Editing Chirp (section)

== Uses and occurrences ==
=== Chirp modulation ===
Chirp modulation, or linear frequency modulation for digital communication, was patented by [[Sidney Darlington]] in 1954 with significant later work performed by Winkler{{Who|date=February 2025}} in 1962. This type of modulation employs sinusoidal waveforms whose instantaneous frequency increases or decreases linearly over time. These waveforms are commonly referred to as linear chirps or simply chirps.

Hence the rate at which their frequency changes is called the ''chirp rate''. In binary chirp modulation, binary data is transmitted by mapping the bits into chirps of opposite chirp rates. For instance, over one bit period "1" is assigned a chirp with positive rate ''a'' and "0" a chirp with negative rate −''a''. Chirps have been heavily used in [[radar]] applications and as a result advanced sources for transmission and [[matched filter]]s for reception of linear chirps are available.

[[File:P-type-chirplets-for-image-processing.png|thumb|upright=1.3|(a) In image processing, direct periodicity seldom occurs, but, rather, periodicity-in-perspective is encountered. (b) Repeating structures like the alternating dark space inside the windows, and light space of the white concrete, "chirp" (increase in frequency) towards the right. (c) Thus the best fit chirp for image processing is often a projective chirp.]]

=== Chirplet transform ===
{{main article|Chirplet transform}}

Another kind of chirp is the projective chirp, of the form:
<math display="block">g = f\left[\frac{a \cdot x + b}{c \cdot x + 1}\right],</math>
having the three parameters ''a'' (scale), ''b'' (translation), and ''c'' (chirpiness). The projective chirp is ideally suited to [[image processing]], and forms the basis for the projective [[chirplet transform]].<ref name="Mann">Mann, Steve and Haykin, Simon;  The Chirplet Transform: A generalization of Gabor's Logon Transform; Vision Interface '91.[http://wearcam.org/chirplet/vi91scans/index.htm]</ref>

=== Key chirp ===
A change in frequency of [[Morse code]] from the desired frequency, due to poor stability in the [[Radio frequency|RF]] [[oscillator]], is known as '''chirp''',<ref>The Beginner's Handbook of Amateur Radio By Clay Laster</ref> and in the [[R-S-T system]] is given an appended letter 'C'.
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