Highly Integrated 3D-Radar System at 240GHz

除了测量精度和分辨率外，可靠性、稳健性、尺寸和价格等重要因素决定了传感器的应用领域。雷达系统具有即使在恶劣条件下(例如烟雾)也能提供良好结果的优势。具有二维角分辨率的雷达系统大多体积大，价格昂贵。除了用高聚焦天线进行机械扫描外，天线阵列的角分辨率主要可以通过两种方法实现：通过改变单个辐射单元的相位进行电子扫描，或者使用数字波束形成同时对所有方向进行电子估计。在第一种情况下，可用信噪比(SNR)受测量周期的限制，因为必须顺序扫描不同的方向。除了硬件复杂度高，特别是在二维情况下，数字波束形成需要巨大的计算能力，这导致了更高的成本和更大的功率需求。在这里，雷达波束通过相移网络在频率上旋转一维，在另一维上旋转。结合优化的收发信机结构，开发了用于环境监测(工业生产区域自动驾驶车辆的室内跟踪或碰撞保护)的3D毫米波雷达传感器。尤其是在高频段，采用二维天线阵的雷达具有广阔的应用前景。较小的波长(例如，240 GHz下的1.25 mm)允许将天线阵列与几个元件集成在紧凑的模块中。此外，由于波长较小，可以将被动相控馈电网络作为Butler矩阵与有源元件一起直接在砷化镓上实现，从而可以优化雷达系统的信噪比。为了利用天线的频率捷变特性，需要高带宽的片上器件，这给其实现带来了挑战，因为它具有很强的寄生效应。除了距离分辨率之外，FMCW雷达与新型捷变频相控阵的结合以及它的馈电支持二维波达方向(DOA)测量。与数字波束形成相比，这导致在硬件复杂性、信噪比和测量时间之间进行了更有效的权衡。MMIC和天线在封装中的集成是一个特别的挑战，因为不能再使用具有高散热适应性的最先进的波导式封装(分体式)。必须对新的概念进行分析和优化，使天线具有高性能的射频互连以及良好的散热性能。

In addition to measuring accuracy and resolution, important factors as reliability, robustness, size and price determine the fields of application of sensors. Radar systems have the advantage to deliver good results, even under adverse conditions (e.g. smoke). Radar systems with two-dimensional angular resolution are mostly large and expensive. Apart from mechanical scanning with a highly focusing antenna, the angular resolution of an antenna array can be principally achieved by two methods: electronic scanning by changing the phase of the individual radiating elements or to electronically evaluate all directions simultaneously using digital beam-forming. In the first case, the available signal-to-noise ratio (SNR) is limited by the measurement period, since the different directions must be sequentially scanned. Besides the high hardware complexity, especially in a two-dimensional case, digital beam-forming needs huge computing power, which leads to higher costs and significantly larger power requirements.In this project, novel frequency-agile antenna arrays are examined in a hybrid 2D-antenna system. Here, the radar beam is pivoted in one dimension over the frequency and in the other dimension via a phase shift network. Together with optimized transceiver architectures, 3D millimeter wave radar sensors for environmental monitoring (indoor tracking or collision protection for autonomous vehicles in the industrial production area) are developed. Especially at high frequencies, radars with 2D antenna arrays are promising. The small wavelength (e.g. 1.25 mm at 240 GHz) allows integration of antenna arrays with several elements in compact modules. Additionally the small wavelength enables the implementation of passive phase controlling feed networks as the Butler matrix together with active components directly on GaAs and thus can lead to an optimization of the radar system's SNR. To exploit the frequency-agility of the antennas, highly broadband on-chip components are necessary, which poses a challenge on their implementation, due to the strong parasitic effects.Besides the range resolution the combination of FMCW radar with the novel frequency-agile phased array and its feeding with GaAs MMICs allows the direction of arrival (DoA) measurement in two dimensions. This compared to digital beam-forming leads to a more efficient trade-off between hardware complexity, SNR and measurement time. The integration of MMIC and antenna in a package represents a particular challenge because the state of the art waveguide packages (split-block) with their high suitability for heat dissipation can no longer be used. New concepts must be analyzed and optimized with high-performance RF interconnections to the antenna as well as good heat dissipation properties.