Non-Line-Of-Sight Imaging by Millimeter Wave Radar

Non-line-of-sight (NLOS) radar imaging technique aims to reconstruct hidden targets that illuminated wave cannot reach directly, which can greatly expand the range of radar detection. In this paper, inspired by synthetic aperture radar (SAR), an effective two-dimensional (2-D) NLOS imaging technique via multiple input multiple output (MIMO) millimeter-wave (MMW) radar is proposed. In the scheme, a 2-D virtual antenna array is synthesized by MIMO antenna scanning, and the multi-bounces echoes is used to obtain 2-D NLOS imaging. Then an algorithm via mirror symmetry back-projection (MSBP) is presented for 2-D high-precision focusing of these NLOS echoes. Moreover, a cost-effective 79GHz MMW NLOS experiment system is developed for technical validation. The effectiveness of MMW NLOS radar imaging is verified by near-field multi-targets experiment, and high-precision 2-D imaging results of hidden knives are obtained by MSBP method.