Analysis of BiSAR Images Characteristics: From an Electromagnetic Scattering Perspective

Due to the variation of target electromagnetic characteristics with the bistatic synthetic aperture radar (BiSAR) observation angle and frequency, extended targets often appear as multiple discrete points in the imaging results, leading to a loss of structural information. Existing studies have not yet addressed this phenomenon, which can significantly impact the subsequent interpretation and analysis of BiSAR images. To clarify the imaging characteristics of BiSAR, this paper analyzes the morphology and distribution of targets in BiSAR imaging results, considering the electromagnetic scattering characteristics of typical targets, such as linear targets, plates, and dihedrals. Initially, the two-dimensional wavenumber relationship of typical targets is applied to directly derive the imaging morphology and distribution of linear targets in the BiSAR configuration through the wavenumber mapping of the envelope and phase. Next, using the imaging results of the linear target and applying a first-order Taylor approximation for wavenumber inversion, the imaging morphology and distribution of plates and dihedrals are derived. To improve the accuracy of the model in describing dihedrals, we update the scattering model of dihedrals under the BiSAR configuration, building upon the existing model. Additionally, by considering the coupling relationship between target size, BiSAR configuration, and imaging results, the variations in morphology and distribution of these three typical targets with configuration and target size are explored. Furthermore, based on the imaging characteristics of extended targets, the structural information of the targets is estimated, resulting in structured imaging outputs. Numerical simulations are conducted to validate the accuracy of the derived imaging results and characteristics. This paper establishes the relationship between the BiSAR imaging principles and target scattering characteristics, and, for the first time, analyzes the morphology and distribution of extended targets in BiSAR imaging results. These insights enhance the interpretability of BiSAR images and lay the groundwork for more refined image interpretation.