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Improved harmonic analysis based on quadruple-spectrum-line interpolation FFT with multiple cosine window

To improve the accuracy of harmonic analysis in non-synchronous sampling, a new quadruple-spectrum-line(QSL) interpolation FFT algorithm with multiple cosine window is proposed. Firstly, the characteristics in time domain and frequency domain of a multiple cosine window are analyzed, which is 6-term cosine window. Then, the QSL interpolation algorithm is analyzed. And the parameters estimation formulas based on the new algorithm are derived. In the end, the experiments of the algorithm are implemented through the simulated harmonic environment. The experimental results show that the multiple cosine windows have obvious advantages in sidelobe characteristics, which can better suppress the spectrum leakage. And the proposed algorithm can accurately calculate the parameters of each harmonic.