毫米波成像在人体安检领域发挥了重要作用，引起了人们的广泛关注。现有的毫米波近场人体安检成像机制主要分为SISO和MIMO两种。SISO机制可实现快速精确成像，然而随着工作频率的升高，其所需天线数目迅速增长、天线间隔下降，不仅造成了系统成本提升，还使得天线耦合难以被抑制。MIMO机制虽然降低了成像所需的天线数目、增大了天线间隔，但目前无法实现类似SISO机制的快速精确重建。提出了一种可快速精确重建的MIMO近距离成像机制，定量给出了该机制的适用条件。与传统MIMO近距离成像机制不同，该MIMO近距离成像机制通过巧妙地设计MIMO子阵列，使其在近场成像中满足等效相位中心原理。因此它能够直接使用诸如距离迁徙算法（range migration algorithm，RMA）等各种基于SISO机制开发的精确且快速的成像算法去重建图像，兼顾了SISO机制和MIMO机制的优势。E波段的示例表明，在近场毫米波成像中，该MIMO机制与SISO机制具有同等水平的成像质量和成像速度，但相较于SISO机制，该MIMO机制的天线利用率、天线间隔可提升4倍以上。与传统MIMO成像机制相比，该MIMO成像机制不但有更好的成像质量，而且其重建速度大幅提升，在一个成像区域为1 m×1 m×0.2 m，体素尺寸为1.85 mm3的典型成像场景中，比传统MIMO成像机制快近200，000倍。仿真和实验结果验证了该成像机制的有效性。

Millimeter-wave (MMW) imaging is of interest as it has played an essential role in personal surveillance. The existing MMW short-range imaging mechanisms in personal surveillance can be mainly divided into SISO and MIMO. The SISO mechanism can achieve fast and accurate imaging. However, as the operating frequency increases, the number of antennas required increases rapidly, and the antenna spacing decreases, which not only causes an increase in system cost, but also makes it difficult to suppress antenna coupling. Although the MIMO mechanism reduces the number of antennas required for imaging and increases the antenna spacing, it is currently unable to achieve rapid and accurate reconstruction comparable to the SISO mechanism. In this paper, a MIMO short-range imaging mechanism has been proposed, which is well-suitable for fast and accurate reconstruction, and the applicable conditions of the mechanism were given quantitatively. Unlike the traditional MIMO short-range imaging mechanism, the proposed MIMO imaging mechanism satisfies the principle of equivalent phase center (EPC) in short-range imaging by ingeniously designing MIMO sub-arrays. Therefore, it can directly use various accurate and fast imaging algorithms developed for SISO mechanism to reconstruct images, such as range migration algorithm (RMA). It means that the algorithm has the advantages of both SISO mechanism and MIMO mechanism. The demonstrations in E-band show that the proposed MIMO mechanism exhibits the same level of imaging quality and reconstruction speed as SISO mechanism in short-range imaging, but the antenna utilization rate and the antenna spacing can be increased by more than 4 times. When compared with the traditional MIMO imaging mechanism, the proposed MIMO mechanism not only has better imaging quality but also greatly improves the reconstruction speed, which is nearly 200,000 times faster than the traditional MIMO mechanism in a typical imaging scene of 1m×1m×0.2m volume with a voxel size of 1.85 mm3. Both simulation and experimental results verify the effectiveness of the proposed MIMO mechanism.