Spatial-Wideband Effect Compensation for High-Resolution Imaging in MIMO FMCW Radar

Multiple-input and multiple-output (MIMO) frequency-modulated continuous wave (FMCW) radar with large-scale antenna array using a high bandwidth (BW) chirp signal is required to achieve high-resolution radar imaging. However, the design of such a system can result in the spatial-wideband effect, which causes a major problem for the performance of radar systems. In this study, we categorize the spatial-wideband effect of MIMO FMCW radar as the range migration and the beam squint effect. Subsequently, we analyze the degradation degree of the radar performance depending on system parameters. The simulation and experimental results showed that the spatial-wideband effect in radar systems increases the half-power beamwidth (HPBW) of the angle response and decreases the peak power. In addition, this effect gets severe with increasing chirping bandwidth (BW), the number of antenna elements, and target angle. To overcome these issues, we propose a phase compensation method with low computation complexity for real-time implementation. The performance of the proposed method was verified by evaluating the range-angle response using the commercial MIMO FMCW radar development kit. With a total of 86 uniform linear array (ULA) antenna elements and a chirping BW of 3.787 GHz, HPBW of a single target located at 60° was reduced from 2.24° to 1.78° and the peak power of that was enhanced by a factor of 2.05. From these observations, we expect that the proposed method mitigates the spatial-wideband effect of MIMO FMCW radar system, thereby providing an enhanced field of view and radar imaging for high-level autonomous driving systems.