Using FFT engines to process decorrelated GPS signals to establish frequencies of received signals

• US 6,806,827 B2
• Filed: 11/18/2002
• Issued: 10/19/2004
• Est. Priority Date: 11/18/2002
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: RF Micro Devices Incorporated (Qorvo, Inc.)
• Inventors: Keegan, Richard, Cox, Wayne, Colborne, Steve Francis, Warloe, Andreas, Najarian, Richard
• Primary Examiner(s): Issing, Gregory C.
• Application Number:
  US10/298,447
• Publication Number:
  US 20040095275A1
• Time in Patent Office: 701 Days
• Field of Search: 342/357.12, 342/357.15, 342/357.06, 375/150
• US Class Current: 342/357.77
• CPC Class Codes: G01S 19/21 Interference related issues ; Issues related to cross-correlation, spoofing or other methods of denial of service
• CPC Class Codes: G01S 19/29 carrier including Doppler, related G01S19/246 takes precedence
• CPC Class Codes: G01S 19/34 Power consumption
• CPC Class Codes: H04B 1/70752 Partial correlation
• CPC Class Codes: H04B 1/708 Parallel implementation

Abstract

The correlation circuitry of the present invention operates in communication with a controller and transform circuitry to concurrently search a range of frequencies by correlating a received signal from the global positioning system (GPS) with a generated frequency and a generated code at a plurality of time offsets. The output of the correlation circuitry is provided to the transform circuitry, such as fast Fourier transform (FFT) circuitry, that transforms the output of the correlation circuitry. The results from the transformation circuitry are used by a GPS receiver to determine a frequency of the received GPS signal and a time offset associated with a ranging code carried in the received GPS signal.

Claims

1. A GPS receiver comprising:

correlation circuitry adapted to provide data corresponding to a correlation of a signal with a generated frequency and a generated code at a plurality of time offsets, said correlation circuitry comprising a plurality of correlators each adapted to provide a subset of said data corresponding to a correlation of said signal with said generated frequency and said generated code at a one of said plurality of offsets;

circuitry adapted to provide said generated frequency and said generated code at said plurality of time offsets to said correlation circuitry; and

transform circuitry adapted to receive said data and transform each subset of said data into a frequency domain to produce transformed data, which is used by the GPS receiver to determine a frequency of said signal and a time offset associated with a ranging code carried in said signal.

2. The GPS receiver of claim 1 wherein said frequency is within an at least 30,000 Hz range of frequencies and said transformed data covers a frequency range corresponding to said range of frequencies.

3. The GPS receiver of claim 1 wherein each of said plurality of correlators comprises accumulation circuitry adapted to accumulate results of said correlation of said signal with said generated frequency and said generated code at a one of said plurality of offsets to provide a plurality of partial correlation samples forming said subset of said data.

4. The GPS receiver of claim 3 wherein said accumulation circuitry is further adapted to provide each of said plurality of partial correlation samples at approximately thirty-two (32) microsecond intervals for a total of two (2) milliseconds, thereby producing a bin width associated with said transformation circuitry of approximately 500 Hz.

5. The GPS receiver of claim 1 further comprising memory logic adapted to store said data from said correlation circuitry and provide said data to said transform circuitry.

6. The GPS receiver of claim 1 further comprising memory logic adapted to store said transformed data produced by said transform circuitry.

7. The GPS receiver of claim 1 wherein said circuitry is further adapted to determine said frequency of said signal and said time offset associated with said ranging code carried in said signal based on said transformed data produced by said transform circuitry.

8. The GPS receiver of claim 1 wherein said correlation circuitry, said circuitry, and said transform circuitry are integrated into a single semiconductor die.

9. A GPS receiver comprising:

a receiver frontend adapted to receive a radio-frequency signal and provide a baseband signal based on said radio-frequency signal;

correlation circuitry adapted to provide data corresponding to a correlation of said baseband signal with a generated frequency and a generated code at a plurality of time offsets, said correlation circuitry comprising a plurality of correlators each adapted to provide a subset of said data corresponding to a correlation of said baseband signal with said generated frequency and said generated code at a one of said plurality of offsets;

circuitry adapted to provide said generated frequency and said generated code at said plurality of time offset to said correlation circuitry; and

transform circuitry adapted to receive said data and transform each subset of said data into a frequency domain to produce transformed data, which is used by the GPS receiver to determine a frequency of said baseband signal and a time offset associated with a ranging code carried in said baseband signal.

10. The GPS receiver of claim 9 wherein said frequency is within an at least 30,000 Hz range of frequencies and said transformed data covers a frequency range corresponding to said range of frequencies.

11. The GPS receiver of claim 9 wherein each of said plurality of correlators comprises accumulation circuitry adapted to accumulate results of said correlation of said baseband signal with said generated frequency and said generated code at a one of said plurality of offsets to provide a plurality of partial correlation samples forming said subset of said data.

12. The GPS receiver of claim 11 wherein said accumulation circuitry is further adapted to provide each of said plurality of partial correlation samples at approximately thirty-two (32) microsecond intervals for a total of two (2) milliseconds, thereby producing a bin width associated with said transformation circuitry of approximately 500 Hz.

13. The GPS receiver of claim 9 further comprising memory logic adapted to store said data from said correlation circuitry and provide said data to said transform circuitry.

14. The GPS receiver of claim 9 further comprising memory logic adapted to store said transformed data produced by said transform circuitry.

15. The GPS receiver of claim 9 wherein said circuitry is further adapted to determine said frequency of said baseband signal and said time offset associated with said ranging code carried in said baseband signal based on said transformed data produced by said transform circuitry.

16. A GPS receiver comprising:

means for providing data corresponding to a correlation of a signal with a generated frequency and a generated code at a plurality of time offsets, said data comprising a plurality of subsets each corresponding to said correlation of said signal with said generated frequency and said generated code at one of said plurality of time offsets;

means for providing said generated frequency and said generated code at said plurality of time offsets to said means for providing said data; and

means for transforming each subset of said data into a frequency domain to produce transformed data, which is used by the GPS receiver to determine a frequency of said signal and a time offset associated with a ranging code carried in said signal.

17. The GPS receiver of claim 16 wherein said frequency is within an at least 30,000 Hz range of frequencies and said transformed data covers a frequency range corresponding to said range of frequencies.

18. The GPS receiver of claim 16 wherein said means for providing said data comprises a means for accumulating results of said correlation of said signal with said generated frequency and said generated code at said plurality of offsets to provide said data.

19. The GPS receiver of claim 18 wherein said means for accumulating said results is adapted to provide partial correlation samples at approximately thirty-two (32) microsecond intervals for a total of two (2) milliseconds, thereby providing said data and producing a bin width associated with said transformation circuitry of approximately 500 Hz.