Method of controlling a frequency-modulated oscillator of a phase-locked loop circuit

A method of controlling a frequency-modulated oscillator of a phase-locked loop circuit, the method comprising the steps of:

• switching a coarse capacitor of a coarse bank of capacitors of the oscillator to change an output frequency of an output signal of the oscillator from a first frequency to a second frequency;
• determining a coarse frequency information associated with the coarse capacitor and based on at least one of the first frequency and the second frequency;
• writing the coarse frequency information to a look-up table stored in a control unit of the oscillator;
• for a fixed state of the coarse bank of capacitors, subsequently switching at least one fine capacitor of a fine bank of capacitors of the oscillator so that, for every fine capacitor being switched, the output frequency changes from a respective first fine frequency to a respective second fine frequency, wherein fine capacitors of the fine bank of capacitors have capacitances smaller than the capacitances of the coarse capacitors;
• for every fine capacitor being switched, determining a respective fine frequency information associated with the respective fine capacitor and based on at least one of the respective first fine frequency and the respective second fine frequency;
• for every fine capacitor being switched, writing the respective fine frequency information to the look-up table;
• determining a total fine frequency difference between a state, when all fine capacitors are switched in for the fixed state of the coarse bank, and a state, when all fine capacitors are switched out for the fixed state of the coarse bank;
• for a further fixed state of the coarse bank different from the fixed state of the coarse bank, determining a further total fine frequency difference between a state, when all fine capacitors are switched in for the further fixed state of the coarse bank, and a state, when all fine capacitors are switched out for the further state of the coarse bank;
• determining a scaling factor for the further fixed state of the coarse bank based on the ratio between the total fine frequency difference and the further total fine frequency difference;
• and
• writing the scaling factor to the look-up table.

A frequency-modulated oscillator for a phase-locked loop circuit, comprising

• a bank of capacitors;
• and
• a control unit configured to
• switch a capacitor of the bank of capacitors to change an output signal of the oscillator from a first output signal having a first frequency to a second output signal having a second frequency;
• feed the first output signal having the first frequency to a divider of the phase-locked loop circuit, and control the divider by means of a first divider control signal so that a divider output signal corresponds to a reference signal having a reference frequency;
• feed the second output signal having the second frequency to the divider, and control the divider by means of a second divider control signal so that the divider output signal corresponds to the reference signal having the reference frequency;
• determine a frequency information associated with the capacitor and based on at least one of the first frequency and the second frequency and based on at least one of the first divider control signal and the second divider control signal;
• and
• write the frequency information to a look-up table stored in the control unit.