Acquisition through circular correlation by partition for GPS C/A code and P(Y) code

• US 6,567,042 B2
• Filed: 12/04/2000
• Issued: 05/20/2003
• Est. Priority Date: 12/04/2000
• Status: Expired due to Fees

• Current Assignee: Air Force Government of The United States of America As Represented By The Secretary
• Original Assignee: United States Of America As Represented By The Secretary Of The Air Force
• Inventors: Lin, David M., Tsui, James B. Y.
• Primary Examiner(s): Phan, Dao
• Application Number:
  US09/729,627
• Publication Number:
  US 20020067307A1
• Time in Patent Office: 897 Days
• Field of Search: 342/357.05, 342/357.06, 342/357.12, 342/357.15, 701/213, 701/215
• US Class Current: 342/357.77
• CPC Class Codes: G01S 19/29 carrier including Doppler, related G01S19/246 takes precedence
• CPC Class Codes: G01S 19/30 code related G01S19/246 takes precedence
• CPC Class Codes: G01S 19/32 Multimode operation in a single same satellite system, e.g. GPS L1/L2
• CPC Class Codes: H04B 1/7077 Multi-step acquisition, e.g. multi-dwell, coarse-fine or validation

Abstract

An improved global positioning system satellite signal acquisition method and device. The method and device of the invention reduces the number of operations in the block correlation used in determining Doppler frequency and time of the received GPS C/A and P(Y) codes. Reducing the number of operations in block correlation increases acquisition speed and reduces energy requirements, aspects conducive to commercial and military hand held GPS receivers.

Claims

1. An efficient, data processing minimizing GPS data acquisition software method comprising the steps of:

receiving a GPS signal;

considering N data bits of locally generated P code in block-to-block correspondence with N data bits from said receiving step;

manipulating N data bits from said receiving and considering steps into a subdivision of data bits, said subdivision of data bits constituting less than a complete transmitted pattern from said receiving step;

applying a circular fast Fourier transform correlation algorithm on said data bits from said manipulating step;

repeating said applying step until an output of said applying step is above a preselected acquisition threshold value; and

determining time and Doppler frequency of said GPS signal.

2. The efficient, data processing minimizing GPS data acquisition software method of claim 1 wherein said manipulating step comprises the steps of:

first zero padding a block of N data bits from said receiving step to comprise a data block equivalent to 2N; and

second zero padding said block of N data bits of locally generated replica P-code from said considering step to comprise a 2N-point extended data block.

3. The efficient, data processing minimizing GPS data acquisition software method of claim 1 wherein said receiving step further comprises the step of receiving a GPS C/A code signal comprising N data bits.

4. The efficient, data processing minimizing GPS data acquisition software method of claim 1 wherein said receiving step further comprises the step of receiving a GPS P-code signal comprising N data bits.

5. The efficient, data processing minimizing GPS data acquisition software method of claim 1 wherein said receiving step further comprises the step of receiving a GPS C/A and P-code signals comprising N data bits.

6. The efficient, data processing minimizing GPS data acquisition software method of claim 1 wherein said manipulating step comprises the steps of:

adding point-by-point said block of N data bits with a second contiguous block of N data bits forming a pseudo circular data block; and

combining point-by-point a block of N data bits of locally generated P-code with a second contiguous block of N data bits of locally generated P-code forming a pseudo circular data block.

7. The efficient, data processing minimizing GPS data acquisition software method of claim 2, further including, after said applying step, the steps of:

disregarding said second N points of an output from said applying step;

separating said N data points from said disregarding step into M data blocks, each of said M data blocks containing N data points; and

applying an M-point fast Fourier transform thereto.

8. An efficient, data processing minimizing GPS receiving device determining time and Doppler frequency of a GPS signal comprising:

a GPS signal receiving antenna;

a data processor connected to said GPS signal receiving antenna manipulating data from said antenna into N data bits;

a local P-code generator communicating with said data processor generating N data bits of P code in block-to-block correspondence with N data bits from said data processor;

said data processor including a data manipulation algorithm further manipulating N data bits from said received signal and from said locally generated P-code into a subdivision of data bits, said subdivision of data bits constituting less than a complete transmitted pattern received by said antenna; and

a circular fast Fourier transform correlation algorithm applied to said subdivision of data bits, said correlation algorithm applied until an output is above a preselected acquisition threshold value.

9. The efficient, data processing minimizing GPS receiving device of claim 8 wherein said data manipulation within said data processor comprises:

a plurality of data bits of zero value added to said N data bits from said antenna to comprise a data block equivalent to 2N; and

a second plurality of data bits of zero value added to said N data bits from said local P-code generator to comprise a 2N-point extended data block.

10. The efficient, data processing minimizing GPS receiving device of claim 8 wherein said GPS signal receiving antenna further comprises a GPS C/A code, N-data bit signal receiving antenna.

11. The efficient, data processing minimizing GPS receiving device of claim 8 wherein said data processor further comprises:

a contiguous block of N data bits added point-by-point to said block of N data bits forming a pseudo circular data block; and

a second contiguous block of N data bits of locally generated P-code combined point-by-point with a block of N data bits of locally generated P-code forming a pseudo circular data block.

12. The efficient, data processing minimizing GPS receiving device of claim 8, wherein said fast Fourier transform circular correlation algorithm further comprises:

a second block of N points output from said fast Fourier circular correlation application, said second block of N points eliminated from further processing within said data processor;

a subdivision of M data blocks, said M data blocks subdivided from said block of N points and each of said M data blocks containing N data points; and

an M-point fast Fourier transform algorithm applied to said M data blocks.