Abstract: A synthesizer including a voltage-controlled oscillator, a phase-frequency comparator, a variable-rank frequency divider, a command device to control the oscillation frequency of the voltage-controlled oscillator on a frequency which is a multiple of the frequency of the reference signal as a function of the rank of division of the variable-rank frequency divider. The phase-frequency comparator circuit sends a first series and a second series of pulses as a function of the phase advance or delay respectively of the signals applied to its first and second inputs, to charge or discharge an integration capacitor and provide a signal commanding the advance or delay of the frequency and phase of the oscillator as a function of the voltage developed at the terminals of the capacitor.