Method and apparatus for multi-point calibration for synthesizing varying frequency signals
View Patent ↗A fast settling frequency synthesizer is disclosed. The particular capacitor to frequency relationship in the band of operation is first determined. The calculation can be performed by determining the capacitor to frequency relationship at two points and calculating the slope. Once these parameters are known, then, for any change in frequency due to a channel hop, the appropriate capacitor value can be determined.
1. A method of setting a frequency of a frequency synthesizer in a system comprising:
setting a first value for a capacitor to control the frequency synthesizer to generate a signal at a first frequency of the frequency synthesizer;
setting a second value for the capacitor to control the frequency synthesizer to generate the signal at a second frequency;
determining a first mathematical relation between the first value of the capacitor and the first frequency;
determining a second mathematical relation between the second value of the capacitor and the second frequency;
using the first mathematical relation and the second mathematical relation to determine values of the capacitor for a range of frequencies which the frequency synthesizer can be set to generate.
2. The method of claim 1 wherein a band of operation comprises at least one of Bluetooth, 5 GHz or 60 GHz.
3. The method of claim 1 , wherein the first frequency is set higher than a band of operation.
4. The method of claim 1 , wherein the first frequency and the second frequency are fine tuned to find a point of transition of the value of the capacitor.
5. The method of claim 1 , wherein the first value or second value of the capacitor is determined by a binary search.
6. The method of claim 1 , wherein the frequency synthesizer includes a state machine.
7. The method of claim 1 , wherein a difference between the first value of capacitor and second value of capacitor comprises a power of two.
8. The method of claim 7 wherein the power of two comprises 16.
9. The method of claim 1 , wherein the first and second mathematical relations comprise linear relations.
10. The method of claim 1 wherein the system comprises a radio frequency transceiver.
11. A frequency synthesizer apparatus in a system comprising:
a voltage controlled oscillator (VCO) with a varactor;
a phase comparator;
a feedback path between the VCO and the phase comparator with a frequency divider;
a first state machine, wherein the first state machine comprises elements to set a first value of a capacitor associated with the VCO, determine a first frequency for the first value of the capacitor, set a second value of the capacitor, determine a second frequency for the second value of the capacitor, determine a first mathematical relation between the first capacitor value and the first frequency, and determine a second mathematical relation between the second capacitor value and the second frequency; and
a second state machine, wherein the second state machine comprises elements for using the first mathematical relation and the second mathematical relation to calculate the capacitor value for a range of frequencies which the frequency synthesizer can be set to generate.
12. The apparatus of claim 11 , wherein the first and second mathematical relations comprise linear relations.
13. The apparatus of claim 11 , wherein a band of operation comprises at least one of Bluetooth, 5 GHz or 60 GHz.
14. The apparatus of claim 11 , wherein the first frequency is set higher than a band of operation.
15. The apparatus of claim 11 , wherein the first frequency and the second frequency are fine tuned to find a point of transition of the value of the capacitor.
16. The apparatus of claim 11 , wherein the first value or second value of the capacitor is determined by a binary search.
17. The apparatus of claim 11 , wherein the varactor comprises a MOS transistor.
18. The apparatus of claim 11 , wherein a difference between the first value of the capacitor and second value of the capacitor comprises a power of two.
19. The apparatus of claim 18 , wherein the power of two comprises 16.
20. The apparatus of claim 11 , wherein the system comprises a radio frequency transceiver.
21. The apparatus of claim 11 , wherein:
during a calibration mode of the frequency synthesizer apparatus, the first state machine comprises elements to set the first value of the capacitor associated with the VCO, determine the first frequency for the first value of the capacitor, set the second value of the capacitor, determine the second frequency for the second value of the capacitor, determine the first mathematical relation between the first capacitor value and the first frequency, and determine the second mathematical relation between the second capacitor value and the second frequency; and
during the calibration mode of the frequency synthesizer apparatus, the second state machine comprises elements for using the first mathematical relation and the second mathematical relation to calculate the capacitor value for the range of frequencies which the frequency synthesizer can be set to generate.
22. The apparatus of claim 11 , wherein the first state machine comprising elements to set the second value of the capacitor comprises the first state machine comprising elements to increase a setting for the capacitor by a predefined power to the second value to control the frequency synthesizer apparatus to generate a signal at the second frequency.
23. One or more non-transitory machine-readable storage media having instructions stored therein, which when executed by one or more processors causes the one or more processors to perform operations that comprise:
setting a first value for a capacitor to control a frequency synthesizer to generate a signal at a first frequency of the frequency synthesizer;
setting a second value for the capacitor to control the frequency synthesizer to generate the signal at a second frequency;
determining a first mathematical relation between the first value of the capacitor and the first frequency;
determining a second mathematical relation between the second value of the capacitor and the second frequency;
using the first mathematical relation and the second mathematical relation to determine values of the capacitor for a range of frequencies which the frequency synthesizer can be set to generate.
24. The machine-readable storage media of claim 23 , wherein the first frequency is set higher than a band of operation.
25. The machine-readable storage media of claim 23 , wherein the first frequency and the second frequency are fine tuned to find a point of transition of the value of the capacitor.
26. The method of claim 1 , wherein said determining and using the first mathematical relation and the second mathematical relation to determine values of the capacitor for the range of frequencies which the frequency synthesizer can be set to generate is performed during a calibration mode of the frequency synthesizer.
27. The method of claim 1 , wherein said setting the second value for the capacitor to control the frequency synthesizer to generate the signal at the second frequency comprises increasing a setting for the capacitor by a predefined power to the second value to control the frequency synthesizer to generate the signal at the second frequency.