Switch-modulation of a radio-frequency power amplifier by-representing the input signal by the I-signal (1) and Q-signal (9) of the complex components (I+j−Q), and pulse width modulating the I-signal and the Q-signal separately to create a modulated I-signal pulse sequence (3a) and a modulated Q-signal pulse sequence (3b). Further, the pulses corresponding to negative sample values are time-shifted relative the pulses corresponding to positive sample values, and each pulse of the I-signal pulse sequence is delayed by introducing a delaying time shift.