Mitigation of weak targets' masking due to nonlinearities in chirp sequence FMCW automotive radar at 77 GHz

The linearity of the transmitted signal in chirp sequence FMCW radar has a direct impact on the radar baseband, which is used for all target detections and safety functionality. In this paper automotive radar sensors are investigated on the linearity of their transmitted frequency slope. Dominant distortions are analyzed. Results show that distortions can cause peak widening, a wide band SNR degradation and masking of weak targets in critical scenarios. This is investigated by simulations and measurements. Also it is shown that many requirements and counter measures are contrary. A system design has to exhibit an optimum trade-off between a high SNR and a high distance resolution.