This paper presents the development of a full prototype of a millimetre wave sensor for automotive radar in the 77-81GHz frequency band. The interest in millimetre wave sensors has grown significatively in the last ten years. Millimetre-wave automotive sensors are necessary to add data and complement optical devices to allow safety autonomous driving algorithms. The sensor is designed based in the use of FMCW signal in the 77-81 GHz frequency band. The sensor integrates the millimetre-wave antenna, the radio transceiver and the signal-processing unit. Communications with the rest of the vehicle systems and sensors are ensured using fast can-bus. The proposed hardware is modular so the main parts can be used for different application without the design a new set of PCB boards. Part of the system is re-utilizable between different applications.