INTERNALLY FOCUSED RANDOM ARRAYS

A CONCEPT IS PROPOSED FOR NEAR-FIELD FOCUSING AND SCANNING WITH A RANDOM DISTRIBUTED ACOUSTIC ARRAY FOR LONG RANGE SURVEILLANCE. THE ARRAY MAY BE SEVERAL MILES IN DIAMETER AND FOCUSED WITHIN OR OUTSIDE ITS OWN BOUNDARIED PROVIDING IMPROVED TARGET LOCALIZATION IN BOTH RANGE AND AZIMUTH AND REJECTING INTERFERING NOISE SOURCES WITH ITS HIGH RESOLUTION TWO-DIMENSIONAL FOCUS. THE PROPERTIES OF FOCUSED RANDOM ARRAYS ARE DISCUSSED IN DETAIL INCLUDING RESOLUTION, NUMBER OF BEAMS REQUIRED FOR COVERAGE, BANDWIDTH, SIDELOBE LEVEL, AND MAIN BEAM INTERFERENCE REJECTION. INNOVATIVE TECHNIQUES ARE PROPOSED FOR REDUCTION OF THE INHERENTLY HIGH SIDELOABES OF THE FOCUSED RANDOM ARRAY WHICH HAVE THE POTENTIAL OF ACHIEVING HIGH PERFORMANCE WITH A FEASIBLE PROCESSING LOAD. THE FACTORS WHICH INFLUENCE ARRAY CONFIGURATION ARE DISCUSSED AND METHODS ARE PROPOSED FOR DEVELOPING SUCH CONFIGURATIONS TO PROVIDE COVERAGE OF A LARGE AREA WITH AN ACCEPTABLE NUMBER OF BEAMS AND SUFFICIENT ARRAY GAIN. THE EFFECTS ON PROCESSING LOAD ARE ALSO EXAMINED.