An FMCW fractional-N PLL-based synthesizer for integrated 79 GHz automotive radar sensors

A fully-integrated and highly linear 79 GHz FMCW synthesizer that is based on fractional-N PLL and intended for automotive radar applications is presented. The frequency synthesizer covers complete automotive band 77–81 GHz of interest and is able to generate complex modulation waveforms with up to 16 different chirp slopes in the single modulation scheme. This helps eliminating potential ghost targets in multitarget environments by careful radar signal post-processing. High chirp linearity with the worst-case frequency error that is lower than 200 kHz across the full 4 GHz tuning range enables high ranging and radial velocity resolutions. The proposed FMCW synthesizer occupies 1.8mm² of area and dissipates 0.35 W as a stand-alone chip solution in the standard SiGe:C HBT 130nm BiCMOS process technology.