Adaptive code generator for satellite navigation receivers

• US 20070258511A1
• Filed: 05/03/2006
• Published: 11/08/2007
• Est. Priority Date: 05/03/2006
• Status: Active Grant

• Current Assignee: Deere & Company
• Original Assignee: Navcom Technology, Inc. (Deere & Company)
• Inventors: Knight, Jerry, Cahn, Charles, Li, David
• Granted Patent: US 7,860,145 B2
• Time in Patent Office: Days
• US Class Current: 375/149
• CPC Class Codes: G01S 19/30 code related G01S19/246 takes precedence
• CPC Class Codes: G01S 19/33 Multimode operation in different systems which transmit time stamped messages, e.g. GPS/GLONASS
• CPC Class Codes: G01S 19/37 Hardware or software details of the signal processing chain
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 2201/70707 Efficiency-related aspects
• CPC Class Codes: H04B 2201/70715 with application-specific features
• CPC Class Codes: H04J 13/00 Code division multiplex systems for frequency hopping H04B1/713
• CPC Class Codes: H04J 13/10 Code generation

Abstract

A satellite navigation device including a receiver having an adjustable code generator is described. The adjustable code generator is configurable to generate a set of spread-spectrum code signals. Each spread-spectrum code signal has a respective length corresponding to a repetition period. The set of spread-spectrum code signals includes first and second spread-spectrum code signals having distinct first and second lengths.

Claims

1. A satellite navigation device, comprising:

a receiver including an adjustable code generator, the adjustable code generator being configurable to generate a set of spread-spectrum code signals, wherein each spread-spectrum code signal has a respective length corresponding to a repetition period and the set of spread-spectrum code signals includes first and second spread-spectrum code signals having distinct first and second lengths.

2. The satellite navigation system of claim 1, the adjustable code generator further including a feedback loop and a programmable shift register having a number of bits that is greater than or equal to a degree of a composite Galois polynomial corresponding to the set of spread-spectrum code signals.

3. The satellite navigation system of claim 2, wherein the number of bits in the programmable shift register corresponds to a largest sum of degrees of respective polynomials that describe a respective spread-spectrum code signal in the set of spread-spectrum code signals.

4. The satellite navigation system of claim 3, wherein the set of polynomials comprises irreducible Galois Field polynomials.

5. The satellite navigation system of claim 2, the feedback loop further including a programmable feedback mask and a feedback mask table, wherein the feedback mask table contains a set of feedback masks and a respective feedback mask for a respective spread-spectrum code signal is a binary representation of a corresponding polynomial.

6. The satellite navigation system of claim 2, wherein the feedback loop has multiple input bits and a single output bit.

7. The satellite navigation system of claim 6, wherein the single output bit is determined by an exclusive- or tree of the multiple input bits.

8. The satellite navigation system of claim 2, wherein the feedback loop has multiple input bits and multiple output bits.

9. The satellite navigation system of claim 8, wherein each of the multiple output bits is determined by an exclusive- or of an output bit from the programmable shift register and a respective input bit.

10. The satellite navigation system of claim 1, the adjustable code generator further including an initial state table, wherein the initial state table contains a set of initial state vectors and each initial state vector corresponds to initial values of the bits in the programmable shift register corresponding to at least one of the set of spread-spectrum signals.

11. The satellite navigation system of claim 1, the adjustable code generator further including control logic, wherein the control logic determines when a respective spread-spectrum signal generated using the adjustable code generator has reached the respective length and starts the next code period by programming an initial state vector in a set of initial state vectors stored in an initial state vector table into the programmable shift register, and wherein each initial state vector corresponds to initial values of the bits in the programmable shift register corresponding to at least one of the set of spread-spectrum signals.

12. The satellite navigation system of claim 1, the adjustable code generator further including control logic, wherein the control logic determines when a respective spread-spectrum signal generated using the adjustable code generator has reached a termination condition and starts the next code period by programming an initial state vector in a set of initial state vectors stored in an initial state vector table into the programmable shift register, and wherein each initial state vector corresponds to initial values of the bits in the programmable shift register corresponding to at least one of the set of spread-spectrum signals.

13. The satellite navigation system of claim 1, the adjustable code generator further including control logic and a short cycle state table, wherein the short cycle state table contains a set of short cycle state vectors and each short cycle state vector corresponds to values of the bits in the programmable shift register corresponding to at least one of the set of spread-spectrum signals at a pre-determined fraction of the respective length and the control logic determines when a respective spread-spectrum signal generated using the adjustable code generator has reached the pre-determined fraction of the respective length.

14. A satellite navigation device, comprising:

a receiver means including a generator means, the generator means being configurable to generate a set of spread-spectrum code signals, wherein each spread-spectrum code signal has a respective length corresponding to a repetition period and the set of spread-spectrum code signals includes at least two lengths.

15. A method, comprising:

configuring an adjustable code generator to generate a spread-spectrum code signal selected from a set of spread-spectrum code signals; and

generating the spread-spectrum code signal,

wherein each spread-spectrum code signal in the set of spread-spectrum code signals has a respective length corresponding to a repetition period and the set of spread-spectrum code signals includes first and second spread-spectrum code signals having distinct first and second lengths.

16. The method of claim 15, wherein the adjustable code generator further includes a feedback loop and a programmable shift register having a number of bits that is greater than or equal to a degree of a composite Galois polynomial corresponding to the set of spread-spectrum code signals and a feedback loop.

17. The method of claim 16, wherein the number of bits in the programmable shift register corresponds to a largest sum of degrees of respective polynomials that describe a respective spread-spectrum code signal in the set of spread-spectrum code signals.

18. The method of claim 17, wherein the set of polynomials comprises irreducible Galois Field polynomials.

19. The method of claim 16, further comprising selecting a respective feedback mask in a set of feedback masks and feeding back the respective feedback mask using the feedback loop, wherein the respective feedback mask for a respective spread-spectrum code signal is a binary representation of a corresponding polynomial.

20. The method of claim 16, wherein the feedback loop has multiple input bits and a single output bit.

21. The method of claim 20, further comprising determining the single output bit using an exclusive- or tree of the multiple input bits.

22. The method of claim 16, wherein the feedback loop has multiple input bits and multiple output bits.

23. The method of claim 22, further comprising determining each of the multiple output bits using an exclusive- or of an output bit from the programmable shift register and a respective input bit.

24. The method of claim 15, further comprising setting an initial state of the programmable shift register using a respective initial state vector in a set of initial state vectors, wherein each initial state vector corresponds to initial values of the bits in the programmable shift register corresponding to at least one of the set of spread-spectrum signals.

25. The method of claim 15, further comprising determining when a respective spread-spectrum signal generated using the adjustable code generator has reached the respective length using control logic and setting an initial state of the programmable shift register using a respective initial state vector in a set of initial state vectors, wherein each initial state vector corresponds to initial values of the bits in the programmable shift register corresponding to at least one of the set of spread-spectrum signals.

26. The method of claim 15, further comprising determining when a respective spread-spectrum signal generated using the adjustable code generator has reached a termination condition using control logic and setting an initial state of the programmable shift register using a respective initial state vector in a set of initial state vectors, wherein each initial state vector corresponds to initial values of the bits in the programmable shift register corresponding to at least one of the set of spread-spectrum signals.

27. The method of claim 15, further comprising determining when a respective spread-spectrum signal generated using the adjustable code generator has reached a pre-determined fraction of the respective length using control logic and setting a short cycle state of the programmable shift register using a respective short cycle state vector in a set of short cycle state vectors, wherein each short cycle state vector corresponds to values of the bits in the programmable shift register corresponding to at least one of the set of spread-spectrum signals at the pre-determined fraction of the respective length.

28. A computer-program product, comprising:

a computer readable storage medium and a computer program mechanism embedded therein, the computer program mechanism comprising;

instructions for configuring an adjustable code generator to generate a spread-spectrum code signal selected from a set of spread-spectrum code signals; and

instructions for generating the spread-spectrum code signal,

wherein each spread-spectrum code signal in the set of spread-spectrum code signals has a respective length corresponding to a repetition period and the set of spread-spectrum code signals includes first and second spread-spectrum code signals having distinct first and second lengths.

29. A computer, comprising:

a main memory;

a processor with a cache memory; and

a program, stored in the main memory and executed by the processor, the program including instructions for configuring an adjustable code generator to generate a spread-spectrum code signal selected from a set of spread-spectrum code signals; and

instructions for generating the spread-spectrum code signal, wherein each spread-spectrum code signal in the set of spread-spectrum code signals has a respective length corresponding to a repetition period and the set of spread-spectrum code signals includes first and second spread-spectrum code signals having distinct first and second lengths.