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This paper presents two six-port 77 GHz FMCW collision avoidance radar sensor configurations. The first one uses a six-port double balanced mixer for direct frequency conversion and conventional frequency counting to determine the range and velocity of the target. The second one uses a six-port phase/frequency discriminator. Here velocity and range are determined in the same manner by evaluating the beat frequencies which are the slope of the instantaneous phase of the beat signals. Unlike other six-port collision avoidance sensors, measurement data processing techniques are developed to overcome the problems related to the DC current offset and amplitude imbalance, avoiding the need of six-port calibration. Computer simulation shows very good results for both configurations.