The ’’Harmonic‘‘ Rejecting Correlation Function

  • Authors:
  • Douglas Nelson

  • Affiliations:
  • Dept. of Defense, 9800 Savage Rd., Ft. Meade, Md. 20755

  • Venue:
  • Multidimensional Systems and Signal Processing - Special issue on recent developments in time-frequency analysis
  • Year:
  • 1998

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Abstract

Aclassical problem in signal processing is accurate estimationof fundamental frequency/periodicity of periodic signals at lowSNR. Typically, researchers address the estimation problem, assumingthat the signal environment is a sum of sinusoids in white Gaussiannoise. If the signals and noise are pulsed, the situation ismuch more complex since normal FFT based methods result in spectrawhich are sums of harmonic structures. Sorting radar signalscan be especially difficult since there may be many pulsed signalspresent in a low SNR impulsive noise environment. In this paper,a method equivalent to integration along a hyperbola on the Wignerdistribution is presented. This transform, which is closely relatedto both the Fourier transform and the correlation function, hasthe property that a periodic signal produces an expected non-zerocomplex-valued bulge at only the fundamental. The phase, magnitudeand position of the correlation bulge are sufficient to characterizethe time-domain pulse train. Finally, a simple super-resolutionmethod is presented which may be used to refine the fundamentalfrequency/period estimate.