High Frequency Characteristics Research Articles

Acoustic Rocket Signatures Collected by Smartphones

Rockets generate complex acoustic signatures that can be detected over a thousand kilometers from their source. While many far-field acoustic rocket signatures have been collected and released to the public, very few signatures collected at distances less than 100 km are available. This work presents a curated and annotated dataset of acoustic signatures of 243 rocket launches collected by a network of smartphones stationed at distances between 10 and 70 km from the launch sites, resulting in 1089 individual recordings. Due to the frequency dependence of atmospheric attenuation and the relatively short propagation distances, higher-frequency features not preserved in most publicly available data are observed. The signals are time-aligned to allow for different segments of the signal (ignition, launch, trajectory, chronology) to be more easily examined and compared. Initial analysis of the features of these rocket launch stages is performed, observed features are compared to those found in the existing literature, and comparisons between signals from launches of different rocket types are made. The dataset is annotated and made available to the public to aid future analysis of the characteristics and source mechanisms of rocket acoustics as well as applications such as rocket detection and classification models.

Advantages and Challenges of Graphene Transistors for High-Frequency Applications

Graphene is regarded as an ideal material for next-generation high-frequency (HF) electronic devices, attributed to its unique two-dimensional structure, high carrier mobility, and exceptional electrical properties. In recent years, the limitations of conventional silicon-based technologies for high-frequency applications have become increasingly apparent, resulting in heightened interest in graphene transistors, which exhibit significant potential for applications in wireless communications, radar systems, and terahertz technology. These transistors exhibit high cutoff frequency and low noise characteristics, along with favorable bipolar properties, which provide them with significant advantages in radio frequency (RF) applications. However, despite the significant theoretical advantages of graphene materials, their practical application is still restricted by multiple factors. Specifically, insufficient voltage gain from weak current saturation, material uniformity issues, and large-scale production challenges have restricted the widespread adoption of graphene transistors in high-frequency electronic devices. This paper reviews the relevant literature, examines the disparity between the electrical performance and practical applications of graphene transistors, and identifies the key factors influencing their implementation. The results demonstrate that targeted bandgap engineering, innovative device architectures, and the exploration of new materials can help graphene transistors can mitigate existing challenges and position themselves as key components in future HF electronic devices, driving significant advancements and broader integration of related technologies.

High-frequency characterization of AlGaN/GaN MIS-HEMTs and HEMTs at cryogenic temperatures

High-frequency characterization of AlGaN/GaN MIS-HEMTs and HEMTs at cryogenic temperatures

Integrated DC arc model and DC arc detection approach based on K‐line diagram and spectrum integral difference

AbstractIn the low voltage direct current (LVDC) systems, the occurrence of DC series arc faults poses a significant threat to the safe operation of the system. This paper develops an accurate arc model for the arc fault simulation. The proposed arc model consists the steady‐state impedance, high frequency characteristics, and dynamic characteristics of the arc. Additionally, this paper proposes an arc detection algorithm combining the K‐line diagram and the spectrum integral difference of the arc current in the LVDC systems. This algorithm can identify four circuit states: normal operation, arc fault, switching action, and load mutation, which addresses the challenge of arc fault detection in complex working conditions. The STM32F407 microcontroller is utilized to design a DC series arc fault detector. Online detection tests demonstrate that the arc faults can be accurately detected and isolated within 37 ms, meeting the requirement of the UL1699B standard, with an accuracy rate of 99.33%. These achievements not only enhance the safety of the LVDC systems but also provide valuable references for the development of arc fault detection technology.

A ridge-loaded staggered double-vane slow wave structure for terahertz radiation sources

A ridge-loaded staggered double-vane slow-wave structure is proposed for terahertz radiation sources employing a sheet electron beam. This slow-wave structure has the advantages of enhanced electric field and energy density distribution and improved interaction impedance in the beam-wave interaction region. High-frequency characteristics are investigated for the proposed slow wave structure and compared with those of the staggered double-vane slow wave structure. The slow wave structure is fabricated and experimentally tested for transmission and reflection properties, revealing above -2 dB and below -17 dB at 0.34 THz for a backward wave oscillator. Steady transmission of the 21.7 kV sheet electron beam is achieved by designing a periodic cusped magnetic system (0.2 T) along with a sheet electron beam gun (50 mA). Beam-wave interaction simulations utilizing 100 periods demonstrate a peak power of 14 W and continuous frequency tuning from 0.295-0.375 THz for the proposed slow wave structure, whereas the staggered double-vane slow wave structure achieves 8.5 W peak power and frequency tuning from 0.308-0.366 THz. The sensitivity of the output power to the added ridge geometry is also analyzed. These findings indicate that the novel ridge-loaded staggered double vane slow-wave structure is promising for developing high-power broad frequency tunable terahertz radiation sources.

Estimation of the High-Frequency Feature Slope in Gravitational Wave Signals from Core Collapse Supernovae Using Machine Learning

We conducted an in-depth exploration of the use of different machine learning (ML) for regression algorithms, including Linear, Ridge, LASSO, Bayesian Ridge, Decision Tree, and a variety of Deep Neural Network (DNN) architectures, to estimate the slope of the high-frequency feature (HFF), a prominent emergent feature found in the gravitational wave (GW) signals of core collapse supernovae (CCSN). We created a data set of CCSN GW signals generated by an analytical model that mimics the characteristics of the signals obtained from numerical simulations, particularly the HFF. This enabled us to simulate a wide range of HFF slope values and analyze their properties. We opted to employ ML for regression techniques, particularly a supervised learning approach, to analyze the data set due to the parameter chosen for estimating the slope of the HFF. This type of architecture is ideal for this purpose as it can detect the connections between input and output data. In addition, it is suitable for handling high-dimensional input data and produces efficient results with low computational cost. We evaluated the efficiency and performance of the ML algorithms using a set of metrics to measure their ability to accurately predict the HFF slope within the data set. The results showed that a DNN algorithm for regression exhibits the highest accuracy in estimating the slope of the HFF.

Roof stability analysis model of super-long fully mechanized working face and its application

The strata behavior of a fully mechanized working face is obviously different from that of a short working face after the dip length of the coal face is lengthened. In view of the characteristics of high frequency, high peak value and large range of weighting in super-long working faces, a mechanical analysis model based on elastic foundation beam theory was established according to the bearing characteristics of hydraulic support and immediate roof. The results show that the roof deflection is positively correlated with the working face length, and with the increase of the working face length, the roof deflection in more areas has a larger value and it gradually changes from a single peak to multiple peaks. The roof stability decreases with the in-crease of the working face length and the decrease of length-thickness ratio. The research results are verified in working faces of different lengths in Buertai Coal Mine, and the phenomena of roof caving in different regions and asynchronous weighting in the face are explained. This study at-tempts to provide a theoretical basis for the roof treatment of super-long working faces.

Research on the application of 3D GPR in the detection of road collapse diseases in loess region of Ningxia

Abstract In recent years, the loess region of Ningxia is faced with severe challenges of road collapse diseases. Such diseases have the characteristics of strong suddenness, high frequency and difficult prediction. Coupled with complex causes, traditional detection methods are often difficult to achieve effective, rapid detection and accurate response, posing a major threat to the local social economy and public safety. This paper focuses on the application of three-dimensional radar technology in road collapse diseases detection in the loess region of Ningxia, aiming to explore an efficient, non-destructive and rapid diseases detection and verification method, so as to achieve timely and accurate detection and verification of collapse diseases. In this study, the Guyuan area with complex geological conditions was selected as a demonstration, and advanced 3D ground penetrating radar equipment was used to conduct fine scanning of the structures under the roads in the selected area. Through comparative analysis of radar images and actual geological structures, the 3D radar could accurately identify and locate potential underground voidage, cavitation and porosity and other hidden hazards. It provides the possibility for the early detection and prevention of collapse diseases. The research results of this paper verify the applicability and reliability of 3D ground penetrating radar in road collapse diseases in loess area of Ningxia, providing a reference example for road safety detection under similar geological conditions, and also providing strong support for road safety management and emergency response.

Generating tailored high frequency features in core collapse supernova gravitational wave signals applicable in LIGO interferometric studies

In this article, we introduce a methodology based on an analytical model of a damped harmonic oscillator subject to random forcing to generate transient gravitational wave signals. Such a model incorporates a simulated linear high-frequency component that mirrors the growing characteristic frequency over time observed in numerical simulations of core-collapse supernova gravitational wave signals. Unlike traditional numerical simulations, the method proposed in this study requires minimal computational resources, which makes it particularly advantageous for tasks such as data analysis, detection, and reconstruction of gravitational wave transients. To verify the physical accuracy of the generated signals, they are compared against the amplitude spectral of current LIGO interferometers and a 3D numerical simulation of a core-collapse supernova gravitational wave signal from the Andresen et al. 2017 model s15.nr. The results indicate that this approach is effective in generating scalable signals that align with LIGO interferometric data, offering potential utility in various gravitational wave transient investigations.

Coupled evolution of basin structure and fluids recorded by microfractures: A case study of deep-buried ordovician in the tarim basin

The fluid activity in the deep strata of sedimentary basins is commonly related to tectonic activity, and the cements filled in fractures are a good carrier for the tectonic-fluid coupling evolution. Compared to macrofractures, microfractures have characteristics of high frequency and easy identifiable periods. Abundant microfractures infilled by carbonate cements (MCCFs) developed in carbonates of the Ordovician Yingshan and Yijianfang formations in the platform basin area of the Tarim Basin. Based on the study of petrology, U-Pb dating, and geochemical characteristics, this study determined the stages of MCCFs and clarified the tectonic-fluid coupling evolution process recorded by MCCFs in the study area. The formation order of these MCCFs is D1, C1, C2, D2, C3, and C4. The precipitation times of MCCFs have a good correspondence with orogeny around the Tarim Basin and active times of strike-slip faults in the platform basin area. The six stages of MCCFs in the Ordovician Yingshan and Yijianfang formations in the SLU recorded the tectonic-fluid coupling evolution process of concentrated seawater in the late Middle Ordovician, meteoric water at late Ordovician, organic acids during the Silurian, Mg-rich hot brine at the end Devonian-early Carboniferous, and magmatic hydrothermal fluids during the Permian. This not only indicates a close connection between fluid activity and tectonic activity in sedimentary basins, but also confirms that the formation of MCCFs in carbonate formations is closely related to regional tectonic-fluid coupling activities. This study provides a good example for studying macro scale tectonic-fluid coupling activities in basins using microfractures.

LapUNet: a novel approach to monocular depth estimation using dynamic laplacian residual U-shape networks

Monocular depth estimation is an important but challenging task. Although the performance has been improved by adopting various encoder-decoder architectures, the estimated depth maps lack structure details and clear edges due to simple repeated upsampling. To solve this problem, this paper presents the novel LapUNet (Laplacian U-shape networks), in which the encoder adopts ResNeXt101, and the decoder is constructed with the novel DLRU (dynamic Laplacian residual U-shape) module. The DLRU module based on the U-shape structure can supplement high-frequency features by fusing dynamic Laplacian residual into the process of upsampling, and the residual is dynamically learnable due to the addition of convolutional operation. Also, the ASPP (atrous spatial pyramid pooling) module is introduced to capture image context at multiple scales though multiple parallel atrous convolutional layers, and the depth map fusion module is used for combining high and low frequency features from depth maps with different spatial resolution. Experiments demonstrate that the proposed model with moderate model size is superior to other previous competitors on the KITTI and NYU Depth V2 datasets. Furthermore, 3D reconstruction and target ranging by utilizing the estimated depth maps prove the effectiveness of our proposed method.

Frequency and Genetic Analysis of Porcine Circovirus Type 2, Which Circulated between 2014 and 2021 in Jiangsu, China

Porcine circovirus-associated diseases, caused by porcine circovirus type 2 (PCV2), are widespread and result in significant economic losses to the global swine industry. PCV2 can currently be divided into nine genotypes (PCV2a to PCV2i), with the currently dominant one being the PCV2d genotype. In this study, 2675 samples from 804 pig farms in 13 cities in Jiangsu Province, China, were collected between 2014 and 2021 and subjected to polymerase chain reaction analysis to investigate the frequency and genetic diversity of PCV2. The results showed that 41.42% (1108/2675) of samples tested positive for PCV2. The researchers further analyzed the genetic characteristics of 251 PCV2 strains and found that they belonged to the following four genotypes: PCV2a, PCV2b, PCV2d, and PCV2i. The dominant genotype was PCV2d, with a frequency of 49.80% (125/251). The detection rate of PCV2b was significantly higher than those of PCV2a and PCV2i, at 35.46% (89/251), 7.57% (19/251), and 7.17% (18/251), respectively. The percentage of different genotypes of PCV2 varied irregularly over time. We have further revealed the fingerprint of PCV2i genomic nucleotides for the first time. In conclusion, this study illustrates the high frequency and evolutionary features of PCV2 in Jiangsu Province over the past few years.

AMTrack:Transformer tracking via action information and mix-frequency features

Nowadays, Transformer-based visual tracking algorithms have been developing quickly because of the self-attention mechanism of Transformer, which has the capability to model global information. Although the self-attention mechanism in Transformer can effectively capture long-range dependencies in feature space, they only use flattened two-dimensional features and are unable to capture long-range temporal dependencies. Furthermore, since the self-attention in Transformer functions as a low-pass filter, it picks up on low-frequency features of the target while ignoring high-frequency features. This research suggests a Transformer tracker based on action information and mix-frequency features (AMTrack) to address these problems. Specifically, to address the lack of temporal remote dependencies, we introduce the target action aware module and the target action offset module. The target action aware module sets up several pathways to extract spatio-temporal, channel, and motion feature independently. In contrast, the target action offset module computes the target’s offset information by computing relative feature maps. Furthermore, in order to address the imbalance between high and low frequency features, we propose a mix-frequency attention and multi-frequency self-attention convolutional block. The mix-frequency attention uses high-frequency features within partitioned local windows as input for the high-frequency branch and average-pooled low-frequency features as the input for the low-frequency branch, calculating attention scores in both branches respectively. The multi-frequency self-attention convolutional block uses self-attention to capture low-frequency features and convolution to capture high-frequency features. Extensive experiments are carried out on eight challenging tracking datasets (e.g., OTB100 (Object Tracking Benchmark 100), NFS (Need For Speed), UAV123 (Unmanned Aerial Vehicles 123), TC128 (Temple Color 128), VOT2018 (Visual Object Tracking 2018), LaSOT (Large-scale Single Object Tracking), TrackingNet (Tracking Network), GOT-10k (Generic Object Tracking-10k)), and the experimental results show that our tracker achieves excellent tracking performance when compared with several state-of-the-art tracking algorithms. The experimental results show that on LaSOT, the success rates AUC (Area Under Curve), PNorm, and P reach 65.8%, 69.2%, and 68.0%, respectively, where the AUC value is 2.1% higher than the baseline algorithm TrDiMP (Transformer Discriminative Model Prediction). On other datasets, our tracker also achieves excellent tracking performance.

Zn-Zr substituted M-type Sr-hexaferrites for effective electromagnetic wave absorptions in the 26.5–40 GHz range

This study explores the electromagnetic (EM) wave absorption properties of Zn-Zr substituted M-type Sr-hexaferrites (SrFe12–2xZnxZrxO19, x = 0.3, 0.4, 0.5, 0.6) integrated into polymer composites (10 wt%, epoxy or rubber). The hexaferrite powders were synthesized using solid-state reaction processes with and without the molten-salt (M-S) method. Compared to non-M-S samples, those processed with M-S exhibited larger grain sizes and more defined grain edge shapes without clustering. High-frequency characteristics (ε', ε", μ', and μ") and EM wave absorption properties, specifically reflection loss (RL), were evaluated over the frequency range of 26.5 ≤ f ≤ 40 GHz. Regardless of the M-S method application, hexaferrite-epoxy composites (10 wt%) demonstrated excellent EM wave absorption properties with RLmin < −40 dB and a shifting absorption band corresponding to variations in x, reflecting changes in the ferromagnetic resonance frequency (fFMR). For the x = 0.4 sample, flexible rubber binder (10 wt%) sheets dispersed with hexaferrite powder were fabricated, showing superior broadband absorption characteristics compared to epoxy composites. In rubber sheet form, M-S processed samples exhibited enhanced μ', μ" spectra and improved absorption performance compared to non-M-S samples. The M-S processed hexaferrite-rubber sheet demonstrated broad EM wave performance with RL < −10 dB across the entire frequency range, achieving RLmin = −61 dB at 32 GHz. This study underscores the potential of Zn-Zr-substituted SrM-polymer composites for robust EM wave absorption performance in the Ka-band (26.5–40 GHz), crucial for applications in 5 G communication frequencies.

Interconnect‐Integrated GaInP/AlGaAs Schottky Photodetector Array with Heterojunction‐Assisted Enhanced Photovoltaic Effect for Automotive Speed Measurement Systems

AbstractReducing power consumption has always been a pressing issue for integrated circuits. Currently, there is a strong interest in the development of self‐powered photodetectors with low power consumption, high quantum efficiency, and high integration. In this work, a novel GaInP/AlGaAs photodetector is developed, where the photovoltaic effect of the Schottky junction is enhanced by the assistance of underneath GaInP/AlGaAs heterojunction, achieving near unity quantum efficiency, high integration, and ultrafast response speed. A single device exhibits a responsivity (R) of 467 mA W−1 in photovoltaic mode, a specific detectivity (D*) of 1.43 × 1011 Jones, a power conversion efficiency (PCE) of 14.5%, and an external quantum efficiency (EQE) of 96.56%. Further, an interconnect integration technique is used to integrate 81 individual detector units onto a 5 × 5 mm2 chip, resulting in a detector array that significantly improves the optical response. The device array has a high frequency feature with a fast response of 19 µs and a −3 dB bandwidth of 21.34 kHz. The interconnect chip is further integrated with a STM32 chip to realize an automotive speed measurement system. This work provides a novel technological solution for a high‐frequency, highly integrated photodetector array using heterojunction‐assisted enhanced GaInP Schottky junctions.

Black holes in Starobinsky-Bel-Robinson Gravity and the breakdown of quasinormal modes/null geodesics correspondence

We show that perturbations of a scalar field in the background of the spherically symmetric black hole obtained with the Starobinsky-Bel-Robinson Gravity are unstable unless the dimensionless coupling β describing the compactification of M-theory is small enough. In the sector of stability quasinormal spectrum show peculiar behavior both in the frequency and time domains: the ringing consists of two stages where two different modes dominate. The WKB method does not reproduce part of the spectrum including the fundamental mode, which is responsible for the first stage of the ringing. As a result, the correspondence between the high frequency quasinormal modes and characteristics of the null geodesics reproduces only one branch of the eikonal spectrum. The frequencies are obtained with the help of three methods (Frobenius, WKB and time-domain integration) with excellent agreement among them.

Study on the high resistivity and resonant frequency characteristics of Eu-doped NiZnCo ferrites

To fulfill the urgent demand for materials suitable for contemporary high-frequency applications, Eu-substituted Ni0.55Zn0.35Co0.1EuxFe2-xO4 (NZCEF, 0 ≤ x ≤ 0.10) composite ferrites were successfully synthesized by a solid-state reaction method, demonstrating characteristics apt for high-frequency functionalities. Detailed examination via SEM and EDS confirmed the compositional purity of these ferrites. Microstructural analysis indicates that the incorporation of europium results in a reduction of the average grain size in NZCEF composites, enhancing the material's densification. Measurements of resistivity and dielectric properties reveal that Eu doping affects the concentration of Fe2+ and Fe3+ ions as well as lattice defects within the ferrite, thereby leading to higher dielectric constants and resistivity (ρ, 6.51 × 108 Ω m). Magnetic analysis confirms that the substitution with Eu ions significantly increases both the coercivity and the ferromagnetic resonance frequency (fr), from 25.7 Oe and 445 MHz to 45.73 Oe and 1.22 GHz, respectively. This improvement is attributed to changes in grain size and domain wall motion. Consequently, Eu3+-substituted NZCEF ferrites exhibit superior electromagnetic properties, making them ideal candidates for advanced high-frequency material applications.

A time-averaged method to analyze slender rods moving in tubes

The motion of slender rods in narrow tubes involves the coupling of axial movements and transverse vibrations, in which the transverse vibration exhibits high frequency and chaotic characteristics. These characteristics render the computational cost of the time integration to the motions of rods and tubes expensive. To solve this problem, this paper proposes a novel time-averaged method, which contains two innovations: 1) By time averaging the traditional dynamic equations, the time-averaged dynamic equations describing the rod-tube system are established based on the time-averaged concept used in turbulence problems; 2) Two time-averaged contact models are developed, by fitting the time-averaged sample set using the polishing function and the machine learning, respectively, to construct the relationship between the time-averaged contact gaps and the time-averaged contact forces. The time-averaged method can use a large time step, which is far larger than that required for the time integration of traditional methods, thus reducing the computational cost. Inclined and rolling experiments of the rod-tube system, as well as numerical experiments of the control rod drop in a nuclear reactor, are conducted to validate the accuracy of the time-averaged method. Comparative analyses are carried out between the time-averaged method and six continuous contact models, demonstrating the high computational efficiency of the proposed method. Moreover, the experimental results can provide benchmark data for algorithm verification for scholars studying dynamic contact algorithms.

Design and High-Frequency Characterization of a Wafer-Scale Vertical Bridge Structure Nanoscale Vacuum Electronic Device

Design and High-Frequency Characterization of a Wafer-Scale Vertical Bridge Structure Nanoscale Vacuum Electronic Device

Leading Edge Glass Interposer for High Frequency Application

As electronic product becomes smaller and lighter with an increasing number of function, the demand for high density and high integration becomes stronger. Interposers for system in package will became more and more important for advanced electronic systems. Silicon interposers with through silicon vias (TSV) and back end of line (BEOL) wiring offer compelling benefits for 2.5D and 3D system integration; however, they are limited by high cost and high electrical loss. On the other hand, glass has many properties that make it an ideal substrate for interposer substrates such as; ultra high resistivity, adjustable thermal expansion (CTE) and manufacturability with large panel size. As the industry moves toward 5G (28 GHz and beyond), the requirements for materials have become more challenging. The major engineering requirements for 5G and beyond are low loss, precision manufacturing and low cost. Because of the short-wave length, extreme attenuation and low-cost requirements, the holy grail in the industry is ultra-miniaturized mm-wave structures. To achieve high-speed 5G communication standards, miniaturization and short signal pathways are required. This paper presents first the demonstration of glass interposers with fine pitch metalized through via. We studied basic characteristics of twin types of TGVs filled type and conformal type. Simulations were done frequency up to 60GHz using 3D electromagnetic field analysis. High frequency transmission characteristics were actually measured and compare with TGV with co planer wave guide. We also compare three types of Cu plating method with through via, full filling plating, conformal plating, and half fill plating are compared with process capability using X ray observation. In second section, We design and demonstrate advanced through via (TGV) substrates and multi-layer RDL’s. To demonstrate the performance of glass as a substrate material, we will build interposers with fine pitch TGV with metallization coupled with double sided routing distribution layers utilizing low loss dielectric polymer layers. The basic structure will consist of transmission line structures on top substrate with TGVs connecting top to the bottom side of the circuit. Trace, pitch and TGV diameter are optimized to achieve impedance matching by electro-magnetic simulation analysis. This test structure will compare the electrical performance of three types of transmission line structure coplanar waveguides (CPWs), micro strip line and strip line with low loss dielectrics. This comparison showed that the insertion loss of wiring layers were -1dB at 30GHz on CPWs. In third section, we model high frequency characteristics for 2.5D high speed transmission applications using basic high frequency characteristics. When coupled with the stability of glass, the ability to form fine pitch vias and multi-layer RDL’s makes the low risk choice for devices with high frequency applications.