A transmitter comprises a device (20) for frequency up-conversion of a communication signal having at least two consecutive frequency conversion stages, a power amplifier (27) for amplifying the output signal therefrom for obtaining a transmission signal and means (29) for extracting the transmission signal. It also has a device for frequency down-conversion of said extracted transmission signal to the same frequency as the communication signal before said up-conversion for creating a feedback signal. Said two devices use the same local oscillators (25, 26). The transmitter also has means for signal parameter adaptation of the communication signal on basis of the feedback signal for obtaining a desired character of the transmission signal. The frequency down-conversion device comprises a local oscillator combiner (30) producing a combined frequency signal used for frequency down-conversion of the transmission signal reducing the number of conversion stages in the path of the extracted transmission signal with respect to the corresponding number of the frequency up-conversion device.