A Forward 3-D Scattering Center Modeling Approach of Complex Targets With Deep Cavities for SAR Image Interpretation

The structure with multiple reflections is commonly observed in radar targets and can form dominant scattering sources. However, their scattering centers (SCs) tend to deviate from the expected target region and display instability with changing observation angles, complicating SC analysis and interpretation. To elucidate the mapping relationship between apparent SC and target geometry with multiple reflections, this article proposes a forward approach to establish the 3-D parametric SC model for complex targets, particularly those with deep cavities. The forward-constructed model is a concise combination of clear physical parameters that are characterized by robust inferential and descriptive capabilities. Specifically, we first utilize ray tracing and clustering techniques to discretize the scattering of a target into several component-level scattering sources. Then, for each source, a set of physically relevant parameters is calculated in a forward (cause-to-effect) manner, incorporating a deeper understanding of the high-frequency mechanisms. This direct quantitative deductive modeling approach allows for the simultaneous attachment of scattering mechanisms and target information to the SC model. Meanwhile, the physical formation process of the SC type (localized or distributed) and 3-D position is explicated in multiple scattering scenarios. Finally, the efficacy of this forward modeling is validated through comparisons between the model-reconstructed and high-frequency (or full-wave) simulated high-resolution range profiles (HRRPs) or synthetic aperture radar (SAR) images of cavities and complex targets. In addition, those numerical examples also demonstrate the interpretation capabilities of the proposed forward model.