Estimation of amplitudes, frequencies and phases of multitone signal components using low sidelobe time windows

Uncertainty in DFT-based estimates of the amplitude, frequency and phase of tonal components of a signal due to leakage are discussed. An algorithm is described for estimating the amplitude with significantly reduced scalloping loss, high frequency resolution and correct phase in the presence of leakage. The algorithm utilises a low-sidelobe window, typically the Blackman-Harris (1978) 4-term type, and uses all lines in the mainlobe. The noise performance of the algorithm is described. The processing gain obtained with the new algorithm is compared with figures obtained when only the largest line in the mainlobe is used. Amplitude, frequency and phase estimates are virtually unbiased. Standard deviations of the errors are related to the power spectral density of additive noise. Simulation results are presented to quantify the effect of leakage from closely spaced frequencies with possible partial overlap of mainlobes