Chirp Z-transform (CZT) is a

 generalization of the discrete Fourier transform
 (DFT). While the DFT samples the Z plane at
 uniformly-spaced points along the unit circle, the
 chirp Z-transform samples along spiral arcs in the
 Z-plane, corresponding to straight lines in the
 S plane. The DFT, real DFT, and zoom DFT can be
 calculated as special cases of the CZT.