Model, Source and Analysis of BiSAR Maritime Moving Target’s Spatial Resolution

High-resolution imaging of maritime moving targets is of critical importance for maritime domain awareness and defense applications. Bistatic synthetic aperture radar (BiSAR) enables imaging for both stationary scenes and dynamic targets, where spatial resolution serves as a fundamental metric for system design and performance evaluation. While the resolution for static scenes can be derived from platform kinematics, it is invalid for moving targets owing to unknown translational motion and three-dimensional oscillations. Two fundamental limitations hinder current resolution analysis for moving targets: 1) direct application of such static-scene formulations to moving targets yields inaccurate resolution results, leading to failure of the system design; 2) the resolution of moving targets depends on numerous factors, necessitating both quantitative and qualitative understanding of its statistical behavior. To address this issue, the resolution model and physical source of BiSAR maritime moving targets have been systematically established and comprehensively characterized. First, the echo signal model of a maritime moving target in BiSAR is established, and the two-dimensional spatial resolution model is derived based on the gradient resolution theory. Subsequently, the Azimuth Resolution Contribution Index (ARCI) is proposed to quantitatively evaluate the individual contributions of the transmitter, receiver, and target motion to the azimuth resolution. Finally, a comprehensive analysis was conducted to investigate the time-varying characteristics of resolution and ARCI, as well as to analyze the impact of sea states, target rotation parameters, and platform configuration. The validity of the proposed ARCI and the derived theoretical framework is confirmed through numerical simulations.