ASA 125th Meeting Ottawa 1993 May

4aUW7. Model-based matched-filter processing of Doppler-shifted signals in a time dispersive ocean environment.

J.-P. Herm

SACLANT Undersea Res. Ctr., Viale Bartolomeo, 400, I-19138 La Spezia, Italy

W. I. Roderick

Naval Undersea Warfare Ctr. Div., Newport, RI 02841-5047

Dispersive multipath propagation in an ocean medium distorts wideband linear frequency-modulated (LFM) transmitted signals. As a result, the performance of correlation receivers is degraded if the receiver does not account for the Doppler of the incoming signal or the multipath (energy splitting) in the medium. In this study, results are presented that demonstrate that the performance of a conventional correlation can be improved if the reference (replica) channel is compensated in both Doppler and time dispersion. The 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 and Doppler compensated. The channel impulse responses were predicted with a broadband propagation model using environmental (sound velocity) data. The data were collected during a February 1990 experiment conducted in deep water in an area west of Sardinia. The acoustic data set consisted of linear frequency-modulated signals, with a time-bandwidth product of 4000, transmitted from a moving source and received on a towed array. Comparison with conventional processing shows improvement (about 3 dB) in peak output signal-to-noise ratio for the propagation conditions encountered in the experiment. [Work supported by ONR.]