Harmonic Parameter Estimation Based on the ApFFT/ApDTFT Spectral Scenario with Low Mutual Interference

In order to improve the accuracy of multi-tone parameter estimation, we propose a scheme derived from a novel spectral scenario based on all-phase Fast Fourier Transform (apFFT)/all-phase discrete-time Fourier Transform (apDTFT). This scheme is constructed based on the following architecture. Firstly, we theoretically extend the original discrete apFFT analysis to the proposed continuous apDTFT analysis, so that two excellent spectral properties (suppression of spectral leakage and phase invariance) hold across the entire frequency axis. Secondly, on the basis of apFFT/apDTFT, we design a single-tone interpolator and its improved version with frequency-shift iteration. Thirdly, we derive a multi-tone harmonic estimator, which can further reduce the mutual spectral interference under the apFFT-/apDTFT-based spectral scenario. Both numerical and experimental results demonstrate that, even with one fewer sample, the proposed apFFT-/apDTFT-based estimator achieves higher accuracy across individual harmonics and inter-harmonics than the FFT-/DTFT-based estimator.