Defining acceptable phase-modulated nonlinearities in 77 GHz FMCW automotive radar systems

A method to determine the maximum allowable frequency error of a PLL generated FMCW radar slope is presented. Using the side lobe suppression as a metric, the maximum frequency error in a linear FMCW slope is defined based on the used window function. With higher distortion frequency a higher side lobe suppression is required. It is shown that for fast chirp sequence modulation in the absence of any additional counter measures, the minimum allowable frequency error is on the order of a few kHz, which is nearly impossible to be achieved by commercial radar systems.