Waveguide invariance for active sonar.

Abstract

Active sonar signal processing in shallow water has proven to be a challenging problem due to the strong interaction of sound with the boundaries of the channel and the dependence on typically unknown environmental parameters. This has motivated research on properties of acoustic propagation that are not sensitive to those factors, such as the waveguide invariance. The invariance principle has found application in passive sonar signal processing by relating the frequency content of a broadband source to the range between source and receiver. More recently, experimental evidence has suggested that a similar structure exists for active sonar. This structure provides additional information about the location of a target, and information can be exploited in sonar processing algorithms such as target tracking. Data from several sea experiments have been analyzed to determine the behavior of the active invariance, and tank experiments have been designed to confirm the presence of the range‐frequency structure in signals reflected by a moving target. This presentation provides an overview of the active invariance phenomena and describes the performance of a target tracking formulation that incorporates invariance structure into the state space representation for improved performance.