RC and SC filter compensation in a radio transceiver

• US 20040183602A1
• Filed: 03/21/2003
• Published: 09/23/2004
• Est. Priority Date: 03/21/2003
• Status: Active Grant

• Current Assignee: WSOU Investments, LLC (WSOU Holdings, LLC)
• Original Assignee: Nokia Corporation
• Inventors: Maunuksela, Jaako, Vepsalainen, Jussi, Honkanen, Tuomas
• Granted Patent: US 7,002,417 B2
• Time in Patent Office: Days
• US Class Current: 331/17
• CPC Class Codes: H03C 3/0925 applying frequency modulation at the divider in the feedback loop
• CPC Class Codes: H03C 3/0933 using fractional frequency division in the feedback loop of the phase locked loop
• CPC Class Codes: H03C 3/0991 including calibration means or calibration methods
• CPC Class Codes: H03L 7/093 using special filtering or amplification characteristics in the loop H03L7/087 - H03L7/091 take precedence
• CPC Class Codes: H03L 7/1974 for fractional frequency division

Abstract

Disclosed is apparatus for operating with an RC filter (26, 26A), and a corresponding method. The apparatus includes circuitry (32) for use in measuring an actual value of at least one filter component and a controller (34), coupled to the measurement circuitry, for determining at least one adaptive filter (36, 46) coefficient using the measured actual value to so as to compensate for a deviation of at least one filter component value from an ideal value. Where the filter is embodied as an RC network, the circuitry measures an actual value of both a resistor and a capacitor, and the controller uses the measured actual value of the capacitor when determining the value of a resistor.

Claims

1. A method to operate a phase lock loop (PLL), comprising:

measuring an actual value of at least one loop filter component; and

determining at least one adaptive filter coefficient using the measured actual value to so as to compensate the phase lock loop for a deviation of at least one loop filter component value from an ideal value.

2. A method as in claim 1, where the loop filter comprises an RC network, and where measuring measures an actual value of both a resistor and a capacitor.

3. A method as in claim 1, where the loop filter comprises an RC network, and where measuring measures an actual value of a capacitor, and then uses the measured actual value of the capacitor when measuring the value of a resistor.

4. A method as in claim 1, where the loop filter comprises an RC network, and where measuring comprises:

determining a first amount of time required to charge a capacitor from a constant current source from an initial voltage to a threshold voltage;

determining the actual value of the capacitor using the first amount of time;

determining a second amount of time required to charge the capacitor from the initial voltage to the threshold voltage using a predetermined voltage applied through a resistor; and

determining the actual value of the resistor using the second amount of time and the determined actual value of the capacitor.

5. A method as in claim 1, where the PLL forms a part of a mobile station, and where measuring and determining occur when the mobile station is not involved in a call.

6. A method as in claim 5, where measuring and determining operate with actual resistor and capacitor components of the loop filter.

7. A method as in claim 1, where the PLL forms a part of a mobile station, and where measuring and determining occur when the mobile station is involved in a call.

8. A method as in claim 7, where measuring and determining operate with surrogate resistor and capacitor components of the loop filter.

9. A method as in claim 1, where the loop filter comprises a switched capacitor (SC) network, and where measuring measures an actual value of a capacitor.

10. A method as in claim 1, where the deviation is due at least in part to integrated circuit process variations.

11. A method as in claim 1, where the deviation is due at least in part to variations in temperature.

12. A method as in claim 1, where the PLL forms a part of a mobile station, and where measuring and determining are executed at power-on.

13. A method as in claim 1, where the PLL forms a part of a mobile station, and where measuring and determining are executed as a factory calibration procedure, and further comprising storing the at least one adaptive filter coefficient in a non-volatile memory of the mobile station.

14. A method as in claim 1, where the PLL forms a part of a mobile station, where the deviation is due at least in part to variations in temperature, where measuring and determining are executed as a factory calibration procedure at a plurality of different temperatures, and further comprising storing a plurality adaptive filter coefficients in a look-up table in a non-volatile memory of the mobile station.

15. A method as in claim 1, where the PLL forms a part of a transmitter of a mobile station, and where measuring and determining are executed when at least one of changing a transmission power level and changing a transmission channel.

16. A method as in claim 1, where the loop filter comprises an RC network, where measuring is used to determine a value of parameters k_R and k_C, and further comprising calculating the actual value of a resistor (R_act) and a capacitor (C_act) using k_R and k_C, respectively.

17. A method as in claim 1, where the PLL forms a part of a polar transmitter of a mobile station.

18. A method as in claim 1, where the at least one filter coefficient is obtained from an s-domain transfer function by performing a z-transformation.

19. A method as in claim 18, where the z-transformation employs a bilinear transformation comprising normalizing a pre-emphasis function, and substituting for s using a z transformation operation that includes using a prewarping factor, having a value that is a function of digital sample time, so as to compensate for the nonlinear z-transformation.

20. A method to operate a receiver of a mobile station, comprising:

measuring an actual value of the at least one receiver filter component value; and

determining at least one downstream adaptive filter coefficient using the measured actual value to so as to compensate the receiver for a deviation of at least one filter component value from an ideal value.

21. A method as in claim 20, where the filter comprises an RC network, and where measuring measures an actual value of both a resistor and a capacitor.

22. A method as in claim 20, where the filter comprises an RC network, and where measuring measures an actual value of a capacitor, and then uses the measured actual value of the capacitor when measuring the value of a resistor.

23. A method as in claim 20, where the filter comprises an RC network, and where measuring comprises:

determining a first amount of time required to charge a capacitor from a constant current source from an initial voltage to a threshold voltage;

determining the actual value of the capacitor using the first amount of time;

determining a second amount of time required to charge the capacitor from the initial voltage to the threshold voltage using a predetermined voltage applied through a resistor; and

determining the actual value of the resistor using the second amount of time and the determined actual value of the capacitor.

24. A method as in claim 20, where measuring and determining occur when the mobile station is not involved in a call, and where measuring and determining operate with actual resistor and capacitor components of the receiver filter.

25. A method as in claim 20, where measuring and determining occur when the mobile station is involved in a call, and where measuring and determining operate with surrogate resistor and capacitor components of the receiver filter.

26. A method as in claim 20, where the filter comprises a switched capacitor (SC) network, and where measuring measures an actual value of a capacitor.

27. A method as in claim 20, where the deviation is due at least in part to integrated circuit process variations and to variations in temperature.

28. A method as in claim 20, where measuring and determining are executed at power-on of the mobile station.

29. A method as in claim 20, where measuring and determining are executed as a factory calibration procedure, and further comprising storing the at least one adaptive filter coefficient in a non-volatile memory of the mobile station.

30. A method as in claim 20, where the deviation is due at least in part to variations in temperature, where measuring and determining are executed as a factory calibration procedure at a plurality of different temperatures, and further comprising storing a plurality adaptive filter coefficients in a look-up table in a non-volatile memory of the mobile station.

31. A method as in claim 20, where the filter comprises an RC network, where measuring is used to determine a value of parameters k_R and k_C, and further comprising calculating the actual value of a resistor (R_act) and a capacitor (C_act) using k_R anf k_C, respectively.

32. A method as in claim 20, where the at least one filter coefficient is obtained from an s-domain transfer function by performing a z-transformation.

33. A method as in claim 32, where the z-transformation employs a bilinear transformation comprising normalizing a pre-emphasis function, and substituting for s using a z transformation operation that includes using a prewarping factor, having a value that is a function of digital sample time, so as to compensate for the nonlinear z-transformation.

34. Apparatus for operating with an RC filter comprising components integrated upon an integrated circuit, comprising:

circuitry, included as apart of said integrated circuit, for use in measuring an actual value of at least one filter component; and

a controller, coupled to said measurement circuitry, for determining at least one adaptive filter coefficient using the measured actual value to so as to compensate for a deviation of at least one filter component value from an ideal value.

35. Apparatus as in claim 34, where the filter comprises an RC network, and where said circuitry measures an actual value of both a resistor and a capacitor.

36. Apparatus as in claim 34, where the filter comprises an RC network, and where said circuitry measures an actual value of a capacitor, and said controller then uses the measured actual value of the capacitor when determining the value of a resistor.

37. Apparatus as in claim 34, where the filter comprises an RC network, and where said measuring circuitry comprises:

means for determining a first amount of time required to charge a capacitor from a constant current source from an initial voltage to a threshold voltage, and where said controller determines the actual value of the capacitor using the first amount of time; and

means for determining a second amount of time required to charge the capacitor from the initial voltage to the threshold voltage using a predetermined voltage applied through a resistor; and

where said controller determines the actual value of the resistor using the second amount of time and the determined actual value of the capacitor.

38. Apparatus as in claim 34, where the filter comprises a loop filter of a phased lock loop (PLL), and where the adaptive filter is coupled to a fractional-N divider in a feedback path of the PLL.

39. Apparatus as in claim 34, where the PLL forms a part of a polar transmitter of a mobile station.

40. Apparatus as in claim 34, where the filter comprises a receive filter of a mobile station, and where the adaptive filter is coupled downstream from the receive filter.

41. Apparatus as in claim 34, where the filter comprises a switched capacitor (SC) network, and where said circuitry measures an actual value of a capacitor.

42. Apparatus as in claim 34, where said apparatus operates at least one of, at a turn-on time of the apparatus, during a factory calibration procedure, at a periodic rate, during a change in operating conditions including a change in an RF transmitter channel, a change in an RF transmitter level or a change in an RF receiver gain, and when said controller detects a change in operating temperature.