Receive diversity in GNSS receivers

• US 8,736,490 B2
• Filed: 02/27/2012
• Issued: 05/27/2014
• Est. Priority Date: 06/24/2009
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Simic, Emilija M., Rowitch, Douglas Neal, Raman, Sundar
• Primary Examiner(s): LIU, HARRY K
• Application Number:
  US13/406,291
• Publication Number:
  US 20120154212A1
• Time in Patent Office: 820 Days
• Field of Search: 342/357.76
• US Class Current: 342/357.76
• 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 19/36 relating to the receiver frond end
• CPC Class Codes: H04B 2201/70715 with application-specific features

Abstract

The subject matter disclosed herein relates to receiving one or more SPS signals at two or more physically separated antennae. In an aspect, signals from the physically separated antennae may be downconverted into complex digital signals that may undergo further processing to improve one or more performance metrics related to position estimation operations, for example.

Claims

1. A method, comprising:

receiving one or more satellite positioning system (SPS) signals at two or more physically separated antennae of a mobile station, said two or more antennae to provide a respective two or more radio frequency signals to a receiver of the mobile station;

downconverting one or more of said radio frequency signals in one or more respective paths of a front end of the receiver to generate two or more complex digital signals comprising in-phase and quadrature components; and

processing the two or more complex digital signals at least in part to improve one or more performance metrics related to position estimation operations, including combining the two or more complex digital signals according to a non-coherent combining algorithm to generate a combined digital signal;

wherein said non-coherent combining algorithm comprises despreading and rotating each of the two or more complex digital signals, respectively, and combining the despread signals in a non-coherent combining operation to produce the combined digital signal.

2. The method of claim 1, wherein said processing additionally comprises detecting one or more peaks of the combined digital signal.

3. The method of claim 1, wherein said non-coherent combining operation of said non-coherent combining algorithm comprises:

coherently accumulating the results of the despreading and rotating operations for the two or more complex digital signals, respectively;

non-coherently accumulating the results of the coherent accumulation for the two or more complex digital signals, respectively; and

adding the two or more non-coherent accumulations to generate the combined digital signal.

4. The method of claim 3, wherein said adding the two or more non-coherent accumulations comprises a weighed sum depending, at least in part, on respective gains of the two or more antennae.

5. The method of claim 4, further comprising:

performing two or more sequential shallow searches using said two or more radio frequency signals from the respective two or more antennae and using a single receiver path, said shallow searches to yield two or more performance metrics associated with the respective two or more shallow searches; and

selecting at least one weight value for said adding based at least in part on the respective gains.

6. The method of claim 5, wherein said two or more performance metrics comprise numbers of space vehicles acquired from the two or more radio frequency signals, respectively.

7. The method of claim 5, wherein said two or more performance metrics are based at least in part on signal strength estimates from the two or more radio frequency signals, respectively.

29. The method of claim 1, wherein despreading and rotating comprises despreading and rotating each one of the two or more complex digital signals in a separate receiver path than each of the other ones of the two or more complex digital signals.

30. The method of claim 3, wherein coherently accumulating comprises coherently accumulating each one of the two or more complex digital signals in a separate receiver path than each of the other ones of the two or more complex digital signals.

31. The method of claim 3, wherein non-coherently accumulating comprises non-coherently accumulating each one of the two or more complex digital signals in a separate receiver path than each of the other ones of the two or more complex digital signals.

8. A mobile station, comprising:

two or more physically separated antennae to receive one or more SPS signals and to provide a respective two or more radio frequency signals;

a receiver comprising two or more paths to receive the two or more radio frequency signals from the respective two or more antennae, the two or more paths comprising a respective two or more complex mixers to downconvert one or more of said radio frequency signals to generate two or more complex digital signals, each complex digital signal comprising in-phase and quadrature components; and

a digital baseband processing engine to process the two or more complex digital signals at least in part to improve one or more performance metrics related to position estimation operations, including a combining unit configured to combine the two or more complex digital signals according to a non-coherent combining algorithm to generate a combined digital signal;

wherein said non-coherent combining algorithm comprises despreading and rotating each of the two or more complex digital signals, respectively, and combining the despread signals in a non-coherent combining operation to produce the combined digital signal.

9. The mobile station of claim 8, said digital baseband processing engine to additionally process by detecting one or more peaks of the combined signal.

10. The mobile station of claim 8, said non-coherent combining operation comprises:

coherently accumulating the results of the dispreading and rotating operations for the two or more complex digital signals, respectively;

non-coherently accumulating the results of the coherent accumulation for the two or more complex digital signals, respectively; and

adding the two or more non-coherent accumulations to generate the combined digital signal.

11. The mobile station of claim 10, said combining unit to add the two or more non-coherent accumulations at least in part by utilizing a weighed sum depending, at least in part, on respective gains of the two or more antennae.

12. The mobile station of claim 11, said digital baseband processing engine further to perform two or more sequential shallow searches using said two or more radio frequency signals from the respective two or more antennae and using a single receiver path, said shallow searches to yield two or more performance metrics associated with the respective two or more shallow searches, said digital baseband processing engine further to select at least one weight value for said add based at least in part on the respective gains.

13. The mobile station of claim 12, wherein said two or more performance metrics comprise numbers of space vehicles acquired from the two or more radio frequency signals, respectively.

14. The mobile station of claim 12, wherein said two or more performance metrics comprise signal strength estimates from the two or more radio frequency signals, respectively.

32. The mobile station of claim 8, wherein despreading and rotating comprises dispreading and rotating each one of the two or more complex digital signals in a separate receiver path than each of the other ones of the two or more complex digital signals.

33. The mobile station of claim 10, wherein coherently accumulating comprises coherently accumulating each one of the two or more complex digital signals in a separate receiver path than each of the other ones of the two or more complex digital signals.

34. The mobile station of claim 10, wherein non-coherently accumulating comprises non-coherently accumulating each one of the two or more complex digital signals in a separate receiver path than each of the other ones of the two or more complex digital signals.

15. An apparatus, comprising:

means for receiving one or more satellite positioning system (SPS) signals at two or more physically separated antennae of a mobile station, said two or more antennae to provide a respective two or more radio frequency signals to a receiver of the mobile station;

means for downconverting one or more of said radio frequency signals in two or more respective paths of a front end of the receiver to generate two or more complex digital signals, each complex digital signal comprising in-phase and quadrature components; and

means for processing the two or more complex digital signals at least in part to improve one or more performance metrics related to position estimation operations, including means for combining the two or more complex digital signals according to a non-coherent combining algorithm to generate a combined digital signal;

wherein said means for combining comprises means for despreading and rotating each of the two or more complex digital signals, respectively, and means for combining the despread signals in a non-coherent combining operation to produce the combined digital signal.

16. The apparatus of claim 15, wherein said means for processing additionally comprises means for detecting one or more peaks of the combined digital signal.

17. The apparatus of claim 15, wherein said means for combining the the despread signals according to the non-coherent combining operation comprises:

means for coherently accumulating the results of the despreading and rotating operations for the two or more complex digital signals, respectively;

means for non-coherently accumulating the results of the coherent accumulation for the two or more complex digital signals, respectively; and

means for adding the two or more non-coherent accumulations to generate the combined digital signal.

18. The apparatus of claim 17, wherein said means for adding the two or more non-coherent accumulations comprises means for performing a weighed sum depending, at least in part, on respective gains of the two or more antennae.

19. The apparatus of claim 17, further comprising:

means for performing two or more sequential shallow searches using said two or more radio frequency signals from the respective two or more antennae and using a single receiver path, said shallow searches to yield two or more performance metrics associated with the respective two or more shallow searches; and

means for selecting at least one weight value for said means for adding based at least in part on a comparison of the two or more performance metrics.

20. The apparatus of claim 19, wherein said two or more performance metrics comprise numbers of space vehicles acquired from the two or more radio frequency signals, respectively.

21. The apparatus of claim 19, wherein said two or more performance metrics are based at least in part on signal strength estimates from the two or more radio frequency signals, respectively.

35. The apparatus of claim 15, wherein despreading and rotating comprises dispreading and rotating each one of the two or more complex digital signals in a separate receiver path than each of the other ones of the two or more complex digital signals.

36. The apparatus of claim 17, wherein coherently accumulating comprises coherently accumulating each one of the two or more complex digital signals in a separate receiver path than each of the other ones of the two or more complex digital signals.

37. The apparatus of claim 18, wherein non-coherently accumulating comprises non-coherently accumulating each one of the two or more complex digital signals in a separate receiver path than each of the other ones of the two or more complex digital signals.

22. An article, comprising a non-transitory storage medium having stored thereon instructions that, if executed by a processor of a mobile station, direct the processor to:

process two or more complex digital signals, each digital signal comprising in-phase and quadrature components, to perform position estimation operations that combine the two or more complex digital signals according to a non-coherent combining algorithm to generate a combined digital signal, wherein said non-coherent combining algorithm comprises despreading and rotating each of the two or more complex digital signals, respectively, and combining the despread signals in a non-coherent combining operation to produce the combined digital signal;

wherein said two or more complex digital signals are derived from one or more SPS signals received at two or more physically separated antennae of the mobile station.

23. The article of claim 22, wherein the storage medium has stored thereon further instructions that, if executed, further direct the processor to detect one or more peaks of the combined digital signal.

24. The article of claim 22, wherein the storage medium has stored thereon further instructions that, if executed, further direct the processor to perform the non-coherent combining operation by:

coherently accumulating the results of the dispreading and rotating operations for the two or more complex digital signals, respectively;

non-coherently accumulating the results of the coherent accumulation for the two or more complex digital signals, respectively; and

adding the non-coherent accumulations to generate the combined digital signal.

25. The article of claim 24, wherein the storage medium has stored thereon further instructions that, if executed, further direct the processor to add the non-coherent accumulations utilizing a weighed sum depending, at least in part, on respective gains of the two or more antennae.

26. The article of claim 25, wherein the storage medium has stored thereon further instructions that, if executed, further direct the processor to:

perform two or more sequential shallow searches using said two or more radio frequency signals from the respective two or more antennae and using a single receiver path, said shallow searches to yield two or more performance metrics associated with the respective two or more shallow searches; and

select at least one weight value for said add based at least in part on the respective gains.

27. The article of claim 26, wherein said two or more performance metrics comprise numbers of space vehicles acquired from the two or more radio frequency signals, respectively.

28. The article of claim 26, wherein said two or more performance metrics comprise signal strength estimates from the two or more radio frequency signals, respectively.

38. The article of claim 22, wherein despreading and rotating comprises dispreading and rotating each one of the two or more complex digital signals in a separate receiver path than each of the other ones of the two or more complex digital signals.

39. The article of claim 24, wherein coherently accumulating comprises coherently accumulating each one of the two or more complex digital signals in a separate receiver path than each of the other ones of the two or more complex digital signals.

40. The article of claim 24, wherein non-coherently accumulating comprises non-coherently accumulating each one of the two or more complex digital signals in a separate receiver path than each of the other ones of the two or more complex digital signals.