ACOUSTIC MODEL-BASED MATCHED-FILTER PROCESSING FOR FADING TIME-DISPERSIVE OCEAN CHANNELS - THEORY AND EXPERIMENT

Propagation effects degrade the performance of active sonar systems operating in either deep or shallow water. The ocean medium distorts the transmitted signals by time dispersion and as a result, the performance (signal-to-noise ratio) of correlation receivers is reduced if the receiver does not account for energy spreading. Results from this study demonstrate that the performance of a conventional matched filter can be improved if the reference (replica) channel compensates for the distortion. A model-based matched filter is generated by correlating the received signal with a reference channel that consists of the transmitted signal convolved with the impulse response of the medium. The channel impulse responses are predicted with a broadband propagation model using in situ sound speed measured data and archival bottom loss data. The relative performance of conventional and model-based matched filter processing is compared for large time-bandwidth product linear frequency modulated signals propagating in a dispersive waveguide. From ducted propagation measurements conducted in an area west of Sardinia, the model-based matched filter localizes the depths of both the source and receiving array and the range between them. The peak signal-to-noise ratio for the model-based matched filter is always larger than the conventional.