An antenna concept for compact millimeter-wave radar sensors that desire a fan-beam radiation pattern is proposed. It combines an end-fire antenna on a ceramic substrate with a cylindrical parabolic reflector that can be integrated in the sensor's metal housing. The concept allows a direct interconnection from the active components to the antenna in a flip-chip attachment. It is validated with a 77-GHz Yagi-Uda antenna on a 127-mum thick Alumina substrate by measurements with a probe-based measurement setup. The measured return loss, gain, and radiation patterns of the antenna without and with the reflector are given.