Sparse estimation of backscattered echoes from underwater object using integrated dictionaries

The problem of time-delays estimation of backscattered echoes from underwater targets is presented using a sparse reconstruction framework employing an integrated dictionary. To achieve high resolution, the used dictionary is usually defined over a finely spaced grid over the region of interest. Such a procedure may result in problems of being computational cumbersome or suffering from basis mismatch. In addition, the shape of the backscattered echoes may differ significantly from the expected waveforms used to form the dictionary, causing further mismatch problems. To alleviate such problems, the use of an integrated dictionary framework is introduced. Unlike traditional dictionaries that are defined over a set of grid points, the elements in an integrated dictionary are formed by integrating the expected waveform over bands of the parameter space. The resulting dictionary may be used to find initial regions of the parameters of interest using a smaller dictionary than otherwise required, without suffering a loss of performance. The elements can also better match with the backscattered echoes, even if these differ from their expected shape. Simulated results of the backscattered echoes from a cylindrical shell, as well as results from experimental measurements, illustrate the performance of the proposed method. © 2018 Acoustical Society of America.