Improved passive ranging algorithm based on the waveguide invariant theory

A Double-horizontal-array (DHA) passive ranging algorithm is proposed. Based on the waveguide invariant theory, the interference fringes can be extracted by applying the Radon transform to the interference structure obtained by spectral analysis of the tracking beamform output of each array. The passive ranging accuracy can be improved by adopting the interference striations in the two interference structures whose slopes are identical combined with the traditional passive ranging algorithm. Simulation and analysis of positioning accuracy indicate that the improved passive ranging algorithms are simple and can greatly improve the ranging accuracy. The improved passive ranging algorithms can estimate the target range without detailed prior knowledge of the marine environment, which provides guidelines for towed line arrays when used for passive ranging.