Acquisition in phase demodulation: application to ranging in radar/sonar systems

Ranging in radar/sonar systems is cast as a phase/frequency detection problem. In phase/frequency demodulation, there are two stages: acquisition, which resolves the global prior uncertainty before phase/frequency locking; and tracking, which follows the phase/frequency variations. In this work, ranging corresponds to absolute phase acquisition formulated as a global nonlinear filtering problem. The proposed solution propagates the associated multimodal density and generates a process relating global covariance with the single modes common covariance. Acquisition is then defined as the first passage of this process across a given threshold. Statistics such as acquisition time histograms and acquisition performance, characterizing the behavior of the developed estimator/detector, are obtained by Monte Carlo simulations.