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Through applying a 4‐MHz linear frequency modulation waveform, which has high range resolution and signal intensity, we successfully detected for the first time the ionospheric 150‐km echo enhancement at 430–450 MHz of the Ultra‐High‐Frequency (UHF) band using the newly built Sanya Incoherent Scatter Radar (SYISR). The obtained low signal enhancement (less than 0.5 dB) explains why previous UHF experiments did not detect them. We also found that our measured fine structure shows a much wider forbidden region than previous results and covers a much larger altitudinal and local time region. In comparison with recent upper‐hybrid instability theory and simulation, our results confirmed the predicted higher altitude occurrence, wider gaps between enhancements, the turn corner feature around sunrise, and perhaps the weak enhancement, which provide an independent evaluation of the newly proposed mechanism in UHF band. Future UHF experiments could further improve the physical understanding of 150‐km echo phenomenon. Plain Language Summary: In the altitude range of 130–170 km above the Earth's surface, the electrons ionized by the solar radiation effecting on the neutrals can generate enhanced radar echo with specific layered structures if the radar beam points perpendicular to or slightly off perpendicular to the geomagnetic field. Up to date, this phenomenon was only detected by lower frequency radars (30–60 MHz). Its physical mechanism has been a puzzle over several decades. Recently, due primarily to the advancement of numerical simulation technology and the improvement of computing power, this puzzle was resolved well by the newly proposed across scales energy transformation physical mechanism in several recent publications. However, these simulations also concluded that it is hard to be detected by higher frequency radars. In this paper, using our newly built Sanya Incoherent Scatter Radar, we applied a novel experimental setup to gain very high range resolution and signal intensity. We finally successfully detected this phenomenon in 430–450 MHz. By comparing our results with previous measurements and theoretical simulation, we can enhance current physical understanding from the perspective of observations. Key Points: Successful first detection of daytime 150‐km echoes in the Ultra‐High‐Frequency band with Sanya Incoherent Scatter RadarWe detected wider forbidden region and larger altitudinal and local time coverage than previous resultsNarrow layering features not following the zenith angle point to field‐aligned irregularitie echoes [ABSTRACT FROM AUTHOR]

Abstract Through applying a 4‐MHz linear frequency modulation waveform, which has high range resolution and signal intensity, we successfully detected for the first time the ionospheric 150‐km echo enhancement at 430–450 MHz of the Ultra‐High‐Frequency (UHF) band using the newly built Sanya Incoherent Scatter Radar (SYISR). The obtained low signal enhancement (less than 0.5 dB) explains why previous UHF experiments did not detect them. We also found that our measured fine structure shows a much wider forbidden region than previous results and covers a much larger altitudinal and local time region. In comparison with recent upper‐hybrid instability theory and simulation, our results confirmed the predicted higher altitude occurrence, wider gaps between enhancements, the turn corner feature around sunrise, and perhaps the weak enhancement, which provide an independent evaluation of the newly proposed mechanism in UHF band. Future UHF experiments could further improve the physical understanding of 150‐km echo phenomenon.

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Through in-depth analysis of Ultra high frequency (UHF) stock price change data, more reasonable discrete dynamic distribution models are proposed in this paper. Firstly, we classify the price changes into several categories. Then, temporal convolutional network (TCN) is utilized to predict the conditional probability for each category. Furthermore, attention mechanism is added into the TCN architecture to model the time-varying distribution for stock price change data. Empirical research on constituent stocks of Chinese Shenzhen Stock Exchange 100 Index (SZSE 100) found that the TCN framework model and the TCN (attention) framework have a better overall performance than GARCH family models and the long short-term memory (LSTM) framework model for the description of the dynamic process of the UHF stock price change sequence. In addition, the scale of the dataset reached nearly 10 million, to the best of our knowledge, there has been no previous attempt to apply TCN to such a large-scale UHF transaction price dataset in Chinese stock market. [ABSTRACT FROM AUTHOR]

Bushings are essential components in a power transformer where incipient partial discharge (PD) activities and its detection and diagnosis cannot be ignorant. In this paper, an oil-impregnated paper (OIP) bushing is modeled to investigate that the oil gaps between the flange and condenser body in a typical OIP bushing provide a feasible path to trace the electromagnetic signal. As a non-destructive method, UHF (Ultra High Frequency) is proposed to detect 4 typical inside and outside PD defects of 110 kV bushings. To analyze the parameters of different defects, not only phase-resolved partial discharge (PRPD) is presented, but also 16 detailed time-domain and frequency-domain parameters of UHF signal are involved. Then feature extraction and selection are conducted through comparative principal component analysis (PCA) and extremely randomized trees (ET) algorithms. It is revealed that the selected features are representative and ET greatly reduces the amount of data whilst ensuring high accuracy. Fault diagnosis for bushing is finally achieved via support vector machine (SVM) with the selected features. The presented work of bushing PD detection based on UHF sensors provides a complete solution for the bushing diagnosis in potential field application and maintenance. [ABSTRACT FROM AUTHOR]

The study focuses on testing the protection of computing technology and peripheral devices based on radio-frequency identification (RFID) technology in a selected corporate organization. The potential of RFID technology is also employed to obtain statistical data about real-time use of the devices. Based on the comparison of high and ultra high frequency of RFID technology, the appropriate variant was selected for operation, selected devices were tagged with RFID tags, and the success of their detection was monitored both in the test period and in real operation. After three months' operation, the cost connected with protection implementation and its benefits was assessed. The main benefit is reducing the number of stolen devices. Users' tendency to bypass the protection was minimal. A further result of this study is determining the overall value of computing technology and peripheral devices to be protected against loss caused by theft that would make the investment in RFID technology pay off for the corporation. It was confirmed that deploying this type of protection pays off for the organization in four years thanks to the prevention of direct losses. After the assessment of the results, a possible future use of RFID potential beyond the protection itself is considered, that would optimize a corporation's inventory and track the movement of individual devices among users. These considerations include, in particular, the efficiency of use of IT staff working time, the prevention of unavailability of devices and the increase of the level of IT service provided to users.

Abstract This paper presents an outdoor long-range (from 315 m up to 5.3 km) fixed channel campaign for both ultra high frequency and super high frequency bands with co-polarized horizontal and vertical antenna configurations. It investigates the channel characteristics of device to device communication scenarios underlaying the 5th generation networks by providing detailed research. Both line of sight and non-line of sight measurements in 1.3 GHz and 5.8 GHz frequency bands with bandwidth up to 600 MHz were conducted. The path loss, root mean square delay spread, coherence bandwidth, and channel frequency response variation are characterized. We observed that the variation is negligible in microcell line of sight environment for both above mentioned frequencies, whereas it significantly increases with frequency in different macrocell non-line of sight environments. The distance dependency of path loss was also derived. It was observed that the root mean square delay spread decreases with frequency for both line of sight microcell and non-line of sight macrocell measurements. A dependency between the root mean square delay spread and transmitter-receiver distance in non-line of sight environments was also captured. The relation between the coherence bandwidth and the root mean square delay spread was depicted. It demonstrates an exponential function in all considered channel combinations.

In order to implement the interweave cognitive radio solutions, the research for finding sparsely utilized spectrum bands has revealed the VHF and UHF television broadcast bands, known as television white spaces (TVWS) as the foremost candidate. The TVWS quantification and throughput analysis conducted via several measurement attempts and field trials uncover various facets of the TVWS spectrum measurement. Consequently, the conclusions obtained may be processed to get a statistical knowledge about spectrum availability in a particular geographic region and hence utilized for spectrum management. This paper explores inherent methodologies used for TVWS assessment and provides a comprehensive overview of the TVWS regulatory norms, results obtained by TVWS measurement campaigns and field trials conducted worldwide. In addition, research issues, implementation challenges and future directions for TVWS measurement procedure are highlighted. [ABSTRACT FROM AUTHOR]

Partial discharges are the main insulation defects encountered in gas-insulated switchgears. When it occurs inside the gas-insulated switchgear cavity, it degrades insulation, and, sooner or later, causes a breakdown. Therefore, it is important to discover insulation defects as early as possible, locate the discharge, and perform both defect identification and maintenance. Current ultra high frequency-based partial discharge location methods mainly use time delay. To obtain accurate delay times, however, a very high sampling rate is needed, which requires expensive hardware and greatly limits its application. Therefore, in this article, a localization method based on received signal strength indicator ranging is proposed, and location estimation is carried out. An easily implementable particle swarm optimization algorithm with high positioning accuracy is selected to compensate for the low positioning accuracy of current received signal strength indicator ranging methods. To further improve positioning accuracy, the convergence conditions of the particle swarm optimization are investigated, and, considering their constraints, an improved particle swarm optimization algorithm is proposed. By combining the characteristics of ultra high frequency wireless sensor array positioning, the particle size is optimized. The simulation results show that the location accuracy using the ultra high frequency switchgear partial discharge location method based on received signal strength indicator ranging with the improved particle swarm optimization algorithm performs significantly better. [ABSTRACT FROM AUTHOR]

A Linear Array Antenna (LAA), a subsystem of a Wireless Communication System (WCS), with 12 number of dipole elements are optimally designed using Gravitational Search Algorithm (GSA). GSA being one of the suitable optimisation algorithms, used to optimise many design parameters of this subsystem to get a number of desired performance parameters using a simple weighted sum type multi-objective function. The LAA subsystem is designed here, mainly to realise high directivity, high front-to-maximum-side-lobe-level, and low half power beam width for WCS application at ultra high frequency. The LAA designed using GSA is also validated using MININEC for transparency. The successful optimal design approaches, application, and comparative study of this system with an un-optimised system presented here can also be extended to other antennas.

To address the issue of white noise at partial discharge (PD) ultra high frequency (UHF) signal in gas insulated substation (GIS), this paper develops an external sensor and proposes new empirical mode decomposition (EMD) denoising method based on autocorrelation coefficient and similar wavelet soft threshold. Four types of typical GIS defects at the PD UHF signal were obtained through experiment. The autocorrelation coefficient of intrinsic mode functions (IMF) components at the PD UHF signal was computed, the cut-off point between the noise signal dominant mode and the UHF signal dominant mode was found. The similar wavelet soft threshold denoising was performed on the signal which is dominated by the noise signal, all the UHF signals were finally reconstructed. The signal-to-noise ratio computed by the proposed denoising method was compared with the one computed by the wavelet denoising method, the results shows that the proposed denoising method in this paper is more effective than the wavelet denoising method. [ABSTRACT FROM AUTHOR]

An approach to silicon low noise amplifier (LNA) optimization, intended for use in the CAD Advanced Design System, has been presented. The approach is based on a technique using the contour plots of LNA parameters such as operating current, transistor width, impedancematching circuit elements, minimizing the noise figure of the LNA, and providing sufficient gain and VSWR. The ability to use the models of real silicon passive and active elements, and consider the impact of the bond wires inductance is an advantage of the proposed approach. LNA optimization procedure consists of three steps. The first step is a schematic selection of the input stage LNA, specifying the operating current and providing input impedance matching. At the second step an optimization procedure with the built-in CAD optimization tools is used to calculate the contour plots of LNA parameters at one frequency point for all implementable set of values of the operating current and the input stage transistor width. Finally, optimal values of selected LNA schematic elements are defined using the calculated contour plots. The presented approach has been tested at 1,4 GHz LNA design, intended for use in a global positioning system receiver, to be implemented in a 0,35 um SOI CMOS process. The LNA provides a forward gain of 19 dB with a noise figure of only 1.6 dB, VSWR of 1,45 while drawing 60 mW from a 3,3 V supply.