inherently nonlinear stiffness behavior, which are suited to low-frequency ambient excitation. The investigated harvester consists of a levitating magnet suspended between two fixed outer magnets via repulsive magnetic forces, with a pickup coil converting oscillatory motion into electrical energy under base excitation. The primary source of difficulty in this system is the nonlinear magnetic restoring force F_mag and the electromechanical transduction coefficient γ, which must be pre-characterized via semi-analytical or finite element methods before any solution can be attempted. Therefore, the accurate pre-characterization of both F_mag and γ is the essential foundation of the entire modelling process. A Fourier space semi-analytical approach is proposed and developed, transforming a three-dimensional magnetostatic problem into a computationally efficient one-dimensional spectral calculation without remeshing. The semi-analytical predictions were validated against COMSOL finite element simulations, and their strong mutual agreement confirmed the accuracy of the proposed method before embedding it into the motion's coupled nonlinear equations.

Conventional multi loop control of diode clamped active power filters suffers from response conflicts and slow regulation due to strong coupling among DC voltage, neutral point potential, and reactive power. This paper proposes a single agent deep deterministic policy gradient (DDPG) framework for multi objective cooperative control. Unlike generic DRL applications, our design retains the current PI inner loop for hardware safety. At the same time, a single agent replaces the three outer loops (voltage, neutral point, and reactive power) to eliminate cascade coupling. A composite reward function based on the L2 norm - rather than linear weighting - quadratically penalizes large errors, forcing the agent to prioritize the most severe deviations and resolve multi objective conflicts optimally. Simulations show that the proposed strategy reduces grid side current THD from 6.7% to 1.09%, cuts midpoint balancing and DC bus settling times by 50% and 66.67% respectively, achieves zero overshoot and zero steady state error, and exhibits strong robustness under voltage sags and load surges. This work offers a customized, low tuning effort intelligent solution for power quality control in complex grids.

In this manuscript, a well-designed multiband cavity-backed X-shaped slot antenna is presented using substrate-integrated waveguide (SIW) technology. Its performance is optimized for the K and Ku bands to suit various advanced communication scenarios. Including an X-shaped slot in this design leads to significant advantages, such as better impedance matching, broadside radiation pattern, and multiband operation. In addition, it shows decent gain values of 6.89 dB at 15.02 GHz, 6.91 dB at 15.90 GHz, and 7.12 dB at frequency 19.58 GHz. This is accomplished by the innovative application of X slots on the substrate integrated waveguide (SIW) cavity. Simulated and experimental results validate multiband antenna operation and exceptional performance, highlighting its potentially high suitability for state-of-the-art millimeter-wave applications, such as satellite communications and radar systems. This compact structure, along with the proposed antenna performance metrics, confirms its feasibility for future wireless communication systems. This progress enables further developments in SIW-based antenna technology.

Receiver nonlinearity degrades signal quality in modern wireless systems. This paper proposes an adaptive post-distorter using Chebyshev polynomials as basis functions to improve numerical stability and convergence speed. Unlike conventional or distributionmatched bases, the Chebyshev basis ensures a well-conditioned input correlation matrix regardless of signal distribution. This property, together with the minimax approximation, enables the RLS algorithm to converge within a few pilot symbols - an order of magnitude faster than the power-series basis. Experiments on a real wideband receiver with OFDM and WCDMA signals show significant ACPR improvements over the power-series and Legendre bases. The proposed approach exhibits robust performance, fast convergence, and broad applicability.

This letter presents a cross-coupled SIW filter with a quasi-elliptic response and improved stopband suppression. For cross-coupled SIW filters, suppressing spurious modes often requires rearranging feeding ports, but this rearrangement tends to increase port-to-port crosstalk and limit achievable out-of-band rejection. To address this inherent issue, we keep port positions unchanged and change the port configuration from conventional microstrip lines to an opposite-face GCPW feeding structure. The input and output ports are placed on opposite metal layers, with their ground planes separated by the dielectric substrate. Simulation results show that the port-to-port crosstalk is reduced from -25 to -40 dB to below -100 dB. Measured results show that the proposed filter maintains a similar stopband width as the previous design, while the suppression of the first spurious passband is improved by about 20 dB, reaching better than -50 dB. The improvement is achieved without hybrid structures or extra fabrication steps.