A 77-GHz FMCW radar using a digital phase-locked synthesizer

A digital phase-locked synthesizer for application in a 77-GHz frequency modulated continuous wave (FMCW) radar is presented. It consists of a digital phase discriminator, a digital loop filter, highpass modulation, and predistortion of the VCO tuning characteristic. An additional feature is the ability to store the previous phase errors for iterative adaptation of the loop filter coefficients and the highpass modulation parameter. A radar system has been built to compare the proposed digital synthesizer to an offset-loop based one in actual radar measurements.