In electromagnetics and antenna theory, the aperture of an antenna is defined as "A surface, near or on an antenna, on which it is convenient to make
assumptions regarding the field values for the purpose of computing fields at external points. The aperture is often taken as that portion of a plane surface near the antenna, perpendicular to the direction of maximum radiation, through which the major part of the radiation passes."
The effective area of an antenna is defined as "In a given direction, the ratio of the available power at the terminals of a receiving antenna to the power flux density of a plane wave incident on the antenna from that direction, the wave being polarization matched to the antenna." Of particular note in this definition is that both effective area and power flux density are functions of incident angle of a plane wave. Assume a plane wave from a particular direction , which are the azimuth and elevation angles relative to the array normal, has a power flux density ; this is the amount of power passing through a unit area normal to the direction of the plane wave of one square meter.
By definition, if an antenna delivers watts to the transmission line connected to its output terminals when irradiated by a uniform field of power density watts per square meter, the antenna's effective area for the direction of that plane wave is given by
The power accepted by the antenna (the power at the antenna terminals) is less than the power received by an antenna by the radiation efficiency of the antenna. is equal to the power density of the electromagnetic energy , where is the unit vector normal to the array aperture, multiplied by the physical aperture area . The incoming radiation is assumed to have the same polarization as the antenna. Therefore,
and
The effective area of an antenna or aperture is based upon a receiving antenna. However, due to reciprocity, an antenna's directivity in receiving and transmitting are identical, so the power transmitted by an antenna in different directions (the radiation pattern) is also proportional to the effective area .
This page is automatically generated and may contain information that is not correct, complete, up-to-date, or relevant to your search query. The same applies to every other page on this website. Please make sure to verify the information with EPFL's official sources.
Les antennes sont utilisées dans une multitude d'applications de communications et de détection, demandant des fréquences et propriétés d'antennes très différentes. Ce cours décrit la théorie de base
Introduction to analog CMOS design for Remote Biosensors on Chip. Understanding and designing of active and remotely powered biosensing systems. Basic understanding of eh wireless transmission of teh
This lecture is oriented towards the study of audio engineering, with a special focus on room acoustics applications. The learning outcomes will be the techniques for microphones and loudspeaker desig
In electromagnetics, directivity is a parameter of an antenna or optical system which measures the degree to which the radiation emitted is concentrated in a single direction. It is the ratio of the radiation intensity in a given direction from the antenna to the radiation intensity averaged over all directions. Therefore, the directivity of a hypothetical isotropic radiator is 1, or 0 dBi. An antenna's directivity is greater than its gain by an efficiency factor, radiation efficiency.
In telecommunications and radar engineering, antenna boresight is the axis of maximum gain (maximum radiated power) of a directional antenna. For most antennas the boresight is the axis of symmetry of the antenna. For example, for axial-fed dish antennas, the antenna boresight is the axis of symmetry of the parabolic dish, and the antenna radiation pattern (the main lobe) is symmetrical about the boresight axis. Most antennas boresight axis is fixed by their shape and cannot be changed.
In classical electromagnetism, reciprocity refers to a variety of related theorems involving the interchange of time-harmonic electric current densities (sources) and the resulting electromagnetic fields in Maxwell's equations for time-invariant linear media under certain constraints. Reciprocity is closely related to the concept of symmetric operators from linear algebra, applied to electromagnetism.
This course covers the principles and practices of radio astronomical observations, in particular with modern interferometers. Topics range from radio telescope technology to the measurement equation
Learn the basics of plasma, one of the fundamental states of matter, and the different types of models used to describe it, including fluid and kinetic.
Learn the basics of plasma, one of the fundamental states of matter, and the different types of models used to describe it, including fluid and kinetic.
Covers antenna radiation, beam width, network factor, and antenna synthesis.
Explores reciprocity of powers, capture surface, linear wire antennas, and radar cross-section examples.
Explores radiation at antennas, reciprocity, directivity, and the Friis formula.
Advanced antenna system (AAS) is a viable option for 5G millimeter-wave (mmWave) applications. AAS single element is favored to be dual-polarized, wideband, high gain, and compact in order to be utilized for 5G antenna arrays. In this paper, a low complexi ...
Electrically connected and plasmonically enhanced molecular junctions combine the optical functionalities of high field confinement and enhancement (cavity function), and of high radiative efficiency (antenna function) with the electrical functionalities o ...
Amer Chemical Soc2024
,
This contribution presents the design of a compact circularly polarized antenna featuring beamwidth reconfiguration in both the horizontal and vertical planes. The observed radiation patterns in each of the reconfigurable states present axial symmetry and ...