Signal Propagation Characteristics Research Articles

Transformer partial discharge location technology based on gradient oil temperature

IntroductionThe traditional partial discharge localization improvement strategy mainly starts from the intelligent algorithm, but fails to consider the influence of core winding and oil temperature on partial discharge positioning.MethodsThis paper also considers the influence of the iron core winding and oil temperature. Through finite element simulation, a transformer model was established to analyze the propagation characteristics of ultrasonic signals generated by partial discharge under the interference of gradient oil temperature and winding. The chaotic firefly-particle swarm hybrid algorithm is proposed, and through the calculation of Shubert’s multi-peak function. Finally, a partial discharge defect platform based on gradient oil temperature was built to verify the chaotic firefly-particle swarm hybrid localization algorithm.ResultsThe ultrasonic velocity generated by partial discharge in transformers cannot be fixed, and it is suggested that ultrasonic sensors should be installed near the center of the top of the transformer. The proposed algorithm can be better optimized in the case of multiple local extreme points. Under gradient oil temperature experiments, the algorithm achieves positioning errors less than 100 and 55 mm for cases with and without winding obstruction, respectively, with average positioning errors of 74.2 and 35.2 mm.DiscussionThe positioning method in this paper can provide a technical reference for the partial discharge positioning of transformers in actual operation.

Millimeter wave–3D massive MIMO: Deep prior‐aided graph neural network combining with hierarchical residual learning for beamspace channel estimation

SummaryMillimeter Wave (mmWave) communication has emerged as a transformative technology at the forefront of wireless communication. One of the key challenges in harnessing the potential of mmWave technology is overcoming the increased susceptibility to propagation losses and environmental obstacles. To address these challenges, Three‐Dimensional Massive Multiple‐Input Multiple‐Output (3D Massive MIMO) systems have gained traction. The 3D aspect extends this concept by considering the elevation dimension, allowing for enhanced spatial resolution and coverage. Accurate estimation of the channel in 3D Massive MIMO scenarios is particularly challenging because of the complex propagation characteristics of mmWave signals. This paper introduces an efficient‐Aided Graph Neural Network Combining with Hierarchical Residual Learning (DPrGNN‐HrResNetL), designed specifically for beamspace Channel Estimation (CE)in mmWave‐Massive MIMO environments. The proposed model leverages deep priors and GNN mechanisms to enhance the extraction of spatial features, while hierarchical residual connections facilitate effective information flow through the network. DPrGNN enables the model to capture and understand complex spatial relationships among different antenna elements. The incorporation of deep priors provides a mechanism for leveraging prior knowledge about channel characteristics. This enhances the efficiency of the learning process, allowing the model to learn and adapt more effectively. The integration of hierarchical residual connections facilitates effective information flow through the network. This is particularly important for modeling complex dependencies within the beamspace channel data, enhancing the learning capacity of the network. The performance of the DPrGNN‐HrResNetL model is evaluated across a range of Signal‐to‐Noise Ratios (SNRs), utilizing metrics such as Normalized Mean Squared Error (NMSE) to measure the accuracy of the estimation. The outcomes underscore the resilience and efficacy of the DPrGNN‐HrResNetL approach in achieving precise CE within demanding mmWave scenarios.

Online adaptation of fourier series-based acoustic transfer function model and its application to sound source localization and separation

In this paper, we propose an online adaptation method for Fourier series-based acoustic transfer function (FS-ATF) models for robot audition systems using microphone array signal processing. The ATF represents the characteristics of signal propagation from a sound source to a microphone, which is essential for sound source localization (SSL) and sound source separation (SSS). For practical applications in dynamically changing real-world environments, ATF models must satisfy two criteria: (1) they must be adaptable to changes in the acoustic environment; and (2) they must be lightweight to be suitable for resource-constrained systems, such as robots with limited memory and computational capacity. The proposed method addresses these challenges using Fourier series expansions for interpolation, which reduces the memory footprint of the ATF model and facilitates online adaptation to acoustic environmental changes. The experimental results demonstrate that the proposed online adaptation method both improves the SSL and SSS performance while reducing the size of the ATF model, which represents a significant improvement over existing online ATF adaptation methods.

Method for lightning flashover types identification on transmission lines utilizing OPGW optical polarization state signal characteristics

The Optical Fiber Composite Overhead Ground Wire (OPGW) has undergone rapid development and has been extensively applied in the realm of intelligent power system status monitoring. This article conducts research on lightning signal waveform in optical fibers within the context of lightning fault location using the OPGW optical polarization state method. A transmission line model is simulated employing ATP-EMTP to capture electrical characteristics when lightning strikes the OPGW. Subsequently, by employing the Faraday magneto-optical effect principle, electrical signals are transformed into optical polarization states within the internal fibers of OPGW. Using such data, the optical signal propagation characteristics when lightning strikes OPGW are deduced. Finally, a method for discerning between induced lightning and direct lightning strikes through the analysis of time-frequency domain characteristics in OPGW. This method addresses the limitation of traditional OPGW lightning monitoring, which is unable to deduce electrical signals, thus achieving precise identification of lightning-induced transient faults in transmission lines.

Novel Intelligent Methods for Channel Path Classification and Model Determination Based on Blind Source Signals

In this paper, the urban signal propagation characteristics based on the location of blind sources are investigated. To address the issue of blind electromagnetic radiation sources in complex urban environments, intelligent methods for propagation channel path classification, and model determination are brought forth based on field test data. The intelligent classification method distinguishes between the Line-of-Sight (LoS) path channel and a direct path, the LoS multipath channel with a direct path and other multiple paths, and the Non-Line-of-Sight (NLoS) multipath channel without a direct path from the source to the test point. The modeling aspect determines the model type to which the received signal belongs based on the statistical model derived from the tested data of a specific source. A validation measurement system was constructed for the FM broadcasting band, and validation campaigns were conducted in the city of Wuhan. The process and analysis of the data using this method demonstrate the accurate distinction of the different propagation path channels and models and involve the construction of a statistical model for the FM band in Wuhan’s urban area.

Research on the 3D indoor positioning technology based on feature light source

Nowadays, positioning technologies mainly consist of three methods: positioning based on satellites, positioning based on RF and positioning based on self-contained sensors. However, due to the complex propagation characteristics of wireless signals in indoor environments, the existing positioning technologies widely used in outdoor environments cannot meet the requirements of indoor applications. Compared to outdoor environments, indoor environments are more complex, and wireless signals are affected by various factors, making it difficult for existing indoor positioning systems to meet the requirements of high accuracy and low cost. Thus, a three-dimensional indoor positioning technology based on a characteristic light source and a spherical lighting device is proposed in this paper to solve the problems. The technology measures the angle of the optical signal through a spherical lighting device, which can receive light in all directions and obtain height information compared with flat mode. Pseudo-source interference caused by the wave nature of light will not be introduced with the use of the particle nature of light. Array layout and optimization algorithms can further improve positioning accuracy. A simulation experiment in Matlab is conducted. The experimental results and the analysis of accuracy confirmed that the positioning accuracy can be controlled within a small error. Three-dimensional indoor positioning technology can achieve high accuracy at a low cost.

An intelligent financial data mining system using a fuzzy clustering multimedia approach

In order to improve the effect of financial data mining, this paper analyzes the financial data mining system combined with fuzzy clustering multimedia tool algorithm, builds an intelligent model to intelligently process financial data, and studies a multi-layer financial data protection structure model. According to the propagation characteristics of the financial data signal at the uniform cutoff and the theoretical knowledge of the electron microscopic motion, this paper analyzes the calculation formulas of the reflected power and the absorbed power of the financial data to the cutoff. Moreover, this paper improves the effect of fuzzy analysis of financial data and builds a financial data mining system based on fuzzy clustering multimedia tool. The simulation study shows that the financial data mining system based on fuzzy clustering multimedia tool proposed in this paper can effectively improve the effect of financial data mining.

Spatial propagation characteristics of acoustic emission signals in parallel steel wire cables

Accurate spatial propagation characteristics facilitate damage spatial localization, which is crucial for assessing the condition of parallel steel wire cables (PSWC). Existing studies have focused on the longitudinal propagation of acoustic emission (AE) signals, limiting accurate spatial damage assessment. This study comprehensively explored the spatial propagation characteristics of AE signals in PSWC using finite elements and attenuation tests. AE signals propagate hexagonally on the transverse section, with different amplitude attenuation rates at different angles—8% at 0° and 60°, 5 % at 30° and 45°. Additionally, AE signals exhibit oscillatory propagation between different wires in the longitudinal direction. The longitudinal speed (5706 m/s) is approximately 4.2 times faster than the transverse speed (1371 m/s), and the propagation path can be simplified as longitudinal and then transverse, offering valuable guidance for damage localization. The optimum frequency is 150 kHz in the transverse direction and 30 kHz in the longitudinal direction.

Detection and Propagation Characteristics of Partial Discharge Optical Signal Based on Fluorescent Fiber Sensor

Detection and Propagation Characteristics of Partial Discharge Optical Signal Based on Fluorescent Fiber Sensor

Analysis of 5.8 GHz Network for Line of Sight (LOS) and Non-Line of Sight (NLOS) in Suburban Environment

This paper presents the findings of radio wave characterization based on the measurement data at 5.8 GHz. The measurement data were collected by a testbed channel, which links with the following scenarios: a single tree, a row of trees, a row of trees and a road, a row of trees, a road, and a building. These experiments were conducted at University Teknologi Malaysia (UTM) Skudai, Johor to represent the suburban environment. The links consist of pairs of transmitting and receiving antennas that deploy the path of a line of sight (LOS) and non-line of sight (NLOS) radio propagation wave networks. Based on the measurement data analysis, the general issue concerning the statistical probability distribution and the characteristics of LOS and NLOS are examined and discussed. Note that 5.8 GHz technology can be used in both LOS and NLOS scenarios, but its performance varies based on the presence of obstacles and signal propagation characteristics. Other prominent experimental analysis methods, such as hypothesis testing and goodness of fit tests, are implemented to consolidate the findings. The analysis found that the empirical probability density function of LOS and NLOS channels follows Gaussian, Rayleigh, and Rician distribution. Predicting specific future technological developments, such as the availability of 5.8 GHz technology, is challenging because it depends on various factors, including research and development efforts, regulatory decisions, market demand, and technological advancements.

Analysis of 5.8 GHz Network for Line of Sight (LOS) and Non-Line of Sight (NLOS) in Suburban Environment

This paper presents the findings of radio wave characterization based on the measurement data at 5.8 GHz. The measurement data were collected by a testbed channel, which links with the following scenarios: a single tree, a row of trees, a row of trees and a road, a row of trees, a road, and a building. These experiments were conducted at University Teknologi Malaysia (UTM) Skudai, Johor to represent the suburban environment. The links consist of pairs of transmitting and receiving antennas that deploy the path of a line of sight (LOS) and non-line of sight (NLOS) radio propagation wave networks. Based on the measurement data analysis, the general issue concerning the statistical probability distribution and the characteristics of LOS and NLOS are examined and discussed. Note that 5.8 GHz technology can be used in both LOS and NLOS scenarios, but its performance varies based on the presence of obstacles and signal propagation characteristics. Other prominent experimental analysis methods, such as hypothesis testing and goodness of fit tests, are implemented to consolidate the findings. The analysis found that the empirical probability density function of LOS and NLOS channels follows Gaussian, Rayleigh, and Rician distribution. Predicting specific future technological developments, such as the availability of 5.8 GHz technology, is challenging because it depends on various factors, including research and development efforts, regulatory decisions, market demand, and technological advancements.

Spatial and Temporal Distribution of Northwest Cape Transmitter (19.8 kHz) Radio Signals Using Data Collected by the China Seismo-Electromagnetic Satellite

Very Low Frequency (VLF) waves radiated from ground-based transmitters are crucial for long-distance communication and underwater navigation. These waves can reflect between the Earth’s surface and the ionosphere for Earth–ionosphere waveguide propagation. Additionally, they can penetrate not only the ionosphere but also the magnetosphere, where they interact with high-energy particles in the radiation belt. Therefore, studying the spatial and temporal distribution of VLF radio signals holds significant importance. Such research enables us to understand the propagation characteristics of VLF signals, their interaction with radiation belt particles, and their response to space weather and lithospheric activity events. In this paper, we investigate the seasonal variations in the intensity of the Northwest Cape (NWC) transmitter (19.8 kHz) radio signals at satellite altitude and the displacement of the electric field’s peak center. Our analysis is based on the nightly China Seismo-Electromagnetic Satellite (CSES) data from 2019 to 2021. The results reveal the following: (1) There is no significant seasonal variation in the electric field strength within a small area (2.5° radius) around the NWC transmitter. However, a clear seasonal variation in the electric field strength is observed within a larger area (15° radius), with higher strength during winter compared with summer. (2) The power spectral density of the electric field remains constant within the peak central area (approximately 1~2° radius), but it decays with distance outside this region, showing a north–south asymmetry. Moreover, the decay rate of the radiation electric field is slower in the northern direction than in the southern direction. (3) The center of the electric field moves northward from summer to winter and southward from winter to summer. (4) In winter, VLF waves radiated by the NWC transmitter may predominantly propagate by being ducted toward the conjugate hemisphere.

Simulation study of partial discharge UHF signal propagation characteristics in GIS

Insulation defects inside a Gas Insulated Switchgear (GIS) can generate partial discharges, and the current pulses caused by them can excite ultra-high frequency (UHF) electromagnetic waves. To study the attenuation characteristics of UHF signal propagation in GIS, simulation models of the straight cylinder, insulator, L-type, and T-type structures are established by CST simulation software. Then the propagation characteristics of partial discharge UHF signal are studied and analyzed. The simulation results show that the electromagnetic wave propagates in each structure inside the GIS with different degrees of attenuation. When passing through insulators continuously, the first insulator has the most serious attenuation; when passing through T-shaped structures, the attenuation of T-shaped vertical branches is more serious than linear branches.

Distributed loss-amplification modeling for the mid-infrared signal propagating in the myelinated and demyelinated nerve.

The terahertz (THz) to infrared (IR) neural signal model is a potential mechanism for explaining neural communication. Myelinated neurons could be a lossy dielectric waveguide that can propagate these THz-IR neural signals. We propose an electromagnetic loss-amplification model to describe the propagation characteristics of mid-IR signals on myelinated neurons. During transmission with loss and amplification, neural signal intensity can be consistently maintained at 15.9pW in bands 55 to 75THz. This phenomenon becomes more pronounced as the number of myelin sheaths increases. However, escalated degrees of demyelination result in a reduction of signal intensity from 15.9 to 10pW. This phenomenon eventually disrupts the process of loss amplification, consequently impeding the transmission of the signal. These results may contribute to a deeper understanding of mid-IR signal propagation mechanisms in myelinated nerves and studies of diseases associated with demyelination.

Joint Precoding for Active Intelligent Transmitting Surface Empowered Outdoor-to-Indoor Communication in mmWave Cellular Networks

Outdoor-to-indoor communications in millimeter-wave (mmWave) cellular networks have been one challenging research problem due to the severe attenuation and the high penetration loss caused by propagation characteristics of mmWave signals. We propose a viable solution to implement the outdoor-to-indoor mmWave communication with the aid of an active intelligent transmitting surface (active-ITS), where the active-ITS allows the incoming signal from an outdoor base station (BS) to pass through the surface and be received by indoor users (UEs) after shifting its phase and magnifying its amplitude. Then, the problem of joint precoding of the BS and active-ITS is investigated to maximize the weighted sum-rate (WSR) of the system. An efficient block coordinate descent (BCD) based algorithm is developed to solve it with the suboptimal solutions in nearly closed-forms. In addition, to reduce the size and hardware cost of active-ITSs, we provide a block-amplifying architecture to partially remove the circuit components for power-amplifying, where multiple transmissive-type elements (TEs) in each block share the same power amplifier. Simulations indicate that active-ITS has the potential of achieving a given performance with much fewer TEs compared to the passive-ITS under the same total system power consumption, which makes it suitable for application to the space-limited and aesthetic-needed scenario, and the performance degradation caused by the block-amplifying architecture is negligible.

The frontooccipital interaction mechanism of high-frequency acoustoelectric signal.

Based on acoustoelectric effect, acoustoelectric brain imaging has been proposed, which is a high spatiotemporal resolution neural imaging method. At the focal spot, brain electrical activity is encoded by focused ultrasound, and corresponding high-frequency acoustoelectric signal is generated. Previous studies have revealed that acoustoelectric signal can also be detected in other non-focal brain regions. However, the processing mechanism of acoustoelectric signal between different brain regions remains sparse. Here, with acoustoelectric signal generated in the left primary visual cortex, we investigated the spatial distribution characteristics and temporal propagation characteristics of acoustoelectric signal in the transmission. We observed a strongest transmission strength within the frontal lobe, and the global temporal statistics indicated that the frontal lobe features in acoustoelectric signal transmission. Then, cross-frequency phase-amplitude coupling was used to investigate the coordinated activity in the AE signal band range between frontal and occipital lobes. The results showed that intra-structural cross-frequency coupling and cross-structural coupling co-occurred between these two lobes, and, accordingly, high-frequency brain activity in the frontal lobe was effectively coordinated by distant occipital lobe. This study revealed the frontooccipital long-range interaction mechanism of acoustoelectric signal, which is the foundation of improving the performance of acoustoelectric brain imaging.

Performance Analysis of Cellular Ultradense IoT Networks With Wireless Backhauls

The rising era of smart living requires unprecedented advancements in cellular networks to support the communications of the Internet of Things (IoT), referred to as Machine-Type Communication (MTC). Hence, we consider an Ultra-Dense Network (UDN) environment supported by wireless backhaul links and investigate the achievable performance gains for MTC. By doing so, we avoid the complexity, cost, and/or infeasibility of providing fiber backhaul links for the massive number of Small Cells (SCs) found in UDNs. We utilize the Millimeter Wave (mmWave) band to support the communications between the IoT Devices (IoTDs) and their serving SCs. By doing so, the excess available bandwidth can be used to support a massive number of IoTDs while the propagation characteristics of the mmWave signals can be exploited to mitigate the severe Inter-Cell Interference (ICI) found in UDNs. In this regard, we formulate a mathematical framework using tools from stochastic geometry to derive analytical expressions for the density of supported IoTDs and the average capacities per SC on both the Access Link (AL) and the Backhaul Link (BH). In addition, we obtain a tight lower bound of the average capacity per SC under the considered wireless limited-capacity backhaul links. The obtained results show the existence of an optimal active SC density that maximizes SC utilization.

Joint Trajectory Design and User Scheduling for Secure Aerial Underlay IoT Systems

Unmanned aerial vehicles (UAVs) have been widely employed to enhance the end-to-end performance of wireless communications since the links between UAVs and terrestrial nodes are line-of-sight (LoS) with high probability. However, the broadcast characteristics of signal propagation in LoS links make them vulnerable to being wiretapped by malicious eavesdroppers, which poses a considerable challenge to the security of wireless communications. In this work, we investigate the security of aerial underlay Internet of Things (IoT) systems by jointly designing trajectory and user scheduling. An airborne base station transmits confidential messages to secondary users utilizing the same spectrum as the primary network. An aerial jammer transmits jamming signals to suppress the eavesdropper to enhance secrecy performance. The uncertainty of eavesdropping node locations is considered, and the average secrecy rate of the secondary user is maximized by optimizing multiple users’ scheduling, the UAVs’ trajectory, and transmit power. To solve the non-convex optimization problem with mixed multi-integer variable problem, we propose an iterative algorithm based on block coordinate descent and successive convex approximation. Numerical results verify the effectiveness of our proposed algorithm and demonstrate that our scheme is beneficial in improving the secrecy performance of aerial underlay IoT systems.

Insights on Polar Day Antarctica Radio Propagation Using Amateur Radio Beacons on Circumnavigating Balloons

We deployed six pico balloons with 20 m transmitters (14.09 MHz) from Neumayer Station III in the 2022 Antarctic summer. Our objective was to evaluate ionospheric propagation in lower latitudes. Leveraging the Weak Signal Propagation Reporter (WSPR) protocol, we transmitted and received telemetry data on a global scale. Each balloon remained airborne for over a month, with one completing eight circumnavigations of the southern hemisphere, transmitting WSPR beacon data for 98 days. Our analysis focused on signal propagation characteristics in the polar ionosphere and surrounding regions, considering factors such as location relative to the WSPR network and solar elevation angles. Alignment between solar elevation angles at transmitting and receiving stations indicated a relationship with signal reception; lower solar elevation angles proved crucial for long-range propagation. We discovered that, beyond a solar angle of 60 degrees above the horizon, no decodes were recorded beyond 7500 km. Most signal spots were observed within a 1000–5000 km range and solar elevation angles ranging from 1 to 80 degrees. Over Antarctica, spot occurrences peaked around 4 UTC, particularly during the early hours of the day. Our findings demonstrate the usefulness of pico balloons for propagation studies, providing insights into the WSPR network’s coverage over Antarctica and surrounding lower latitudes.

The Lens Effects of Hypersonic Plasma Sheath on Terahertz Signals

Plasma sheaths enveloping reentry and hypersonic vehicles in near space could yield communication blackout. Terahertz (THz) communications are considered as a potential approach to solve the blackout problem. Many previous studies have been carried out to investigate the propagation characteristics of THz signals in plasma sheaths. Yet, the impacts of plasma sheath on the signal transmission direction are not clear enough so far. In this study, three atmospheric window frequencies in the THz band, which are 94, 140, and 220 GHz, are taken, for example, to model the transmission directions for obliquely propagating THz signals in a blunt-coned plasma sheath. The change of signal transmission directions is investigated. Based on the study, it is found that the THz signals are focalized by the plasma sheath. Further analysis shows that the plasma sheath acts as a “lens system” to the transmitting THz signals. The plasma sheath defocuses the transmitting signals at the beginning and then focuses the signals. The mechanism for that behavior is analyzed. The impacts of the lens effects on the THz relay communication for hypersonic vehicles are qualitatively discussed based on the study.