Patent ID: 7734261

Claim:
A method of calibrating an analog I/Q modulator in a high-frequency transmitter, in which an input signal is weighted in an in-phase path and in a quadrature phase path by respectively a first and a second compensation coefficient prior to the I/Q modulation, and an output signal is produced, comprising: in a first method step, providing the high-frequency transmitter in a second method step, the first compensation coefficients C I , C Q ( 3 ), which affect the sideband suppression of the output signal, and the second compensation coefficients D I , D Q ( 3 ), which affect the carrier suppression of the output signal ( 12 ), are in each case set to a first predefined value C I,1 , C Q,1 , D I,1 and D Q,1 , in that the input of the I/Q modulator ( 1 ) is supplied with an input signal which satisfies a rotating exponential function with the frequency f 0 , a first I/Q modulator output signal ( 12 ) is produced and fed to a first evaluation and the result of the first evaluation is stored, in that, in a third method step, the first and second compensation coefficients ( 3 ) are in each case set to a second defined value C I,2, D I,2 and D Q,2 and a second I/Q modulator output signal ( 12 ) is produced, fed to a second evaluation and the result of the second evaluation is stored, in that, in a fourth method step, the first and second compensation coefficients ( 3 ) are in each case set to a third defined value C I,3, D I,3 and D Q,3 and a third I/Q modulator output signal ( 12 ) is produced, fed to a third evaluation and the result of the third evaluation is stored, in that, in a fifth method step, improved compensation coefficients ( 3 ) which reduce at least one of an amplitude, a phase imbalance of the I/Q modulator ( 1 ) and an amplitude of the residual carrier are calculated for the first and second compensation coefficients ( 3 ) from the results stored in the second, third and fourth method steps, and wherein the second, third, fourth and fifth method steps are repeated using these improved compensation coefficients ( 3 ) until at least one of the error of the amplitude and a phase response of the I/Q modulator ( 1 ) lies below a defined threshold value or a defined number of run-throughs of the method is reached.