A traditional system mm-wave radar system consists of mm-wave ICs, signal process ICs and antennas and is wired together by assorted high speed interconnects. The interconnects, ranging from digital high speed IOs to mm-wave waveguides, often form bottlenecks in the radar system, inducing high system complexity and high power consumption, and IO bandwidth-limiting the signal processing power. In this presentation, we will illustrate how we used a Radar-on-Chip (ROC) design to remove some of these bottlenecks and developed a high performance mm-wave radar system for autonomous driving.