ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

2aUW26. Nonlinear transformations for spatial matched filtering (detect-on-track).

Yung P. Lee

Science Applications International Corp., 1710 Goodridge Dr., McLean, VA 22102

Haw-Jye Shyu

Naval Res. Lab., Washington, DC 20375

A detect-on-track algorithm based on the Hough transform has been applied to acoustic broadband correlograms for passive detection and localization. The Hough transform integrates (sums) the amplitudes along a set of delay curves of interest. The delay curves are calculated over a range of closest point of approach (CPA), speed, and heading of the targets. When normalized by the number of points, the Hough transform computes the arithmetic-mean along the track. This process is referred to as an arithmetic-sum (AS) transform. This AS transform optimally reduces the variance of the noise, but can also generate significant ambiguous sidelobes. To reduce the sidelobe, two nonlinear transforms are proposed: The logarithmic-sum (LS) transform and the harmonic-sum (HS) transform. The LS-transform sums dB's while the HS-transform sums the reciprocal of the amplitudes along the track. When normalized by the number of points, the LS transform computes the geometric-mean and the HS transform computes the harmonic-mean along the track. Simulations show that the nonlinear transforms perform the same as the AS transform in noise-limited environments but outperform the AS transform in sidelobe-limited environments.