Methods and systems for doppler frequency shift removal and correlation for software-based receivers

• US 7,679,551 B2
• Filed: 05/23/2007
• Issued: 03/16/2010
• Est. Priority Date: 05/24/2006
• Status: Expired due to Fees

• Current Assignee: University Technologies International LP
• Original Assignee: UTI Limited Partnership
• Inventors: Lachapelle, Gérard, Petovello, Mark Gregory
• Primary Examiner(s): PHAN, DAO LINDA
• Application Number:
  US11/805,718
• Publication Number:
  US 20080007448A1
• Time in Patent Office: 1,028 Days
• Field of Search: 342/357.02, 342/357.05, 342/357.06, 342/357.12, 342/357.13, 701/207, 701/213, 702/106
• US Class Current: 342/357.57
• CPC Class Codes: G01S 19/29 carrier including Doppler, related G01S19/246 takes precedence
• CPC Class Codes: G01S 19/37 Hardware or software details of the signal processing chain

Abstract

Embodiments of the invention provide a method for effecting Doppler removal and correlation for software-based receivers. For one embodiment of the invention Doppler removal is performed concurrently for all received communications signals. For one embodiment of the invention, a single frequency selected to effect Doppler removal, multiple communications signals having Doppler frequency shift are received from corresponding communications signal sources, and a Doppler removal process is performed concurrently for each received communication signal. A correlation process is then performed, the correlation process having an integration interval divided into multiple sub-intervals.

Claims

1. A method comprising:

selecting a single frequency to effect Doppler removal;

receiving multiple communications signals having Doppler frequency shift from corresponding communications signal sources;

performing a Doppler removal process using the selected single frequency, the Doppler removal process performed concurrently for each received communication signal; and

performing a correlation process, the correlation process having an integration interval divided into multiple sub-intervals.

2. The method of claim 1 wherein a single frequency Doppler removal lookup table is created for the selected single frequency.

3. The method of the claim 1 wherein each of the received communications signals is a GNSS signal received from a corresponding satellite.

4. The method of claim 3 wherein performing a Doppler removal process includes downconverting each of the multiple received communications signals concurrently.

5. The method of the claim 1 wherein the selected single frequency is dynamically determined based upon a frequency of one or more of the multiple received communications signals.

6. The method of claim 1 wherein each of the multiple sub-intervals is the same length.

7. The method of claim 1 wherein the number of sub-intervals is determined independently for each of the communications signal sources.

8. An apparatus comprising:

an antenna for receiving multiple communications signals having Doppler frequency shift from corresponding communications signal sources; and

signal processing means for performing a Doppler removal process concurrently for each received communication signal, the Doppler removal process effected using a single selected frequency and performing a correlation process, the correlation process having an integration interval divided into multiple sub-intervals.

9. The apparatus of the claim 8 wherein a single frequency Doppler removal lookup table is created for the selected single frequency.

10. The apparatus of claim 8 wherein each of the received communications signals is a GNSS signal received from a corresponding satellite.

11. The apparatus of claim 10 wherein performing a Doppler removal process includes downconverting each of the multiple received communications signals concurrently.

12. The apparatus of the claim 9 wherein the selected single frequency is dynamically determined based upon a frequency of one or more of the multiple received communications signals.

13. The apparatus of claim 8 wherein each of the multiple sub-intervals is the same length.

14. The apparatus of claim 8 wherein the number of sub-intervals is determined independently for each of the communications signal sources.

15. A machine-readable medium that provides executable instructions, which when executed by a processor, cause the processor to perform a method, the method comprising:

selecting a single frequency to effect Doppler removal;

receiving multiple communications signals having Doppler frequency shift from corresponding communications signal sources;

performing a Doppler removal process using the selected single frequency, the Doppler removal process performed concurrently for each received communication signal; and

performing a correlation process, the correlation process having an integration interval divided into multiple sub-intervals.

16. The machine-readable medium of claim 15 wherein a single frequency Doppler removal lookup table is created for the selected single frequency.

17. The machine-readable medium of the claim 15 wherein each of the received communications signals is a GNSS signal received from a corresponding satellite.

18. The machine-readable medium of claim 17 wherein performing a Doppler removal process includes downconverting each of the multiple received communications signals concurrently.

19. The machine-readable medium of the claim 15 wherein the selected single frequency is dynamically determined based upon a frequency of one or more of the multiple received communications signals.

20. The machine-readable medium of claim 15 wherein each of the multiple sub-intervals is the same length.

21. The machine-readable medium of claim 15 wherein the number of sub-intervals is determined independently for each of the communications signal sources.