In the process of digital signal processing, DFT can be roughly determined each harmonic frequency, amplitude and phase of experimental signal. For a single harmonic, the amplitude zoom spectrum and phase spectrum have specific features near the harmonic frequency. Through analysis and comparison, a single frequency zoom spectrum and rectangle window spectrum is very similar, and so as the criterion, the digital signal included several frequency harmonic can be determined. Then select the appropriate parameter range and step size to combine for cycle calculation. And make the single frequency zoom spectrum a rectangle window spectrum approximatively. Harmonic parameters can restore from the intensive frequency digital signal. Calculation precision was slightly lower than those of single-frequency harmonic zoom spectrum calculation. The method can better solve the situation variety of two intensive frequency spectrum analyses. More intensive frequencys spectrum analyses need a large amount time to compute.
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