An Approximate Fast Fourier Transform Technique for Vernier Spectral Analysis.

摘要

An approximate and quick fast Fourier transform technique for vernier spectral analysis is derived and tested for several candidate time-and delay-weightings,and for overlaps of the time weightings. For 50percent overlap,the use of a simple cosine lobe for the time weighting yields spurious spectral sidelobes at least 23dB below the main peak,whereas Dolph-Chebyshev time weighting achieves -33dB sidelobes. For 75percent overlap,use of a (cosine)(sup 5) lobe for the time weighting yields sibelobes at least 54dB down,whereas Dolph-Chebyshev time weighting achieves -86dB sidelobes. In both cases of overlap,use of delay weighting is also required and is taken as a Hanning weighting. Extensions to other overlaps and weightings are possible from the fundamental relations presented and from the sample program furnished. (Author)