The present disclosure relates to a concept for calibrating an IQ modulator. A calibration method comprises setting one or more control values of the IQ modulator corresponding to a desired constellation point of a constellation diagram to generate an IQ modulating signal; mixing the IQ modulating signal with a carrier signal to generate an IQ modulated transmit signal; transmitting the IQ modulated transmit signal towards a predefined object at a predefined location; receiving a reflection of the IQ modulated transmit signal from the predefined object; mixing the received reflection of the IQ modulated transmit signal with the carrier signal to generate a down-converted receive signal; comparing amplitude and/or phase of the down-converted receive signal with the desired constellation point of the constellation diagram; and adjusting the one or more control values of the IQ modulator until a deviation between the amplitude and/or phase of the received down-converted signal and the desired constellation point falls below a predefined threshold.