Search Results (648)

We present in this paper a low-power impulse-radio ultra-wideband (IR-UWB) transmitter architecture for neural implants. It features a duty-cycled phase-locked loop (PLL) and a co-designed compact fractal antenna. To suppress the carrier frequency drift inherent in open-loop ring oscillators while maintaining ultra-low power consumption, a hybrid PLL-oscillator upconversion scheme integrated with a switch-controlled voltage-holding module is proposed. Operating at a 10% duty cycle, the PLL consumes merely 90 $\mu$W and achieves a locking frequency of 4.25 GHz with a peak-to-peak jitter of 2.14 ps. Furthermore, to eliminate the bulky output matching network, an 8 mm × 10 mm coplanar-waveguide-fed fractal antenna is co-designed to present the conjugate impedance required by the power amplifier output, significantly advancing the miniaturization and energy efficiency of the neural implant. The complete transmitter was fabricated in TSMC 40 nm CMOS, with a supply voltage of 1.0 V, and in vitro wireless experiments through 18 mm of porcine tissue validated the design with a total power consumption of 0.58 mW. Full article

To address the issue that voltage signals in the measurement circuits of distribution network feeders are susceptible to non-uniform sampling, wideband interference, and phase distortion during operation, which fails to meet the accuracy requirements of on-line verification, a high-precision measurement technology for feeder calibration reference voltage based on PIA-bidirectional FIR is proposed. Taking the bus voltage of the distribution network as the on-line reference benchmark, the proposed technology adopts a three-stage collaborative processing framework consisting of cubic spline Hermite interpolation reconstruction via PIA, bidirectional FIR filtering, and improved VMD-TLS-ESPRIT parameter identification to extract high-fidelity amplitude, phase, and frequency parameters of voltage. It can serve as a reference source for live on-line verification of feeder measurement circuits. Simulation results demonstrated that the amplitude error of waveforms reconstructed by the proposed technology was less than 0.05%, the phase error better than 0.36 arcseconds, and the frequency tracking error superior to 0.001 Hz. Compared with conventional methods, the presented technology achieves higher frequency tracking accuracy and better phase stability, which can effectively satisfy the demands of on-line verification for measurement circuits of distribution feeders. Full article

As the available spectrum in the conventional C band becomes increasingly limited, ultra-wideband transmission across the O–U wavelength range (1260–1675 nm) provides a promising approach to increasing optical fiber link capacity. To support performance evaluation and preliminary fiber-link selection, this study compares standard single-mode fiber (SMF), pure-silica-core fiber (PSCF), and hollow-core fiber (HCF) links across the O–U bands. A transmission-performance analysis framework was established based on the Gaussian noise (GN) model. Band-specific amplifier parameters and fiber-specific span configurations were incorporated to evaluate transmission reach, optimum launch power, and theoretical capacity. Auxiliary simulations were conducted using VPIphotonics Design Suite 11.1 (VPIphotonics GmbH, Berlin, Germany) for representative C-band cases to examine the consistency of the overall trends predicted by the theoretical analysis. The GN-model analysis and auxiliary simulations show consistent overall trends, indicating that the GN model can serve as a computationally efficient tool for comparative link assessment and preliminary fiber-link selection. Under the unified analytical framework and consistently defined engineering constraints, PSCF offers a clear transmission-reach advantage over conventional SMF, whereas HCF shows greater theoretical power tolerance and capacity potential under the adopted representative parameter assumptions. Under the adopted non-saturated reference operating conditions, the per-channel capacity of HCF is approximately 34–54% higher than that of SMF in the S, C, L, and U bands and also clearly exceeds that of PSCF. These HCF results should be interpreted as model-based theoretical estimates, since practical performance may be affected by loss, dispersion uncertainty, splice/connector loss, bending sensitivity, and mode coupling. Full article

This paper presents a corrugated Vivaldi antenna architecture targeting sub-6 GHz and millimeter-wave frequency bands for 5G CubeSat applications, combining experimental validation at sub-6 GHz with a simulation-based scaling study at 26.5 GHz. Existing CubeSat antenna designs either target a single frequency band or rely on complex metamaterial structures incompatible with nanosatellite fabrication constraints. To address this gap, a single-element corrugated Vivaldi antenna measuring 90 mm × 80 mm is designed, fabricated on FR-4 substrate, and experimentally validated at 3.5 GHz, confirming a wide impedance bandwidth of 2.75 GHz and a peak gain of 9.6 dBi. The strong agreement between CST Studio Suite simulations and measurements validates the electromagnetic solver configuration, which is subsequently applied, as a simulation-based design study, to a geometrically scaled version on Taconic RF-60A substrate operating at 26.5 GHz. The miniaturized single-element version achieves a simulated 17 GHz ultra-wideband response and 6 dBi gain in a 7.32 mm × 6.32 mm footprint. Two- and four-element array configurations at 26.5 GHz demonstrate systematic simulated gain progression to 9 dBi and 13 dBi, respectively, with beamwidth narrowing from 49° to 30°. All 26.5 GHz designs are simulated with lossy copper metallization ($\sigma =5.8\times {10}^7$ S/m) and are entirely simulation-based; experimental mmWave validation is a designated target for future work. These results establish a validated design and scaling roadmap for corrugated Vivaldi antennas spanning sub-6 GHz and millimeter-wave bands, offering a cost-effective and CubeSat-compatible solution for high-data-rate inter-satellite communication links. Full article

Power wireless sensor networks (PWSNs) provide essential field-level sensing and communication support for smart grids, where topology authenticity directly affects communication reliability and network operation. However, wormhole attacks can forge false adjacency relationships through low-latency tunnels, thereby disrupting topology consistency and misleading routing decisions. In practical power environments, metallic obstruction, multipath reflection, and non-line-of-sight (NLOS) propagation may further cause normal-ranging anomalies to resemble attack-induced topology distortion, making reliable wormhole attack detection challenging. To address this issue, this paper proposes a topology-stress-based wormhole attack defense method with ultra-wideband (UWB) physical-layer awareness. The first-path power ratio and root-mean-square delay spread extracted from UWB channel impulse responses are used to evaluate link-ranging reliability and construct adaptive stiffness coefficients. Local backbone links are modeled as virtual springs, and a topology stress indicator is derived from the residual deformation after potential-energy minimization to quantify the geometric inconsistency caused by forged adjacency relationships. Furthermore, a Beta-based temporal evidence fusion mechanism is introduced to support graded node access decisions and improve decision stability. Simulation and hardware validation results demonstrate that the proposed method effectively suppresses NLOS-induced false alarms while maintaining high sensitivity to wormhole attacks. Compared with representative baseline methods, it achieves more stable detection performance under increasing ranging errors and different attack intensities. Hardware experiments further show that topology stress can clearly distinguish normal links, NLOS-affected links, and forged wormhole links, confirming its effectiveness for topology-authenticity verification in power wireless sensor networks. Full article

This paper presents a low-profile wideband in-phase-fed microstrip patch antenna (MPA) operating with TM₆₀, TM₀₄, TM₆₂, TM₂₄, TM₄₄, TM₈₂, and TM₈₀ modes. First, a rectangular in-phase-fed MPA is theoretically analyzed to clarify how these seven modes can be effectively utilized for bandwidth enhancement. Then, a transverse slot is incorporated into the patch to progressively move the resonance of the TM₀₄, TM₂₄, and TM₄₄ modes toward that of the TM₆₀ mode. Afterward, a pair of longitudinal slots is further employed to bring the TM₆₂, TM₈₂, and TM₈₀ modes closer to the TM₆₀ mode. In addition, another pair of longitudinal slots is introduced to improve the impedance matching performance. In this way, the seven modes are properly redistributed and grouped within the desired frequency range, thereby enabling broadband operation. Finally, an antenna prototype is manufactured and tested. The experimental results demonstrate that the antenna provides an impedance bandwidth covering 4.4–6.9 GHz while maintaining stable radiation performance, which is about 25 times wider than that of the conventional counterpart. More importantly, the antenna profile is as low as approximately 0.056λ₀. Full article

When photovoltaic (PV) power plants are connected to weak alternating current (AC) grids, the interaction between the plant and grid may induce wideband oscillation, posing a serious threat to the stability of grid-connected PV systems. To address this problem, this paper proposes an oscillation suppression method based on adaptive supplementary damping control of a Static Var Generator (SVG). First, a sequence impedance model of a PV power plant integrated with an SVG is established, and the Nyquist criterion is employed to analyze the mechanism underlying wideband oscillations. Then, a supplementary damping controller implemented in the SVG is designed to reshape the impedance characteristics of the PV power plant and enhance system damping. Furthermore, a Variational Mode Decomposition–Prony modal identification algorithm is introduced to extract oscillation mode information in real time. Based on the identified oscillation frequency, the parameters of the damping controller are adaptively adjusted, thereby improving the suppression capability for wideband oscillations with varying frequencies. Finally, a grid-connected PV power plant model with an SVG is developed, and the performance of the proposed adaptive suppression strategy is compared with that of conventional supplementary damping control. The results demonstrate that the proposed strategy provides stronger robustness and adaptability, effectively suppresses wideband oscillations under different operating conditions, and improves the stability of grid-connected PV systems. Full article

To evaluate the influence of near-field ground scattering on ultra-wideband (UWB) fuze performance, this paper presents an efficient operator-expansion time-domain physical optics (OE-TD-PO) framework. This method extends conventional far-field TD-PO to electrically large, dispersive rough surfaces under near-field excitation. By leveraging the local plane wave approximation (LPA) and time-domain Kirchhoff approximation (KA), the complex scattering process is decomposed into independent element-wise responses, which reduces the coupling between geometry and wave propagation. The scattering physics of each facet are represented using closed-form material and geometric operators. The material operator accounts for frequency-dependent dispersion and polarimetric reflection, while the geometric operator models intra-facet delay spread in the time domain. An excitation-order expansion of the transient dipole radiation formula is introduced to decouple the source waveform from spatial facet loops, yielding radiation, induction, and static components corresponding to the derivative, proportional, and integral terms of the excitation signal. This decoupling reduces computational complexity while preserving physical fidelity. Validated against analytical and numerical benchmarks, the proposed method effectively quantifies terrain-induced ranging biases and initiation reliability, providing a rigorous basis for adaptive error compensation and gain control in UWB fuzes across diverse environments. Full article

Background/Objectives: Recurrent acute otitis media (AOM) in children is known to cause cumulative cochlear and vestibular injury. Whether a single fulminant episode severe enough to require surgical intervention produces an analogous long-term audiovestibular signature, and whether infection severity contributes to outcome independently of cumulative episode count, is unclear. The present study addressed this gap. Methods: In this single-centre retrospective cohort study, 65 paediatric patients who had undergone surgical treatment for acute mastoiditis—the fulminant form of AOM—between July 2001 and March 2021 were assessed a median of 11.5 years after surgery. Of these, 35 had undergone mastoidectomy with tympanostomy and 30 had undergone tympanostomy alone because their episode had not been severe enough to require mastoidectomy. Thirty-two age-matched healthy volunteers (one ear each) formed the control group, yielding 97 ears in three groups (Group TM, 35 ears; Group T, 30 ears; Group C, 32 ears). Extended high-frequency pure-tone audiometry (125–20 kHz), distortion-product otoacoustic emissions (DPOAEs), single-frequency and wideband tympanometry, ipsilateral acoustic reflex thresholds, and lateral-canal vestibulo-ocular reflex gain were measured. Results: Both operated groups showed significantly elevated audiometric thresholds in the high- and extended high-frequency ranges compared with controls (HTA: χ² = 24.25, p < 0.001), with corresponding reductions in DPOAE amplitudes (HTA: χ² = 25.04, p < 0.001). Group TM did not differ significantly from Group T at any frequency band, indicating a negligible additional contribution of mastoidectomy itself. Acoustic reflex thresholds were elevated in Group TM. Vestibulo-ocular reflex gain was within reference ranges in all groups. Conclusions: A single fulminant episode of acute middle-ear infection in childhood—whether severe enough to require mastoidectomy or treated by tympanostomy alone—was associated, more than a decade later, with significantly elevated audiometric thresholds closely resembling those reported after multiple recurrent infections, supporting an effect of infection severity independent of cumulative episode count. Long-term audiological follow-up with extended high-frequency audiometry and otoacoustic emission testing is warranted, irrespective of whether mastoidectomy was required. Full article

This paper presents a 0.5–67 GHz static 1:2 frequency divider implemented in a commercial 0.7 μm InGaAs/InP DHBT technology. Instead of migrating to a more advanced process or introducing complex speed-enhancement circuits, a selective transistor scaling strategy is adopted, where only the critical switching and latching differential pairs in the CML master–slave core are implemented using 0.5 μm high-f_T DHBTs, while the input/output buffers, bias circuits, and non-critical devices remain based on standard 0.7 μm transistors. This approach reduces the parasitic capacitances at speed-limiting nodes and improves the high-frequency operation of the divider with minimal circuit and process overhead. The fabricated divider achieves a continuous operating bandwidth from 0.5 to 67 GHz, a full-band input power range from −5 to +10 dBm, a single-ended output power higher than −10 dBm, and an SSB phase noise of −141.03 dBc/Hz at 100 kHz offset with a 30 GHz input. These results demonstrate that selective core transistor scaling provides an effective and practical route for upgrading wideband static frequency dividers on mature InP DHBT platforms. Full article

This paper presents a wideband pattern-reconfigurable antenna designed for 360° horizontal sensing with angle-of-arrival (AoA) estimation capability. The antenna features a unique three-layer planar architecture, where a microstrip circular array is integrated between two metallic plates to enhance radiation stability and bandwidth. By employing a single-pole four-throw (SP4T) switching circuit, the array generates four steerable beams covering the entire azimuthal plane. Experimental results show that the prototype achieves a 10 dB return loss impedance bandwidth of 50% (4.0–6.0 GHz) and a peak gain of 8.3 dBi. Based on this antenna, a correlation-coefficient-based AoA estimation approach is implemented. The measured results demonstrate reliable estimation performance, with a mean angular error of less than 1.5° over the 360° horizontal plane across the operating frequency range. The proposed design provides a compact and low-complexity solution for practical wideband direction-finding applications in next-generation wireless systems. Full article

The NMR resonator is the sensor responsible for transmitting RF pulses and receiving detection signals, and its tuning and matching are crucial to acquiring high-sensitivity NMR signals. Automated tuning and matching (ATM) is therefore essential for rapid, accurate, and continuously efficient testing. Existing NMR ATM methods still primarily rely on iterative search strategies, whose dominant cost arises from repeated hardware measurements and waiting periods, often requiring multiple measurement cycles before convergence. The emergence of in situ NMR detection of high-concentration ionic samples has further increased the demand for real-time, rapid ATM with a large dynamic range, posing a major challenge to conventional approaches. This paper proposes a physics-informed few-shot learning method for automatic tuning and matching over wideband and multi-resonance-frequency NMR scenarios. The tuning-and-matching problem is formulated as a structure and frequency-conditioned function regression task, and a conditional neural process (CNP) is introduced to learn cross-task priors and directly predict the states of tunable components from only a small number of real-machine context measurements. A physics regularizer based on the local sensitivity of the input impedance is further designed to impose stronger penalties on errors under high-Q narrowband operating conditions without relying on proprietary analytical circuit models. Simulation studies and real NMR experiments are conducted on multiple circuit topologies and multiple target frequencies using only a small number of NMR samples. The results demonstrate consistent improvements in key metrics, including accuracy of tuning and matching and the number of collected real-machine samples required per task. In particular, with only 100 sampled tuning/matching capacitor points and 20 on-hardware collected samples, the proposed method already delivers satisfactory tuning-and-matching performance. The method achieves an attractive accuracy–cost tradeoff across both cross-topology and cross-frequency scenarios, and shows strong potential for few-shot, rapid, real-time detection. Full article

Against the background of observed climate change, which increases the risk of glacier-system degradation and the formation of hidden crevasses, the development of lightweight, wideband, and highly directional antenna systems has become a key factor in ensuring the safety of logistics operations and enhancing the spatial resolution and interpretability of ground-penetrating radar monitoring of near-surface snow–ice layers. The effectiveness of such systems is largely determined by the characteristics of the antenna unit, including the operating frequency band, gain, radiation pattern, weight, and resilience under extreme climatic conditions. The aim of this review is to provide a systematic analysis of modern Vivaldi antenna designs and Vivaldi-based antenna arrays, as well as to assess their prospects for application in X-band ground-penetrating radar systems for probing Antarctic snow-ice media. The paper considers the main types of ground-penetrating radar (GPR) antennas, their advantages and limitations, substantiates the priority of detecting hazardous near-surface inhomogeneities, and analyzes the capabilities of the X-band for the high-resolution identification of these inhomogeneities. Particular attention is paid to modern modifications of Vivaldi antennas, including antipodal, balanced, director-loaded, metamaterial-based, and array configurations. The analysis shows that Vivaldi antennas represent a promising basis for lightweight, wideband, and directional GPR systems; however, they require further improvement in terms of gain enhancement, sidelobe and back-lobe suppression, radiation-pattern stabilization, and adaptation to Antarctic operating conditions. Future research should focus on the development of adaptive and phased Vivaldi arrays, the use of metamaterials, Electromagnetic Band-Gap/Frequency-Selective Surfaces (EBG/FSS) structures, and director elements, the creation of lightweight, frost-resistant substrate materials, the advancement of multi-polarization multiple-input multiple-output (MIMO) systems, and the integration of antenna arrays with synthetic aperture radar (SAR) processing adapted to a multilayer snow–ice medium. Full article

This paper presents a compact fractal-based super-wideband multiple-input multiple-output (MIMO) antenna for millimeter-wave (mmWave) 5G new radio (NR) and prospective 6G applications. The MIMO system comprises four Koch fractal monopole elements integrated with a modified shared ground plane. By adopting the second Koch iteration, the antenna achieves enhanced impedance bandwidth and stable radiation behavior compared with lower-order iterations. The elements are arranged in a polarization-diversity configuration within a 30 × 30 mm² footprint on a 0.8 mm-thick Rogers RO4835 substrate (ε_r = 3.5, δ = 0.0025). The proposed design provides an impedance bandwidth exceeding 14 GHz over 26.5–41 GHz, covering key bands at 28, 32, 38, and 40 GHz, while maintaining high inter-element isolation (around 30 dB over the operating range). The optimized ground modification enables a fully connected common ground and suppresses mutual coupling without additional decoupling structures. The antenna achieves 4–6 dBi realized gain with radiation efficiency exceeding 95%. MIMO performance metrics, including the envelope correlation coefficient (ECC), mean effective gain (MEG), and diversity gain (DG), confirm excellent diversity characteristics. The antenna is further evaluated under bending, demonstrating stable matching and isolation for conformal and wearable scenarios, and the concept is extendable to a non-planar 12-port configuration within the same footprint. Measured results agree well with simulations, validating the proposed design for wideband mmWave 5G/6G devices. Full article

Cooperative localization for multi-Unmanned Aerial Vehicle (UAV) systems in GPS-degraded environments is often compromised by ideal-communication or uniform-quality assumptions. This paper proposes Quality-Aware Distributed State Estimation (QA-DSE), which combines three operational quality factors—freshness (Age of Information), accuracy (covariance trace), and link reliability (packet loss and channel noise)—into a single multiplicative score $q_{ij}$, modulated by a bounded history-consistency factor based on velocity-propagated self-trajectory continuity. A dual-constraint AND-gate on AoI and covariance trace excludes jointly degraded neighbors, while admitted neighbors are fused through a quality-squared information-matrix update under a stated bounded residual cross-correlation assumption, with an adaptive Covariance-Intersection fallback when the assumption is stressed. Under explicit observability, bounded-noise, bounded-quality, joint-connectivity, and bounded residual cross-correlation assumptions, we establish mean-square bounded error, exponential convergence at a rate inherited from the Kalman update operator, $O\left(n^3+nm\right)$ per-step complexity, Bounded-Input Bounded-Output (BIBO) stability, soft attenuation of single-axis faults (Theorem 4), and hard exclusion under joint AoI–covariance violation (Theorem 5). Under a Ultra-Wideband (UWB)-style cooperative-observation model, Monte Carlo experiments across five scenarios show 74.08–74.24% position- Root Mean Square Error (RMSE) reductions over Covariance Intersection, with the relative advantage held within 73.04–74.24% as the fleet scales from 3 to 50 UAVs; QA-DSE remains within 8.1% of an idealized no-cooperation single-vehicle Kalman filter, demonstrating graceful degradation rather than improvement above that floor. Per-step Central Processing Unit (CPU) time scales from 0.09 ms (5 UAVs) to 0.31 ms (50 UAVs); embedded validation is left to future work. Full article