Abstract: The spectral components of both an original signal and a shifted version of the signal, for example a signal which is subjected to a time delay relative to the original signal, are obtained by means of Fourier Transform. This gives sets of first and second spectral components corresponding respectively to the original signal and the shifted signal. The phases of at least one pair of corresponding first and second spectral components are obtained, and subtracted to give a phase difference. The first aspect of the method measures the frequency of corresponding constituent of the original signal from the said phase difference based on a prior knowledge of the amount of shift. Further, having measured the frequency, one can measure the initial phase and amplitude of corresponding constituent of the signal.

Abstract: An apparatus for analyzing a signal takes the Fourier Transform of both an original signal and a shifted signal, which has previously been subjected to a shift, for example a time shift, relative to the original signal. This gives sets of first and second frequency components corresponding respectively to the original signal and the shifted signal. The arguments of at least one pair of corresponding first and second frequency components are calculated, and subtracted to give a phase difference. From this phase difference, the frequency of the corresponding constituent of the original signal can be determined. Further, having obtained the frequency, one can calculate the initial phase and amplitude of the corresponding constituent of the original signal. The signal can vary temporally or spatially.