Verfahren zur Steuerung eines mit einem Modulationseingang versehenen Frequenzsynthetisierers

The frequency synthesizer comprises a voltage-controlled oscillator (VCO) followed by a phase-lock loop (PLL) itself followed by a first low-pass filter (LP1) which delivers a servo-control signal (A). The oscillator receives as control signal a combination of the servo-control signal (A) and of a modulation signal applied to the modulation input (I), the synthesizer including at least one additional filter (LP2,...LPn) and means for substituting the additional filter (LP2,...LPn) for the first filter (LP1) in response to a selection signal. It is characterised in that the selection signal is produced by a selection module (T) from an identification signal (J) identifying which of the filters (LP1,...LPn) is to be introduced between the phase-lock loop (PLL) and the oscillator (VCO), depending on the nature of the modulation signal.