Search Results (570)

In this paper, a 4 × 4 planar helical antenna (PHA) array fed by a three-dimensional substrate integrated waveguide (SIW) power splitter is presented. The 4 × 4 array is composed of four 1 × 4 PHA subarrays, and each subarray is fed by the SIW power splitter. Since the helical antenna is end-fire, it could not be integrated into a 4 × 4 array in a 2-D plane. In order to realize a 4 × 4 array, a SIW twist vertical transition structure is designed to connect the subarray with the SIW power splitter. Finally, the proposed 4 × 4 helical antenna array is implemented and fabricated for measurement. The center frequency of the PHA is 11 GHz, the impedance bandwidth (IBW) is 10.16–11.99 GHz (16.64%), and the axial ratio bandwidth (ARBW) is 10.53–11.47 GHz with the peak gain of 18.44 dBi. The simulation and measurement results match each other well; therefore, the effectiveness of the proposed design is verified. Full article

High-speed airborne platforms impose stringent aerodynamic constraints that restrict traditional planar antenna designs. Concurrently, multi-component echoes from extended targets and complex propagation environments induce strong signal coherence, severely degrading spatial angle estimation. To address these dual challenges, this paper proposes a straight-curved hybrid L-shaped asymmetric conformal array hardware topology tailored for cylindrical radomes. Building upon this, a millimeter-wave radar 3D point cloud imaging framework is developed for coherent targets. An orthogonal virtual manifold transformation is first devised to effectively compensate for the non-linear phase distortion induced by the conformal topology. Subsequently, a cascaded Forward-Backward Spatial Smoothing (FBSS) and Root-MUSIC framework is used for efficient signal decoherence. To resolve angle mismatches, a global cost function based on the cross-covariance Frobenius norm is formulated, which pairs independent angles and significantly suppresses spatial ghost targets. Systematic evaluations using 3D computer vision metrics demonstrate that the proposed method achieves accurate geometric restoration of aircraft targets with coherent signals. In the representative simulation, the method obtains a median point-wise localization error of 0.3986 m, a Chamfer Distance (CD) of 0.9695 m², an Earth Mover’s Distance (EMD) of 1.9504 m, and a spatial angular resolution of 1.0° under the stated test conditions. Under the stated simulation assumptions, boundary analyses indicate stable reconstruction around a post-pulse-compression SNR of −8.0 dB and a conformal curvature of 12.50 m⁻¹ ($r=0.08$ m), providing simulation-based design references for conformal radar 3D imaging. Full article

This work presents a fast and general formulation for the directivity computation of planar antenna arrays composed of radiating elements modeled as ${\cos }^q\theta$ transmitters. The main novelty in the proposed formulation as compared to the literature is the fact that an arbitrary number of different radiating elements, each one characterized by a different q-factor, can be considered. The proposed framework enables the evaluation and validation of array architectures previously introduced in the literature, including concentric-ring configurations with tapered element sizes. A unified expression is derived in which the directivity depends solely on two inputs: the array factor and the class-dependent radiating element size. This reduced representation allows real-time computation of directivity, even for electrically large planar arrays comprising multiple rings and heterogeneous element classes. The resulting computational complexity is significantly lower than that of classical integral-based approaches traditionally used for directivity evaluation. Numerical results confirm that the proposed formulation yields accurate directivity values that are fully consistent with existing analytical and numerical results reported in the literature. Full article

Bistable electrowetting displays (BEWDs) have become a competitive technical solution for low-power and static display fields due to their unique zero-power-consumption holding characteristics. However, traditional BEWD pixels face problems such as high driving voltage, complex processes, high cost, open structures, and difficulty in high-resolution array fabrication. Aiming at these bottlenecks, this paper proposes a closed stereoscopic bistable EWD pixel structure driven by planar and non-planar electrodes, and completes the design, fabrication, and performance verification of the device. The fabrication process proposed in this paper combines photolithography and inkjet printing, featuring simple process, low cost, closed pixels, and low driving voltage, which solves the key problems of traditional processes. The research results provide a feasible process route and experimental basis for the development of low-power bistable electrowetting display devices. Full article

Flexible pressure sensors featuring high sensitivity, a broad detection range, and excellent stability are pivotal components for high-precision electronic skins and human health monitoring. To circumvent the limitations of existing sensors in maintaining high responsiveness across extensive pressure ranges, herein, a novel flexible capacitive pressure sensor is developed based on a 3D porous ionogel foam composite (IL/EG/PVA@MF) coupled with a planar electrode array. This device leverages the synergistic structural engineering of the 3D hyperelastic melamine foam (MF) skeleton and the pressure-regulated fringe-field distribution and iontronic interfacial polarization of the porous ionogel. Experimental evaluations demonstrate that the sensor achieves a high normalized sensitivity of 62.45 kPa⁻¹ (2–10 kPa) and maintains reliable piecewise linear sensing performance across a broad working range of 0–50 kPa, accompanied by a rapid response time of within 8 ms. Furthermore, the sensor exhibits outstanding performance consistency after 6000 compression-release cycles at 50 kPa, verifying its good mechanical durability. In practical applications, the device can monitor diverse physiological signals with high fidelity, ranging from subtle radial artery pulses to large-scale joint movements and specific coughing patterns, underscoring its broad potential for integrated wearable systems and intelligent healthcare. Full article

Limited snapshots and element-wise gain–phase mismatch jointly impair covariance estimation and array manifold accuracy in uniform planar arrays. This paper proposes a deep robust adaptive beamforming framework that combines statistical base-weight generation, element-wise array manifold calibration, and regularized response projection. The base-weight network extracts finite-snapshot covariance information, whereas the calibration network estimates a physically bounded element-wise complex-gain vector from covariance features and nominal direction context. Phase-aligned auxiliary supervision makes the calibration loss invariant to the unidentifiable common phase and is required only during training. The calibrated steering vectors define a closed-form minimum-distance projection that preserves the normalized base weight’s desired direction response while suppressing the calibrated interference responses. Across three training seeds, the method achieves 23.43 ± 0.06 dB output SINR and a −52.48 ± 0.09 dB average null level, improving the former by 5.64 dB and deepening the latter by 5.11 dB relative to the best-performing baseline under the main test distribution. Experiments on mismatch severity, input SNR, snapshot number, direction-of-arrival errors, controlled ablations, and computational cost characterize the performance and limitations of the method under the stated synthetic-array model. Full article

Broadband Capon direction-of-arrival estimation is computationally demanding because covariance processing, spatial spectrum evaluation, and steering-vector construction are repeatedly performed over multiple frequency bins and candidate directions. This study presents an efficient framework for horizontal-plane sound source azimuth estimation by combining pairwise Capon processing with recursive steering-vector generation. The array is partitioned into ordered two-microphone pairs, enabling independent $2\times 2$ covariance processing. Each pair estimates a local angle relative to its directed baseline, and the resulting constraints are fused according to the array geometry. In the implemented orthogonal cross array, both pairs lie in the horizontal plane and provide complementary components of the planar source direction. A general fusion formulation is also provided for non-orthogonal baselines and non-coincident pair midpoints. The frequency-linear phase structure of the pairwise steering vector is exploited to replace repeated trigonometric evaluations across DFT bins with recursive complex rotations. Across 80 single-source trials, the proposed method achieved an MAE of $1.88°$, an RMSE of $3.54°$, and 100% of estimates within $\pm 10°$. The steering-vector generation time decreased from 165.69 ms to 66.77 ms, while the total measured component time decreased from 172.14 ms to 70.92 ms. Additional evaluations of multi-source resolution, reverberation, moving sources, numerical stability, and irregular arrays demonstrate a practical trade-off between computational efficiency and localization robustness. Full article

Antimicrobial resistance (AMR), largely driven by the inappropriate and excessive use of antibiotics, requires rapid and reliable bacterial detection and antibiotic susceptibility testing (AST), as conventional culture-based methods remain time-intensive. Here, we report a real-time, label-free interdigitated wave electrode array (IWEA) that combines dielectrophoretic (DEP) enrichment with impedance spectroscopy for rapid bacterial detection and AST. The proposed IWEA was designed and optimized via COMSOL Multiphysics to enhance DEP-relevant electric-field strength, thereby improving DEP-assisted bacterial enrichment compared to conventional planar interdigitated electrodes. The platform enabled sensitive detection of both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) in 0.1× PBS across 10–10⁵ CFU/mL within 30 min using DEP-assisted preconcentration (100 kHz, 10 V_pp), outperforming passive (non-DEP) operation (10²–10⁵ CFU/mL). For AST, bacterial responses to vancomycin, gentamicin, and ampicillin were monitored through impedance variations following DEP-based enrichment. Susceptible bacteria produced concentration-dependent reductions in ΔZ/Z₀, whereas resistant bacteria showed similar responses to untreated controls. Quantitative assessment yielded CC₅₀ values of 2.86 ± 0.22 µg/mL and 3.06 ± 0.20 µg/mL for vancomycin and gentamicin against S. aureus, and 4.59 ± 0.30 µg/mL for gentamicin against E. coli. Resistance profiles of S. aureus to ampicillin and E. coli to vancomycin and ampicillin were clearly distinguished. SEM imaging and disk diffusion assays independently validated the impedance-derived susceptibility results. Collectively, this IWEA platform offers a rapid, label-free, and quantitative approach for bacterial detection and AST, with strong potential for antimicrobial screening and point-of-care diagnostics. Full article

Accurate spatial alignment is essential for improving the performance of beamforming-based wireless power transfer systems. Nevertheless, conventional search methods usually face a trade-off between scanning complexity and estimation accuracy, especially when the receiver location is unknown in three-dimensional space. In this paper, a Received Signal Strength Indicator (RSSI)-based multi-stage beam scanning algorithm is proposed for joint azimuth, elevation, and distance estimation in a wireless power transfer system. The proposed algorithm performs hierarchical coarse scanning, refined scanning, angular local adjustment, fine distance search, and peak interpolation to determine the optimal spatial focus point. Unlike random search and conventional hierarchical scanning methods, the proposed method not only performs coarse-to-fine beam candidate selection but also introduces sub-grid interpolation and final local 3D refinement to overcome the resolution limitation of discrete grid scanning. Then, near-field focusing beamforming weights are designed according to the estimated spatial parameters to maximize the received signal strength. A simulation model is established at 900 MHz using a 4 × 3 uniform planar transmit array and a four-element receive array under a Rician channel. The results demonstrate that the proposed algorithm reduces both angular and distance estimation errors, thereby improving three-dimensional positioning accuracy. The proposed method is suitable for low-complexity and high-accuracy three-dimensional beam alignment in wireless power transfer applications. Full article

Millimeter-wave vehicular communication links are prone to blockage and suffer from severe path loss, and high mobility leads to rapidly time-varying channels. In addition, large-scale reconfigurable intelligent surface (RIS) arrays impose substantial channel-estimation overhead and phase-optimization complexity. To address these issues, a group-based and position-aided phase-optimization method is proposed for RIS-assisted millimeter-wave vehicular communications. First, an RIS-assisted uplink system is modeled with a multi-antenna base station (BS), an RIS configured as a uniform planar array (UPA) and a single-antenna vehicular terminal. Channel expressions are formulated for the direct vehicle–BS link, the vehicle–RIS link and the RIS–BS link. Rician fading, line-of-sight (LoS)-dominated millimeter-wave propagation, mobility-induced Doppler shifts and a standardized path-loss model for urban microcell street-canyon scenarios are incorporated to characterize the RIS-assisted vehicular cascaded channel. Based on this model, an optimization problem for the RIS phase-shift matrix is formulated under discrete phase-shift constraints to maximize the achievable rate per unit bandwidth. To avoid the exponential increase in complexity caused by conventional exhaustive search as the number of RIS reflecting elements increases, a successive refinement algorithm is introduced to derive an equivalent channel-gain expression. The original phase-optimization problem is then transformed into an element-wise iterative update process, thereby reducing the computational complexity of large-scale RIS phase configuration. To further reduce the reliance on full channel state information (CSI), two low-overhead phase-optimization schemes are designed. In the group-based scheme, the RIS reflecting elements are partitioned into several subgroups, with all elements in each subgroup constrained to share the same phase shift. This design reduces both the channel-estimation dimensionality and the number of optimization variables. In the position-aided scheme, the spatial coordinates of the BS, RIS and vehicle are used to derive the link distances and the associated angles of arrival and departure. Based on these geometric parameters, the vehicle–RIS–BS cascaded channel is reconstructed and a corresponding phase-alignment strategy is designed. The simulation results demonstrate that both proposed schemes achieve rates of approximately 6.5 bits ${\mathrm{s}}^{-1}{\mathrm{H}\mathrm{z}}^{-1}$ at a transmit power of 30 dBm and outperform existing phase-optimization techniques. When the successive refinement algorithm is applied, the computation time required for phase optimization with a 256-element RIS remains below 0.01 s. Under high-mobility conditions, both proposed schemes approach the performance upper bound achieved with perfect CSI, demonstrating strong robustness to channel variations. Full article

Sparse antenna arrays are attractive for compact microwave and millimeter-wave front ends because they can achieve prescribed radiation performance with fewer radiating elements, thereby reducing the number of feeding channels, hardware cost, weight, and power consumption. However, the joint optimization of element positions and complex excitations remains challenging, since the element positions enter the array factor nonlinearly and the element-count objective is inherently combinatorial. This paper presents an iterative reweighted ℓ₁ synthesis framework for sparse antenna arrays with continuous element positions. At each iteration, position perturbations are introduced and the array factor is linearized using a first-order Taylor expansion within a trust region. The resulting non-convex sparse synthesis problem is then approximated by convex programing through an iteratively reweighted ℓ₁ relaxation, allowing the excitation amplitudes, phases, and element positions to be updated simultaneously. Additional aperture, minimum-spacing, and minimum-directivity requirements are formulated as convex constraints and incorporated when required, enabling joint control of sparsity, sidelobe level, physical layout, and radiation performance. The proposed method is validated through four representative examples, including a shaped-beam linear array, a tri-pattern reconfigurable linear array, a planar pencil-beam array, and a directivity-constrained planar array. Compared with fixed-grid reweighted ℓ₁ methods under the same specifications, the proposed approach produces sparser layouts while avoiding the grid-resolution limitation. In the directivity-constrained benchmark, it also achieves competitive element reduction while enforcing a prescribed minimum element spacing. These results indicate that the proposed framework provides a flexible and practical synthesis tool for compact and integrated sparse antenna-array design. Full article

The goal of this work is to develop an optimized framework for ultrasonic guided wave imaging in order to increase the precision of damage localization in planar structures. This work is novel in that it refines the Reconstruction Algorithm for Probabilistic Inspection of Damage (RAPID) by assessing how the scaling factor β affects imaging resolution. To track structural integrity, the technique makes use of a surface-mounted array of twelve piezoelectric transducers (PZT). Numerical simulations were performed on an aluminum plate with through-hole defect in order to assess the performance. To replicate realistic Lamb wave interactions, a finite element model was created using CIVA SHM software (version 2023). MATLAB (version 2022) was used to process the obtained signals in order to produce probabilistic defect distribution maps. The RAPID algorithm, optimized with a scaling factor β = 1.05, achieves relative localization accuracy, according to numerical results. The study provides a solid numerical foundation for further experimental validation by confirming that the suggested configuration detects structural damage. Full article

This paper presents two partially reflective surface (PRS)-based techniques to enhance the performance of a 24-GHz object detection radar system. The first technique employs a flat PRS superstrate to increase antenna gain and thereby extend the detection range, while the second utilizes an inclined PRS structure to achieve passive beamforming and directional control. The conventional radar module consists of a 1 × 4 transmit array and two 1 × 4 receive arrays implemented on the opposite side of the PCB from the RF circuitry. Although increasing the number of antenna elements is an effective way to improve antenna gain and detection range, such an approach inevitably enlarges the antenna area and increases system complexity. In contrast, the proposed PRS-based structures enhance the effective aperture efficiency without expanding the planar dimensions of the antenna. The flat PRS configuration improves the antenna gain by approximately 5.8 dB (4.3 dB in Tx and 1.5 dB in Rx), which corresponds to a theoretical detection range extension of approximately 40% according to the radar range equation. Furthermore, the inclined PRS introduces a spatial phase variation across the aperture, resulting in passive beam steering of approximately −10 degrees while preserving the gain enhancement effect. Prototypes of both configurations were fabricated, and the measured results show good agreement with full-wave simulation data. These techniques provide compact and low-complexity solutions for extending detection range and enabling directional sensing in 24-GHz object detection radar applications. Full article

Acoustically levitated thin reflective plates provide a promising approach for contactless optical beam steering by eliminating mechanical hinges, sliding interfaces, and the associated wear and friction losses. However, unlike conventional spherical particles or droplets, thin planar reflectors exhibit highly geometry-dependent acoustic force distributions and are highly susceptible to lateral drift and angular destabilization when the acoustic field is dynamically reconfigured for beam steering. Here, we present a theoretical and simulation-based stability analysis of an acoustically levitated thin reflective plate driven by a phase-controlled dual-array acoustic field. A reduced-order model based on the Gor’kov potential is developed to characterize the acoustic potential landscape, escape-barrier depth, and local restoring stiffness during phase-gradient-induced mirror tilting. The simulations reveal that increasing the phase gradient progressively distorts the trapping potential and reduces the available trapping stability margin. Among the translational degrees of freedom, the lateral restoring stiffness deteriorates much more rapidly than the axial stiffness, indicating that lateral slippage is the primary instability pathway during continuous steering. Parametric analysis further shows that thinner mirrors with larger radii can improve trapping stability by increasing the effective acoustic interaction area while reducing gravitational and inertial penalties. The influence of non-ideal acoustic driving conditions is also evaluated to determine practical operating limits for stable operation. These results clarify the stability mechanisms governing acoustically suspended planar reflectors and provide theoretical design guidelines for robust contactless optical beam-steering systems. Full article

High-precision and resilient indoor positioning is a fundamental requirement for the autonomous operation of mobile robots in GNSS-denied environments. While visual sensors are commonly used for odometry, their operational reliability can be compromised in challenging scenarios such as drastic illumination fluctuations and sparse-textured environments. To address these sensor limitations, this study presents MVO, a magneto-visual odometry framework that explores indoor magnetic field anomalies as complementary constraints for visual odometry. By integrating a 30-magnetometer planar array model with a stereo camera, the proposed system establishes a multi-modal perception framework for indoor spaces. In the frontend, magnetic field gradient information is utilized to provide relative-pose constraints, which assist in the matching of image feature points and help maintain tracking continuity under visual degradation. In the backend, a factor graph optimization (FGO) framework incorporates magnetic relative-pose factors and visual reprojection factors into a unified optimization objective, which is then solved using the incremental smoothing and mapping 2 (iSAM2) algorithm. Frontend-level simulations are conducted to analyze the effects of magnetometer spatial configuration, sensor number, and calibration-error sensitivity on magnetic relative-pose estimation and covariance. Trajectory-level evaluations are further performed on the EuRoC dataset augmented with high-fidelity synthesized magnetic field data, including localization accuracy and computational load. Under this synthesized magnetic field setting, MVO shows improved localization accuracy and moderate computational load compared with the selected MSCKF-Stereo and VINS-Fusion reference baselines. These results provide a simulation-based feasibility validation of integrating magnetic field constraints with visual information for indoor odometry, while validation with real magnetometer array measurements remains future work. Full article