Broadband-DORT applied to bistatic active sonar

The decomposition of the time reversal operator (DORT) is a single frequency method of spatially isolating scatterers with a multiple-source/multiple-receiver system [C. Prada, S. Manneville, D. Spoliansky, and M. Fink, J. Acoust. Soc. Am. 99, 2067–2076 (1996)]. This technique has 8 been extended into a coherent, broadband method. Broadband DORT has also been shown to isolate resolvable scatterers at various depths and ranges in a bistatic, active sonar in shallow water. Several limitations of the method are demonstrated through the use of numerical simulations and backpropagations. One limitation is the resolvability of a system in shallow water. The dependence of resolution on environmental parameters, e.g., signal-to-noise ratio, water depth, bottom parameters and sound speed profile—and system parameters—e.g., frequency content and source/receiver configuration—is shown by forming images of a single scatterer, two scatterers and many scatterers. The limits of continuity over frequency of the broadband singular vectors and values caused by frequency fading are also shown through data visualization techniques. [Work supported by ONR.]