Compensation for missing sensors in a real-time measurement beamformer system

In the system described in this paper, an array of hydrophones with a fixed geometry is used to make accurate underwater acoustic measurements over a large frequency range. The beamforming coefficients used to weight each sensor have been optimized over the full frequency range to provide the desired accuracy for a constant beam width and high noise reduction for the ocean environment. These coefficients must be developed for numerous angular beam widths and for several steering angles, requiring considerable time (several hours) to generate off-line using parallel digital signal processors. To make the number of coefficients manageable, the array symmetry has been utilized. When sensors are missing due to inevitable failures, this symmetry no longer exists, and a new method is required to handle the arbitrary array geometry. Also, failures can occur unexpectedly, making it unreasonable to redesign the coefficients for changes in array geometry. This paper describes a compensation method that has proven successful in regaining the desired amplitude level of the beam response without modifying the existing sensor coefficients.