Method and apparatus for selecting a frequency generating element

• US 7,746,179 B1
• Filed: 09/12/2007
• Issued: 06/29/2010
• Est. Priority Date: 09/13/2006
• Status: Active Grant

• Current Assignee: Qorvo US, Inc. (Qorvo, Inc.)
• Original Assignee: RF Micro Devices Incorporated (Qorvo, Inc.)
• Inventors: Walker, David, Koupal, Robert, King, Nathaniel Jr.
• Primary Examiner(s): Chang; Joseph
• Assistant Examiner(s): SHIN, JEFFREY M
• Application Number:
  US11/900,691
• Time in Patent Office: 1,021 Days
• Field of Search: 331/10, 331/16, 331/44, 331/46, 331/179
• US Class Current: 331/10
• CPC Class Codes: H03L 7/0891 the up-down pulses controlling source and sink current generators, e.g. a charge pump
• CPC Class Codes: H03L 7/099 concerning mainly the controlled oscillator of the loop
• CPC Class Codes: H03L 7/113 using frequency discriminator
• CPC Class Codes: H03L 7/18 using a frequency divider or counter in the loop H03L7/20, H03L7/22 take precedence

Abstract

A method and apparatus for selecting an optimum VCO from an array of VCOs is disclosed. Each VCO in the array has an output range and a limit. In one embodiment, a search set of VCOs is designated as all VCOs in a system. The limit is compared to a tuning value which corresponds to a desired calibration frequency. The comparison divides the array of VCOs into a searched set and a non-searched set. The process is repeated until the non-searched set comprises only one VCO. In another embodiment, the VCOs are ordered such that there is a middle VCO. A VCO in the middle of the array is selected. The limit of the middle VCO is compared to a tuning limit. Based on the comparison, another VCO is selected. The process repeats N times, where N is the logarithm, base 2, of the total number of VCOs to be searched. at the end of the search, an optimum VCO will be found.

Claims

1. A method of selecting a frequency generating element from an array of M frequency generating elements, each element having an output frequency range, the range having an upper frequency limit and a lower frequency limit, wherein the upper frequency limit is higher than the lower frequency limit, corresponding to an input tuning voltage range having an upper tuning limit and a lower tuning limit comprising:

a. arranging the frequency generating elements into an order by their output frequencies, such that there is a middle frequency generating element;

b. determining a reference tuning voltage corresponding to a lowest practical gain of a frequency generating element;

c. determining a reference frequency corresponding to a lowest practical gain of a frequency generating element;

d. starting a binary search by selecting the middle frequency generating element and assigning a search variable, having an initial value of M/2;

e. comparing the reference tuning voltage to the upper tuning limit of the frequency generating element that has been selected, thereby determining a next frequency generating element to be selected;

f. dividing the search variable by two if the search variable does not equal one, thereby determining a new value for the search variable; and

g. repeating the steps of comparing and dividing for a number of iterations.

2. The method in claim 1 wherein the frequency generating element is comprised of any among a list of:

at least one VCO, a binary switchable resonator, a tunable resonator, a combination thereof, and the array of frequency generating elements is comprised of any among a list of;

an array of VCOs, an array of binary switchable resonators, an array of tunable resonators, a combination thereof.

3. The method of claim 1, wherein the step of determining a next frequency generating element comprises selecting a frequency generating element down in the order, by an increment equivalent to the search variable if the reference tuning voltage is greater than the upper tuning limit of the selected frequency generating element, otherwise selecting a frequency generating element up in the order by the increment equivalent to the search variable in the event a next iteration is performed.

4. The method of claim 3, wherein all frequency generating elements have a positive gain, the reference frequency corresponds to a high extreme operating frequency and the frequency generating elements are ordered such that the element with the highest frequency range is lowest in the order.

5. The method of claim 3, wherein all frequency generating elements have a negative gain, the reference frequency corresponds to a low extreme operating frequency, and the frequency generating elements are ordered such that the element with the lowest frequency range is lowest in the order.

6. The method of claim 1, wherein the step of determining a next frequency generating element comprises selecting a frequency generating element up in the order, by an increment equivalent to the search variable if the reference tuning voltage is greater than the upper tuning limit of the selected frequency generating element, otherwise selecting a frequency generating element down in the order by the increment equivalent to the search variable in the event a next iteration is performed.

7. The method of claim 6, wherein all frequency generating elements have a positive gain, the reference frequency corresponds to a high extreme operating frequency and the frequency generating elements are ordered such that the element with the lowest frequency range is lowest in the order.

8. The method of claim 6, wherein all frequency generating elements have a negative gain, the reference frequency corresponds to a low extreme operating frequency and the frequency generating elements are ordered such that the element with the highest frequency range is lowest in the order.

9. A method of selecting an optimum frequency generating among an array of M frequency generating elements, each frequency generating element having a range of output frequencies having an upper tuning frequency and a lower tuning frequency, wherein the upper tuning frequency is higher than the lower tuning frequency, corresponding to an input tuning voltage range having an upper tuning limit and a lower tuning limit, the method comprising:

a. arranging the frequency generating elements into an order by their output frequencies, such that there is a middle frequency generating element;

b. determining a reference tuning voltage corresponding to a lowest practical gain of a frequency generating element;

c. determining a reference frequency corresponding to a lowest practical gain of a frequency generating element;

d. starting a binary search by selecting the middle frequency generating element and assigning a search variable, having an initial value of M/2;

e. comparing the reference tuning voltage to the lower tuning limit of the frequency generating element that has been selected, thereby determining a next frequency generating element to be selected;

f. dividing the search variable by two if the search variable does not equal one, thereby determining a new value for the search variable; and

g. repeating the steps of comparing and dividing for a number of iterations.

10. The method in claim 9, wherein the frequency generating element is comprised of any among a list of:

at least one VCO, a binary switchable resonator, a tunable resonator, a combination thereof, and the array of frequency generating elements is comprised of any among a list of;

an array of VCOs, an array of binary switchable resonators, an array of tunable resonators, a combination thereof.

11. The method of claim 9, wherein the step of determining a next frequency generating element comprises selecting a frequency generating element down in the order, by an increment equivalent to the search variable if the reference tuning voltage is less than the lower tuning limit of the selected frequency generating element, otherwise selecting a frequency generating element up in the order by the increment equivalent to the search variable in the event a next iteration is performed.

12. The method of claim 11, wherein all frequency generating elements have a positive gain, the reference frequency corresponds to a low extreme operating frequency and the frequency generating elements are ordered such that the element with the lowest frequency range is lowest in the order.

13. The method of claim 11, wherein all frequency generating elements have a negative gain and the reference frequency corresponds to a high extreme operating frequency, and the frequency generating elements are ordered such that the element with the highest frequency range is lowest in the order.

14. The method of claim 9, wherein the step of determining a next frequency generating element comprises selecting a frequency generating element up in the order, by an increment equivalent to the search variable if the reference tuning voltage is greater than the lower tuning limit of the selected frequency generating element, otherwise selecting a frequency generating element down in the order by the increment equivalent to the search variable in the event a next iteration is performed.

15. The method of claim 14, wherein all frequency generating elements have a positive gain, the reference frequency corresponds to a low extreme operating frequency and the frequency generating elements are ordered such that the element with the highest frequency range is lowest in the order.

16. The method of claim 14, wherein all frequency generating elements have a negative gain, the reference frequency corresponds to a high extreme operating frequency and the frequency generating elements are ordered such that the element with the lowest frequency range is lowest in the order.

17. An electric circuit for selecting a frequency generating element from an array of M frequency generating elements, each element having an output frequency range, the range having an upper frequency limit and a lower frequency limit, wherein the upper frequency limit is higher than the lower frequency limit corresponding to an input tuning voltage range having an upper tuning limit and a lower tuning limit, comprising:

a. means for arranging the frequency generating elements into an order by their output frequencies, such that there is a middle frequency generating element;

b. means for determining a reference tuning voltage corresponding to a lowest practical gain of a frequency generating element;

c. means for determining a reference frequency corresponding to a lowest practical gain of a frequency generating element;

d. means for starting a binary search by selecting the middle frequency generating element and assigning a search variable, having an initial value of M/2;

e. means for comparing the tuning voltage to the upper tuning limit of the frequency generating element that has been selected, thereby determining a next frequency generating element to be selected;

f. means for dividing the search variable by two if the search variable does not equal one, thereby determining a new value for the search variable; and

g. means for repeating the steps of comparing and dividing for a number of iterations.

18. The electric circuit in claim 17, wherein the frequency generating element is comprised of any among a list of:

at least one VCO, a binary switchable resonator, a tunable resonator, a combination thereof, and the array of frequency generating elements is comprised of any among a list of;

an array of VCOs, an array of binary switchable resonators, an array of tunable resonators, a combination thereof.

19. The electric circuit of claim 17, wherein the means for determining a next frequency generating element comprises a means for selecting a frequency generating element down in the order, by an increment equivalent to the search variable if the reference tuning voltage is greater than the upper tuning limit of the selected frequency generating element, otherwise selecting a frequency generating element up in the order by the increment equivalent to the search variable in the event a next iteration is performed.

20. The electric circuit of claim 19, wherein all frequency generating elements have a positive gain, the reference frequency corresponds to a high extreme operating frequency and the frequency generating elements are ordered such that the element with the highest frequency is lowest in the order.

21. The electric circuit of claim 19, wherein all frequency generating elements have a negative gain, the reference frequency corresponds to a low extreme operating frequency and the frequency generating elements are ordered such that the element with the lowest frequency is lowest in the order.

22. The electric circuit of claim 17, wherein the means for determining a next frequency generating element comprises means for selecting a frequency generating element up in the order, by an increment equivalent to the search variable if the reference tuning voltage is greater than the upper tuning limit of the selected frequency generating element, otherwise selecting a frequency generating element down in the order by the increment equivalent to the search variable in the event a next iteration is performed.

23. The electric circuit of claim 22, wherein all frequency generating elements have a positive gain, the reference frequency corresponds to a high extreme operating frequency and the frequency generating elements are ordered such that the element with the lowest frequency is lowest in the order.

24. The electric circuit of claim 22, wherein all frequency generating elements have a negative gain, the reference frequency corresponds to a low extreme operating frequency and the frequency generating elements are ordered such that the element with the highest frequency is lowest in the order.

25. An electric circuit for selecting an optimum frequency generating among an array of M frequency generating elements, each element having an output frequency range, the range having an upper frequency limit and a lower frequency limit, wherein the upper frequency limit is higher than the lower frequency limit corresponding to an input tuning voltage range having an upper tuning limit and a lower tuning limit, comprising:

a. means for arranging the frequency generating elements into an order by their output frequencies, such that there is a middle frequency generating element;

b. means for determining a reference tuning voltage corresponding to a lowest practical gain of a frequency generating element;

c. means for determining a reference frequency corresponding to a lowest practical gain of a frequency generating element;

d. means for starting a binary search by selecting the middle frequency generating element and assigning a search variable, having an initial value of M/2;

e. means for comparing the tuning voltage to the lower tuning limit of the frequency generating element that has been selected, thereby determining a next frequency generating element to be selected;

f. means for dividing the search variable by two if the search variable does not equal one, thereby determining a new value for the search variable; and

g. means for repeating the steps of comparing and dividing for a number of iterations.

26. The electric circuit in claim 25, wherein the frequency generating element is comprised of any among a list of:

at least one VCO, a binary switchable resonator, a tunable resonator, a combination thereof, and the array of frequency generating elements is comprised of any among a list of;

an array of VCOs, an array of binary switchable resonators, an array of tunable resonators, a combination thereof.

27. The electric circuit of claim 25, wherein the means for determining a next frequency generating element comprises means for selecting a frequency generating element down in the order, by an increment equivalent to the search variable if the reference tuning voltage is less than the lower tuning limit of the selected frequency generating element, otherwise selecting a frequency generating element up in the order by the increment equivalent to the search variable, in the event a next iteration is performed.

28. The electric circuit of claim 27, wherein all frequency generating elements have a positive gain, the reference frequency corresponds to a low extreme operating frequency and the frequency generating elements are ordered such that the frequency generating element with the lowest frequency is lowest in the order.

29. The electric circuit of claim 27, wherein all frequency generating elements have a negative gain, the reference frequency corresponds to a high extreme operating frequency and the frequency generating elements are ordered such that the frequency generating element with the highest frequency is lowest in the order.

30. The electric circuit of claim 25, wherein the means for determining a next frequency generating element comprises means for selecting a frequency generating element up in the order, by an increment equivalent to the search variable if the reference tuning voltage is less than the lower tuning limit of the selected frequency generating element, otherwise selecting a frequency generating element down in the order by the increment equivalent to the search variable, in the event a next iteration is performed.

31. The electric circuit of claim 30, wherein all frequency generating elements have a positive gain the reference frequency corresponds to a low extreme operating frequency and the frequency generating elements are ordered such that the frequency generating element with the highest frequency is lowest in the order.

32. The electric circuit of claim 30, wherein all frequency generating elements have a negative gain the reference frequency corresponds to a high extreme operating frequency and the frequency generating elements are ordered such that the frequency generating element with the lowest frequency is lowest in the order.