Optimization of the spectrum of digital diagnostic signals to improve the analysis of harmonic parameters using resampling algorithms

Abstract

The paper discusses the influence of resampling distortions on the quality of spectral resolution optimization in diagnostic signals digitally recorded for objects in a steady state. Analysis of harmonic parameters and detection of foreign frequencies, which are most often interpreted as fault results, may be problematic because of the spectral leakage effect. The reason is that some frequencies which are not actually present in the signal can be observed in the DFT (discrete Fourier transform) vector. In addition, actual existing frequencies may be distorted. The use of window functions most often reduces the effect of spectral leakage, but also increases harmonic distortion. When the signal contains only the fundamental frequency and harmonics, it is possible to adjust its spectral resolution to eliminate any distortion for regular frequencies. If the algorithms which perform the analysis of the diagnostic signal require a fixed number samples, high quality resampling should be used.