Automotive Radar Doppler Division MIMO With Velocity Ambiguity Resolving Capabilities

Automotive radar is stepping up Direction of Arrival (DOA) estimation performance by increasing the number of transmitters per radar. To use more transmitters, while maintaining target coherence in a Multiple Input Multiple Output (MIMO) radar, new waveforms are needed beyond time division techniques. In this work a novel Doppler division based MIMO technique is presented. With this technique transmitted signals are orthogonalized with frequency offsets in the Doppler dimension. A spectral gap is created in the Doppler spectrum which allows detection of velocity ambiguity thus extending the maximum unambiguous velocity and correcting cyclic rotation of the transmitter ordering. A special, novel, version of the technique, using quadrature encoding, is presented which allows the simultaneous use of three transmitters using only binary phase shifters while maintaining the Doppler spectral gap.