Satellite navigation system having redundant signal processing and matched filtering

• US 6,311,127 B1
• Filed: 09/02/1999
• Issued: 10/30/2001
• Est. Priority Date: 09/02/1999
• Status: Expired due to Term

• Current Assignee: Rockwell Collins, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Rockwell Collins, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Thuringer, Daniel J., McCall, Daryl L., Stratton, D. Alexander
• Primary Examiner(s): Nguyen, Tan
• Assistant Examiner(s): Donnelly, Arthur D.
• Application Number:
  US09/388,972
• Time in Patent Office: 789 Days
• Field of Search: 701/213, 701/215, 701/225, 342/357.06, 342/357.12, 342/358, 342/450
• US Class Current: 701/213
• 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 19/24 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 19/30 code related G01S19/246 takes precedence

Abstract

Satellite navigation systems and receivers of the invention include an antenna which receives satellite signals from multiple satellites. Radio frequency circuitry coupled to the antenna converts the satellite signals into intermediate signals. Multiple signal processors coupled to the radio frequency circuitry implement similar or identical signal processing algorithms on the received satellite signals to provide redundant ranging information (i.e., code and carrier measurements). One or more navigation processors coupled to the signal processors process the ranging information and provide positioning data outputs. The navigation processor implements smoothing filter functions that combine the redundant ranging data in a manner which enhances the positional accuracy. The navigation processor also implements unique fault-detection filter functions on the redundant ranging information. The characteristic response of the fault-detection filter functions are matched to the response of the smoothing filter functions, ensuring that signal-processing faults are detected and before the smoothed data exhibits excessive errors.

Claims

1. A satellite navigation system comprising:

an antenna adapted to receive satellite signals transmitted from a plurality of satellites;

radio frequency circuitry coupled to the antenna and adapted to convert the satellite signals into intermediate signals;

a first signal processor coupled to the radio frequency circuitry and adapted to implement first signal processing algorithms on the intermediate signals to obtain first signal processor ranging information;

a second signal processor coupled to the radio frequency circuitry and adapted to implement the same first signal processing algorithms on the intermediate signals as implemented by the first signal processor to obtain second signal processor ranging information; and

a navigation processor coupled to each of the first and second signal processors, the navigation processor implementing a smoothing filter function on linear combinations of the first signal processor ranging information and the second signal processor ranging information, the navigation processor also implementing a fault detection and exclusion filter function to provide fault detection residual information, wherein features of the fault detection and exclusion filter function are matched to features of the smoothing filter function.

2. The satellite navigation system of claim 1, wherein the radio frequency circuitry is adapted to convert the satellite signals into intermediate signals which are indicative of code pseudorange measurements and of carrier phase measurements and wherein the first and second signal processors are adapted to implement the first signal processing algorithms to obtain the ranging information, the first signal processor ranging information and the second signal processor ranging information each including the code pseudorange measurements and the carrier phase measurements.

3. The satellite navigation system of claim 2, wherein the navigation processor is adapted to implement the fault detection and exclusion filter function and to compare the code pseudorange measurements provided by the first signal processor to the code pseudorange measurements provided by the second signal processor.

4. The satellite navigation system of claim 3, wherein the navigation processor is adapted to implement the smoothing filter function to provide carrier smoothed code pseudorange measurements as a function of unsmoothed code pseudorange measurements and as a function of the carrier phase measurements.

5. The satellite navigation system of claim 4, wherein the navigation processor is adapted to implement the fault detection and exclusion filter function such that the fault detection and exclusion filter function is equivalent to the smoothing filter function, thereby matching the characteristics of the fault detection and exclusion filter function to the features of the smoothing filter function.

6. The satellite navigation system of claim 5, wherein the fault detection and exclusion filter function is a first order equivalent to the smoothing filter function.

7. The satellite navigation system of claim 6, wherein the smoothing filter function implemented by the navigation processor generates a carrier-smoothed pseudorange output P_S(t_j) using the relationship:

8. The satellite navigation system of claim 7, wherein the fault detection and exclusion filter function implemented by the navigation processor generates unsmoothed pseudorange residuals B_i(t_j) using the relationship:

9. The satellite navigation system of claim 1, wherein the antenna and the radio frequency circuitry further include a separate antenna and radio frequency circuitry combination associated with, and providing the intermediate signals to, each of the first and second signal processors.

10. A method of generating navigation data using a satellite navigation system receiver, the method comprising:

receiving satellite signals transmitted from a plurality of satellites;

converting the satellite signals into intermediate signals;

performing first signal processor algorithms on the positioning signals using a first signal processor to obtain first signal processor ranging information;

performing the same first signal processor algorithms on the positioning signals using a second signal processor to obtain second signal processor ranging information;

performing a smoothing filter function on linear combinations of the first signal processor ranging information and the second signal processor ranging information using a navigation processor to generate smoothed positioning information;

performing a fault detection and exclusion filter function, having features which are matched to features of the smoothing filter function, to provide fault detection residual information to detect faults in the positioning information outputs and exclude erroneous data from the navigation solution.

11. The method of claim 10, wherein converting the satellite signals into intermediate signals further comprises converting the satellite signals into ranging signals which are indicative of code pseudorange measurements and of carrier phase measurements.

12. The method of claim 11, wherein performing the first signal processor algorithms on the intermediate signals using the first and second signal processors includes performing the first signal processing algorithms to obtain as the first signal processor ranging information and the second signal processor ranging information code pseudorange measurements and carrier phase measurements.

13. The method of claim 12, wherein performing the smoothing filter function further comprises providing carrier smoothed code pseudorange measurements as a function of unsmoothed code pseudorange measurements and as a function of the carrier phase measurements.

14. The method of claim 13, wherein performing the fault detection and exclusion filter function further comprises performing the fault detection and exclusion filter function such that it'"'"'s characteristic response is equivalent to the smoothing filter function, thereby matching the characteristics of the fault detection and exclusion filter function to the features of the smoothing filter function.

15. The method of claim 14, wherein performing the fault detection and exclusion filter function further comprises performing the fault detection and exclusion filter function such that it is a first order equivalent to the smoothing filter function.

16. The method of claim 15, wherein performing the smoothing filter function further comprises generating a carrier-smoothed pseudorange output P_S(t_j) using the relationship:

17. The method of claim 16, wherein performing the fault detection and exclusion filter function further comprises generating unsmoothed pseudorange residuals B_i(t_j) using the relationship:

18. The method of claim 14, and further comprising generating a position indicative output, using the navigation processor, as a function of the smoothed positioning information.