A method of calibrating a radar system of a vehicle is disclosed. A source signal is transmitted from a transmitter at a target at a selected location from the radar system. An echo signal is received as a reflection of the source signal from the target at an in-phase channel and quadrature channel of a receiver. A range space for the echo signal is obtained that includes a target peak corresponding to the target, wherein the range space includes a ghost peak for the target resulting from an IQ difference between the in-phase and quadrature channels. The IQ difference between the in-phase and quadrature channels is adjusted to reduce an amplitude of the ghost frequency peak.