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This paper describes the results of current research at DREA in which techniques of optimum array processing are being applied to active sonar. We are presenting these results at the Advanced Study Institute in order to illustrate some actual applications for such processing and to point out some of the practical considerations which arise in real systems. In particular, the paper concerns the problems which arise when the individual sensor elements have a complicated directivity pattern themselves. This is a common phenomenon in active systems where the receiving sensors are complex resonant structures and are housed in a dome or towed body presenting various baffling and diffraction effects. Most treatments of array processing consider ideal elements which have well behaved directivity properties and are transparent to the field. The results of this paper show that where these properties are not met, careful in situ array measurements are required, and even with such measurements practical array gains may not be as good as predictions based on ideal sensors.
List of contents
Subject 3.- Optimum Antenna Processing: A Modular Approach.- The Forgotten Algorithm in Adaptive Beamforming.- The Effects of Signal and Weight Coefficient Quantisation in Adaptive Array Processors.- Adaptive Beamforming in an Active Doppler Sonar.- Adaptive Array Processing Experiments at HF.- Separation and Representation of Sources and Signals by a Linear Antenna.- Complementarity of Propagation Model Design with Array Processing.- Spectral Signal Set Extraction.- A Constrained Adaptive Beamformer Tolerant of Array Gain and Phase Errors.- Signal Extraction Algorithms for Adaptive Processing of Array Data.- Properties of the Discrete Fourier Transform (DFT).- An Adaptive Beamformer Which Implements Constraints Using an Auxiliary Array Preprocessor.- Subject 4 - Displays, Pattern Recognition, Human Decision.- Error and Reject Tradeoff for Nearest Neighbor Decision Rules.- Two-Dimensional Spectral Analysis for Image Coding, Processing and Recognition: An Approach Based on Some Properties of the Human Visual System.- Subject 5 - Relevant Inputs from Other Fields.- Spectrum Analysis.- Autoregressive and Maximum Likelihood Spectral Analysis.- Confidence Intervals for Maximum Entropy Spectral Estimates.- Team Decision Theory in the Optimal Control of a Communication Network.- Topological Structure in Group Transforms.- Some Signal Processing Aspects in Medical Ultrasound.- Recherche ET Caracterisation De Dependances Lineares Entre Signaux Par Analyse Interspectrale. Applications.- Subject 6 - Modern Processor Architecture and Techniques.- Linear Signal Processing Architectures.- Surface-Acoustic-Wave Devices for Signal Processing.- One/Two Dimensional Digital Signal Processors.- Surface-Acoustic-Wave Fourier-Transform Processors.- High Resolution Sonar SimulationTechniques.- Summaries of Workshops.- Properties of time/space Variant Channel.- Autoregressive Spectral Analysis.- Adaptive Array Processing.- Index of Names.
