Bistatic cylindrical millimeter-wave imaging for accurate reconstruction of high-contrast concave objects

A high-contrast target with complex shape, especially concave surfaces, often exhibits 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 are often confined in limited scattering angles. Under this specific requirement for transceiver setup, a bistatic cylindrical aperture synthesis technique is proposed to obtain accurate images of concave object despite strong high-order scattering. To verify this method, simulated imaging results in bistatic near-field cylindrical imaging geometry are presented. Finally, the effectiveness of artifact reduction is confirmed by experimental results of complex metallic targets with concave outlines.