Fast acquisition engine

• US 8,164,519 B1
• Filed: 05/19/2009
• Issued: 04/24/2012
• Est. Priority Date: 05/20/2008
• Status: Active Grant

• Current Assignee: U-Blox AG (u-blox Holding AG)
• Original Assignee: U-Blox AG (u-blox Holding AG)
• Inventors: Bedoya Martinez, Mario A., Williams, Gareth, Tester, David P.
• Primary Examiner(s): Phan, Dao
• Application Number:
  US12/468,242
• Time in Patent Office: 1,071 Days
• Field of Search: 342/357.25, 342/357.63, 342/357.69, 342/357.71, 701/207, 701/213
• US Class Current: 342/357.69
• CPC Class Codes: G01S 19/24 Acquisition or tracking or demodulation of signals transmitted by the system synchronisation aspects of direct sequence spread spectrum modulation H04B1/7073
• CPC Class Codes: G01S 19/34 Power consumption

Abstract

A method of fast acquisition of a location of a device is disclosed. The method generally includes the steps of (A) repeatedly powering up automatically (i) a radio receiver and (ii) a given subset of a plurality of correlators in some of a plurality of search engines in the device, (B) buffering first data of a plurality of position signals received through the radio receiver over a first period, each of the position signals comprising a respective one of a plurality of code sequences, (C) searching through the first data with the correlators to find at least one of the code sequences, each of the correlators using a search window comprising a fraction of a code length of the code sequences and (D) generating an output signal carrying a location of the device based on the position signals corresponding to the code sequences that were found.

Claims

1. A method of fast acquisition of a location of a device, comprising the steps of:

(A) repeatedly powering up automatically (i) a radio receiver and (ii) a given subset of a plurality of correlators in some of a plurality of search engines in said device;

(B) buffering first data of a plurality of position signals received through said radio receiver over a first period, each of said position signals comprising a respective one of a plurality of code sequences;

(C) searching through said first data with said correlators to find at least one of said code sequences, each of said correlators using a search window comprising a fraction of a code length of said code sequences; and

(D) generating an output signal carrying a location of said device based on said position signals corresponding to said code sequences that were found.

2. The method according to claim 1, further comprising the step of:

accumulating at most 24 correlation peaks corresponding to each of said code sequences being searched, said correlation peaks comprising (i) a first group of highest peaks used in evaluating acquisition of said code sequences and (ii) a second group of candidate peaks.

3. The method according to claim 2, further comprising the step of:

entering each new correlation peak detected as one of said candidate peaks.

4. The method according to claim 1, further comprising the steps of:

generating a plurality of coherent scores by coherently integrating said code sequences respectively during said search through said first data; and

generating a plurality of non-coherent scores by non-coherently integrating said code sequences respectively during said search through said first data, said non-coherent integration being performed in parallel with said coherent integration.

5. The method according to claim 4, further comprising the step of:

calculating a plurality of signal strengths of said position signals as differences between said coherent scores and said non-coherent scores respectively.

6. The method according to claim 5, further comprising the step of:

buffering second data of said position signals received through said radio receiver over a second period upon finding at least one acceptable signal among said position signals from said search through said first data.

7. The method according to claim 6, further comprising the step of:

integrating said code sequences of said acceptable signals with said second data using (i) said non-coherent integration where said acceptable signals are strong and (ii) said coherent integration where said acceptable signals are weak.

8. The method according to claim 1, further comprising the step of:

powering up at least one more of said correlators in response to failing to find at least one acceptable signal among said position signals from said search through said first data.

9. The method according to claim 8, further comprising the step of:

buffering second data of said position signals received through said radio receiver over a second period upon failing to find said at least one acceptable signal.

10. The method according to claim 9, further comprising the step of:

searching through said second data with said correlators to find at least one of said code sequences.

11. A device comprising:

a radio receiver configured to receive first data of a plurality of position signals during a first period, each of said position signals comprising a respective one of a plurality of code sequences; and

a processor comprising a plurality of search engines, each of said search engines comprising a plurality of correlators, in a reacquisition mode, said processor is configured to (i) repeatedly power up automatically (a) said radio receiver and (b) a given subset of a plurality of correlators in some of said search engines, (ii) buffer said first data, (iii) search through said first data with said correlators to find at least one of said code sequences, each of said correlators using a search window comprising a fraction of a code length of said code sequences, and (iv) generate an output signal carrying a location of said device based on said position signals corresponding to said code sequences that were found.

12. The device according to claim 11, wherein said search engines together operate on at most 32 code-phase-frequency channels while in said re-acquisition mode, each of said codephase-frequency channels comprising one respective I-channel and one respective Q-channel.

13. The device according to claim 11, wherein said given subset comprises at most four of said correlators in each of said search engines.

14. The device according to claim 11, wherein said fraction of said code sequences comprises at most 32 chips.

15. The device according to claim 11, wherein said processor is configured to power up all of said correlators in all of said search engines while in a full search mode.

16. The device according to claim 11, wherein said processor is further configured to concatenate said correlators in each of said search engines to consider all of said code length.

17. The device according to claim 11, wherein said processor comprises four code generators.

18. The device according to claim 11, wherein processor is further configured to buffer second data of position signals received through said radio receiver over a second period after searching through said first data.

19. The device according to claim 11, wherein said processor is further configured to power up at least one more of said correlators in response to failing to find at least one acceptable signal in said first data in said reacquisition mode.

20. A device comprising:

means for receiving first data of a plurality of position signals during a first period, each of said position signals comprising a respective one of a plurality of code sequences; and

means for processing comprising a plurality of search engines, each of said search engines comprising a plurality of correlators, said means for processing is configured to (i) repeatedly powering up automatically (a) said means for receiving and (b) a given subset of a plurality of correlators in some of said search engines, (ii) buffer said first data, (iii) search through said first data with said correlators to find at least one of said code sequences, each of said correlators using a search window comprising a fraction of a code length of said code sequences, and (iv) generate an output signal carrying a location of said device based on said position signals corresponding to said code sequences that were found.

21. A method of fast acquisition of a location of a device, comprising the steps of:

(A) powering up automatically, in a reacquisition mode, (i) a radio receiver and (ii) a given subset of a plurality of correlators in some of a plurality of search engines in said device;

(B) buffering first data of a plurality of position signals received through said radio receiver from at least one satellite over a first period, each of said position signals comprising a respective one of a plurality of code sequences;

(C) white hot searching through said first data with said correlators to find at least one of said code sequences, each of said correlators using a search window comprising a fraction of a code length of said code sequences;

(D) powering up another correlator if at least one code sequence is not found;

(E) generating an output signal carrying a location of said device based on said position signals corresponding to said code sequences that were found;

(F) repeating steps (B), (C), (D), and (E) if not all correlators have been powered up; and

(F) entering a cold start mode of the device if all of the correlators are powered up and the entire search window has been searched and no code sequence is found.

22. A device comprising:

a radio receiver configured to receive first data of a plurality of position signals from at least one satellite during a first period, each of said position signals comprising a respective one of a plurality of code sequences; and

a processor comprising a plurality of search engines, each of said search engines comprising a plurality of correlators, in a reacquisition mode, said processor is configured to (i) repeatedly power up (a) said radio receiver and (b) a given subset of a plurality of correlators in some of said search engines, (ii) buffer said first data, (iii) white hot search through said first data with said correlators to find at least one of said code sequences, each of said correlators using a search window comprising a fraction of a code length of said code sequences, (iv) power up another correlator if at least one code sequence is not found, and (v) generate an output signal carrying a location of said device based on said position signals corresponding to said code sequences that were found,

the processor further configured to repeat said buffer, power up another correlator and generate an output signal if not all correlators have been powered up, and enter a cold start mode if all of the correlators are powered up and the entire search window has been searched and no code sequence is found.