TABLE OF CONTENTS Yung P. Lee
Element-space pre-Doppler STAP [2] is two-dimensional fully adaptive processing that coherently combines the signals from the elements of an array and the multiple snapshots of coherent signals to obtain large spatial and temporal signal gain, suppress interference and provide target detection in azimuth and velocity. Computational complexity and the need to estimate the interference from limited snapshots make it difficult for real-time implementation. A few cost effective algorithms having real-time capability are mentioned in Reference 3. The adjacent filter beamspace post-Doppler STAP is a reduced-dimension partially adaptive approach. It performs a Doppler filtering with a temporal Fourier transform and a spatial filtering with the conventional beamforming before adaptive processing. The adaptive processing is done in a selected subspace including a few beams and a few Doppler bins [4].
In the complex multipath underwater environment, signals propagate along a vertical slice of ocean within a critical angle defined by the boundary condition of the local ocean environment. Because of the spread in vertical propagation angles, signals observed by a horizontal array will be spread into many horizontal beams when signals arrive off the broadside direction. This is illustrated in Figure 18.1. In addition, signals that propagate in different...
