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.
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.
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.
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.
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.
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.
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!
隨著光伏發電系統快速發展,以及電動汽車充電樁的普及,傳統的剩余電流保護器無法滿足實際需求。介紹了一款B型剩余電流保護器,采用磁調制剩余電流互感器和零序電流互感器采集剩余電流。根據GB/T 22794—2017標準要求,可識別1 kHz及以下的正弦交流、帶和不帶直流分量的脈動直流、平滑直流等剩余電流信號。經信號調理電路將電壓信號送到單片機進行采集和判斷。通過試驗測試,該樣機在測試精度和速度上均符合國家標準的相關要求。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.
