dorsal/arxiv
View SchemaHow an antenna launches its input power into radiation: the pattern of the Poynting vector at and near an antenna
| Authors | J. David Jackson |
|---|---|
| Categories | |
| ArXiv ID | physics/0506053 |
| URL | https://arxiv.org/abs/physics/0506053 |
| DOI | 10.1119/1.2063069 |
Abstract
In this paper I first address the question of whether the seat of the power radiated by an antenna made of conducting members is distributed over the ``arms'' of the antenna according to -J . E, where J is the specified current density and E is the electric field produced by that source. Poynting's theorem permits only a global identification of the total input power, usually from a localized generator, with the total power radiated to infinity, not a local correspondence of -J . E dv with some specific radiated power, r^2 S . n dO. I then describe a model antenna consisting of two perfectly conducting hemispheres of radius a separated by a small equatorial gap across which occurs the driving oscillatory electric field. The fields and surface current are determined by solution of the boundary value problem. In contrast to the first approach (not a boundary value problem), the tangential electric field vanishes on the metallic surface. There is no radial Poynting vector normal to the surface. Numerical examples are shown to illustrate how the energy flows from the input region of the gap and is guided near the antenna by its ``arms'' until it is launched at larger r/a into the radiation pattern determined by the value of ka.
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"abstract": "In this paper I first address the question of whether the seat of the power\nradiated by an antenna made of conducting members is distributed over the\n``arms\u0027\u0027 of the antenna according to -J . E, where J is the specified current\ndensity and E is the electric field produced by that source. Poynting\u0027s theorem\npermits only a global identification of the total input power, usually from a\nlocalized generator, with the total power radiated to infinity, not a local\ncorrespondence of -J . E dv with some specific radiated power, r^2 S . n dO. I\nthen describe a model antenna consisting of two perfectly conducting\nhemispheres of radius a separated by a small equatorial gap across which occurs\nthe driving oscillatory electric field. The fields and surface current are\ndetermined by solution of the boundary value problem. In contrast to the first\napproach (not a boundary value problem), the tangential electric field vanishes\non the metallic surface. There is no radial Poynting vector normal to the\nsurface. Numerical examples are shown to illustrate how the energy flows from\nthe input region of the gap and is guided near the antenna by its ``arms\u0027\u0027\nuntil it is launched at larger r/a into the radiation pattern determined by the\nvalue of ka.",
"arxiv_id": "physics/0506053",
"authors": [
"J. David Jackson"
],
"categories": [
"physics.class-ph"
],
"doi": "10.1119/1.2063069",
"title": "How an antenna launches its input power into radiation: the pattern of the Poynting vector at and near an antenna",
"url": "https://arxiv.org/abs/physics/0506053"
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