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

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

**Yung P. Lee
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*Science Applications International Corp., 1710 Goodridge Dr., McLean, VA
22102
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**Haw-Jye Shyu
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*Naval Res. Lab., Washington, DC 20375
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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.