Geoffrey S. Edelson
Lockheed Sanders, Inc., MAN6-2000, P.O. Box 868, Nashua, NH 03061-0868
Ivars P. Kirsteins
SACLANT Undersea Research Centre, Viale San Bartolomeo, 400, 1-19138 La Spezia, Italy
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. We propose a maximum likelihood type approach 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.