Christopher W. Bogart
T. C. Yang
Naval Res. Lab., Code 5123, Washington, DC 20375
Matched-mode processing determines the source location (range, depth, and bearing) by matching the mode replica function with the mode amplitude decomposed from data. Mode decomposition has been successfully demonstrated for a vertical array or multi-vertical arrays that constitute a (three-dimensional) filled volumetric array. For these cases, the intrinsic difference of the matched-field and matched-mode processing lies in how the normal modes are processed (decomposed) by each method. For a sparse three-dimensional array such as a slanted vertical array, a slack array, or a horizontal line array, mode decomposition is not a straightforward process. A brute force and an approximate mode decomposition method are presented here; the latter has the simplicity of requiring only one mode decomposition for matched mode processing for all bearings. It is also shown that the performance of a sparse array is related to the accuracy of mode decomposition as previously demonstrated for a vertical array.