Wiener–Khinchin theorem

In applied mathematics and statistics, the Wiener–Khinchin theorem or Wiener–Khintchine theorem, also known as the Wiener–Khinchin–Einstein theorem or the Khinchin–Kolmogorov theorem, states that the power spectral density of a wide-sense-stationary random process is equal to the Fourier transform of that process's autocorrelation function.