A planar MIMO UWB array design for high-resolution microwave imaging

In this paper, a planar multiple input multiple output MIMO UWB array is proposed for 3D microwave imaging applications. According to the virtual array concept, the advantage of the MIMO array lies on improving the angular resolution with a reduced number of antennas, and achieve the same resolution as a fully populated conventional arrays. In addition, the UWB systems provide a better range resolution thanks to their large bandwidth. The frequency diversity and its influence on the system's resolution is also studied. For the MIMO array, an optimal UWB antenna element is designed with more than 128% of fractional bandwidth with no considerable distortion of the transmitted impulse. For the imaging algorithm, the Back-projection algorithm is implemented and used for the reconstruction of the images. In order to study the performance of the designed system, the full-wave electromagnetic simulator CST MWS is used which allow the modelling in three-dimensions (3D). The resulting images of a different target materials and dielectric properties confirm the reliability of the proposed system and the impact of the spatial and frequency diversity in the resolution improvement while considerably reducing the cost of the MIMO UWB array.