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In power systems, disturbances between 2 kHz and 150 kHz are called "Supraharmonics" (SH). Although supraharmonics are not a new concept; It has only attracted the attention of researchers, engineers and manufacturers of end-user devices in recent years. Electromagnetic compatibility (EMC) tests, which are required for placing electrical/electronic devices on the market, require the measurement of harmonic currents (50 Hz-2000 Hz) and the measurement of conducted emission values. However, studies and research in the supraharmonic range are quite limited. As systems using semi-conductor technologies with high power and switching in the kHz range such as photovoltaic energy systems, electric vehicle fast charging stations, high speed digital communication systems become widespread, supraharmonics have also begun to be effective in power distribution systems and cause problems. Today, the struggle against high-frequency disturbances caused by the increased use of electrical and electronic devices, switched power electronic devices and power line communication (PLC) devices is even more prominent. Research conducted in recent years have revealed that disturbances between 2 kHz and 150 kHz cause measurement errors in smart meters, audible noise, malfunctions and performance reductions in electrical devices. In this study, sources of supraharmonics, the problems they cause in devices and networks, measurement methods of supraharmonics and related standards, supraharmonic simulation of sample devices and analysis by measurement are given. Measurements and simulation results show that focusing only on EMC requirements in device designs can cause supraharmonics to be neglected, thus negatively affecting the network and other devices. [ABSTRACT FROM AUTHOR]

In the early 21st century, governments developed national broadband plans to supply high-speed broadband networks for the emerging digital economy and to enable digital services delivery. Most national broadband plans are now focused on moving to ever faster networks, but there is a growing need to develop national digital communications strategies to focus on the demand-side of the broadband "eco-system". In this paper, we outline the approaches adopted by the United States, Canada, the United Kingdom, Singapore, and Korea to assist in the development (or renewal) of Australia's national broadband strategy, or, as we prefer, national digital communications strategy. The paper draws on the lessons learned from the case-study countries and the recent pandemic and considers some theoretical aspects of the broadband ecosystem. We conclude by suggesting a process to re-evaluate Australia's national digital communications strategy as it rolls forward, and to incorporate recent international trends to develop demand-side policies to enable greater adoption and use of existing broadband infrastructure and digital services. [ABSTRACT FROM AUTHOR]

Air travel is growing at an alarming rate. However, according to the latest research report by Eurocontrol on European aviation, the growth of air traffic will be limited by the available spectrum resources. As one of the means to provide air/ground (A/G) broadband communication, the L-band digital aeronautical communication system (LDACS) is becoming the preferred model for final deployment and has received continuous attention. Based on various spectrum measurement studies, the international civil aviation organization (ICAO) has identified multiple 1 MHz vacant bands between adjacent distance measuring equipment (DME) signals for LDACS. In order to improve spectrum efficiency, the concept of dynamic spectrum access (DSA) can be applied to the LDACS, which requires the use of spectrum sensing methods to detect the spectrum holes of DME users. In this paper, an adaptive threshold energy detection spectrum sensing method is proposed based on the characteristics of DME pulse signals. Firstly, the energy of the received signal is estimated to construct the detection statistics, and the equations of detection probability and false alarm probability are established. Secondly, the adaptive threshold is calculated using the maximum likelihood decision criterion under the assumption of a constant probability of false alarm. Thirdly, the detection statistic is compared to the adaptive threshold to determine the spectrum occupancy state in the decision-making stage. Finally, the result is transmitted back to the transmitter for the best spectrum resource allocation. According to the simulation analysis, the adaptive threshold energy detection-based sensing method outperforms the energy-difference detection method under low signal-to-noise ratio (SNR) conditions. Meanwhile, it has superior adaptability since the adaptive threshold can be adaptively changed according to the channel. [ABSTRACT FROM AUTHOR]

Information is a critically important, yet hard to measure, component on policy innovation across state governments. Widespread use of broadband has made it easier for governments to observe other actors, increasing the amount of policy information, while also diversifying the sources of information available to policymakers. This should translate into making governments more innovative over time and quicker to adapt to challenges. At the same time, the Internet may disrupt previous existing flows of information by decreasing the importance of geographic proximity and creating more nationalized or global information networks. We argue that the growth of broadband has made states more innovative over time, while also reducing the reliance on neighboring state adoptions for policy solutions as the information environment becomes both richer and more nationalized. We estimate a pooled event history analysis on hundreds of policies comparing the treatment period (2000–2016) with a control condition (last two decades of the 20th century) and find that states with higher broadband subscriptions are more innovative overall and less reliant on geographic contiguity for policy solutions. The growth of information flows due to digital communications has led to states becoming more innovative while also operating in a more nationalized network. [ABSTRACT FROM AUTHOR]

We propose a theoretical mechanism and new coding strategy to realize extremely accurate manipulations of nonlinear electromagnetic harmonics in ultrawide frequency band based on a time-domain digital coding metasurface (TDCM). Using the proposed mechanism and coding strategy, we design and fabricate a millimeter-wave (mmWave) TDCM, which is composed of reprogrammable meta-atoms embedded with positive-intrinsic-negative diodes. By controlling the duty ratios and time delays of the digital coding sequences loaded on a TDCM, experimental results show that both amplitudes and phases of different harmonics can be engineered at will simultaneously and precisely in broad frequency band from 22 to 33 GHz, even when the coding states are imperfect, which is in good agreement with theoretical calculations. Based on the fabricated high-performance TDCM, we further propose and experimentally realize a large-capacity mmWave wireless communication system, where 256 quadrature amplitude modulation, along with other schemes, is demonstrated. The new wireless communication system has a much simpler architecture than the currently used mmWave wireless systems, and hence can significantly reduce the hardware cost. We believe that the proposed method and system architecture can find vast application in future mmWave and terahertz-wave wireless communication and radar systems. [ABSTRACT FROM AUTHOR]

This document is an editorial published in Frontiers in Marine Science on the topic of maritime broadband communications and networking. The editorial highlights the importance of digitalization in the maritime industry and the need for new broadband communication technology to support various maritime activities. The document also mentions six published papers that cover different aspects of maritime networking and broadband communications, including topics such as maritime radio channel measurement and modeling, collision avoidance, and satellite systems. The authors conclude that further research in this area is needed to advance maritime broadband communications and networking. [Extracted from the article]