Modeling and Removing Doppler Division Multiplexing Spurs in Automotive MIMO Radar

Doppler division multiplexing (DDM) is a popular slow-time modulation technique for automotive multiple-input and multiple-output (MIMO) radars. It requires accurate transmit phase shifters to avoid artifacts such as spurs that would degrade the radar system’s performance. This article proposes a system impact analysis of the constellation imbalance of the phase shifter. The spurs formation is modeled in a second part to understand the information they convey on the constellation imbalance. Subsequently, this information is exploited as a base for a novel constellation imbalance estimation algorithm. The estimation is finally utilized to predistort the phase shifter. The DDM spur model and the constellation imbalance estimation method are evaluated on a recorded automotive radar dataset. The results show that the imbalance in the phase shifter constellation can be reduced such that all spurs are suppressed below the noise floor. With the presented method, the DDM MIMO radar system can autonomously evaluate when recalibration is needed and perform self-calibration on the road to maintain the system’s performance throughout its life cycle.