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