Noise temperature (antenna): Difference between revisions
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In [[telecommunication]], '''antenna noise temperature''' is the temperature of a hypothetical resistor at the input of an ideal [[signal noise|noise]]-free receiver that would generate the same [[Work (physics)|output]] [[noise power]] per unit [[Bandwidth (signal processing)|bandwidth]] as that at the [[antenna (radio)|antenna]] output at a specified [[frequency]]. In other words, antenna noise temperature is a parameter that describes how much noise an antenna produces in a given environment. This temperature is not the physical temperature of the antenna. Moreover, an antenna does not have an intrinsic "antenna temperature" associated with it; rather the temperature depends on its gain pattern and the thermal environment that it is placed in. |
In [[telecommunication]], '''antenna noise temperature''' is the temperature of a hypothetical resistor at the input of an ideal [[signal noise|noise]]-free receiver that would generate the same [[Work (physics)|output]] [[noise power]] per unit [[Bandwidth (signal processing)|bandwidth]] as that at the [[antenna (radio)|antenna]] output at a specified [[frequency]]. In other words, antenna noise temperature is a parameter that describes how much noise an antenna produces in a given environment. This temperature is not the physical temperature of the antenna. Moreover, an antenna does not have an intrinsic "antenna temperature" associated with it; rather the temperature depends on its gain pattern, pointing direction, and the thermal environment that it is placed in. |
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Antenna noise temperature has contributions from |
Antenna noise temperature has contributions from many sources, including: |
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*[[Cosmic |
*[[Cosmic background radiation]] |
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*[[Galactic radiation]] |
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*Earth heating |
*Earth heating |
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*The [[sun]] |
*The [[sun]] |
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*The [[moon]] |
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*Electrical devices |
*Electrical devices |
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*The antenna itself |
*The antenna itself |
Revision as of 17:26, 22 March 2022
![]() | This article includes a list of references, related reading, or external links, but its sources remain unclear because it lacks inline citations. (January 2013) |
In telecommunication, antenna noise temperature is the temperature of a hypothetical resistor at the input of an ideal noise-free receiver that would generate the same output noise power per unit bandwidth as that at the antenna output at a specified frequency. In other words, antenna noise temperature is a parameter that describes how much noise an antenna produces in a given environment. This temperature is not the physical temperature of the antenna. Moreover, an antenna does not have an intrinsic "antenna temperature" associated with it; rather the temperature depends on its gain pattern, pointing direction, and the thermal environment that it is placed in.
Antenna noise temperature has contributions from many sources, including:
- Cosmic background radiation
- Galactic radiation
- Earth heating
- The sun
- The moon
- Electrical devices
- The antenna itself
Galactic noise is high below 1000 MHz. At around 150 MHz, it is approximately 1000 K. At 2500 MHz, it has leveled off to around 10 K.
Earth has an accepted standard temperature of 288 K.
The level of the sun's contribution depends on the solar flux. It is given by
- where is the solar flux,
- is the wavelength,
- and is the gain of the antenna in decibels.
The antenna noise temperature depends on antenna coupling to all noise sources in its environment as well as on noise generated within the antenna. That is, in a directional antenna, the portion of the noise source that the antenna's main and side lobes intersect contribute proportionally.
For example, a satellite antenna may not receive noise contribution from the earth in its main lobe, but sidelobes will contribute a portion of the 288K earth noise to its overall noise temperature.
See also
References
The Arrl Uhf/Microwave Experimenter's Manual. Newington: American Radio Relay League. 1990. ISBN 0-87259-312-6.
"ITU P.372 : Radio noise". ITU. Retrieved 4 July 2019.