Moscow Mathematical Papyrus: Difference between revisions
en>Rezabot m r2.7.1) (Robot: Adding gl:Papiro de Moscova |
en>Proz →Other papyri: link |
||
| Line 1: | Line 1: | ||
{{about|fundamental noise processes|noise arising from outside sources|electromagnetic compatibility|and|electromagnetic interference}} | |||
In electronics, '''noise''' is a random fluctuation in an electrical signal, a characteristic of all [[electronics|electronic]] [[electrical circuit|circuits]].<ref name=noise>{{cite book |first=C. D. |last=Motchenbacher |first2=J. A. |last2=Connelly |title=Low-noise electronic system design |publisher=Wiley Interscience |year=1993 |isbn= |doi= }}</ref> Noise generated by electronic devices varies greatly, as it can be produced by several different effects. [[Thermal noise]] is unavoidable at non-zero temperature (see [[fluctuation-dissipation theorem]]), while other types depend mostly on device type (such as [[shot noise]],<ref name=noise/><ref name=shot>{{cite journal |first=L. B. |last=Kish |first2=C. G. |last2=Granqvist |title=Noise in nanotechnology |journal=Microelectronics Reliability |volume=40 |issue=11 |date=November 2000 |pages=1833–1837 |publisher=Elsevier |doi=10.1016/S0026-2714(00)00063-9 }}</ref> which needs steep potential barrier) or manufacturing quality and [[semiconductor]] defects, such as conductance fluctuations, including [[1/f noise]]. | |||
In [[communication system]]s, noise is an error or undesired random disturbance of a useful information [[signal (electrical engineering)|signal]] in a [[communication channel]]. The noise is a summation of unwanted or disturbing energy from natural and sometimes man-made sources. Noise is, however, typically distinguished from [[Interference (communication)|interference]], (e.g. [[cross-talk]], deliberate [[Radio jamming|jamming]] or other unwanted [[electromagnetic interference]] from specific transmitters), for example in the [[signal-to-noise ratio]] (SNR), [[signal-to-interference ratio]] (SIR) and [[signal to noise plus interference|signal-to-noise plus interference ratio]] (SNIR) measures. Noise is also typically distinguished from [[distortion]], which is an unwanted systematic alteration of the signal waveform by the communication equipment, for example in the [[signal-to-noise and distortion ratio]] (SINAD). In a carrier-modulated passband analog communication system, a certain [[carrier-to-noise ratio]] (CNR) at the radio receiver input would result in a certain [[signal-to-noise ratio]] in the detected message signal. In a digital communications system, a certain [[Eb/N0|''E''<sub>b</sub>/''N''<sub>0</sub>]] (normalized signal-to-noise ratio) would result in a certain [[bit error rate]] (BER). | |||
While noise is generally unwanted, it can serve a useful purpose in some applications, such as [[random number generation]] or [[Noise (electronics)#Dither|dithering]]. | |||
==Noise types== | |||
===Thermal noise=== | |||
{{Main|Johnson–Nyquist noise}} | |||
Johnson–Nyquist noise<ref name=noise/> (sometimes thermal, Johnson or Nyquist noise) is unavoidable, and generated by the random thermal motion of charge carriers (usually [[electron]]s), inside an [[electrical conductor]], which happens regardless of any applied [[voltage]]. | |||
Thermal noise is approximately [[white noise|white]], meaning that its [[power spectral density]] is nearly equal throughout the [[frequency spectrum]]. The amplitude of the signal has very nearly a [[Gaussian]] [[probability density function]]. A communication system affected by thermal noise is often modeled as an [[additive white Gaussian noise]] (AWGN) channel. | |||
The [[root mean square]] (RMS) voltage due to thermal noise <math>v_n</math>, generated in a resistance ''R'' ([[ohms]]) over bandwidth Δ''f'' ([[hertz]]), is given by | |||
:<math> | |||
v_{n} = \sqrt{ 4 k_B T R \Delta f } | |||
</math> | |||
where ''k<sub>B</sub>'' is [[Boltzmann's constant]] ([[joule]]s per [[kelvin]]) and ''T'' is the resistor's absolute [[temperature]] (kelvin). | |||
As the amount of thermal noise generated depends upon the temperature of the circuit, very sensitive circuits such as [[preamplifier]]s in [[radio telescope]]s are sometimes cooled in [[liquid nitrogen]] to reduce the noise level. | |||
===Shot noise=== | |||
{{Main|Shot noise}} | |||
Shot noise in electronic devices results from unavoidable random statistical fluctuations of the [[electric current]] when the charge carriers (such as [[electron]]s) traverse a gap. The current is a flow of discrete charges, and the fluctuation in the arrivals of those charges creates shot noise. Shot noise is similar to the noise created by rain falling on a tin roof. The flow of rain may be relatively constant, but the raindrops arrive discretely. | |||
The root-mean-square value of the shot noise current ''i<sub>n</sub>'' is given by the Schottky formula | |||
:<math>i_n = \sqrt{2 I q \Delta B} </math> | |||
where ''I'' is the DC current, ''q'' is the charge of an electron, and ''ΔB'' is the bandwidth in hertz. | |||
The shot noise assumes independent arrivals. [[Vacuum tube]]s have shot noise because the electrons randomly leave the cathode and arrive at the anode (plate). A tube may not exhibit the full shot noise effect: the presence of a [[space charge]] tends to smooth out the arrival times (and thus reduce the randomness of the current). | |||
Conductors and resistors do not have shot noise because they do not have a gap. | |||
===Flicker noise=== | |||
{{Main|Flicker noise}} | |||
Flicker noise, also known as 1/''f'' noise, is a signal or process with a [[frequency spectrum]] that falls off steadily into the higher frequencies, with a [[pink noise|pink]] spectrum. It occurs in almost all electronic devices, and results from a variety of effects, though always related to a direct current. | |||
===Burst noise=== | |||
{{Main|Burst noise}} | |||
Burst noise consists of sudden step-like transitions between two or more levels (non-[[Gaussian]]), as high as several hundred [[microvolt]]s, at random and unpredictable times. Each shift in offset voltage or current lasts for several milliseconds, and the intervals between pulses tend to be in the [[Audio frequencies|audio]] range (less than 100 [[hertz|Hz]]), leading to the term ''popcorn noise'' for the popping or crackling sounds it produces in audio circuits. | |||
===Transit-time noise=== | |||
If the time taken by the electrons from traveling from emitter to collector becomes comparable to the period of the signal being amplified, that is, at frequencies above [[Very high frequency|VHF]] and beyond, so-called transit-time effect takes place and noise input [[admittance]] of the [[transistor]] increases. From the frequency at which this effect becomes significant it goes on increasing with frequency and quickly dominates over other terms. | |||
===Avalanche noise=== | |||
Avalanche noise is the noise produced when a junction diode is operated at the onset of [[avalanche breakdown]], a [[semiconductor junction]] phenomenon in which carriers in a high voltage gradient develop sufficient energy to dislodge additional carriers through physical impact, creating ragged current flows. | |||
==Coupled noise== | |||
{{See also|Electromagnetic compatibility}} | |||
[[Energy]] external of the receiver can couple noise, also by [[energy conversion]]. Generally this is done by [[fundamental interaction]], in electronics mainly by [[Inductive coupling]] and/or [[capacitive coupling]]. | |||
===Atmospheric noise (static noise)=== | |||
{{Main|Atmospheric noise}} | |||
This noise is also called static noise and it is the natural source of disturbance caused by [[lightning]] discharge of in thunderstorm and the natural(electrical) disturbances occurring in the nature. | |||
===Industrial noise=== | |||
Sources such as automobiles, aircraft, ignition electric motors and switching gear, High [[voltage]] wires and [[fluorescent lamp]]s cause industrial noise. These noises are produced by the discharge present in all these operations. | |||
===Extraterrestrial noise=== | |||
Noise from outside the Earth include: | |||
====Solar noise==== | |||
The noise which has its source in the disturbance of [[Sun]] is called solar noise. Under normal conditions there is constant [[radiation]] from sun due to its high temperature. Electrical disturbances also create noise such as [[corona discharge]]. [[Sunspot]]s also produce noise. | |||
====Cosmic noise==== | |||
{{Main|Cosmic noise}} | |||
Distant stars also generate noise called cosmic noise. Since these stars are far away so individual effect is not sufficient to generate a noise which disturb our [[Communications system]] but as they are large in number so collective effect makes noise in air appreciable. The effect of cosmic noise has been observed from 8Mhz to 1.43Ghz. | |||
=== Reduction of noise coupling=== | |||
In many cases noise found on a signal in a circuit is unwanted. When creating a circuit, one usually wants a true output of what the circuit has accomplished. There are many different noise reduction techniques that can change a noisy altered output signal to a more theoretical output signal. | |||
#Faraday cage – A [[Faraday cage]] is a good way to reduce the overall noise in a complete circuit. The Faraday cage can be thought of as an enclosure that separates the complete circuit from outside power lines and any other signal that may alter the true signal. A Faraday cage will usually block out most electromagnetic and electrostatic noise. | |||
#Capacitive coupling – A current through two resistors, or any other type of conductor, close to each other in a circuit can create unwanted [[capacitive coupling]]. If this happens an AC signal from one part of the circuit can be accidentally picked up in another part. The two resistors (conductors) act like a capacitor thus transferring AC signals. There may be other reasons for which capacitive coupling is wanted but then it would not be thought of as electronic noise. | |||
#Ground loops – When grounding a circuit, it is important to avoid [[Ground loop (electricity)|ground loops]]. Ground loops occur when there is a voltage drop between the two ground potentials. Since ground is thought of as 0V, the presence of a voltage is undesirable at any point of a ground bus. If this is the case, it would not be a true ground. A good way to fix this is to bring all the ground wires to the same potential in a ground bus. | |||
#Shielding cables – In general, using [[shielded cable]]s to protect the wires from unwanted noise frequencies in a sensitive circuit is good practice. A shielded wire can be thought of as a small Faraday cage for a specific wire as it uses a plastic or rubber enclosing the true wire. Just outside of the rubber/plastic covering is a conductive metal that intercepts any noise signal. Because the conductive metal is grounded, the noise signal runs straight to ground before ever getting to the true wire. It is important to ground the shield at only one end to avoid a ground loop on the shield. | |||
#Twisted pair wiring – [[Twisted pair|Twisting wires]] very tightly together in a circuit will dramatically reduce electromagnetic noise. Twisting the wires decreases the loop size in which a magnetic field can run through to produce a current between the wires. Even if the wires are twisted very tightly, there may still be small loops somewhere between them, but because they are twisted the magnetic field going through the smaller loops induces a current flowing in opposite ways in each wire and thus cancelling them out. | |||
#Notch filters – Notch filters or [[Band-stop filter|band-rejection filters]] are essential when eliminating a specific noise frequency. For example, in most cases the power lines within a building run at 60 Hz. Sometimes a sensitive circuit will pick up this 60 Hz noise through some unwanted antenna (could be as simple as a wire in the circuit). Running the output through a notch filter at 60 Hz will amplify the desired signal without amplifying the 60 Hz noise. So in a sense the noise will be lost at the output of the filter. | |||
==Quantification== | |||
The '''noise level''' in an electronic system is typically measured as an electrical [[Power (physics)|power]] ''N'' in [[watt]]s or [[decibel|dBm]], a [[root mean square]] (RMS) voltage (identical to the noise [[standard deviation]]) in volts, [[decibel|dBμV]] or a [[mean squared error]] (MSE) in volts squared. Noise may also be characterized by its [[probability distribution]] and [[noise spectral density]] ''N''<sub>0</sub>(''f'') in watts per hertz. | |||
A noise signal is typically considered as a linear addition to a useful information signal. Typical signal quality measures involving noise are [[signal-to-noise ratio]] (SNR or ''S''/''N''), [[signal-to-quantization noise ratio]] (SQNR) in [[Analog to digital converter|analog-to-digital conversion]] and compression, [[peak signal-to-noise ratio]] (PSNR) in image and video coding, [[Eb/N0|''E''<sub>b</sub>/''N''<sub>0</sub>]] in digital transmission, [[carrier to noise ratio]] (CNR) before the detector in carrier-modulated systems, and [[noise figure]] in cascaded amplifiers. | |||
Noise is a random process, characterized by [[Stochastic process|stochastic]] properties such as its [[variance]], [[Probability distribution|distribution]], and [[spectral density]]. The spectral distribution of noise can vary with [[frequency]], so its power density is measured in watts per hertz (W/Hz). Since the power in a [[resistor|resistive]] element is proportional to the square of the voltage across it, noise voltage (density) can be described by taking the square root of the noise power density, resulting in volts per root hertz (<math>\scriptstyle \mathrm{V}/\sqrt{\mathrm{Hz}}</math>). [[Integrated circuit]] devices, such as [[operational amplifiers]] commonly quote [[equivalent input noise]] level in these terms (at room temperature). | |||
Noise power is measured in watts or [[decibel]]s (dB) relative to a standard power, usually indicated by adding a suffix after dB. Examples of electrical noise-level measurement units are [[dBu]], [[dBm0]], [[dBrn]], [[dBrnC]], and dBrn(''f''<sub>1</sub> − ''f''<sub>2</sub>), dBrn(144-[[line (electrical engineering)|line]]). | |||
Noise levels are usually viewed in opposition to [[signal level]]s and so are often seen as part of a [[signal-to-noise ratio]] (SNR). Telecommunication systems strive to increase the ratio of signal level to noise level in order to effectively transmit data. In practice, if the transmitted signal falls below the level of the noise (often designated as the [[noise floor]]) in the system, data can no longer be decoded at the receiver. Noise in telecommunication systems is a product of both internal and external sources to the system. | |||
==Dither== | |||
If the noise source is correlated with the signal, such as in the case of [[quantisation error]], the intentional introduction of additional noise, called [[dither]], can reduce overall noise in the bandwidth of interest. This technique allows retrieval of signals below the nominal detection threshold of an instrument. This is an example of [[stochastic resonance]]. | |||
==See also== | |||
* [[Discovery of cosmic microwave background radiation]] | |||
* [[Generation–recombination noise]] | |||
* [[Matched filter]] for noise reduction in modems | |||
* [[Noise reduction]] and [[noise cancellation]] for audio and images | |||
* [[Error correction]] for digital signals subject to noise. | |||
* [[Phonon noise]] | |||
==Notes== | |||
{{reflist}} | |||
==References== | |||
{{More footnotes|date=September 2011}} | |||
* [http://www.sengpielaudio.com/calculator-noise.htm White noise calculator, thermal noise - Voltage in microvolts, conversion to noise level in dBu and dBV and vice versa] | |||
* {{FS1037C MS188}} | |||
* Scherz, Paul. (2006, Nov 14) ''Practical Electronics for Inventors''. ed. McGraw-Hill. | |||
==Further reading== | |||
* {{cite book | |||
| author=Sh. Kogan | |||
| title=Electronic Noise and Fluctuations in Solids | |||
| publisher=Cambridge University Press | |||
| year=1996 | |||
| isbn=0-521-46034-4}} | |||
==External links== | |||
* [http://www.c-c-i.com/node/77 Active Filter (Sallen & Key) Noise Study] | |||
{{Noise}} | |||
{{Analogue TV transmitter topics}} | |||
[[Category:Electronics]] | |||
[[Category:Noise| ]] | |||
[[ar:ضجيج (إلكترونيات)]] | |||
[[ca:Soroll (comunicació)]] | |||
[[cs:Šum]] | |||
[[de:Stromrauschen]] | |||
[[es:Ruido (comunicación)]] | |||
[[fr:Bruit (électronique)]] | |||
[[it:Rumore (elettronica)]] | |||
[[he:רעש (פיזיקה)]] | |||
[[ja:ノイズ (電子工学)]] | |||
[[fi:Kohina]] | |||
[[zh:雜訊]] | |||
Latest revision as of 20:40, 24 January 2014
29 yr old Orthopaedic Surgeon Grippo from Saint-Paul, spends time with interests including model railways, top property developers in singapore developers in singapore and dolls. Finished a cruise ship experience that included passing by Runic Stones and Church.
In electronics, noise is a random fluctuation in an electrical signal, a characteristic of all electronic circuits.[1] Noise generated by electronic devices varies greatly, as it can be produced by several different effects. Thermal noise is unavoidable at non-zero temperature (see fluctuation-dissipation theorem), while other types depend mostly on device type (such as shot noise,[1][2] which needs steep potential barrier) or manufacturing quality and semiconductor defects, such as conductance fluctuations, including 1/f noise.
In communication systems, noise is an error or undesired random disturbance of a useful information signal in a communication channel. The noise is a summation of unwanted or disturbing energy from natural and sometimes man-made sources. Noise is, however, typically distinguished from interference, (e.g. cross-talk, deliberate jamming or other unwanted electromagnetic interference from specific transmitters), for example in the signal-to-noise ratio (SNR), signal-to-interference ratio (SIR) and signal-to-noise plus interference ratio (SNIR) measures. Noise is also typically distinguished from distortion, which is an unwanted systematic alteration of the signal waveform by the communication equipment, for example in the signal-to-noise and distortion ratio (SINAD). In a carrier-modulated passband analog communication system, a certain carrier-to-noise ratio (CNR) at the radio receiver input would result in a certain signal-to-noise ratio in the detected message signal. In a digital communications system, a certain Eb/N0 (normalized signal-to-noise ratio) would result in a certain bit error rate (BER).
While noise is generally unwanted, it can serve a useful purpose in some applications, such as random number generation or dithering.
Noise types
Thermal noise
Mining Engineer (Excluding Oil ) Truman from Alma, loves to spend time knotting, largest property developers in singapore developers in singapore and stamp collecting. Recently had a family visit to Urnes Stave Church.
Johnson–Nyquist noise[1] (sometimes thermal, Johnson or Nyquist noise) is unavoidable, and generated by the random thermal motion of charge carriers (usually electrons), inside an electrical conductor, which happens regardless of any applied voltage.
Thermal noise is approximately white, meaning that its power spectral density is nearly equal throughout the frequency spectrum. The amplitude of the signal has very nearly a Gaussian probability density function. A communication system affected by thermal noise is often modeled as an additive white Gaussian noise (AWGN) channel.
The root mean square (RMS) voltage due to thermal noise , generated in a resistance R (ohms) over bandwidth Δf (hertz), is given by
where kB is Boltzmann's constant (joules per kelvin) and T is the resistor's absolute temperature (kelvin).
As the amount of thermal noise generated depends upon the temperature of the circuit, very sensitive circuits such as preamplifiers in radio telescopes are sometimes cooled in liquid nitrogen to reduce the noise level.
Shot noise
Mining Engineer (Excluding Oil ) Truman from Alma, loves to spend time knotting, largest property developers in singapore developers in singapore and stamp collecting. Recently had a family visit to Urnes Stave Church.
Shot noise in electronic devices results from unavoidable random statistical fluctuations of the electric current when the charge carriers (such as electrons) traverse a gap. The current is a flow of discrete charges, and the fluctuation in the arrivals of those charges creates shot noise. Shot noise is similar to the noise created by rain falling on a tin roof. The flow of rain may be relatively constant, but the raindrops arrive discretely.
The root-mean-square value of the shot noise current in is given by the Schottky formula
where I is the DC current, q is the charge of an electron, and ΔB is the bandwidth in hertz.
The shot noise assumes independent arrivals. Vacuum tubes have shot noise because the electrons randomly leave the cathode and arrive at the anode (plate). A tube may not exhibit the full shot noise effect: the presence of a space charge tends to smooth out the arrival times (and thus reduce the randomness of the current).
Conductors and resistors do not have shot noise because they do not have a gap.
Flicker noise
Mining Engineer (Excluding Oil ) Truman from Alma, loves to spend time knotting, largest property developers in singapore developers in singapore and stamp collecting. Recently had a family visit to Urnes Stave Church. Flicker noise, also known as 1/f noise, is a signal or process with a frequency spectrum that falls off steadily into the higher frequencies, with a pink spectrum. It occurs in almost all electronic devices, and results from a variety of effects, though always related to a direct current.
Burst noise
Mining Engineer (Excluding Oil ) Truman from Alma, loves to spend time knotting, largest property developers in singapore developers in singapore and stamp collecting. Recently had a family visit to Urnes Stave Church. Burst noise consists of sudden step-like transitions between two or more levels (non-Gaussian), as high as several hundred microvolts, at random and unpredictable times. Each shift in offset voltage or current lasts for several milliseconds, and the intervals between pulses tend to be in the audio range (less than 100 Hz), leading to the term popcorn noise for the popping or crackling sounds it produces in audio circuits.
Transit-time noise
If the time taken by the electrons from traveling from emitter to collector becomes comparable to the period of the signal being amplified, that is, at frequencies above VHF and beyond, so-called transit-time effect takes place and noise input admittance of the transistor increases. From the frequency at which this effect becomes significant it goes on increasing with frequency and quickly dominates over other terms.
Avalanche noise
Avalanche noise is the noise produced when a junction diode is operated at the onset of avalanche breakdown, a semiconductor junction phenomenon in which carriers in a high voltage gradient develop sufficient energy to dislodge additional carriers through physical impact, creating ragged current flows.
Coupled noise
DTZ's public sale group in Singapore auctions all forms of residential, workplace and retail properties, outlets, homes, lodges, boarding homes, industrial buildings and development websites. Auctions are at present held as soon as a month.
We will not only get you a property at a rock-backside price but also in an space that you've got longed for. You simply must chill out back after giving us the accountability. We will assure you 100% satisfaction. Since we now have been working in the Singapore actual property market for a very long time, we know the place you may get the best property at the right price. You will also be extremely benefited by choosing us, as we may even let you know about the precise time to invest in the Singapore actual property market.
The Hexacube is offering new ec launch singapore business property for sale Singapore investors want to contemplate. Residents of the realm will likely appreciate that they'll customize the business area that they wish to purchase as properly. This venture represents one of the crucial expansive buildings offered in Singapore up to now. Many investors will possible want to try how they will customise the property that they do determine to buy by means of here. This location has offered folks the prospect that they should understand extra about how this course of can work as well.
Singapore has been beckoning to traders ever since the value of properties in Singapore started sky rocketing just a few years again. Many businesses have their places of work in Singapore and prefer to own their own workplace area within the country once they decide to have a everlasting office. Rentals in Singapore in the corporate sector can make sense for some time until a business has discovered a agency footing. Finding Commercial Property Singapore takes a variety of time and effort but might be very rewarding in the long term.
is changing into a rising pattern among Singaporeans as the standard of living is increasing over time and more Singaporeans have abundance of capital to invest on properties. Investing in the personal properties in Singapore I would like to applaud you for arising with such a book which covers the secrets and techniques and tips of among the profitable Singapore property buyers. I believe many novice investors will profit quite a bit from studying and making use of some of the tips shared by the gurus." – Woo Chee Hoe Special bonus for consumers of Secrets of Singapore Property Gurus Actually, I can't consider one other resource on the market that teaches you all the points above about Singapore property at such a low value. Can you? Condominium For Sale (D09) – Yong An Park For Lease
In 12 months 2013, c ommercial retails, shoebox residences and mass market properties continued to be the celebrities of the property market. Models are snapped up in report time and at document breaking prices. Builders are having fun with overwhelming demand and patrons need more. We feel that these segments of the property market are booming is a repercussion of the property cooling measures no.6 and no. 7. With additional buyer's stamp responsibility imposed on residential properties, buyers change their focus to commercial and industrial properties. I imagine every property purchasers need their property funding to understand in value.
Energy external of the receiver can couple noise, also by energy conversion. Generally this is done by fundamental interaction, in electronics mainly by Inductive coupling and/or capacitive coupling.
Atmospheric noise (static noise)
Mining Engineer (Excluding Oil ) Truman from Alma, loves to spend time knotting, largest property developers in singapore developers in singapore and stamp collecting. Recently had a family visit to Urnes Stave Church. This noise is also called static noise and it is the natural source of disturbance caused by lightning discharge of in thunderstorm and the natural(electrical) disturbances occurring in the nature.
Industrial noise
Sources such as automobiles, aircraft, ignition electric motors and switching gear, High voltage wires and fluorescent lamps cause industrial noise. These noises are produced by the discharge present in all these operations.
Extraterrestrial noise
Noise from outside the Earth include:
Solar noise
The noise which has its source in the disturbance of Sun is called solar noise. Under normal conditions there is constant radiation from sun due to its high temperature. Electrical disturbances also create noise such as corona discharge. Sunspots also produce noise.
Cosmic noise
Mining Engineer (Excluding Oil ) Truman from Alma, loves to spend time knotting, largest property developers in singapore developers in singapore and stamp collecting. Recently had a family visit to Urnes Stave Church. Distant stars also generate noise called cosmic noise. Since these stars are far away so individual effect is not sufficient to generate a noise which disturb our Communications system but as they are large in number so collective effect makes noise in air appreciable. The effect of cosmic noise has been observed from 8Mhz to 1.43Ghz.
Reduction of noise coupling
In many cases noise found on a signal in a circuit is unwanted. When creating a circuit, one usually wants a true output of what the circuit has accomplished. There are many different noise reduction techniques that can change a noisy altered output signal to a more theoretical output signal.
- Faraday cage – A Faraday cage is a good way to reduce the overall noise in a complete circuit. The Faraday cage can be thought of as an enclosure that separates the complete circuit from outside power lines and any other signal that may alter the true signal. A Faraday cage will usually block out most electromagnetic and electrostatic noise.
- Capacitive coupling – A current through two resistors, or any other type of conductor, close to each other in a circuit can create unwanted capacitive coupling. If this happens an AC signal from one part of the circuit can be accidentally picked up in another part. The two resistors (conductors) act like a capacitor thus transferring AC signals. There may be other reasons for which capacitive coupling is wanted but then it would not be thought of as electronic noise.
- Ground loops – When grounding a circuit, it is important to avoid ground loops. Ground loops occur when there is a voltage drop between the two ground potentials. Since ground is thought of as 0V, the presence of a voltage is undesirable at any point of a ground bus. If this is the case, it would not be a true ground. A good way to fix this is to bring all the ground wires to the same potential in a ground bus.
- Shielding cables – In general, using shielded cables to protect the wires from unwanted noise frequencies in a sensitive circuit is good practice. A shielded wire can be thought of as a small Faraday cage for a specific wire as it uses a plastic or rubber enclosing the true wire. Just outside of the rubber/plastic covering is a conductive metal that intercepts any noise signal. Because the conductive metal is grounded, the noise signal runs straight to ground before ever getting to the true wire. It is important to ground the shield at only one end to avoid a ground loop on the shield.
- Twisted pair wiring – Twisting wires very tightly together in a circuit will dramatically reduce electromagnetic noise. Twisting the wires decreases the loop size in which a magnetic field can run through to produce a current between the wires. Even if the wires are twisted very tightly, there may still be small loops somewhere between them, but because they are twisted the magnetic field going through the smaller loops induces a current flowing in opposite ways in each wire and thus cancelling them out.
- Notch filters – Notch filters or band-rejection filters are essential when eliminating a specific noise frequency. For example, in most cases the power lines within a building run at 60 Hz. Sometimes a sensitive circuit will pick up this 60 Hz noise through some unwanted antenna (could be as simple as a wire in the circuit). Running the output through a notch filter at 60 Hz will amplify the desired signal without amplifying the 60 Hz noise. So in a sense the noise will be lost at the output of the filter.
Quantification
The noise level in an electronic system is typically measured as an electrical power N in watts or dBm, a root mean square (RMS) voltage (identical to the noise standard deviation) in volts, dBμV or a mean squared error (MSE) in volts squared. Noise may also be characterized by its probability distribution and noise spectral density N0(f) in watts per hertz.
A noise signal is typically considered as a linear addition to a useful information signal. Typical signal quality measures involving noise are signal-to-noise ratio (SNR or S/N), signal-to-quantization noise ratio (SQNR) in analog-to-digital conversion and compression, peak signal-to-noise ratio (PSNR) in image and video coding, Eb/N0 in digital transmission, carrier to noise ratio (CNR) before the detector in carrier-modulated systems, and noise figure in cascaded amplifiers.
Noise is a random process, characterized by stochastic properties such as its variance, distribution, and spectral density. The spectral distribution of noise can vary with frequency, so its power density is measured in watts per hertz (W/Hz). Since the power in a resistive element is proportional to the square of the voltage across it, noise voltage (density) can be described by taking the square root of the noise power density, resulting in volts per root hertz (). Integrated circuit devices, such as operational amplifiers commonly quote equivalent input noise level in these terms (at room temperature).
Noise power is measured in watts or decibels (dB) relative to a standard power, usually indicated by adding a suffix after dB. Examples of electrical noise-level measurement units are dBu, dBm0, dBrn, dBrnC, and dBrn(f1 − f2), dBrn(144-line).
Noise levels are usually viewed in opposition to signal levels and so are often seen as part of a signal-to-noise ratio (SNR). Telecommunication systems strive to increase the ratio of signal level to noise level in order to effectively transmit data. In practice, if the transmitted signal falls below the level of the noise (often designated as the noise floor) in the system, data can no longer be decoded at the receiver. Noise in telecommunication systems is a product of both internal and external sources to the system.
Dither
If the noise source is correlated with the signal, such as in the case of quantisation error, the intentional introduction of additional noise, called dither, can reduce overall noise in the bandwidth of interest. This technique allows retrieval of signals below the nominal detection threshold of an instrument. This is an example of stochastic resonance.
See also
- Discovery of cosmic microwave background radiation
- Generation–recombination noise
- Matched filter for noise reduction in modems
- Noise reduction and noise cancellation for audio and images
- Error correction for digital signals subject to noise.
- Phonon noise
Notes
43 year old Petroleum Engineer Harry from Deep River, usually spends time with hobbies and interests like renting movies, property developers in singapore new condominium and vehicle racing. Constantly enjoys going to destinations like Camino Real de Tierra Adentro.
References
- White noise calculator, thermal noise - Voltage in microvolts, conversion to noise level in dBu and dBV and vice versa
- Template:FS1037C MS188
- Scherz, Paul. (2006, Nov 14) Practical Electronics for Inventors. ed. McGraw-Hill.
Further reading
- 20 year-old Real Estate Agent Rusty from Saint-Paul, has hobbies and interests which includes monopoly, property developers in singapore and poker. Will soon undertake a contiki trip that may include going to the Lower Valley of the Omo.
My blog: http://www.primaboinca.com/view_profile.php?userid=5889534
External links
Template:Noise Template:Analogue TV transmitter topics
ar:ضجيج (إلكترونيات) ca:Soroll (comunicació) cs:Šum de:Stromrauschen es:Ruido (comunicación) fr:Bruit (électronique) it:Rumore (elettronica) he:רעש (פיזיקה) ja:ノイズ (電子工学) fi:Kohina zh:雜訊
- ↑ 1.0 1.1 1.2 20 year-old Real Estate Agent Rusty from Saint-Paul, has hobbies and interests which includes monopoly, property developers in singapore and poker. Will soon undertake a contiki trip that may include going to the Lower Valley of the Omo.
My blog: http://www.primaboinca.com/view_profile.php?userid=5889534 - ↑ One of the biggest reasons investing in a Singapore new launch is an effective things is as a result of it is doable to be lent massive quantities of money at very low interest rates that you should utilize to purchase it. Then, if property values continue to go up, then you'll get a really high return on funding (ROI). Simply make sure you purchase one of the higher properties, reminiscent of the ones at Fernvale the Riverbank or any Singapore landed property Get Earnings by means of Renting
In its statement, the singapore property listing - website link, government claimed that the majority citizens buying their first residence won't be hurt by the new measures. Some concessions can even be prolonged to chose teams of consumers, similar to married couples with a minimum of one Singaporean partner who are purchasing their second property so long as they intend to promote their first residential property. Lower the LTV limit on housing loans granted by monetary establishments regulated by MAS from 70% to 60% for property purchasers who are individuals with a number of outstanding housing loans on the time of the brand new housing purchase. Singapore Property Measures - 30 August 2010 The most popular seek for the number of bedrooms in Singapore is 4, followed by 2 and three. Lush Acres EC @ Sengkang
Discover out more about real estate funding in the area, together with info on international funding incentives and property possession. Many Singaporeans have been investing in property across the causeway in recent years, attracted by comparatively low prices. However, those who need to exit their investments quickly are likely to face significant challenges when trying to sell their property – and could finally be stuck with a property they can't sell. Career improvement programmes, in-house valuation, auctions and administrative help, venture advertising and marketing, skilled talks and traisning are continuously planned for the sales associates to help them obtain better outcomes for his or her shoppers while at Knight Frank Singapore. No change Present Rules
Extending the tax exemption would help. The exemption, which may be as a lot as $2 million per family, covers individuals who negotiate a principal reduction on their existing mortgage, sell their house short (i.e., for lower than the excellent loans), or take part in a foreclosure course of. An extension of theexemption would seem like a common-sense means to assist stabilize the housing market, but the political turmoil around the fiscal-cliff negotiations means widespread sense could not win out. Home Minority Chief Nancy Pelosi (D-Calif.) believes that the mortgage relief provision will be on the table during the grand-cut price talks, in response to communications director Nadeam Elshami. Buying or promoting of blue mild bulbs is unlawful.
A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running
The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more
There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang