Delta-sigma based dual-port modulation scheme and calibration techniques for similar modulation schemes

A PLL frequency synthesizer for generating a frequency modulated output signal, comprising:

• a phase locked loop circuit for generating an output signal at a predetermined frequency band and having a controlled oscillator, a reference frequency source, a phase/frequency detector, a loop filter and a frequency divider in a feedback path of a loop;
• a digital Δ-Σ modulator having an input for a clock signal from either one of the frequency divider and the reference frequency source, for controlling a division ratio of the frequency divider;
• a modulation circuit for applying an analog modulation signal to the input of the Δ-Σ modulator and for adding simultaneously the analog modulation signal to an input of the controlled oscillator, the modulation circuit having a digital-to-analog converter for adding an analog signal corresponding to the analog modulation signal to the input of the controlled oscillator;
• an analog-to-digital converter for applying a digital modulation signal corresponding to the analog modulation signal to the input of the Δ-Σ modulator;
• a gain adjusting mechanism in a high frequency modulation path for adjusting a level of the modulation signal being added to the input of the controlled oscillator to set a desired frequency deviation at an output of the controlled oscillator in response to a calibration signal;
• and
• a calibration circuit for generating the calibration signal in response to outputs of the reference frequency source and the frequency divider.

A PLL frequency synthesizer for generating a frequency modulated output signal, comprising:

• a phase locked loop circuit for generating an output signal at a predetermined frequency band and having a controlled oscillator, a reference frequency source, a phase/frequency detector, a loop filter and a frequency divider in a feedback path of a loop;
• a digital Δ-Σ modulator having an input and for taking in a clock signal from either one of the frequency divider and the reference frequency source, for controlling a division ratio of the frequency divider;
• a modulation circuit for applying an analog modulation signal to the input of the Δ-Σ modulator and for adding simultaneously the analog modulation signal to an input of the controlled oscillator;
• an analog-to-digital converter for applying a digital modulation signal corresponding to the analog modulation signal to the input of the Δ-Σ modulator;
• a gain adjusting mechanism in a high frequency modulation path for adjusting a level of the modulation signal being added to the input of the controlled oscillator to set a desired frequency deviation at an output of the controlled oscillator in response to a calibration signal;
• and
• a calibration circuit for generating the calibration signal in response to outputs of the reference frequency source and the frequency divider.

A method of generating a frequency modulated output signal, comprising steps of:

• generating an output signal by the phase locked loop circuit which includes a controlled oscillator, a reference frequency source, a phase frequency detector, a loop filter and a frequency divider in a feedback path of a loop;
• providing a modulation signal;
• adding the modulation signal simultaneously to an input of the controlled oscillator and to an input of a Δ-Σ modulator which takes in a clock from either one of the reference frequency source and the frequency divider, for controlling a division ratio of the divider in the feedback path of the loop to modulate the output of the phase locked loop circuit by the modulation signal;
• generating a calibration signal in response to the output of the controlled oscillator relative to the reference frequency;
• and
• applying the calibration signal to set the level of the modulation signal applied to the input of the controlled oscillator by way of a setting mechanism for calibrating a gain of a high frequency path.

A method of generating a frequency modulated output signal using a dual port modulation scheme of a phase lock loop circuit, comprising steps of:

• generating an output signal by the phase locked loop circuit which includes a controlled oscillator, a reference frequency source, a phase frequency detector, a loop filter and a frequency divider in a feedback path of a loop;
• providing a digital modulation signal;
• converting the digital modulation signal to an analog modulation signal;
• simultaneously adding the analog modulation signal to an input of the controlled oscillator and the digital modulation signal to an input of a digital Δ-Σ modulator which takes in a clock from either one of the following, the reference frequency source or the frequency divider, for controlling a division ratio of the divider in the feedback path of the loop to modulate the output of the phase locked loop circuit by the modulation signal;
• generating a calibration signal in response to the output of the controlled oscillator relative to the reference frequency;
• and
• applying the calibration signal to set the level of the modulation signal applied to the input of the controlled oscillator by way of a setting mechanism for calibrating a gain of a high frequency path.

A method of generating a frequency modulated output signal, comprising steps of:

• generating an output signal by the phase locked loop circuit which includes a controlled oscillator, a reference frequency source, a phase frequency detector, a loop filter and a frequency divider in a feedback path of a loop;
• providing an analog modulation signal;
• converting the analog modulation signal to a digital modulation signal;
• simultaneously adding the analog modulation signal to an input of the controlled oscillator and the digital modulation signal to an input of a digital Δ-Σ modulator which takes in a clock from either one of the reference frequency source and the frequency divider, for controlling a division ratio of the divider in the feedback path of the loop to modulate the output of the phase locked loop circuit by the modulation signal;
• generating a calibration signal in response to the output of the controlled oscillator relative to the reference frequency;
• and
• applying the calibration signal to set the level of the modulation signal applied to the input of the controlled oscillator by way of a setting mechanism for calibrating a gain of a high frequency path.