Accurate Microwave Imaging of Concave Targets Based on High-Order Scattering Separation Using Modified Complex Exponential Model

Microwave and millimeter-wave (MMW) imaging is an important technique for target detection and classification. However, the accuracy of image reconstruction can be significantly affected when dealing with complex concave targets due to strong high-order scattering. Since the majority of information on the target shape is contained in the scattered waves, which exhibit only first-order interactions with the object, separating high-order scattered waves can be beneficial in reducing the artifacts during the imaging of concave targets. In this article, a novel technique based on high-order scattering signal separation is proposed for accurate imaging of concave structures. The modified complex exponential (MCE) model is applied to separate the entire scattering signal into several components. According to the phase difference of the odd and even reflection times (RTs), the two types of scattering components can be classified and recognized. Furthermore, by considering the interleaving of distance relationship between these components, it is possible to separate the first reflection from high-order odd reflections. Through elimination of the high-order scattering components, the artifacts can be significantly reduced, leading to imaging results that closely resemble the actual structure of the target. The simulation and measurement results of both typical and complex concave targets verify the effectiveness and practicability of the proposed method.