32.6 A 76-to-81GHz Direct-Digital 7b 14GS/s Double-Balanced I/Q Mixing-DAC Radar-Waveform Synthesizer

Automotive radars that can achieve angular resolution below 1 degree require virtual MIMO antenna arrays with hundreds of elements. To operate such arrays without compromising range and velocity resolution and to have a sufficient SNR for a long-range operation, FMCW MIMO radars require fast chirps of hundreds of MHz within a few microseconds in combination with slow-time code-division multiple-access (CDMA) and doppler-division multiple-access (DDMA) MIMO implemented with phase rotators. Scaling radar performance with FMCW waveforms [1] becomes limited by microsecond chirp settling time of conventional fractional-N synthesizers [2, 3], wasting a substantial fraction of the available radar frame and limiting implementation efficiency.