Method and apparatus for calibrating frequency

• US 20120229178A1
• Filed: 03/07/2012
• Published: 09/13/2012
• Est. Priority Date: 03/08/2011
• Status: Abandoned Application

• Current Assignee: Rfdot Microelectronics, Inc.
• Original Assignee: Rfdot Microelectronics, Inc.
• Inventors: Feng, Xiangguang, Gu, Qilong, Yu, Qi
• Application Number:
  US13/414,540
• Publication Number:
  US 20120229178A1
• Time in Patent Office: Days
• US Class Current: 327/115
• CPC Class Codes: G04G 3/04 Temperature-compensating arrangements

Abstract

Methods and apparatuses for calibrating frequency are provided according to the embodiment of the present disclosure. A method for calibrating frequency may comprise: providing an actual frequency of a reference frequency signal and a frequency offset between the actual frequency of the reference frequency signal and the expected frequency of the reference frequency signal; determining a frequency division ratio according to the frequency of a target frequency signal and the expected frequency of the reference frequency signal; determining a calibration value of the frequency division ratio according to the frequency offset; providing a calibrated frequency division ratio by calibrating the frequency division ratio according to the calibration value; and providing the target frequency signal by dividing the frequency of the reference frequency signal according to the calibrated frequency division ratio.

Claims

1. A method of calibrating frequency, the method comprising:

providing an actual frequency of a reference frequency signal and a frequency offset between the actual frequency of the reference frequency signal and an expected frequency of the reference frequency signal;

determining a frequency division ratio according to the frequency of a target frequency signal and the expected frequency of the reference frequency signal;

determining a calibration value of the frequency division ratio according to the frequency offset;

providing a calibrated frequency division ratio by calibrating the frequency division ratio according to the calibration value; and

providing the target frequency signal by dividing the frequency of the reference frequency signal according to the calibrated frequency division ratio.

2. A method as recited in claim 1, wherein the frequency division ratio is the ratio between the expected frequency of the reference frequency signal and the frequency of the target frequency signal;

wherein the calibration value includes an integral calibration value and a fractional calibration value;

wherein the step for providing the calibrated frequency division ratio by calibrating the frequency division ratio according to the calibration value comprises the steps of;

providing the integral part of the calibrated frequency division ratio by adding or subtracting the frequency division ratio from the integral calibration value; and

taking the fractional calibration value as the residual part of the calibrated frequency division ratio.

3. A method as recited in claim 2, wherein providing the target frequency signal by dividing the frequency of the reference frequency signal according to the calibrated frequency division ratio comprises:

providing a counting value by counting the cycles of the reference frequency signal; and

starting one cycle of the target frequency signal when the counting value starts from an initial value, and ending the cycle of the target frequency signal when the counting value reaches to the integral part of the calibrated frequency division ratio, and re-counting the cycles of the reference frequency signal from the initial value to generate the next cycle of the target frequency signal;

wherein, when one cycle of the target frequency signal is generated, the fractional calibration value is added to the residual part of the calibrated frequency division ratio, and, after accumulated residues reaches an integer value, a post-carry integral part of the calibrated frequency division ratio is provided by adding a carry from the integer value to the integral part of the calibrated frequency division ratio, and the fractional calibration value is continuously added to the new residual part of the calibrated frequency division ratio;

after one cycle of the target frequency signal is generated according to the post-carry integral part of the calibrated frequency division ratio, the post-carry integral part of the calibrated frequency division ratio is reset to the initial integral value.

4. A method as recited in claim 2, wherein the integral calibration value and the fractional calibration value is determined according to, respectively, the number of cycles and the residue cycles of the expected frequency within 1/f_t of the frequency offset;

wherein f_t is the frequency of the target frequency signal.

5. A method as recited in claim 1, wherein the frequency division ratio is equal to one half of the ratio between the expected frequency of the reference frequency signal and the frequency of the target frequency signal, and the calibration value includes an integral calibration value and a fractional calibration value;

wherein the step of providing calibrated frequency division ratio by calibrating frequency division ratio according to the calibration value comprises the steps of;

providing the integral part of the calibrated frequency division ratio by adding or subtracting the integral calibration value to or from the frequency division ratio; and

providing the fractional calibration value as the residual part of the calibrated frequency division ratio.

6. A method as recited in claim 5, wherein providing the target frequency signal by dividing the frequency of the reference frequency signal according to the calibrated frequency division ratio comprises:

providing a counting value by counting the cycles of the reference frequency signal; and

inverting the target frequency signal when the count value reaches the calibrated frequency division ratio, and recounting the cycles of the reference frequency signal by starting from an initial value of the counting value;

wherein, after a half cycle of the target frequency signal is generated, the fractional calibration value is added to the residual part of the calibrated frequency division ratio, and, after accumulated residues reach an integer value, a post-carry integer of the calibrated frequency division ratio is provided by adding a carry from the integer value to the integral part of the calibrated frequency division ratio, and the fractional calibration value is continuously added to the new residual part of the calibrated frequency division ratio;

wherein, after one half cycle of target frequency signal is generated according to the post-carry integral part of the calibrated frequency division ratio, the post-carry integral part of the calibrated frequency division ratio is reset to the initial integral value.

7. A method as recited in claim 5, wherein the integral calibration value and the fractional calibration value are determined according to, respectively, the number of double cycles and the residue of double cycles of the expected frequency within ½

f_t of the frequency offset;

wherein f_t is the frequency of the target frequency signal.

8. An apparatus for calibrating frequency, comprising:

a first module, configured to acquire a temperature of a crystal oscillator and provide the temperature;

a second module, configured to provide the actual frequency of a reference frequency signal from the crystal oscillator;

a third module, configured to provide a frequency offset between the actual frequency of the reference frequency signal and the expected frequency of the reference frequency signal according to the temperature; and

a fourth module, configured to determine a frequency division ratio according to the frequency of the target frequency signal and the expected frequency of the reference frequency signal, determine a calibration value of the frequency division ratio according to the frequency offset, provide the calibrated frequency division ratio by calibrating the frequency division ratio according to the calibration value, and determine the target frequency signal by dividing the frequency of the reference frequency signal according to the calibrated frequency division ratio.

9. An apparatus as recited in claim 8, wherein the frequency division ratio is the ratio between the expected frequency of the reference frequency signal and the frequency of the target frequency signal and the calibration value comprises an integral calibration value and a fractional calibration value;

wherein providing the calibrated frequency division ratio by calibrating the frequency division ratio according to the calibration value comprises;

providing the integral part of the calibrated frequency division ratio by adding or subtracting the integral calibration value to or from the frequency division ratio; and

providing the fractional calibration value as the residual part of the calibrated frequency division ratio.

10. An apparatus as recited in claim 9, wherein the step of determining the target frequency signal by dividing the frequency of the reference frequency signal according to the calibrated frequency division ratio comprises:

providing a counting value by counting the cycles of the reference frequency signal;

starting one cycle of the target frequency signal when the counting value starts from an initial value, and ending the cycle of the target frequency signal when the counting value reaches the integral part of the calibrated frequency division ratio; and

re-counting the cycles of the reference frequency signal from the initial value to generate the next cycle of the target frequency signal;

wherein, when a cycle of the target frequency signal is generated, the fractional calibration value is added to the residual part of the calibrated frequency division ratio, and, after accumulated residues reaches an integer value, a post-carry integral part of the calibrated frequency division ratio is provided by adding a carry from the integer value to the integral part of the calibrated frequency division ratio, and the fractional calibration value is continuously added to the new residual part of the calibrated frequency division ratio;

wherein, after one cycle of the target frequency signal is obtained according to the post-carry integral part of the calibrated frequency division ratio, the post-carry integral part of the calibrated frequency division ratio is reset to the initial integral part of the calibrated frequency division ratio.

11. An apparatus as recited in claim 9, wherein the integral calibration value and the fractional calibration value are determined according to, respectively, the number of cycles and the residue cycles of the expected frequency within 1/f_t of the frequency offset;

wherein f_t is the frequency of the target frequency signal.

12. An apparatus as recited in claim 8, wherein the frequency division ratio is equal to one half of the ratio between the expected frequency of the reference frequency signal and the frequency of the target frequency signal, and the calibration value includes an integral calibration value and a fractional calibration value;

wherein providing calibrated frequency division ratio by calibrating frequency division ratio according to the calibration value comprises;

providing the integral part of the calibrated frequency division ratio by adding or subtracting the integral calibration value to or from the frequency division ratio; and

providing the fractional calibration value as the residual part of the calibrated frequency division ratio.

13. An apparatus as recited in claim 12, wherein providing the target frequency signal by dividing the frequency of the reference frequency signal according to the calibrated frequency division ratio comprises:

providing a counting value by counting the cycles of the reference frequency signal; and

inverting the target frequency signal when the count value reaches the calibrated frequency division ratio, and recounting the cycles of the reference frequency signal by starting from an initial value of the counting value;

wherein, after a half cycle of the target frequency signal is generated, the fractional calibration value is added to the residual part of the calibrated frequency division ratio, and, after accumulated residues reach an integer value, a post-carry integer of the calibrated frequency division ratio is provided by adding a carry from the integer value to the integral part of the calibrated frequency division ratio, and the fractional calibration value is continuously added to the new residual part of the calibrated frequency division ratio;

wherein, after one half cycle of target frequency signal is generated according to the post-carry integral part of the calibrated frequency division ratio, the post-carry integral part of the calibrated frequency division ratio is reset to the initial integral value.

14. An apparatus as recited in claim 12, wherein the integral calibration value and the fractional calibration value are determined according to, respectively, the number of double cycles and the residue of double cycles of the expected frequency within ½

f_t of the frequency offset;

wherein f_t is the frequency of the target frequency signal.