An ultra-wideband pulse generator, for radio communication at frequencies of 2 to 11 GHz comprises an oscillator providing an output signal at carrier frequency F0 followed by a radiofrequency switching transistor and a control circuit controlling the gate of the transistor to turn it on for duration T corresponding to the desired duration of a UWB pulse. The control circuit is arranged to successively apply, during the same UWB pulse, a first gate voltage turning the transistor on with first internal resistance value for a first part of duration T, a second gate voltage that turns the transistor on with second internal resistance value, different from the first, for a second part of duration T. These internal resistances cause the oscillation to be attenuated differently for duration T of the pulse, allowing the spectrum of the pulse to maintain it within the spectral templates imposed by the radio communication standards.