Iterative filter circuit calibration

• US 7,761,067 B1
• Filed: 04/21/2004
• Issued: 07/20/2010
• Est. Priority Date: 05/15/2003
• Status: Expired due to Fees

• Current Assignee: Marvell International Limited (Marvell Technology Group Limited)
• Original Assignee: Marvell International Limited (Marvell Technology Group Limited)
• Inventors: Loeb, Wayne A., Tsai, King Chun, Son, Sang Won
• Primary Examiner(s): Urban; Edward
• Assistant Examiner(s): HU, RUI MENG
• Application Number:
  US10/830,117
• Time in Patent Office: 2,281 Days
• Field of Search: 455/62, 455/63.1, 455/67.13, 4551141-1153, 455119-1274, 455/266
• US Class Current: 455/127.2
• CPC Class Codes: H03H 2007/013 Notch or bandstop filters
• CPC Class Codes: H03H 2210/012 Centre frequency; Cut-off frequency
• CPC Class Codes: H03H 2210/015 Quality factor or bandwidth
• CPC Class Codes: H03H 7/12 Bandpass or bandstop filters with adjustable bandwidth and fixed centre frequency H03H7/09 takes precedence; automatic control of bandwidth in amplifiers H03G5/16
• CPC Class Codes: H03J 2200/10 Tuning of a resonator by means of digitally controlled capacitor bank
• CPC Class Codes: H04B 1/0475 with means for limiting noise, interference or distortion H04B1/0483 takes precedence
• CPC Class Codes: H04B 1/1638 Special circuits to enhance selectivity of receivers not otherwise provided for resonant circuits H03H
• CPC Class Codes: H04B 1/30 for homodyne or synchrodyne receivers demodulator circuits H03D1/22

Abstract

Apparatus, systems, and methods implementing techniques for calibrating a filter circuit. A comparator generates an output based on a filter output amplitude signal and a reference amplitude signal. A calibration logic unit receives the comparator output and produces a component code that is used by the filter circuit to adjust one or more component values.

Claims

1. A filter calibration circuit, consisting of:

a DC voltage source operable to produce a reference amplitude signal;

an amplitude detector configured to receive an output signal from a variable gain stage and produce an amplitude signal, wherein the output signal from the variable gain stage is produced by modifying an amplitude of an output signal produced by a filter circuit, which comprises capacitive components to be calibrated to a desired frequency;

a comparator operable to generate a comparator output based on the amplitude signal of the amplitude detector and the reference amplitude signal of the DC voltage source; and

a calibration logic unit, separate from the comparator, operable to

receive the comparator output,

produce a digital gain code based on the comparator output to adjust a gain of the variable gain stage, and

produce a digital component code corresponding to switches associated with the capacitive components in the filter circuit to be used by the filter circuit in adjusting a combined value of the capacitive components in the filter circuit by selectively turning on or off one or more of the switches associated with the capacitive components to control a number of the capacitive components active in the filter circuit to calibrate the filter circuit to the desired frequency.

2. The filter calibration circuit of claim 1, wherein:

the filter circuit includes an LC tank circuit.

3. The filter calibration circuit of claim 1, wherein:

the calibration logic unit includes a digital signal processor.

4. The filter calibration circuit of claim 3, wherein:

the digital signal processor includes the comparator.

5. The filter calibration circuit of claim 1, wherein:

the calibration logic unit includes a logic circuit.

6. The filter calibration circuit of claim 5, wherein:

the logic circuit includes the comparator.

7. The filter calibration circuit of claim 1, wherein:

the capacitive components are monolithically fabricated on a semiconductor substrate.

8. The filter calibration circuit of claim 1, wherein:

the filter calibration circuit is operable to calibrate the filter circuit to the desired frequency automatically when the filter calibration circuit is connected to a power source.

9. The filter calibration circuit of claim 1, wherein:

the filter calibration circuit is operable to calibrate the filter circuit to the desired frequency without requiring a reduction in a quality factor of the filter circuit.

10. The filter calibration circuit of claim 1, wherein:

the filter calibration circuit is operable to calibrate the filter circuit to the desired frequency without requiring manual calibration of the filter circuit.

11. The filter calibration circuit of claim 1, wherein:

the filter calibration circuit is compliant with any of IEEE standards 802.11, 802.11a, 802.11b, 802.11e, 802.11g, 802.11h, 802.11i, 802.11n, and 802.16.

12. A filter calibration circuit, consisting of:

means for sourcing a reference amplitude signal;

an amplitude detector means for receiving an output signal from a variable gain stage and producing an amplitude signal, wherein the output signal from the variable gain stake is produced by modifying an amplitude of an output signal produced by a filter circuit, which comprises capacitive components to be calibrated to a desired frequency;

comparing means for generating a comparator output based on the amplitude signal of the amplitude detector means and the reference amplitude signal of the means for sourcing a reference amplitude signal; and

code generating means, separate from the comparing means, for

receiving the comparator output,

producing a digital gain code based on the comparator output to adjust a gain of the variable gain stage, and

producing a digital component code corresponding to switching means associated with the capacitive means to be used by the filtering means in adjusting a combined value of the capacitive component means in the filtering means by selectively turning on or off one or more of the switching means associated with the capacitive means to control a number of the capacitive means active in the filtering means to calibrate the filtering means to the desired frequency.

13. The filter calibration circuit of claim 12, wherein:

the filtering means includes an LC tank circuit means.

14. The filter calibration circuit of claim 12, wherein:

the code generating means includes a digital signal processing means.

15. The filter calibration circuit of claim 14, wherein:

the digital signal processing means includes the comparing means.

16. The filter calibration circuit of claim 12, wherein:

the code generating means includes a logic circuit means.

17. The filter calibration circuit of claim 16, wherein:

the logic circuit means includes the comparing means.

18. The filter calibration circuit of claim 12, wherein:

the capacitive means are monolithically fabricated on a semiconductor substrate.

19. The filter calibration circuit of claim 12, wherein:

the filter calibration circuit is operable to calibrate the filtering means to the desired frequency automatically when the filter calibration circuit is connected to a power source means.

20. The filter calibration circuit of claim 12, wherein:

the filter calibration circuit is operable to calibrate the filtering means to the desired frequency without requiring a reduction in a quality factor of the filtering means.

21. The filter calibration circuit of claim 12, wherein:

the filter calibration circuit is operable to calibrate the filtering means to the desired frequency without requiring manual calibration of the filtering means.

22. The filter calibration circuit of claim 12, wherein:

the filter calibration circuit is compliant with any of IEEE standards 802.11, 802.11a, 802.11b, 802.11e, 802.11g, 802.11h, 802.11i, 802.11n, and 802.16.

23. A method for calibrating a filter circuit, which comprises capacitive components, the filter circuit receiving an input signal and producing a filtered output signal, the method comprising:

initializing a digital component code corresponding to switches associated with capacitive components in the filter circuit to a value such that an initial peak frequency of the filter circuit is below or above a desired frequency;

initializing a digital gain code to a value such that a modified filtered output signal produced by a variable gain stage is greater than a DC reference voltage, wherein the variable gain stage is modifying the filtered output signal based on the initialized digital gain code;

producing an amplitude signal corresponding to the modified filtered output signal produced by the variable gain stage modifying the filtered output signal based on the digital gain code;

generating a comparator output based on the amplitude signal and the DC reference voltage; and

adjusting the digital gain code and the digital component code in combination until the comparator output indicates that the filter circuit is calibrated at the desired frequency;

wherein adjusting the digital component code adjusts a combined value of the capacitive components in the filter circuit by selectively turning on or off one or more of the switches associated with the capacitive components to control a number of the capacitive components active in the filter circuit to calibrate the filter circuit at the desired frequency.

24. The method of claim 23, wherein:

generating the comparator output includes digitally generating the comparator output.

25. The method of claim 23, wherein:

adjusting the combined value of the capacitive components comprises turning on or off one or more of the switches associated with the capacitive components monolithically fabricated on a semiconductor substrate.

26. The method of claim 23, further comprising:

calibrating the filter circuit automatically when the filter circuit is connected to a power source.

27. The method of claim 23, further comprising:

calibrating the filter circuit without requiring a reduction in a quality factor of the filter circuit.

28. The method of claim 23, further comprising:

calibrating the filter circuit without requiring manual calibration of the filter circuit.

29. The method of claim 23, wherein:

the method is compliant with any of IEEE standards 802.11, 802.11a, 802.11b, 802;

11e, 802.11g, 802.11h, 802.11i, 802.11n, and 802.16.

30. The method of claim 23, wherein adjusting the digital gain code and the digital component code in combination until the comparator output indicates that the filter circuit is calibrated at the desired frequency comprises:

decrementing a value of the digital gain code from the initialized value until the comparator output indicates that the amplitude signal is less than the DC reference voltage;

incrementing a value of the digital component code;

returning to the decrementing of the value of the digital gain code when the comparator output indicates that the amplitude signal is greater than the reference voltage; and

decrementing the value of the digital component code when the comparator output indicates that the amplitude is less than the reference voltage after the incrementing the value of the digital component code.

31. A wireless transceiver, comprising:

a transmitter operable to transmit a modulated carrier signal, the transmitter including

a filter circuit, which comprises capacitive components, operable to filter the modulated carrier signal and produce a filter output signal;

a variable gain stage to adjust an amplitude of the filter output signal; and

a calibration circuit operable to calibrate the filter circuit to a desired frequency and adjust a gain of the variable gain stage to adjust the amplitude of the filter output signal, the calibration circuit consisting of;

a DC voltage source operable to produce a reference amplitude signal;

an amplitude detector to receive an output signal from the variable gain stage and produce an amplitude signal;

a comparator operable to generate a comparator output based on the amplitude signal of the amplitude detector and the reference amplitude signal of the DC voltage source; and

a calibration logic unit, separate from the comparator, operable to

receive the comparator output

produce a digital gain code based on the comparator output to adjust a gain of the variable gain stage, and

produce a digital component code corresponding to switches associated with the capacitive components in the filter circuit to be used by the filter circuit in adjusting a combined value of the capacitive components in the filter circuit by selectively turning on or off one or more of the switches associated with the capacitive components to control a number of the capacitive components active in the filter circuit to calibrate the filter circuit to the desired frequency.

32. The wireless transceiver of claim 31, wherein:

the filter circuit includes an LC tank circuit.

33. The wireless transceiver of claim 31, wherein:

the calibration logic unit includes a digital signal processor.

34. The wireless transceiver of claim 33, wherein:

the digital signal processor includes the comparator.

35. The wireless transceiver of claim 31, wherein:

the calibration logic unit includes a logic circuit.

36. The wireless transceiver of claim 35, wherein:

the logic circuit includes the comparator.

37. The wireless transceiver of claim 31, wherein:

the capacitive components are monolithically fabricated on a semiconductor substrate.

38. The wireless transceiver of claim 31, wherein:

the calibration circuit is operable to calibrate the filter circuit to the desired frequency automatically when the calibration circuit is connected to a power source.

39. The wireless transceiver of claim 31, wherein:

the calibration circuit is operable to calibrate the filter circuit to the desired frequency without requiring a reduction in a quality factor of the filter circuit.

40. The wireless transceiver of claim 31, wherein:

the calibration circuit is operable to calibrate the filter circuit to the desired frequency without requiring manual calibration of the filter circuit.

41. The wireless transceiver of claim 31, wherein:

the wireless transceiver is compliant with any of IEEE standards 802.11, 802.11a, 802.11b, 802.11e, 802.11g, 802.11h, 802.11i, 802;

11n, and 802.16.

42. A wireless transceiver, comprising:

transmitting means for transmitting a modulated carrier signal, the transmitting means including

a filtering means, which comprises capacitive means for filtering the modulated carrier signal and producing a filter output signal;

a variable gain stage means for adjusting an amplitude of the filter output signal; and

calibrating means for calibrating the filtering means to a desired frequency and adjusting a gain of the variable gain stage to adjust the amplitude of the filter output signal, the calibrating means consisting of;

means for sourcing a reference amplitude signal,

an amplitude detector means for receiving an output signal from the variable gain stage and produce an amplitude signal,

comparing means for generating a comparator output based on the amplitude signal of the amplitude detector means and the reference amplitude signal of the means for sourcing a reference amplitude signal, and

code generating means, separate from the comparing means, for

receiving the comparator output,

producing a digital gain code based on the comparator output to adjust a gain of the variable gain stage means, and

producing a digital component code corresponding to switching means associated with the capacitive means in the filtering means to be used by the filtering means in adjusting a combined value of the capacitive means in the filtering means, by selectively turning on or off one or more of the switching means associated with the capacitive means to control a number of the capacitive means active in the filtering means to calibrate the filtering means to the desired frequency.

43. The wireless transceiver of claim 42, wherein:

the filtering means includes an LC tank circuit means.

44. The wireless transceiver of claim 42, wherein:

the code generating means includes a digital signal processing means.

45. The wireless transceiver of claim 44, wherein:

the digital signal processing means includes the comparing means.

46. The wireless transceiver of claim 42, wherein:

the code generating means includes a logic circuit means.

47. The wireless transceiver of claim 46, wherein:

the logic circuit means includes the comparing means.

48. The wireless transceiver of claim 42, wherein:

the capacitive means are monolithically fabricated on a semiconductor substrate.

49. The wireless transceiver of claim 42, wherein:

the calibrating means is operable to calibrate the filtering means to the desired frequency automatically when the calibrating means is connected to a power source means.

50. The wireless transceiver of claim 42, wherein:

the calibrating means is operable to calibrate the filtering means to the desired frequency without requiring a reduction in a quality factor of the filtering means.

51. The wireless transceiver of claim 42, wherein:

the calibrating means is operable to calibrate the filtering means to the desired frequency without requiring manual calibration of the filtering means.

52. The wireless transceiver of claim 42, wherein:

the wireless transceiver is compliant with any of IEEE standards 802.11, 802.11x, 802.11b, 802.11e, 802.11g, 802.11h, 802.11i, 802.11n, and 802.16.