Sonar signal processing and shallow water acoustics

Sonars operating in shallow water usually encounter what signal processors term a reverberation-limited environment; higher signal levels simply lead to higher reverberation and not to improved performance. Consequently, the principal means of improving sonar performance is to use signals appropriate for the task and environment. This implies that robust environmental models are imperative. In both sonar and radar, reverberation, or scattering, is usually modeled to be a random linear system characterized by a scattering function, or some other second moment such as a two-frequency correlation function. Typically, an active sonar resolves a target or an environmental parameter by either range or time gating (high bandwidth signals) or Doppler gating (long duration signals). The resolution properties of a signal are specified by its ambiguity function and the interaction with the scattering function is the single most important factor in determining system performance. This talk will provide a brief overview of some of the signal processing issues for shallow water sonars.