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{{Short description|Quick, temporary change in amplitude of electrical signals}}

[[File:Pulse examples.svg|thumb|Examples of pulse shapes: (a) [[rectangular function|rectangular pulse]], (b) cosine squared (raised cosine) pulse, (c) [[Dirac delta function|Dirac pulse]], (d) [[sinc function|sinc pulse]], (e) [[Gaussian function|Gaussian pulse]]]]

A '''pulse''' in [[signal processing]] is a rapid, transient change in the amplitude of a [[signal]] from a baseline value to a higher or lower value, followed by a rapid return to the baseline value.<ref>Ángela Molina, Joaquín González, ''Pulse Voltammetry in Physical Electrochemistry and Electroanalysis'', Springer, 2015 {{ISBN|3319212516}}.</ref>

==Pulse shapes==
Pulse shapes can arise out of a process called [[pulse shaping]]. Optimum pulse shape depends on the application.

===Rectangular pulse===
These can be found in [[pulse wave]]s, [[Square wave (waveform)|square wave]]s, [[boxcar function]]s, and [[rectangular function]]s. In digital signals the up and down transitions between high and low levels are called the rising [[signal edge|edge]] and the falling edge. In digital systems the detection of these sides or action taken in response is termed edge-triggered, rising or falling depending on which side of rectangular pulse. A [[digital timing diagram]] is an example of a well-ordered collection of rectangular pulses.

===Nyquist pulse===
A Nyquist pulse is one which meets the [[Nyquist ISI criterion]] and is important in data transmission. An example of a pulse which meets this condition is the [[sinc function]]. The sinc pulse is of some significance in signal-processing theory but cannot be produced by a real generator for reasons of causality.

In 2013, Nyquist pulses were produced in an effort to reduce the size of pulses in optical fibers, which enables them to be packed 10 times more closely together, yielding a corresponding 10-fold increase in bandwidth. The pulses were more than 99 percent perfect and were produced using a simple laser and modulator.<ref>{{cite web|author=Joel Detrow |url=http://www.gizmag.com/optical-fiber-throughput-breakthrough/30038/ |title=Pointy pulses improve optical fiber throughput by a factor of 10 |publisher=Gizmag.com |access-date=2013-12-06}}</ref><ref>{{Cite journal |last=Soto |first=Marcelo A. |last2=Alem |first2=Mehdi |last3=Amin Shoaie |first3=Mohammad |last4=Vedadi |first4=Armand |last5=Brès |first5=Camille-Sophie |last6=Thévenaz |first6=Luc |last7=Schneider |first7=Thomas |date=2013-12-04 |title=Optical sinc-shaped Nyquist pulses of exceptional quality |journal=[[Nature Communications]] |language=en |volume=4 |pages=2898 |doi=10.1038/ncomms3898 |issn=2041-1723 |pmc=3863974 |pmid=24301610}}</ref>

===Dirac pulse===
A Dirac pulse has the shape of the [[Dirac delta function]]. It has the properties of infinite amplitude and its integral is the [[Heaviside step function]]. Equivalently, it has zero width and an area under the curve of unity. This is another pulse that cannot be created exactly in real systems, but practical approximations can be achieved. It is used in testing, or theoretically predicting, the [[impulse response]] of devices and systems, particularly [[filter (signal processing)|filters]]. Such responses yield a great deal of information about the system.

===Gaussian pulse===
A Gaussian pulse is shaped as a [[Gaussian function]] and is produced by the impulse response of a [[Gaussian filter]]. It has the properties of maximum steepness of transition with no overshoot and minimum [[group delay]].

== See also ==
*[[Pulse (physics)]]
*[[Wave packet]]

== References ==
{{Reflist}}

{{Authority control}}

[[Category:Signal processing]]
[[Category:Optical communications]]

Pulse (signal processing) - Revision history

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