High sensitivity GLONASS/GPS automatic frequency control

• US 8,754,809 B2
• Filed: 03/04/2011
• Issued: 06/17/2014
• Est. Priority Date: 03/04/2011
• Status: Expired due to Fees

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Zhou, Hao, Cheng, Hao-Jen, Sun, Qinfang
• Primary Examiner(s): Phan, Dao
• Application Number:
  US13/041,312
• Publication Number:
  US 20120223859A1
• Time in Patent Office: 1,201 Days
• Field of Search: 342/357.37, 342/357.59, 342/357.63, 342/357.68, 342/357.75, 701/468, 701/470
• US Class Current: 342/357.63
• CPC Class Codes: G01S 19/29 carrier including Doppler, related G01S19/246 takes precedence

Abstract

Updates to an AFC loop can be performed to provide high-sensitivity tracking. A 20 ms update interval and PDI=10 ms is used for every other update. A setting is used for each update between the 20 ms updates. Notably, the setting uses PDI=5 ms. The setting can include first, second, and third cross-dot pairs associated with a first bit, a second bit, and a cross-bit boundary between the first and second bits, respectively. A sum of these pairs can be scaled down when the signal strength is below a predetermined threshold. In another embodiment, the setting can include a first cross-dot pair associated with a first bit and a second cross-dot pair associated with a second bit. A sum of these pairs can also be scaled down when signal strength is below a predetermined threshold.

Claims

1. A method of providing automatic frequency control (AFC) tracking for reception of GLONASS signals, the method comprising:

determining whether a channel signal to noise ratio (CNo) exceeds a threshold;

when the CNo exceeds the threshold, performing pull-in using a first series of predetection integration (PDI) periods (PDIs) with activated decision-directed flips (DDFs) until a N ms boundary of a GLONASS data bit is found, wherein N is a positive integer, and wherein the activated DDFs selectively adjust polarities of cross-dot pairs generated based on the PDIs; and

using a receiver, performing updates to an AFC loop, wherein performing includes;

using a N ms update interval and PDI=(N/2)ms for every other update; and

using a setting for an update between N ms updates, the setting using PDI=(N/4)ms.

2. The method of claim 1, wherein the setting includes a first cross-dot pair associated with a first bit, a second cross-dot pair associated with a second bit, the second bit being adjacent the first bit, and a third cross-dot pair associated with a cross-bit boundary between the first and second bits.

3. The method of claim 2, further comprising scaling down a sum of the first, second, and third cross-dot pairs by a value less than 1 when signal strength is below a predetermined threshold.

4. The method of claim 1, wherein the setting includes a first cross-dot pair associated with a first bit and a second cross-dot pair associated with a second bit, the second bit being adjacent the first bit.

5. The method of claim 4, further comprising scaling down a sum of the first and second cross-dot pairs by a value less than 1 when signal strength is below a predetermined threshold.

6. A method of providing automatic frequency control (AFC) tracking for reception of GPS signals, the method comprising:

determining whether a channel signal to noise ratio (CNo) exceeds a threshold;

when the CNo exceeds the threshold, performing pull-in using a first series of predetection integration (PDI) periods (PDIs) with activated decision-directed flips (DDFs) until a bit synchronization is achieved, wherein the activated DDFs selectively adjust polarities of cross-dot pairs generated based on the PDIs; and

using a receiver, performing updates to an AFC loop, wherein performing includes;

using a N ms update interval and PDI=(N/2)ms for every other update; and

using a setting for an update between N ms updates, the setting using PDI=(N/4)ms.

7. The method of claim 6, wherein the setting includes a first cross-dot pair associated with a first bit, a second cross-dot pair associated with a second bit, the second bit being adjacent the first bit, and a third cross-dot pair associated with a cross-bit boundary between the first and second bits.

8. The method of claim 7, further comprising scaling down a sum of the first, second, and third cross-dot pairs by a value less than 1 when signal strength is below a predetermined threshold.

9. The method of claim 6, wherein the setting includes a first cross-dot pair associated with a first bit and a second cross-dot pair associated with a second bit, the second bit being adjacent the first bit.

10. The method of claim 9, wherein a sum of the first and second cross-dot pairs is scaled down by a value less than 1 when signal strength is below a predetermined threshold.

11. A method of providing automatic frequency control (AFC) tracking for receipt of GLONASS or GPS signals, the method comprising:

determining whether a channel signal to noise ratio (CNo) exceeds a threshold;

when the CNo exceeds the threshold, performing pull-in using a first series of predetection integration (PDI) periods (PDIs) with activated decision-directed flips (DDFs), wherein the activated DDFs selectively adjust polarities of cross-dot pairs generated based on the PDIs;

when the CNo does not exceed the threshold, using a second series of PDIs with always deactivated DDFs, wherein the always deactivated DDFs do not adjust polarities of cross-dot pairs generated based on the PDIs; and

using a receiver, performing updates to an AFC loop, wherein performing includes;

using a N ms update interval and PDI=(N/2)ms for every other update; and

using a setting for an update between N ms updates, the setting using PDI=(N/4)ms.

12. The method of claim 11, wherein the setting includes a first cross-dot pair associated with a first bit, a second cross-dot pair associated with a second bit, the second bit being adjacent the first bit, and a third cross-dot pair associated with a cross-bit boundary between the first and second bits.

13. The method of claim 12, further comprising scaling down a sum of the first, second, and third cross-dot pairs by a value less than 1 when signal strength is below a predetermined threshold.

14. The method of claim 11, wherein the setting includes a first cross-dot pair associated with a first bit and a second cross-dot pair associated with a second bit, the second bit being adjacent the first bit.

15. The method of claim 14, wherein a sum of the first and second cross-dot pairs is scaled down by a value less than 1 when signal strength is below a predetermined threshold.

16. A method of providing automatic frequency control (AFC) tracking for efficient, high-sensitivity reception of GLONASS or GPS signals, the method comprising:

determining whether a channel signal to noise ratio (CNo) exceeds a threshold;

when the CNo exceeds the threshold, performing pull-in using a first series of predetection integration (PDI) periods (PDIs) with activated decision-directed flips (DDFs), wherein the activated DDFs selectively adjust polarities of cross-dot pairs generated based on the PDIs;

when the CNo does not exceed the threshold, using a second series of PDIs with always deactivated DDFs, wherein the always deactivated DDFs do not adjust polarities of cross-dot pairs generated based on the PDIs; and

using a receiver, performing updates to an AFC loop, wherein performing includes;

after wiping off data bit polarity, applying a PDI longer than 10 ms.