Phase-locked loop frequency synthesizer

A frequency synthesizer including a phase regulation loop including:

• a voltage-controlled oscillator;
• a reference oscillator;
• a phase-locked loop receiving as inputs an output signal from said voltage-controlled oscillator and an output signal from said reference oscillator,
• delivering at its output a control voltage to an input of said voltage-controlled oscillator, and
• including a phase comparator connected directly to the output of said reference oscillator and to an output of said voltage-controlled oscillator via a feedback loop including a counter-divider;
• means for feeding a modulation signal between said phase comparator and the input of said voltage-controlled oscillator;
• modulation compensation means for preparing a compensation signal from said modulation signal and for feeding said compensation signal into said feedback loop upstream of said counter-divider to cancel modulation of a synthesizer output signal, at the output of said voltage-controlled oscillator, applied to an input of said counter-divider;
• determination means for determining the real gain of said voltage-controlled oscillator from at least one measurement parameter, wherein said determination means are adapted to deliver a signal representative of the real gain of said voltage-controlled oscillator;
• divider means having a first input adapted to receive from said determination means the signal representative of the real gain of said voltage-controlled oscillator, and a second input adapted to receive said modulation signal;
• and
• an output delivering said modulation signal, divided by said real gain of said voltage-controlled oscillator, to an input of a summation circuit connected between the input of said voltage-controlled oscillator and a loop filter connected between the output of said phase comparator and the input of said voltage-controlled oscillator.