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Topic: Noise temperature

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	Noise Figure - Microwave Encyclopedia - Microwaves101.com
		Signal to noise ratio always worsens from input to output due to entropy or one of those other depressing laws of the universe; as the S/N ratio at output is less than S/N ratio at input, noise factor is always greater than unity.
		The "290" in the expression is used to denote a standardized temperature, which in this case is close to room temperature (290 K is an IEEE standard).
		Note that noise temperature of an amplifier is not directly related to the temperature of an amplifier.
	www.microwaves101.com /encyclopedia/noisefigure.cfm (898 words)

	Reduce noise in distributed communications systems
		Essentially, noise temperature is the ratio between noise at the terminals of a network and the noise that exists at the reference temperature (290§K) of a totally passive system.
		Noise factor, then, is a multiplier used to predict the amount of amplifier noise power output compared with the noise power output that would occur in a perfect amplifier under the same conditions.
		Noise characteristic is input-based The noise characteristic of any device is fundamentally set by its input network, whether it is the base of a transistor or the first stage of a complex amplifier or receiver.
	mrtmag.com /mag/radio_reduce_noise_distributed/index.html (2846 words)

	Tvro.doc (Site not responding. Last check: 2007-10-20)
		Ground noise pick-up may be reduced, at the expense of gain, by under- illuminating the dish; thus, this factor essentially determines the efficiency of the dish.
		It has a small noise temperature of about 2.7 K. This component is relatively small in relation to the error in estimating the ground noise component and may be omitted from practical calculations.
		The noise increase due to the 0.83 rain fade is given by equation 21 and evaluates to 0.7308 dB.
	aa.1asphost.com /tonyart/tonyt/Applets/Tvro/Tvro.html (3755 words)

	SM 5 BSZ - On noise figures and noise temperatures.
		The noise figure of an amplifier is the amount of noise at the output divided by the amount of noise one would have had from an ideal amplifier with the same gain connected to the same source.
		The noise temperature of a preamplifier is the temperature you would have on a resistor connected to an ideal amplifier to get the same output as you would get from from the real amplifier if connecting it to a resistor that is kept at 0K.
		The noise temperature at the output of an amplifier is the sum of the noise temperature of the source and the noise temperature of the amplifier itself multiplied by the power gain of the amplifier.
	www.nitehawk.com /sm5bsz/pcdsp/ntemp.htm (761 words)

	Noise temperature - Wikipedia, the free encyclopedia
		Noise temperature: At a pair of terminals, the temperature of a passive system having an available noise power per unit bandwidth at a specified frequency equal to that of the actual terminals of a network.
		The transmission line temperature is a measure of the noise power within the receiver bandwidth generated by the resistive losses in the transmission line or waveguide between the antenna and the receiver.
		The transmission line temperature is frequently combined with either the antenna or the receiver temperature, depending on the reference point for the measurement.
	en.wikipedia.org /wiki/Noise_temperature (276 words)

	Noise Contribution Analysis for the Arecibo Gregorian Radio Telescope (Site not responding. Last check: 2007-10-20)
		In a radio telescope, minimizing any contribution to the system noise temperature is of great importance when detecting faint signals in the sky, since the integration time to obtain a given signal to noise ratio varies as the square of the system noise temperature.
		For the purposes of noise temperature calculations, the antenna may be viewed as composed of perfect reflectors and perfect fl bodies, (i.e., the dome), at a given temperature.
		For the purpose of noise calculation, the stop-sphere is a two-temperature surface; its lower hemisphere defines the ground temperature, while the upper hemisphere is at the same temperature as the aperture plane.
	www.ecs.umass.edu /ece/allerton/papers1999/22 (2550 words)

	ESSCO - Radomes and Antennas - Noise Temperature of ESSCO Metal Space Frame Radomes
		Physical blockage of the antenna aperture plane by the metal space frame reduces the effective gain of the antenna system by that amount, but it does not add noise temperature back into the system as would be the case for a resistive loss of the same magnitude.
		The added aperture blockage from the metal space frame does however scatter some amount of sky and ground noise into the aperture plane and the fraction of this scattered energy that is actually collected into the antenna feed system is then seen as added noise due to the radome metal space frame.
		This total radome added noise temperature component is in the range of 7°K to 12°K for typical ESSCO metal space frame radomes using cost effective membranes in the microwave and 20/30 GHz bands.
	www.l-3com.com /essco/resources/noisetemperature.html (779 words)

	SM 5 BSZ - Preamplifier design.
		In the discussion of the noise contributions from the input circuit, represented by R1 in fig.1 the transistor is assumed to be neutralised.
		Noise temperature to add to antenna temperature due to losses in the input circuit of the preamplifier and influence of input losses on S/N ratio.
		The antenna temperature is assumed to be 190K and the transistor temperature is assumed to be 15K.
	www.nitehawk.com /sm5bsz/pcdsp/preamp.htm (2712 words)

	Antenna noise temperature - Wikipedia, the free encyclopedia
		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.
		Note 1: The antenna noise temperature depends on antenna coupling to all noise sources in its environment as well as on noise generated within the antenna.
		Note 2: The antenna noise temperature is a measure of noise whose value is equal to the actual temperature of a passive device.
	en.wikipedia.org /wiki/Antenna_noise_temperature (130 words)

	Noise factor, noise figure, and noise temperature- Developer Zone - National Instruments
		The noise of a system or network can be defined in three different but related ways: noise factor (Fn), noise figure (NF) and equivalent noise temperature (Te); these properties are definable as a simple ratio, decibel ratio or temperature, respectively.
		For components such as resistors, the noise factor is the ratio of the noise produced by a real resistor to the simple thermal noise of an ideal resistor.
		The noise temperature is a means for specifying noise in terms of an equivalent temperature.
	zone.ni.com /devzone/cda/ph/p/id/153 (648 words)

	Noise temperature, Noise Figure and Noise Factor
		Noise temperature is measured in units called Kelvin (K) and these are like Celsius (C) temperature degrees but start at zero for absolute zero temperature so 0 K = -273 deg C 273 K = 0 deg C (ice melts) 290 K = 17 deg C (ambient temperature of a waveguide, for example)
		The noise temperature of the LNA refers to the input of the LNA.
		The noise temperature of the cable after the LNA refers to the input of the cable.
	www.satsig.net /noise.htm (636 words)

	RF Cafe - Noise Figure Calculation Equation Formula
		Noise figure is the increase in noise power of a device from the input to the output that is greater that the signal gain.
		Cascade noise figure calculation is carried out by dealing with gain and noise figure as a ratio rather than decibels, and then converting back to decibels at the end.
		As the following equation shows, cascaded noise figure is effected most profoundly by the noise figure of components closest to the input of the system as long as some positive gain exists in the cascade.
	www.rfcafe.com /references/electrical/noise_figure.htm (249 words)

	Satellite Footprints by Dish Size - Noise Discussion, Terrestrial Interference (TI), Rain Fade, Free Space Loss, Earth ...
		Interference is noise that comes in on the same frequency(ies) as signal and masks (overwhelms) parts or all of the desired signal (see diagram).
		Detectable noise can also be generated through electric motors (I have seen a broken motor mount generate a spurious signal that modulated onto the desired signal), neon lights and even defective automotive ignition systems.
		Earth noise is something we can not control and is generated by the same internal molecular motion of all matter as is the case in system electronics.
	www.geo-orbit.org /sizepgs/Noise.html (4779 words)

	Mike F. Noise Temperature Paper
		For example, bodies at 2000 K (Kelvin), the radiation is primarily in the infrared region and at 10000 K, the radiation is primarily in the visible light region.
		There is also a direct correlation between temperature and the amount of energy emitted, which is described by Planck's law.
		When a radio astronomer looks at a particular point of the sky and says that it has a noise temperature of 1500 K, he/she isn't declaring how hot the body (nebulae, etc) really is, but is providing a measurement of the strength of the radiation from the source at the observed frequency.
	www.bambi.net /mike_f_temperature_paper.html (611 words)

	MMS Noise Figure (Site not responding. Last check: 2007-10-20)
		This may be summarized by saying that the contribution made by a given stage to the overall system noise is the noise temperature of that stage divided by the total gain leading up to that stage.
		If a given stage is allowed to contribute a specific amount, say 1 K, to the overall system noise, then Figure 2 shows the noise temperature (or noise figure) which a given stage is allowed to have as a function of the gain leading up to that stage.
		Figure 2 - Stage noise temperature, as a function of gain leading up to that stage, for various values of the contribution that would be made by that stage to the total system noise.
	dsnra.jpl.nasa.gov /technical/mms_nf.html (1295 words)

	Thermal noise calculation calculator Johnson noise voltage Nyquist dBu dBV - sengpielaudio (Site not responding. Last check: 2007-10-20)
		Thermal noise: Also called Johnson noise, is the random white noise generated by thermal agitation of electrons in a conductor or electronic device.
		It is produced by the thermal agitation of the charges in an electric conductor and is proportional to the absolute temperature of the conductor.
		The Noise factor of a transducer at a specified input frequency is the ratio of (a/b) where "a and b" are:
	www.sengpielaudio.com /calculator-noise.htm (430 words)

	Quantum Noise & Effective Noise Temperature (Text)
		This means that in the optical regime, there is more noise associated with the statistics of the arrival of a given flux of optical photons.
		In microwave communication systems, it is the thermal kT noise of the receiver and sky temperature that limits the detection sensitivity.
		In optical systems, it is usually (ideally) the case that it is the basic quantum shot noise that limits the detection sensitivity.
	www.coseti.org /9006-005.htm (274 words)

	QCA Cryogenically Cooled Amplifiers and Systems
		They are surrounded by the radiation shield (temperature approximately 70K) which impedes the flow of heat from the dewar to the amplifiers.
		The system performs noise figure measurements by switching the input of the LNA between a terminated load at ambient temperature, and one at 77K (or other temperature).
		Noise temperature and gain of our cooled HEMT amplifiers are measured on an automated test system.
	www.quinstar.com /qca_cryogenically_cooled_amplifiers_and_systems.html (1021 words)

	Photo Tips
		Cooler the temperature, lesser the noise, higher the temperature, higher the noise.
		Dark noise is approximately the square root of the dark count.
		Noise distribution is not uniform across RGB channels.
	gfoto.tripod.com /phototips/NoiseReduction.htm (445 words)

	NX7U on AO-40...NEC-2 Analysis of BBQ Grid Dish
		Note that for any axially (z-axis) symmetric pattern, the antenna noise temperature at elevation=0 degrees is (Tgnd+Tsky)/2, since exactly 1/2 of the antenna pattern strikes the warm earth, and 1/2 of the antenna pattern "sees" the cold sky.
		Noise temperature is another indicator of sidelobe levels.
		The noise temperature continues to decline slowly with increasing elevation, as the higher-level close-in sidelobes are pointed to cold sky.
	members.cox.net /nx7u/ao40/bbqdish/BBQGridNec.htm (1921 words)

	Amateur SETI Station: Low Noise Amplifiers (Site not responding. Last check: 2007-10-20)
		The critical parameters to consider in selecting an LNA are its frequency response, gain, and noise temperature.
		Noise temperature is a measure of how much additional noise the LNA adds to your SETI system.
		Noise is sometimes expressed not in Kelvins, but as Noise Figure (in dB) or Noise Factor (a unitless power ratio).
	www.setileague.org /hardware/blklna.htm (814 words)

	Site noise vs. system noise figure
		Antenna noise figure Sometimes you will see the term antenna noise temperature used to describe the level of ambient site noise in which the antenna is placed.
		The noise voltage appearing across the 50V resistor shown in Figure 1 is 0.1096‘V at 290oK in a 15kHz bandwidth.
		Now the resistor is contributing 0.055'V of noise, and the input noise at the receiver is 0.055'V. Because the two noise voltages are non-coherent, the total or resultant noise voltage at the input to the receiver is found from the root-sum-square (RSS) of the two voltages.
	mrtmag.com /mag/radio_site_noise_vs (1578 words)

	Atmoshpheric Noise Temperature (Site not responding. Last check: 2007-10-20)
		The atmospheric noise temperature is a measure in Kelvin of the noise produced by the atmosphere.
		It is a function of the clarity of the air (called cumulative distribution) and the elevation angle of the ground antenna.
		The atmospheric noise temperature added to the antenna system noise temperature the equals the total operating system noise temperature.
	www331.jpl.nasa.gov /~lnkscape/html_pages/LinkInfo/tatm.html (134 words)

	System Noise Temperature
		The overall noise temperature of a receiving system is determined by:
		We already have a 70cm gain antenna pointed at the horizon in the right direction but with 50 feet of RG-58 coax for a feed line (12dB/100ft loss at 450MHz) and no preamplifier. With the antenna pointed at the horizon and outside temperature of 20dC, antenna noise temperature is 293dK.
		Our video receiver has a noise figure of 3.5dBnf (or whatever but it doesn't matter because we are looking for relative improvements).
	showcase.netins.net /web/wallio/SNT.html (477 words)

	2.8 Antenna noise temperature (Site not responding. Last check: 2007-10-20)
		As well as collecting signals antennas also collect external noise from sources such as the ground, the atmosphere (especially if rain or cloud is present), and extraterrestrial sources.
		Antenna noise temperature varies with elevation angle, dish size, frequency and weather conditions.
		Variation with dish size is because a major component of antenna noise is pickup of the ground temperature (say 290K) by the sidelobes of the antenna.
	sina.sharif.edu /~barkeshli/antennas/review/9510_012.htm (209 words)

	Understanding Gaussian Noise
		Match: When the noise source is not buffered from other system components, a well-matched noise source (less than 2:1 VSWR) is recommended.
		Power distribution (white): relates how the noise power is distributed in separate components over the frequency range.
		Temperature coefficient: The rate at which the output power changes over temperature.
	www.micronetics.com /Noise/Gaussian.html (196 words)

	Fiber Modem Dynamic Range
		The method is to add noise to the input of the modem until its noise output increases by 3 dB at a chosen frequency.
		Minicircuits specifies a noise figure of 2.9 dB (275K) for these amplifiers to which is added the nominal temperature of the termination (295k) for a total input noise temperature of 570K.
		Approximate noise temperature measurements of the modem pair S/N 2x9903003 were made at 6 spot frequencies between 50 and 1500 MHz.
	www.cv.nrao.edu /~rfisher/DynamicRng/fibermod.html (1625 words)

	Antenna System Noise Temperature (Site not responding. Last check: 2007-10-20)
		The system noise temperature is a measure in Kelvin of the noise produced by the ground antenna system.
		For the purposes of the program, we consider the ground antenna system to include the receiver, the follow on electronics, the amplifiers etc. The system noise temperature is added to the atmospheric noise temperature to get the total operating noise temperature.
		They were calculated by finding the values of the system temperature for each of the DSN sites with the antennas pointed at at 6, 45, and 90 degrees elevation.
	www331.jpl.nasa.gov /~lnkscape/html_pages/LinkInfo/ts.html (155 words)

	Noise Calibration Systems
		Examples are: receiver noise measurements such as noise figure and effective input noise temperature; calibration of solid state noise sources; evaluation and verification of earth station receivers; and as radiometer reference sources.
		Actual temperature is indicated by a digital readout on the controller front panel.
		The MT155J controller which contains the temperature control circuitry and a digital temperature readout for the thermal termination, the automatic or manual LN fill control circuitry, and the remote noise temperature output switch.
	www.maurymw.com /products/ncsa/noisecalsys/noyzcalsyst.htm (398 words)

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