An exemplary embodiment of the present invention provides a method of measuring I-Q mismatch in a system having a transmitter. The transmitter comprises an in-phase up-converter, a quadrature-phase up-converter, and a power detector. The method of measuring I-Q mismatch comprises measuring an in-phase transmit power at the power detector caused by transmitting an in-phase output signal to the in-phase up-converter, measuring a quadrature-phase transmit power at the power detector caused by transmitting a quadrature-phase output signal to the quadrature-phase up-converter, calculating a transmitter-gain-mismatch as a function of the in-phase transmit power and the quadrature-phase transmit power, measuring an I-Q transmit power at the power detector caused by simultaneously transmitting a gain-mismatch-compensated in-phase output signal to the in-phase up-converter and a gain-mismatch-compensated quadrature-phase output signal to the quadrature-phase up-converter, and calculating a transmitter-phase-mismatch as a function of the I-Q transmit power.