On uncertainty principle for signal concentrations with fractional Fourier transform

The fractional Fourier transform (FRFT) - a generalized form of the classical Fourier transform - has been shown to be a powerful analyzing tool in signal processing. This paper investigates the uncertainty principle for signal concentrations associated with the FRFT. It is shown that if the fraction of a nonzero signals energy on a finite interval in one fractional domain with a certain angle α is specified, then the fraction of its energy on a finite interval in other fractional domain with any angle β (β≠α) must remain below a certain maximum. This is a generalization of the fact that any nonzero signal cannot have arbitrarily large proportions of energy in both a finite time duration and a finite frequency bandwidth. The signals which are the best in achieving simultaneous concentration in two arbitrary fractional domains are derived. Moreover, some applications of the derived theory are presented.