Efficient Adaptive Optical Processing for Sonar Arrays

In this final report we summarize our progress towards developing an innovative algorithm called BEAMTAP Broadband Efficient Adaptive Method for True-time-delay Array Processing for adaptive array processing in broadband scenarios. This approach is especially appropriate for optical implementation of sonar array beamforming. The BEAMTAP algorithm only requires two tapped delay lines, rather than one for every array element as required by conventional time-delay-and-sum beamformers. This efficiency provides a huge hardware savings for large arrays. By separating the delay lines from the adaptive weights, this algorithm can be more easily implemented in optical hardware, making it easier to exploit processing and interfacing advantages of optical systems. We discuss an optical beamforming and jammer-nulling system for sonar array beamforming that utilizes photorefractive crystals for the adaptive weights in combination with time-delay-and-integrate TDI charge-coupled device CCD detector arrays to process the parallel data from optically interrogated arrays of hydrophone sensors. In this report we discuss the operation of BEAMTAP in comparison with LMS time-delay-and-sum array processors and P-vector passive array beamsteering operations, and we demonstrate its operation using numerical simulations.