Editing Chirp (section)

{{Short description|Frequency swept signal}}
{{Other uses}}
{{more citations needed|date=August 2010}}
[[File:Linear-chirp.svg|thumb|upright=1.3|A linear chirp waveform; a sinusoidal wave that increases in frequency linearly over time]]

A '''chirp''' is a [[signal (information theory)|signal]] in which the [[frequency]] increases (''up-chirp'') or decreases (''down-chirp'') with time. In some sources, the term ''chirp'' is used interchangeably with '''sweep signal'''.<ref>Weisstein, Eric W. "Sweep Signal". From MathWorld--A Wolfram Web Resource. http://mathworld.wolfram.com/SweepSignal.html</ref> It is commonly applied to [[sonar]], [[radar]], and [[laser]] systems, and to other applications, such as in [[Spread spectrum|spread-spectrum]] communications (see [[chirp spread spectrum]]). This signal type is biologically inspired and occurs as a phenomenon due to dispersion (a non-linear dependence between frequency and the propagation speed of the wave components). It is usually compensated for by using a matched filter, which can be part of the propagation channel. Depending on the specific performance measure, however, there are better techniques both for radar and communication. Since it was used in radar and space, it has been adopted also for communication standards. For automotive radar applications, it is usually called linear frequency modulated waveform (LFMW).<ref>{{cite journal |last1=Lee |first1=Tae-Yun |last2=Jeon |first2=Se-Yeon |last3=Han |first3=Junghwan |last4=Skvortsov |first4=Vladimir |last5=Nikitin |first5=Konstantin |last6=Ka |first6=Min-Ho |title=A Simplified Technique for Distance and Velocity Measurements of Multiple Moving Objects Using a Linear Frequency Modulated Signal |journal=IEEE Sensors Journal |date=August 2016 |volume=16 |issue=15 |pages=5912–5920 |doi=10.1109/JSEN.2016.2563458 |bibcode=2016ISenJ..16.5912L }}</ref>

In spread-spectrum usage, [[surface acoustic wave]] (SAW) devices are often used to generate and demodulate the chirped signals. In [[optics]], [[ultrashort pulse|ultrashort]] [[laser]] pulses also exhibit chirp, which, in optical transmission systems, interacts with the [[dispersion (optics)|dispersion]] properties of the materials, increasing or decreasing total pulse dispersion as the signal propagates. The name is a reference to the chirping sound made by birds; see [[bird vocalization]].