A Number Estimation Method for Dense Group Target Using Multiangle Incoherent Observations

Accurate estimation of targets' number is a crucial prerequisite for observing group target. Traditional methods estimate target number by resolving targets in the range/angle domain, but they become ineffective when targets are densely distributed or the system resolution is limited. While some super-resolution methods can estimate the number of densely distributed targets, they require the echo signals to remain stationary and suffer performance degradation when the group is highly dynamic and individuals are fast fluctuating. This paper proposes a target number estimation method using multi-angle incoherent observations. Firstly, this paper analyzes the fast fluctuation characteristics of echoes from a highly dynamic and densely distributed group target, and demonstrates the incoherence of echoes at different observation frames. Then the group target's multi-angle observation matrix and the corresponding covariance matrix is constructed. Finally, the relationship between the target number and the eigenvalue distribution of the observation covariance matrix is formulated, and the number is accurately estimated through the principal eigenvalues segmentation. Furthermore, by modifying the cost function of the principal eigenvalues segmentation method based on the Minimum Description Length criterion, this paper improves the “underestimation” issue of principal eigenvalues segmentation under low signal-to-noise ratio conditions. The proposed method can achieve the number estimation of a highly dynamic and densely distributed group target using only a single sensor with limited resolution. Simulation and experimental results demonstrate that the proposed method achieves a correct estimation rate of over <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$80 \%$</tex-math></inline-formula> when the target spacing is less than the range resolution.