Method and apparatus for reducing frequency errors associated with an inter-system scan

• US 7,561,645 B2
• Filed: 09/24/2003
• Issued: 07/14/2009
• Est. Priority Date: 09/26/2002
• Status: Expired due to Fees

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Smith, Alan Andrew, Stuart, legal representative
• Primary Examiner(s): Odom; Curtis B
• Application Number:
  US10/529,434
• Publication Number:
  US 20060111141A1
• Time in Patent Office: 2,120 Days
• Field of Search: 375/371-376,346-350 327/153-163
• US Class Current: 375/347
• CPC Class Codes: H03L 7/085 concerning mainly the frequency- or phase-detection arrangement including the filtering or amplification of its output signal H03L7/10 takes precedence; circuits for comparing the phase or frequency of two mutually-independent oscillations H03D13/00
• CPC Class Codes: H03L 7/095 using a lock detector H03L7/087 takes precedence
• CPC Class Codes: H03L 7/1077 by changing characteristics of the phase or frequency detection means H03L7/1072 takes precedence
• CPC Class Codes: H03L 7/18 using a frequency divider or counter in the loop H03L7/20, H03L7/22 take precedence
• CPC Class Codes: H04B 1/16 Circuits

Abstract

A plural-mode receiver 10 is able to receive signals from a first communication system (e.g. WCDMA) or signals from a second, different communication system e.g. GSM). The receiver 10 comprises a first receiver chain 13, 15,17,19 for receiving signals of the first communication system and a second receiver chain 12, 14, 16, 18 for receiving signals of the second communication system. A reference oscillator 24 is arranged to generate a reference signal for the first receiver chain and the second receiver chain. The receiver also comprises a controller 22 for controlling the reference oscillator 24 so that the oscillator 24 oscillates at frequencies related to signals of the first communication system or signals of the second communication system. The controller 22 records the change in frequency of the oscillator 24 resulting from changing to the frequencies related to signals of the second communication system and a period of time during which signals of the second communication system are received by the second receiver chain. The controller 22 then calculates from the recorded change and the recorded period of time an error vector and changes parameters of the reference oscillator 24, including applying the calculated error vector, so that the oscillator oscillates at frequencies related to signals of the first communication system.

Claims

1. A method of controlling a plural-mode receiver, capable of receiving signals from a first communication system or signals from a second, different communication system, to reduce frequency errors associated with the receiver scanning for signals of the second communication system while receiving signals of the first communication system, the method comprising:

changing parameters of a reference oscillator of the receiver so that the oscillator oscillates at frequencies related to signals of the second communication system;

recording the change in frequency of the oscillator resulting from the adjustment;

receiving signals of the second communication system for a period of time;

recording the period of time;

calculating from the recorded change and the recorded period of time an error vector; and

changing parameters of the reference oscillator, including applying the calculated error vector, so that the oscillator oscillates at frequencies related to signals of the first communication system.

2. A method as claimed in claim 1, further comprising:

receiving data relating to the frequencies of signals of the second communication system;

determining from the received data the parameters of the reference oscillator to cause the oscillator to oscillate at approximately the frequencies related to signals of the second communication system.

3. A method as claimed in claim 2, further comprising:

receiving further data relating to the frequencies of signals of the second communication system;

determining from the received data corrections to be applied to the parameters of the reference oscillator to cause the oscillator to oscillate at substantially the frequencies related to signals of the second communication system.

4. A method as claimed in claim 3, wherein the recorded change in frequency includes the change associated with oscillating at approximately the frequencies related to signals of the second communication system and the change associated with oscillating at substantially the frequencies related to signals of the second communication system.

5. A method as claimed in claim 3 or 4, wherein the period of time comprises both time spent oscillating at approximately the frequencies related to signals of the second communication system and time spent oscillating at substantially the frequencies related to signals of the second communication system.

6. A method as claimed in claim 1, further comprising receiving signals of the of the second communication system containing information pertaining to the second system.

7. A method as claimed in claim 1, wherein the scanning is effected while the receiver is in an idle mode.

8. A plural-mode receiver apparatus for receiving signals from a first communication system or signals from a second, different communication system, the apparatus comprising:

a first receiver chain for receiving signals of the first communication system;

a second receiver chain for receiving signals of the second communication system;

a reference oscillator for generating a reference signal for the first receiver chain and the second receiver chain; and

a controller for;

changing parameters of the reference oscillator so that the oscillator oscillates at frequencies related to signals of the second communication system;

recording the change in frequency of the oscillator resulting from the adjustment;

recording a period of time during which signals of the second communication system are received by the second receiver chain;

calculating from the recorded change and the recorded period of time an error vector; and

changing parameters of the reference oscillator, including applying the calculated error vector, so that the oscillator oscillates at frequencies related to signals of the first communication system.

9. An apparatus as claimed in claim 8, further comprising means for receiving data relating to the frequencies of signals of the second communication system and wherein the controller is arranged to determine from the received data the parameters of the reference oscillator to cause the oscillator to oscillate at approximately the frequencies related to signals of the second communication system.

10. An apparatus as claimed in claim 9, further comprising means for receiving further data relating to the frequencies of signals of the second communication system, and wherein the controller is arranged to determine from the received data corrections to be applied to the parameters of the reference oscillator to cause the oscillator to oscillate at substantially the frequencies related to signals of the second communication system.

11. An apparatus as claimed in claim 10, wherein controller is arranged to record changes in frequency that include the change associated with oscillating at approximately the frequencies related to signals of the second communication system and the change associated with oscillating at substantially the frequencies related to signals of the second communication system.

12. An apparatus as claimed in claim 10 or 11, wherein controller is arranged to calculate the period of time from both time spent oscillating at approximately the frequencies related to signals of the second communication system and time spent oscillating at substantially the frequencies related to signals of the second communication system.

13. An apparatus as claimed in claim 8, wherein the controller is operable while the receiver is in an idle mode.

14. A receiver for receiving signals of a first communication system and signals of a second communication system, the receiver comprising a receiving circuit tunable to receive signals of the first and second communication systems, the receiver being arranged so that, while tuned to receive signals of the first communication system, the receiving circuit can be briefly retuned to receive signals of the second communication system before being tuned back to receive again signals of the first communication system, and so that a correction is made when tuning back to signals of the first communication system depending on tuning changes made while retuning and receiving signals of the second communication system and the duration of the changes.

15. A receiver as claimed in claim 14, wherein the receiving circuit comprises a first receiver chain operable to receive signals from a first communications system and a second receiver chain operable to receive signals from a second communications system.

16. A receiver as claimed in claim 15, further comprising a phase-locked loop circuit associated with the first receiver chain and with the second receiver chain.

17. A receiver as claimed in claim 16, wherein the phase-locked loop circuit comprises a single phase-locked loop configurable to output a signal at a first frequency related with signals of the first communications system or to output a signal at a second frequency related with signals of the second communications system.

18. A receiver as claimed in claim 16 or 17, wherein the phase-locked loop circuit comprises a voltage-controlled temperature-compensated crystal oscillator (VCTCXO) to which the correction is made.

19. A receiver as claimed in claim 15, wherein the first receiver chain is configured to receive signals of a continuous frequency division duplex system.

20. A receiver as claimed in claim 15, wherein the second receiver chain is configured to receive signals of a time division duplex system.

21. A receiver as claimed in claim 19, wherein the first receiver chain is configured to receive WCDMA signals.

22. A receiver as claimed in claim 20, wherein the second receiver chain is configured to receive GSM signals.

23. A receiver as claimed in claim 15, further comprising a controller for controlling the receiver circuit to cause the same to tune between the signals of the first and second communication systems.

24. A receiver as claimed in claim 23, wherein the controller is operable to calculate the correction from the tuning changes made while retuning and receiving signals of the second communication system and the duration of the changes and to apply the correction to the receiver circuit.

25. A method of receiving signals of a first communication system and signals of a second communication system, the method comprising tuning a receiving circuit to receive signals of the first communication system, retuning the receiver circuit to receive signals of the second communication system, tuning the receiver back to receive again signals of the first communication system, determining tuning changes made while retuning and receiving signals of the second communication system and the duration of the changes, calculating from the changes and duration of the changes a correction to be made to the tuning, and making the calculated correction when tuning back to signals of the first communication system.

26. An apparatus for controlling a plural-mode receiver, capable of receiving signals from a first communication system or signals from a second, different communication system, to reduce frequency errors associated with the receiver scanning for signals of the second communication system while receiving signals of the first communication system, comprising:

means for changing parameters of a reference oscillator of the receiver so that the oscillator oscillates at frequencies related to signals of the second communication system;

means for recording the change in frequency of the oscillator resulting from the adjustment;

means for receiving signals of the second communication system for a period of time;

means for recording the period of time;

means for calculating from the recorded change and the recorded period of time an error vector; and

means for changing parameters of the reference oscillator, including applying the calculated error vector, so that the oscillator oscillates at frequencies related to signals of the first communication system.

27. The apparatus as claimed in claim 26, further comprising:

means for receiving data relating to the frequencies of signals of the second communication system;

means for determining from the received data the parameters of the reference oscillator to cause the oscillator to oscillate at approximately the frequencies related to signals of the second communication system.

28. The apparatus as claimed in claim 27, further comprising:

means for receiving further data relating to the frequencies of signals of the second communication system;

means for determining from the received data corrections to be applied to the parameters of the reference oscillator to cause the oscillator to oscillate at substantially the frequencies related to signals of the second communication system.

29. The apparatus as claimed in claim 28, wherein the recorded change in frequency includes the change associated with oscillating at approximately the frequencies related to signals of the second communication system and the change associated with oscillating at substantially the frequencies related to signals of the second communication system.

30. The apparatus as claimed in claim 28, wherein the period of time comprises both time spent oscillating at approximately the frequencies related to signals of the second communication system and time spent oscillating at substantially the frequencies related to signals of the second communication system.

31. The apparatus as claimed in claim 26, wherein the signals of the of the second communication system contain information pertaining to the second system.

32. The apparatus as claimed in claim 26, wherein the scanning is effected while the receiver is in an idle mode.

33. An apparatus for receiving signals of a first communication system and signals of a second communication system, the apparatus comprising means for tuning a receiving circuit to receive signals of the first communication system, means for retuning the receiver circuit to receive signals of the second communication system, means for tuning the receiver back to receive again signals of the first communication system, means for determining tuning changes made while retuning and receiving signals of the second communication system and the duration of the changes, means for calculating from the changes and duration of the changes a correction to be made to the tuning, and means for making the calculated correction when tuning back to signals of the first communication system.