Function: pchirp
PCHIRP  Periodic chirp
  Usage:  g=pchirp(L,n);

  PCHIRP(L,n) returns a periodic, discrete chirp of length L that
  revolves n times around the time-frequency plane in frequency. n must be
  an integer number.

  To get a chirp that revolves around the time-frequency plane in time,
  use :

    dft(pchirp(L,N));  

  The chirp is computed by:
  
      g(l+1) = exp(pi*i*n*(l-ceil(L/2))^2*(L+1)/L) for l=0,...,L-1

  The chirp has absolute value 1 everywhere. To get a chirp with unit
  l^2-norm, divide the chirp by sqrt L.

  Examples:
  ---------

  A spectrogram on a linear scale of an even length chirp:

    sgram(pchirp(40,2),'lin');

  The DFT of the same chirp, now revolving around in time:

    sgram(dft(pchirp(40,2)),'lin');

  An odd-length chirp. Notice that the chirp starts at a frequency between
  two sampling points:

    sgram(pchirp(41,2),'lin');
  

  References:
    H. G. Feichtinger, M. Hazewinkel, N. Kaiblinger, E. Matusiak, and
    M. Neuhauser. Metaplectic operators on c^n. The Quarterly Journal of
    Mathematics, 59(1):15--28, 2008.
    

Url: http://ltfat.github.io/doc/fourier/pchirp.html

See also: dft, expwave.

Package: ltfat