Model-based matched filter processing for delay-Doppler measurement in a multipath dispersive ocean channel

Doppler-resolvent large time-bandwidth product signals transmitted in an ocean medium are distorted as a result of multipath and time dispersive propagation. The delay-Doppler resolution performance of a model-based matched filter and a conventional matched filter are examined against data obtained in an opening range experiment at a deep water site west of Sardinia in February 1990. The transmitted signals were time-dispersed by propagation through a near-surface waveguide and were Doppler shifted (time-expanded) by relative motion of the towed source and receiving array. The received signals were correlated with a family of reference signals accounting for both medium and Doppler effects. The medium Green´s function was modelled using generalized ray theory, and sound speed data measured in situ. Results demonstrate that both the range and relative velocity of the source and receiver were determined correctly if the medium-induced distortion had been modelled properly. Model-based matched filter processing improved the peak output signal-to-noise ratio by 1 to 4 dB for the range-dependent propagation conditions of the experiment.