In recent years, low-cost millimeter-wave CMOS-IC radar have become available and particularly applied to automotive because of its superior environmental tolerance compared to cameras and LiDAR. On the other hand, it is inferior to other sensors in terms of spatial resolution(recognition), making target detection accuracy an issue. This fact limits expanding application like security and others where requires high resolution. MIMO Radar, also known as virtual array, is one of the promising technologies to improve spatial resolution. However, a commercial CMOS-IC generally has only a small number of antennas, which limits the performance improvement. To solve this problem, a recent trend is to increase the number of real antennas by cascading multiple CMOS-ICs on a single substrate, thereby increasing the aperture size of the virtual array and significantly improving spatial resolution. However, when using such a method, reflected waves from targets in short range cannot be regarded as plane waves, where target DoA estimation with conventional(far-field) mode vector degrades accuracy. This paper presents an approach to improve spatial resolution and suppress performance degradation in near-field areas simultaneously by concatenating plural modules, even if a module consists of a single CMOS-IC. Computer simulations and fundamental experiments show that the proposed approach can accurately identify close proximity multiple targets in the near field even by using the far field mode vector, which is low computational burden.
|