pchirp.m

linear time－frequency toolbox

function g=pchirp(L,n)
%PCHIRP  Periodic chirp
%   Usage:  g=pchirp(L,n);
%
%   PCHIRP(L,n) returns a normalized, periodic, discrete chirp of length L
%   that revolves n times around the frequency plane in frequency. n must 
%   be a whole number.
%
%   To get a chirp that revolves around the frequency plane in time, use
% 
%      dft(pchirp(L,N));  
% 
%   The chirp is computed by:
%    
%      g(l+1) = exp(pi*i*n*l^2/L)/sqrt(L) for l=0,...,L-1
% 
%   REFERENCES:
%     M. and Hazewinkel, N. Kaiblinger, E. Matusiak, and M. Neuhauser. Metaplectic
%     operators on C^n. To appear, 2006.

% Compute normalized chirp
g=(exp((0:L-1).^2/L*pi*i*n)/sqrt(L)).';