### ASA 128th Meeting - Austin, Texas - 1994 Nov 28 .. Dec 02

## 4aUW4. Reverberation characterization and suppression in the presence of
channel spreading.

**Geoffrey S. Edelson
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*Lockheed Sanders, Inc., MAN6-2000, P.O. Box 868, Nashua, NH 03061-0868
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**Ivars P. Kirsteins
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*SACLANT Undersea Research Centre, La Spezia, Italy
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In active sonar, the reverberation plus target time series can be modeled
as the joint convolution of the signal with the channel and scatterer impulse
responses. Especially in shallow water, the channel response cannot be
adequately modeled as propagation over discrete paths. A maximum likelihood
type approach is proposed for estimating the arrival times of signals which
have propagated via a continuum of paths, i.e., temporally spread channels. The
channel spreading is included in the model by using a discrete prolate
spheroidal sequence (DPSS) to represent the channel impulse response of given
duration, but unknown shape. Thus the unknown parameters are the arrival times
and the scale factors of the DPSS expansion. The parameters are estimated using
an iterative methodology which decomposes the original data into its
constituent components and then estimates the parameters of the individual
components through a sequence of one-dimensional searches. Experimental data
and computer simulation examples indicate that the method performs well.