A signal processor has an input terminal and an output terminal for use in
a wireless transmitter, for generating a radio frequency signal suitable
for transmission, either with or without further power amplification. The
signal processor separates an input signal into first and second
processing paths, the first processing path generating a pulse train
signal which is a digitised envelope signal, and the second processing
path comprising phase processing means operable to generate a constant
envelope phase signal. An RF switch is operable to switch the phase
signal by means of the pulse train signal.