Two-point modulator with matching gain calibration

A method for use in connection with the operation of a two-point modulator which includes a modulation path for generating a modulation voltage for application to a voltage controlled oscillator of a locked loop circuit, comprising the steps of:

• phase-frequency comparing a reference frequency signal of the locked loop circuit to a feedback frequency signal of the locked loop circuit to generate a voltage control signal applied to an input of the voltage controlled oscillator;
• phase comparing the reference frequency signal of the locked loop circuit to the feedback frequency signal of the locked loop circuit to generate a phase detect signal;
• adjusting a gain of the modulation path for generating the modulation voltage as a function of at least the phase detect signal;
• and
• adding the modulation voltage to the voltage control signal.

A modulation circuit, comprising:

• a locked loop circuit with two-point modulation control comprising a first modulation control point at an input of a voltage controlled oscillator and a second modulation control point at an input of a controllable divider, said locked loop circuit including a phase-frequency detector configured to compare a reference frequency signal with a feedback frequency signal output from the controllable divider;
• a two-point modulation control circuit including a first modulation path having a controllable gain and coupled to one of the first and second modulation control points and having a second modulation path coupled to another of the first and second modulation control points;
• a calibration circuit comprising:
• a phase detector circuit configured to compare the reference frequency signal with the feedback frequency signal to generate a phase detect signal;
• and
• a gain control circuit configured to adjust the controllable gain of the first modulation path as a function of at least the phase detect signal.

A method for use in connection with the operation of a two-point modulator which includes a modulation path for generating a modulation voltage for application to a voltage controlled oscillator of a locked loop circuit, comprising the steps of:

• oversampling input modulation data to generate oversampled modulation data;
• detecting a sign of the oversampled modulation data to generate a sign signal;
• phase comparing a reference frequency signal of the locked loop circuit to a feedback frequency signal of the locked loop circuit to generate a phase detect signal;
• correlating the phase detect signal to the sign signal to generate a gain control signal, wherein values of the sign signal correspond to the input modulation data;
• and
• adjusting a gain of the modulation path for generating the modulation voltage as a function of at least the gain control signal.

A modulation circuit, comprising:

• a locked loop circuit comprising:
• a voltage controlled oscillator configured to output an output frequency signal;
• a phase-frequency detector configured to compare a reference frequency signal with a feedback frequency signal derived from the output frequency signal to generate a voltage control signal;
• and
• a summing circuit configured to add a first modulation control signal to the voltage control signal for application to an input of voltage controlled oscillator;
• and
• a calibration circuit comprising:
• a phase detector circuit configured to compare the reference frequency signal with the feedback frequency signal to generate a phase detect signal;
• a circuit configured to generate the first modulation control signal in response to input modulation data, wherein a gain of the first modulation control signal is set by a gain control signal;
• and
• a gain control circuit configured to generate the gain control signal as a function of the phase detect signal.