Error compensating voltage controlled oscillator

In a system that requires at least one voltage controlled oscillator having (i) a nominal frequency that is produced in response to a given voltage and (ii) a corresponding voltage-to-frequency transfer function, a method of dynamically calibrating the at least one voltage controlled oscillator during initialization or at one or more subsequent times to compensate for variation, from one voltage controlled oscillator to another, in the given voltage that produces the nominal frequency, the corresponding voltage-to-frequency transfer function, or both, the method comprising:

• a step for obtaining one or more reference frequency counts;
• a step for obtaining a plurality of variable frequency counts from a said at least one voltage controlled oscillator that produces a variable frequency in response to more a plurality or control input voltages;
• a step for, based on the one or more reference frequency counts and the variable frequency count, determining a specific one of the control input voltages that produces a nominal output frequency for said at least one voltage controlled oscillator;
• a step for, based on the iteratively obtained variable frequency counts, generating a table that represents at least a portion of a voltage-to-frequency transfer function of said at least one voltage controlled oscillator, wherein the specific one of the control input voltages that produces a nominal output frequency represents a zero point in the table;
• and
• a step for using the stored transfer function to calibrate the output of said at least one voltage controlled oscillator one or more times.

In a system that includes at least one voltage controlled oscillator having (i) a nominal frequency that is produced in response to a given voltage and (ii) a corresponding voltage-to-frequency transfer function, a method of calibrating the at least one voltage controlled oscillator to compensate for variation, from one voltage controlled oscillator to another, in the given voltage that produces the nominal frequency, the corresponding voltage-to-frequency transfer function, or both, even though the given voltage that produces the nominal frequency and the corresponding voltage-to-frequency transfer function for the at least one voltage controlled oscillator are within specified tolerances, the method comprising steps for:

• obtaining a reference frequency count;
• iteratively obtaining a plurality of variable frequency counts corresponding to a plurality of control input voltages;
• generating a table based on the iteratively obtained variable frequency counts, wherein the table represents at least a portion of a voltage-to-frequency transfer function of the selected voltage controlled oscillator;
• for each of one or more of the plurality of control input voltages that produces a frequency greater than the nominal output frequency, storing the corresponding control input voltage in a portion of the table that identifies one or more control input voltages producing frequencies greater than the nominal output frequency;
• for each of one or more of the plurality of control input voltages that produces a frequency less than the nominal output frequency, storing the corresponding control input voltage in a portion of the table that identifies one or more control input voltages producing frequencies less than the nominal output frequency;
• retrieving at least two entries from the table, wherein each of the at least two entries includes a control input voltage and a corresponding frequency;
• deriving an intermediate control input voltage from the at least two entries;
• applying the intermediate control input voltage to the selected voltage controlled oscillator;
• and
• based on the reference frequency count and the variable frequency count, determining if a specific one of the one or more control input voltages produces a nominal output frequency for the selected voltage controlled oscillator.

In a system that includes at least one voltage controlled oscillator having (i) a nominal frequency that is produced in response to a given voltage and (ii) a corresponding voltage to frequency transfer function, a method of calibrating the at least one voltage controlled oscillator to compensate for variation, from one voltage controlled oscillator to another, in the given voltage that produces the nominal frequency, the corresponding voltage to frequency transfer function, or both, even though the given voltage that produces the nominal frequency and the corresponding voltage to frequency transfer function for the at least one voltage controlled oscillator are within specified tolerances, the method comprising acts of:

• counting a reference frequency over a first time interval;
• applying a specific one of one or more control input voltages to a selected voltage controlled oscillator;
• counting a variable frequency produced by the selected voltage controlled oscillator in response to the specific one of the one or more control input voltages, wherein the counting occurs over a second time interval;
• calculating the variable frequency from the reference frequency count, the variable frequency count, the first and second time intervals, and the reference frequency;
• comparing the variable frequency to the nominal frequency to determine if the specific one of the one or more control input voltages produces a nominal output frequency for the selected voltage controlled oscillator;
• retrieving at least two entries from a table, wherein each of the at least two entries includes a control input voltage and a corresponding frequency;
• interpolating between the at least two entries to derive an intermediate control input voltage;
• and
• applying the intermediate control input voltage to the selected voltage controlled oscillator.