Multistatic tracking for continous active sonar using Doppler-bearing measurements

Unlike conventional Pulsed Active Sonar (PAS) which listens for echoes in between short-burst transmissions, Continuous Active Sonar (CAS) attempts to detect echoes amidst the continual interference from source(s) transmitting with nearly 100% duty cycle. The potential advantage of CAS is an increased number of continuous detection opportunities, leading to improved target detection, localization, tracking, and classification. The challenge is detecting the target echoes in the presence of continuous interference. CAS transmission waveforms may be of several types, i.e., frequency modulated waveforms (FMs) which provide good range measurements, continuous waveforms (CWs) which provide good Doppler measurements, or sophisticated broadband waveforms which attempt to provide both good range and Doppler measurements simultaneously. In order to mitigate against the multi-source mutual interference problem, it may be preferred to only use continuous CW transmissions, rather than continuously repeating broadband waveforms. This paper develops a tracking approach based on the Gaussian Mixture Probability Hypothesis Density (GMPHD) filter for multistatic sonar configurations using Doppler-bearing measurements from continuous CW transmissions. From a single fixed source-receiver node, such measurements do not enable precise target state estimates. However, when data fusion and target tracking is performed amongst multiple source-receiver nodes, it is shown that good localization estimates and target tracking may be obtained.