A simple interpolation algorithm for measuring multi-frequency signal based on DFT

For the multi-frequency signal under the condition of asynchronous sampling, the spectral leakages such as the negative frequency leakage, long-range leakage and short-range leakage in Fourier transform will influence the accuracy of harmonic analysis. To reduce the measurement errors caused by these effects, a new interpolated discrete Fourier transform (DFT) algorithm using three greatest spectral lines is presented. In this new algorithm, the analytical formulas for the harmonic frequency are obtained by applying the Chebyshev best approximation theory. These formulas can be easily implemented by hardware multipliers, which is convenient for real-time measurement. The simulation and experiment results show the presented algorithm has high accuracy and good anti-jamming capacity.