To provide a radio frequency signal generator that can generate a broadband fluctuated envelope radio frequency signal with less noise.

This radio frequency amplifier uses an offset phase locked loop to generate a radio frequency signal from a base band signal. In order that the phase locked loop can process a signal with a prescribed amplitude, the signal is given to limiters 5, 19 before being applied to a phase comparator 6. Applying envelope modulation (16) to an output of an RF amplifier stage 11 can restore an envelope.