Investigations on Multipath Artifacts for Dihedral-Angle Objects in Millimeter-Wave Security Imaging

Resolving multipath artifacts in concave objects is one of the keys to the development of millimeter-wave (mmW) security imaging. This paper deals with the multipath artifacts problem of dihedral-angle objects via building a ray-tracing model to analyze multipath echo signals. A novel two-dimensional (2-D) accurate range compensation (ARC) algorithm of a monostatic uniform linear antenna array is proposed to accurately reconstruct dihedral-angle objects with multipath artifacts. Firstly, a 2-D ray-tracing model of dihedral-angle objects is established. The causes of multipath artifacts as well as the propagation characteristics of multipath echo signals are analyzed, and the key information such as the coordinates of equivalent reflection points (ERPs) are extracted from the model. Secondly, a Fourier transform (FT) ranging method is proposed to distinguish multipath echo signals, and a 2-D ARC algorithm is proposed to separate and compensate the echo signals of multiple reflections based on the ray-tracing model. The 2-D ARC algorithm is analyzed and compared with prior art, and the computational complexity and noise robustness of the 2-D ARC algorithm are discussed and analyzed in details. Finally, simulations and experiments are conducted to validate the effectiveness of the 2-D ARC algorithm.