A new prototype of collision avoidance radar sensor at 94 GHz is proposed. The receiver front-end module is realized using a six-port phase/frequency discriminator (SPD). The SPD is composed of four 90/spl deg/ hybrid couplers fabricated in metal blocks using a computer numerically controlled (CNC) milling machine. System simulations to obtain the relative speed of the target and the distance to the target using a SPD model based on 90/spl deg/ hybrid coupler measurement results, are presented. Statistical evaluations of the proposed radar sensor performances are also discussed.