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Antenne radioélectrique

thumb|Antenne rideau HF de télécommunication. thumb|Antennes de réception de la télévision. thumb|Montage d'une antenne de station terrienne au Nicaragua. thumb|upright=1.8|Un diagramme animé d'une antenne dipôle recevant une onde radio. En radioélectricité, une antenne est un dispositif permettant de rayonner (émetteur) ou de capter (récepteur) les ondes électromagnétiques. L'antenne est un élément fondamental dans un système radioélectrique, et ses caractéristiques de rendement, gain, diagramme de rayonnement influencent directement les performances de qualité et de portée du système. Cet article définit les caractéristiques et paramètres généraux des antennes, chaque antenne et application particulière étant développée dans les articles liés. Heinrich Hertz utilisa pour la première fois, en 1888, des antennes pour démontrer l'existence des ondes électromagnétiques prédites par la théorie de Maxwell. Il utilisa des antennes doublet, tant pour la réception que pour l'émission. Il installa même le dipôle émetteur au foyer d'un réflecteur parabolique. Les travaux et les dessins de l'installation furent publiés dans les Annalen der Physik und Chemie (vol. 36, 1889). Le terme « antenne » fut utilisé par Marconi. Une antenne radioélectrique convertit les grandeurs électriques existantes dans un conducteur ou une ligne de transmission (tension et courant) en grandeurs électromagnétiques dans l'espace (champ électrique et champ magnétique). Inversement, en réception, le champ électromagnétique est converti en signal électrique qui peut ensuite être amplifié. thumb|upright=1.8|Animation d'un ondes radio antenne dipôle rayonnant. left|thumb|Schéma géométrique d'une antenne élémentaire. Une antenne élémentaire en émission, dénommée également doublet électrique, est constituée d'une petite longueur de conducteur (petite devant la longueur d'onde ) dans lequel circule un courant alternatif : Dans laquelle est la pulsation, est la fréquence, et est le nombre imaginaire tel que .

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Exercices associés (11)

Bobine rectangulaire

A coil, made of N rectangular turns of length l and of width w, has a resistance R. The coil, which is moving with a constant velocity

{\bf u} = u\,{\bf \hat{x}}

, enters a region subject to a uniform magnetic field

{\bf B}=-B_0\,{\bf \hat{z}}

. We will neglect the self-inductance of the circuit. Calculate the amplitude and direction of the induced current when : the coil is partially inside the region subject to the field B; the coil is entirely in this region ; the coil starts to go out of the regi

Bobine rectangulaire avec inductance

We take the exercise 1 of the previous set of exercices (squared coil going through a zone of magnetic field of length D). Now, we take into account the inductance L of the coil, as well as its resistance R. We will suppose that the coil is moving at a constant velocity v₀.

Calculate and represent the evolution of the current as function of time, from the situation where the coil is completely outside on the left of the field, to the situation where it is completely on the right. We will su

La boule de la mort

xa0 An attraction sometimes seen in fairs consists in a motor-biker entering in a spherical cage and starting to circularly drive faster and faster. At the start of the rotation, the motor-biker is located at the bottom of the sphere, then, as the velocity increases, he goes up. As such, he can reach the medium level of the sphere. In this situation, le body of the motor-biker is horizontal(αu2004=u200490^(∘)). Let us consider a spherical cage of radius R, and a motor-biker (on its motorcycle) seen as a m

Bobine avec courant alternatif

In a coil of radius R, with N turns per meter and of infinite length, an alternative current circulates I(t)u2004=u2004I_(max)u2006cosu2006ωt. Determine the amplitude of the electric field induced at a distance ru2004>u2004R from the axis of the coil. Same question but this time inside of the coil(ru2004

Charge dans une spire circulaire

A charge q is uniformally distributed along a circular coil of radius R. By taking into account the symmetry of the problem, calculate the electric field and the electrostatic potential created by this charge in the point P(0,0,z) located on the axis of the coil. Find the electric field from the potential previously calculated. The symmetry of the problem indicates us that the field is directed along the z axis : $$\cos \theta = \frac{z}{{\mbox{$\resizebox{.16in}{.08in}{\includegraphics{./figures//ScriptR

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Notebooks associés (20)

Voice Transformation Techniques Using Digital Signal Processing

A Gallery of Voice Transformers[1]¶

                                      [2]Paolo Prandoni, [3]LCAV, EPFL

In this notebook we will explore various ways to implement a system that changes the voice of a speaker. Typical applications for these techniques, strictly sorted by plausibility, include international spy missions and prank telephone calls, and devices such as the one displayed here can be easily bought on the web... or in a novelty shop. No description has been provided for t

Digital Simulation of Guitar Feedback in I Feel Fine by The Beatles

I Feel Fine, Digitally[1]¶ This notebook is a little musing inspired by the "internal mechanics" of a very famous audio snippet, namely the guitar sound at the beginning of the song "I Feel Fine", written and recorded by the Beatles in 1964. The historical significance of the record lies in the following claim by John Lennon:

 "I defy anybody to find a record... unless it is some old blues
 record from 1922... that uses feedback that way. So I claim it for
 the Beatles. Before H

Understanding and Plotting the Discrete Fourier Transform (DFT)

Plotting the DFT[1]¶

                                      [2]Paolo Prandoni, [3]LCAV, EPFL

In this notebook we will look at the practical issues associated to plotting the DFT and in particular the DFT of real-world signals. We will examine how to map the DFT coefficients to real-world frequencies and we will investigate the frequency resolution of the DFT and the effects of zero padding. In [1]:

first our usual bookkeeping

%matplotlib inline import matplotlib import matplotlib.p

Understanding the Haar Basis for Grayscale Image Compression

A Basis for Grayscale Images[1]¶

                                      [2]Paolo Prandoni, [3]LCAV, EPFL

The concept of "basis" for a vector space is one of the most profound and fruitful ideas in linear algebra. Basis vectors are the "building blocks" that all other vectors are built from; by "disassembling" a vector into a linear combination of basis elements we are able to "look inside" the vector and highlight many of its relevant features. A vector space has an infinite number o

Exploring the Karplus-Strong Algorithm for Sound Synthesis

The Karplus-Strong Algorithm[1]¶

                                      [2]Paolo Prandoni, [3]LCAV, EPFL

The Karplus-Strong algorithm is a simple method to generate synthetic sounds with arbitrary pitch. In this notebook we will explore a few variations of the method to illustrate some basic notions of discrete-time signal processing. In [1]: %matplotlib inline import matplotlib import matplotlib.pyplot as plt import numpy as np import IPython In [2]: plt.rcParams["figure.figsize"]

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Exercices associés (11)

Bobine rectangulaire

A coil, made of N rectangular turns of length l and of width w, has a resistance R. The coil, which is moving with a constant velocity

{\bf u} = u\,{\bf \hat{x}}

, enters a region subject to a uniform magnetic field

{\bf B}=-B_0\,{\bf \hat{z}}

Bobine rectangulaire avec inductance

Calculate and represent the evolution of the current as function of time, from the situation where the coil is completely outside on the left of the field, to the situation where it is completely on the right. We will su

La boule de la mort

Bobine avec courant alternatif

Charge dans une spire circulaire

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Jan Sickmann Hesthaven

Prof. Hesthaven received an M.Sc. in computational physics from the Technical University of Denmark (DTU) in August 1991. During the studies, the last 6 months of 1989 was spend at JET, the european fusion laboratory in Culham, UK. Following graduation, he was awarded a 3 year fellowship to begin work towards a Ph.D. at Riso National Laboratory in the Department of Optics and Fluid Dynamics. During the 3 years of study, the academic year of 1993-1994 was spend in the Division of Applied Mathematics at Brown University and three 3 months during the summer of 1994 in Department of Mathematics and Statistics at University of New Mexico. In August 1995, he recieved a Ph.D. in Numerical Analysis from the Institute of Mathematical Modelling (DTU). Following graduation in August 1995, he was awarded an NSF Postdoctoral Fellowship in Advanced Scientific Computing and was approinted Visiting Assistant Professor in the Division of Applied Mathematics at Brown University. In December of 1996, he was appointed consultant to the Institute of Computer Applications in Science and Engineering(ICASE) at NASA Langley Research Center (NASA LaRC). As of July 1999, he was appointed Assistant Professor of Applied Mathematics, in September 2000 he was awarded an Alfred P. Sloan Fellowship, as of July 2001 he was awarded a Manning Assistant Professorship, and in March 2002, he was awarded an NSF Career Award. In January 2003, he was promoted to Associate Professor of Applied Mathematics with tenure and in May 2004 he was awarded Philip J. Bray Award for Excellence in Teaching in the Sciences (the highest award given for teaching excellence in all sciences at Brown University). He was promoted to Professor of Applied Mathematics as of July 2005. From October 2006 to June 2013, he was the Founding Director of the Center for Computation and Visualization (CCV) at Brown University. As of October 2007, he holds the (honorary) title of Professor (Adjunct) at the Technical University of Denmark. In November 2009, he successfully defended his dr.techn thesis at the Technical University of Denmark and was rewarded the degree of Doctor Technices -- the highest academic distinction awarded based on ... substantial and lasting contributions that has helped to move the research area forward and penetrated into applications. As grant Co-PI he served from Aug 2010 to June 2013 as Deputy Director of the Institute of Computational and Experimental Research in Mathematics (ICERM), the newest NSF Mathematical Sciences Research Institute. After having spend his entire academic career at Brown University, Prof Hesthaven decided to pursue new challenges and joined the Mathematics Institute of Computational Science and Engineering (MATHICSE) at Ecole Polytechnique Fédérale de Lausanne (EPFL) in Switzerland in July 2013. In March 2014 he was elected SIAM Fellow for contributions to high-order methods for partial differential equations.

Antenne radioélectrique

Chattez avec Graph Search

first our usual bookkeeping

first our usual bookkeeping

Gain Optimization of an Electrically Small Huygens Source Antenna

Revisiting 2D Frequency Scanning Arrays for Low-Complexity 3D Positioning in Spacecraft and IoT Applications

Wideband and Frequency‐Reconfigurable Loop Antenna for Sub‐6 GHz Applications