Abstract: An object detection system for autonomous vehicle, comprising a radar unit and at least one ultra-low phase noise frequency synthesizer, is provided. The radar unit configured for detecting the presence and characteristics of one or more objects in various directions. The radar unit may include a transmitter for transmitting at least one radio signal; and a receiver for receiving the at least one radio signal returned from the one or more objects. The ultra-low phase noise frequency synthesizer may utilize Clocking device, Sampling Reference PLL, at least one fixed frequency divider, DDS and main PLL to reduce phase noise from the returned radio signal. This proposed system overcomes deficiencies of current generation state of the art Radar Systems by providing much lower level of phase noise which would result in improved performance of the radar system in terms of target detection, characterization etc. Further, a method for autonomous vehicle is also disclosed.