Accurate Millimeter-Wave Imaging of Concave Objects Under Multistatic Array Configurations

The accurate imaging of a target with complex shape, especially concave surfaces, has always been a trouble. Since concave surfaces often exhibit strong high-order scattering during forward propagation, which is often misinterpreted as artifacts or phantom targets during imaging. In this work, a bistatic imaging method for reducing artifacts caused by high-order scattering from concave objects under cylindrical millimeter-wave scanning geometry is proposed. The effects of multiple reflections within concave structures are firstly analyzed by using ray-tracing techniques. It is observed that these troublesome multiple reflection echoes often exhibit in uncertain positions with varying of observation angles. Based on this analysis, a multistatic cylindrical aperture synthesis technique is proposed to obtain accurate images of concave object despite strong high-order scattering. To verify this method, simulation and measurement imaging results under multistatic array configurations are presented. Finally, the effectiveness of artifact reduction of complex metallic targets with concave outlines is confirmed.