An Extended 3D Microwave Near-Field Imaging Algorithm for High-order Scattering from Complex-Shaped Coupled Objects

Microwave imaging offers high imaging quality in several applications due to its wide bandwidth and strong penetration properties. However, its imaging accuracy often significantly degrades due to high-order scattering, which leads to prominent high-order imaging artifacts in scenarios with coupled objects. Conventional Born approximation-based algorithms fail to reconstruct coupling boundaries because they cannot recover contours from high-order scattering fields. Meanwhile, existing high-order imaging methods typically rely on prior knowledge of object geometries, limiting their adaptability in practical applications. To address these challenges, this paper proposes a three-dimensional extended imaging algorithm for contour reconstruction of complex-shaped coupled objects using high-order scattering. The method reconstructs object contours from the separated first-order scattering fields and incorporates them into high-order path modeling, enabling accurate focusing of high-order scattering components. As high-order imaging complexity grows rapidly with imaging domain size and scattering order, a coarse-to-fine two-stage focusing method is introduced to enhance computational efficiency. Numerical simulations demonstrate that the proposed algorithm effectively suppresses high-order artifacts and improves the reconstruction accuracy of coupled objects, providing an efficient solution for target detection and imaging in complex scenarios.