An Online Calibration Algorithm for Range-Dependent Phase Imbalance in FMCW Radar Systems

Phase imbalance calibration is an important task for maintaining the desired performance of the radar system in automotive applications. This paper presents an online calibration technique to tackle the range-dependent phase imbalances in frequencymodulated continuous-wave (FMCW) radar systems. Specifically, we focus on the phase imbalances arising from the low-pass filter transfer function mismatches among independent receiver antenna paths. These mismatches can happen due to process variations, thermal change, or aging. The resulting phase imbalances can reduce the radar system's sensitivity and detection performance. The proposed calibration method is implemented in the digital domain by utilizing targets of opportunity in combination with a weighted least squares estimator approach. The performance of our proposed method is evaluated through simulations.