Synthetic Elements for Moving Line Arrays - MP 85-09 (Phase II 47-11)

Towed arrays provide the potential for creating synthetic elements located a fraction of the distance between the actual elements, thus sampling the spatial field at a higher rate and allowing for operation at higher frequencies without grating lobes. Synthetic elements may also be used to fill in for failed sensors. The ability of a passive synthetic aperture sonar (PSAS) towed array system to achieve the performance of the equivalent fully populated array depends on the temporal and spatial coherence of the observed signals. In Phase I, we developed a mathematical framework for analyzing the PSAS system that takes into account the statistical properties of realistic broadband and narrowband signals and noise, developed a set of signal processing algorithms, and analyzed their performance on simulated data. The results showed that coherent processing gains are possible for narrowband signals, but the performance degrades to the performance of the physical array as the signal bandwidth increases. In Phase II, we will continue to develop the PSAS model and derive new signal processing algorithms to handle missing elements, multiple signals, and model uncertainties. The algorithms will be tested on simulated and real data and implemented in an architecture that is suitable for final system integration and deployment.