Before delving into the details of orthogonal frequency division multiplexing (OFDM), relevant background material must be presented first. The purpose of this chapter is to provide the necessary building blocks for the development of OFDM principles. Included in this chapter are reviews of stochastic and random process, discrete-time signals and systems, and the Discrete Fourier Transform (DFT). Tooled with the necessary mathematical foundation, we proceed with an overview of digital communication systems and OFDM communication systems. We conclude the chapter with summaries of the OFDM wireless LAN standards currently in existence and a high-level comparison of single carrier systems versus OFDM.
上传时间： 2020-05-31
上传用户：shancjb
This book was born from the perception that there is much more to spectrum use and sharing than one sees reflected in publications, whether academic, commercial or political. the former – in good research style – tend towards reductionism and concentrate on specific, detailed aspects. commercial publications tend to empha- size the positive aspects and they tend to put promise above practice. Given the ever increasing pace of technology development and recent successes of new wireless technologies, some pundits predict large-scale spectrum scarcity, potentially lead- ing to economic catastrophe. Although economic theory has a hard time explaining recent events that shook the world economy, the notion of spectrum scarcity is intui- tively acceptable, even if not correct or immediately relevant.
上传时间： 2020-06-01
上传用户：shancjb
Short-range communications is one of the most relevant as well as diversified fields of en- deavour in wireless communications. As such, it has been a subject of intense research and development worldwide, particularly in the last decade. There is no reason to believe that this trend will decline. On the contrary, the rapidly crystallizing vision of a hyper-connected world will certainly strengthen the role of short-range communications in the future. Concepts such as wireless social networks, Internet of things, car communications, home and office network- ing, wireless grids and personal communications heavily rely on short-range communications technology.
标签： Communications Short-Range Wireless
上传时间： 2020-06-01
上传用户：shancjb
Describing the relevant detection and estimation theory, this detailed guide provides the background knowledge needed to tackle the design of practical WLAN positioning systems. It sets out key system-level challenges and design considerations in increasing positioningaccuracyandreducingcomputationalcomplexity,examinesdesigntradeoffs, and presents experimental results.
标签： Positioning Systems WLAN
上传时间： 2020-06-01
上传用户：shancjb
Battery systems for energy storage are among the most relevant technologies of the 21 st century. They – in particular modern lithium-ion batteries (LIB) – are enablers for the market success of electric vehicles (EV) as well as for stationary energy storage solutions for balancing fluctuations in electricity grids resulting from the integrationofrenewableenergysourceswithvolatilesupply 1 .BothEVandstationary storage solutions are important because they foster the transition from the usage of fossil energy carriers towards cleaner renewable energy sources. Furthermore, EV cause less local air pollution and noise emissions compared to conventional combustion engine vehicles resulting in better air quality especially in urban areas. Unfortunately, to this day, various technological and economic challenges impede a broad application of batteries for EV as well as for large scale energy storage and load leveling in electricity grids.
标签： Multiscale Simulation Approach
上传时间： 2020-06-07
上传用户：shancjb
This chapter surveys the high temperature and oxygen partial pressure behavior of complex oxide heterostructures as determined by in situ synchrotron X-ray methods. We consider both growth and post-growth behavior, emphasizing the observation of structural and interfacial defects relevant to the size-dependent properties seen in these systems.
标签： Metal-Oxides Thin Film
上传时间： 2020-06-07
上传用户：shancjb
An Arduino core for the ATmega328, ATmega168, ATmega88, ATmega48 and ATmega8, all running a [custom version of Optiboot for increased functionality](#write-to-own-flash). This core requires at least Arduino IDE v1.6.2, where v1.8.5+ is recommended. <br/> **This core gives you two extra IO pins if you're using the internal oscillator!** PB6 and PB7 is mapped to [Arduino pin 20 and 21](#pinout).<br/> If you're into "generic" AVR programming, I'm happy to tell you that all relevant keywords are being highlighted by the IDE through a separate keywords file. Make sure to test the [example files](https://github.com/MCUdude/MiniCore/tree/master/avr/libraries/AVR_examples/examples) (File > Examples > AVR C code examples). Try writing a register name, <i>DDRB</i> for instance, and see for yourself!
标签： MiniCore
上传时间： 2021-02-22
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随着光伏发电系统快速发展,以及电动汽车充电桩的普及,传统的剩余电流保护器无法满足实际需求。介绍了一款B型剩余电流保护器,采用磁调制剩余电流互感器和零序电流互感器采集剩余电流。根据GB/T 22794—2017标准要求,可识别1 kHz及以下的正弦交流、带和不带直流分量的脉动直流、平滑直流等剩余电流信号。经信号调理电路将电压信号送到单片机进行采集和判断。通过试验测试,该样机在测试精度和速度上均符合国家标准的相关要求。The rapid development of photovoltaic power generation systems and the popularity of electric vehicle charging piles make the traditional residual current protective devices unable to meet the actual demand.This paper proposed a type B residual current protective device,which uses the magnetically modulated residual current transformer and the zero sequence current transformer to acquire the residual current.According to the requirements of GB/T 22794—2017,the type B residual current protective device can detect sinusoidal AC residual current of 1kHz and below 1kHz,pulsating DC residual current with and without DC component,smooth DC residual current and so on.The signal processing circuit sends the voltage signal to the MCU for acquisition and judgment.Through experimental tests,the device meets the relevant requirements of national standards in terms of test accuracy and speed.
标签： 电流保护器
上传时间： 2022-03-27
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