In this letter, we derive the distribution characteristics of first-order multipath ghosts in a nested multiple-input–multiple-output (MIMO) through-wall radar and evaluate the efficacy of the phase coherence factor (PCF) in ghost suppression. Different from a synthetic aperture radar, the first-order multipath echoes of a nested MIMO through-wall radar generate several ghosts. For example, for a nested MIMO array composed of a compact receiving subarray and   $M$   spatially dispersed transmitters, there are   $M$   ghosts at the same side of the wall as the array. The   $m$  th ghost is supposed to occur near the intersection of the line, connecting the target and the center of the receiving subarray, and the ellipse whose foci are the positions of the target and the   $m$  th transmitter. Under the assumption of phase uniform distribution clutter, the PCF can suppress the ghosts up to   $-20 \lg(1-\sqrt {(M^{2}-1)/M^{2}})$   dB, which is about 17.46 dB when   $M = 2$  .
['Jiangang Liu', 'Lingjiang Kong', 'Xiaobo Yang', 'Qing Huo Liu']
First-Order Multipath Ghosts' Characteristics and Suppression in MIMO Through-Wall Imaging