I have a question. Why a chirp signal has the Fresnel ripples in slobes? I thought it has the equal amount of frequencies from lowerband to high band, so we should see the flat magnitude. Is that related to the chirp signal is the finite in time? I heard the complex chirp has the flat magnitude but what's the complex chirp?

I tried to reproduce a complex sinusod with the modulated frequency but anyway it has the ripples.


  • 1
    $\begingroup$ that appears to be a chirp having either a rectangular window or no window at all (a constant magnitude). a slightly more generalized chirp is one with a gaussian window or envelope shape. lot'sa nice mathematical properties of the linear chirp with a gaussian window.. to get a constant amplitude, just let the width of the gaussian function go to $\infty$.. $\endgroup$ Nov 23, 2020 at 22:36
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    $\begingroup$ ooops, i pasted in the wrong URL for the gaussian windowed chirp. this is the intended place. $\endgroup$ Nov 23, 2020 at 23:25
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    $\begingroup$ See this post where I provided a windowed chirp optimized for flatness by using a Tukey taper at start and end of the chirp: dsp.stackexchange.com/questions/66541/… But how did you do the cool graphics? $\endgroup$ Nov 24, 2020 at 3:28
  • $\begingroup$ @robert bristow-johnson, thank you, i'll study your link. $\endgroup$
    – John
    Nov 24, 2020 at 17:34
  • $\begingroup$ @Dan Boschen, i made special program to do such graphs. $\endgroup$
    – John
    Nov 24, 2020 at 17:35


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