Abstract: A transmitter circuit means is arranged to provide linear amplification of non-constant envelope modulated RF signals by directly amplitude modulating the transmitter power amplifier with the amplitude component of the baseband signal. In addition, the signal to be transmitted is phase modulated by the In-phase and quadrature components of the baseband signal, and synchronization means arc provided in order to correct any time slippage between the directly applied amplitude modulation and the phase modulation. The modulation synchronisation correction contributes significantly to the linearity of the transmitter.