Systems and methods for improved VCO gain tracking loop
OwnerJames A. Crawfordinventor
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Abstract
Methods and apparatus for calibrating the VCO element of a phase-locked loop to correct for non-linearities are disclosed. The modulation port of the VCO may be characterized to generate a tuning model, which may then be used to generate a correction signal to be combined with an input signal and applied to the VCO modulation port. The tuning model may be based on a third or higher order polynomial generated from a plurality of open-loop frequency measurements of the VCO.
Claims17
Apparatus for calibrating the gain of a voltage controlled oscillator (VCO) in a phase-locked loop (PLL), comprising:
- tuning characteristic measurement logic to measure a tuning characteristic of the VCO;
- tuning model generation logic to generate a tuning model based on the tuning characteristic;
- and
- correction generation logic to generate a correction signal based on the tuning model;
- wherein the tuning characteristic measurement logic to measure a tuning characteristic comprises logic to determine a set of open loop frequency characteristics of the VCO at ones of a plurality of applied test frequencies.
Apparatus for calibrating the gain of a voltage controlled oscillator (VCO) in a phase-locked loop (PLL), comprising:
- tuning characteristic measurement logic to measure a tuning characteristic of the VCO;
- tuning model generation logic to generate a tuning model based on the tuning characteristic;
- correction generation logic to generate a correction signal based on the tuning model;
- and
- logic to:
- apply the correction signal to a VCO input signal to generate a calibrated VCO input signal;
- and
- couple the calibrated VCO input signal to a modulation port of the VCO.
Apparatus for calibrating the gain of a voltage controlled oscillator (VCO) in a phase-locked loop (PLL), comprising:
- tuning characteristic measurement logic to measure a tuning characteristic of the VCO;
- tuning model generation logic to generate a tuning model based on the tuning characteristic;
- and
- correction generation logic to generate a correction signal based on the tuning model;
- wherein the tuning characteristic measurement logic to measure the tuning characteristic comprises:
- a voltage generator configured to generate a set of digital test frequency signals corresponding to a plurality of open loop frequencies to be applied to the VCO;
- a frequency modulation digital to analog converter (DAC) configured to convert the digital frequency test signals to an analog test frequency signal;
- a low pass filter (LPF) coupled to the DAC and the VCO to filter the analog test frequency signal;
- and
- a coarse tuning and frequency measurement state machine coupled to the VCO, said state machine configured to measure a set of open loop frequencies provided by an output of the VCO and store the set of open loop frequency measurements in correspondence with the set of voltage test signals.
A method of operating a phase-locked loop, comprising:
- determining a set of adjustment values for use in linearizing the gain tuning characteristics of a VCO component of the phase-locked loop;
- combining the adjustment values with a frequency modulation signal to generate a calibrated frequency modulation signal;
- and
- applying the calibrated frequency modulation signal to a VCO modulation port;
- wherein the determining a set of adjustment values comprises:
- applying, at ones of a plurality of test frequency levels, ones of a corresponding plurality of frequency test signals to the VCO modulation port;
- allowing the VCO output frequency to settle;
- resetting a frequency counter coupled to a VCO output;
- enabling the frequency counter for a predefined time duration;
- reading the frequency counter count value after expiration of the predefined time duration so as to generate a set open loop frequency test data;
- and
- storing the frequency test data and the corresponding test frequency levels.
A method of calibrating the gain of a VCO, comprising:
- configuring the VCO in an open-loop configuration;
- applying ones of a plurality of frequency test signals to the VCO to generate a corresponding set of VCO tuning characteristics;
- generating a VCO tuning model based on the VCO tuning characteristics;
- and
- generating a VCO correction signal based on the VCO tuning model.
Dependencies are inferred from the claim text.