Any electromagnetic phenomenon capable of impairing the performance of a device, equipment or system, etc.
An electromagnetic disturbance can be electromagnetic noise, an unwanted signal or a change in the
propagation medium itself.
One of the major functions of the physical layer is to move data in the form of electromagnetic signals across a transmission medium. Whether you are collecting numerical statistics from another computer, sending animated pictures from a design workstation, or causing a bell to ring at a distant control center, you are working with the transmission of data across network connections. Chapter 3 discusses the relationship between data, which are created by a device, and electromagnetic signals, which are transmitted over a medium.
Every year, tens of thousands of young engineers and university graduates enter the
fascinating professional field of radio frequency (RF) design. Most of them have a
reasonable understanding of applied mathematics and physics, circuit theory, electromagnetism,
and electronics as well as computers and programming.
The Advanced Signal Processing Handbook: Theory and Implementation for Radar, Sonar, and Medical Imaging Real-Time Systems Stergios Stergiopoulos The Transform and Data Compression Handbook K.R. Rao and P.C.
Communication happens in the form of signals.
Signals are transmission of energy (mechanical, electrical or light) through appropriate
A signal that is constant and changed once conveys single information.
The more changes in the signal, the more information that the signal can convey.
For example, a push can mean one thing and removing it can mean another thing.
In a communication system, data are propagated from one point to another by means of
electromagnetic signals. A signal is a series of analogue or digital data. That is a varying voltage
(either continuous or discrete) with time in an electronic communication system.
Definitions of Data and Signals:
Analog Data - Data represented by a continuous physical quantity whose magnitude is proportion
a suitable function of the data (information). It can have more than two discrete values in
contrast to digital data. ...
This article (see also [1, 2]) considers new methods for multiple electromagnetic source localization
using sensors whose output is a vector corresponding to the complete electric andmagneticfields at the
sensor. These sensors, which will be called vector sensors, can consist for example of two orthogonal
triads of scalar sensors that measure the electric and magnetic field components. Our approach is in
contrast to other articles in this chapter that employ sensor arrays in which the output of each sensor
is a scalar corresponding, for example, to a scalar function of the electric field....
Basic Orthogonal Wavelet Theory
In Chapter 2 we saw how multiresolution analysis (MRA) works for the Haar system. A signal was decomposed into many components on different resolution levels. These components are mutually orthogonal. Despite their attractiveness, the Haar scalets and wavelets are not continuous functions. The discontinuities can create problems when applied to physical modeling. In this chapter we will construct many other orthogonal wavelets that are continuous and may even be smooth functions. ...
A synthetic aperture radar (SAR) is a radar sensor that provides azimuth resolution superior to that achievable with its real beam by synthesizing a long aperture using platform motion. The geometry for the production of the SAR image is shown in Fig. 33.1. The SAR is used to generate an electromagnetic map of the surface of the earth from an airborne or spaceborne platform. This electromagnetic map of the surface
Special and general relativity are the theories describing the physics of space
and time. Space and time are explored with clocks and electromagnetic signals.
Therefore, special and general relativity are related to precise clocks and the
thorough understanding of signal propagation. The ever-increasing accuracy
of clocks together with novel methods for precision time transfer and clock
synchronization are pivotal for the new generation of experiments probing the
validity of Einstein’s theories from subatomic distances to cosmic scales....
Fundamentals of Radio Transmission
In mobile radio systems, unlike wired networks, electromagnetic signals are transmitted in free space (see Figure 2.1). Therefore a total familiarity with the propagation characteristics of radio waves is a prerequisite in the development of mobile radio systems. In principle, the Maxwell equations explain all the phenomena of wave propagation. However, when used in the mobile radio area, this method can result in some complicated calculations or may not be applicable at all if the geometry or material constants are not known exactly....
Low-frequency acoustic energy released within the Earth's crust and mantle mostly
propagates - depending on the density and elasticity of the medium - through several
types of seismic waves categorized as body waves (longitudinal P and transverse S) or
surface waves (long L and ground roll R).
The importance of seismic wave research lies not only in our ability to understand and
predict earthquakes and tsunamis, it also reveals information on the Earth's
composition and features in much the same way as it led to the discovery of
Digitizing is the process of converting a continuos signal (such as sound or video) into
distinct units that the compute or other electronic equipment can process. There are
many ways to digitize things. there is the microphone, which digitizes sound. The
scanner can digitize photos and other images. A digital camera is able to bring video
into the computer.
You can also digitize 3D objects. For that you use a 3D digitizer. These come in many
different shapes and sizes. They usually use lasers to map out the 3D points and create
(BQ) Part 1 book "MRI at a glance" presentation of content: Magnetism and electromagnetism, atomic structure, alignment and precession, resonance and signal generation, resonance and signal generation, contrast mechanisms, conventional spin echo,... and other contents.
Organized primarily by sensor application, the book is cross-referenced with indices of sensor technology. Manufacturers are listed by sensor type. The other contributors and I have attempted to provide a useful handbook with technical explanations that are clear, simple and thorough. We will also attempt to keep it updated as the technology advances.
Practical TCP/IP and Ethernet Networking- P5: The transmitter encodes the information into a suitable form to be transmitted over the
communications channel. The communications channel moves this signal as
electromagnetic energy from the source to one or more destination receivers. The
channel may convert this energy from one form to another, such as electrical to optical
signals, whilst maintaining the integrity of the information so the recipient can understand
the message sent by the transmitter....
Radar and Sensor Systems
Radar stands for radio detection and ranging. It operates by radiating electromagnetic waves and detecting the echo returned from the targets. The nature of an echo signal provides information about the target—range, direction, and velocity. Although radar cannot reorganize the color of the object and resolve the detailed features of the target like the human eye, it can see through darkness, fog and rain, and over a much longer range.
Scientists and mathematicians of the nineteenth century laid the foundation of telecommunication and wireless technology, which has affected all facets of modern society. In 1864, James C. Maxwell put forth fundamental relations of electromagnetic ®elds that not only summed up the research ®ndings of Laplace, Poisson, Faraday, Gauss, and others but also predicted the propagation of electrical signals through space. Heinrich Hertz subsequently veri®ed this in 1887 and Guglielmo Marconi successfully transmitted wireless signals across the Atlantic Ocean in 1900...
The purpose of The Electrical Engineering Handbook, 3rd Edition is to provide a ready reference for the
practicing engineer in industry, government, and academia, as well as aid students of engineering.