Built-in self-test radar unit and method for phase shift measurement therein

A built-in self-test, BIST, radar unit (100) is described. The BIST radar unit (100) comprises: a frequency generation circuit (110) configured to generate a mmW transmit signal; a transmitter circuit comprising: at least one phase shifter (130, 132) configured apply at least one phase shift to the mmW transmit signal; and at least one phase inverter (140, 142) coupled to the at least one phase shifter (130, 132) and configured to invert a phase of the phase shifted mmW transmit signal. A receiver configured to receive and process a received version of the mmW transmit signal. The at least one phase inverter (140, 142) is configured to rotate the phase shifted mmW transmit signal to apply a secondary modulation to the mmW transmit signal; and the receiver is configured to receive and process a received version of the mmW transmit signal to determine an operational state of the BIST radar unit (100) based on a determined phase shift performance of the secondary modulation of the received version of the mmW transmit signal.