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:
The chirp has absolute value 1 everywhere. To get a chirp with unit \(l^2\)-norm, divide the chirp by \(\sqrt L\).
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');
H. G. Feichtinger, M. Hazewinkel, N. Kaiblinger, E. Matusiak, and M. Neuhauser. Metaplectic operators on cn. The Quarterly Journal of Mathematics, 59(1):15--28, 2008.