Deeply-integrated adaptive GPS-based navigator with extended-range code tracking
First Claim
1. A system for determining a multidimensional navigation state for a navigation platform based on radio navigation data transmitted by external terminals comprising:
- a radio navigation data receiver for receiving and amplifying said radio navigation data embedded in noise;
a bank of correlators for extracting said radio navigation data from said noise over a range of delay error, said correlators processing said radio navigation data and said noise to generate correlator output functions indicative of a degree of correlation for each correlator between said radio navigation data and a known internal replica signal, said correlator output functions being non-triangular M code correlator output functions;
an estimator for estimating the radio navigation data signal power and noise power from the correlator output functions; and
a measurement update unit including a nonlinear filter, said measurement update unit for updating the navigation state based on conditional moments of the navigation state calculated as a function of the estimated radio navigation data signal power and noise power, and the correlator outputs.
1 Assignment
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Accused Products
Abstract
A system and method for generating a multidimensional navigation solution utilizes Global Positioning System (GPS) data to obtain highly reliable and accurate navigational solutions in high interference and dynamic environments, at a performance level which has been heretofore unattainable. Additional sensors such as inertial (gyros and accelerometers), altimeters, radars, etc. may be employed in a deeply integrated configuration. The approach taken in the present invention differs from that of previous techniques through its exploitation of nonlinear filtering methods; as a result, the navigation system architecture and processes employed yield significant improvements in navigation system performance, both in code tracking and reacquisition, and in carrier tracking and reacquisition. The improvements are particularly significant at low signal/noise ratios, where conventional approaches are especially susceptible to loss of code lock or carrier lock.
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Citations
82 Claims
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1. A system for determining a multidimensional navigation state for a navigation platform based on radio navigation data transmitted by external terminals comprising:
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a radio navigation data receiver for receiving and amplifying said radio navigation data embedded in noise;
a bank of correlators for extracting said radio navigation data from said noise over a range of delay error, said correlators processing said radio navigation data and said noise to generate correlator output functions indicative of a degree of correlation for each correlator between said radio navigation data and a known internal replica signal, said correlator output functions being non-triangular M code correlator output functions;
an estimator for estimating the radio navigation data signal power and noise power from the correlator output functions; and
a measurement update unit including a nonlinear filter, said measurement update unit for updating the navigation state based on conditional moments of the navigation state calculated as a function of the estimated radio navigation data signal power and noise power, and the correlator outputs. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
a signal power estimator for determining radio navigation data signal power based on correlator moments; and
a noise power estimator for estimating noise power based on the correlator moments and said signal power estimate.
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10. An estimator for estimating signal and noise power in a system for determining a multidimensional navigation state for a navigation platform based on radio navigation data embedded in noise, said radio navigation data signal being received by a radio navigation data receiver including a bank of correlators for extracting said radio navigation data from said noise over a range of delay error, said correlators processing said radio navigation data and said noise to generate correlator output function indicative of degree of correlation for each correlator between said radio navigation data and a known replica signal, said estimator comprising:
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a signal power estimator for determining radio navigation data signal power based on correlator moments;
a noise power estimator for estimating noise power based on the correlator moments and said signal power estimate; and
a nonlinear filter for calculating said correlator moments, which represent statistical expectations of nonlinear functions of line-of-sight position errors, said correlator moments being calculated according to the equation;
- View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
a smoothing function for updating the bias estimate of each correlator according to a smoothing time constant; and
a minimum function for determining the bias estimate as the minimum value of the smoothed bias estimates.
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13. The estimator of claim 10 wherein said correlator moments comprise a first conditional moment comprising a conditional mean.
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14. The estimator of claim 10 wherein the noise power estimate comprises a vector, such that an independent noise power estimate is calculated for each correlator in the correlator bank.
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15. The estimator of claim 10 wherein the bank of correlators comprises an extended-range bank of correlators for extracting said radio navigation data from said noise over an extended range of delay error, said correlators processing said radio navigation data and said noise to generate correlator output functions indicative of degree of correlation for each correlator in the extended-range bank between said radio navigation data and a known internal replica signal.
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16. The estimator of claim 10 further comprising an inertial sensor unit for generating inertial data indicative of the inertial behavior of the platform and wherein the conditional moment of the navigation state is further calculated as a function of the inertial data.
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17. The estimator of claim 10 wherein the radio navigation data comprises Global Positioning System (GPS) data, and wherein the radio navigation data receiver comprises a GPS receiver.
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18. A measurement update unit for updating a navigation state and error covariances of the navigation state of a navigation platform based on radio navigation data transmitted by external terminals and embedded in noise, said radio navigation data signal being received by a radio navigation data receiver including a bank of correlators for extracting said radio navigation data from said noise over a range of delay error, said correlators processing said radio navigation data and said noise to generate correlator output functions indicative of degree of correlation for each correlator between said radio navigation data and a known replica signal, said correlator output functions being non-triangular M code correlator output functions, said measurement update unit comprising:
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a state update unit including a nonlinear filter, said state update unit for updating the navigation state as a function of the correlator output functions weighted by state gain functions, the state gain functions being based on a set of correlator moments, which are calculated with said nonlinear filter and which represent statistical expectations of nonlinear functions of line-of-sight position error, a propagation of a previous navigation state, and an error covariance matrix; and
an error covariance matrix update unit for updating the error covariances of the navigation state based on the correlator moments. - View Dependent Claims (19, 20, 21, 22, 23, 24, 25)
a signal power estimator for determining radio navigation data signal power based on the correlator moments; and
a noise power estimator for estimating noise power based on the correlator moments and said signal power estimate.
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23. The measurement update unit of claim 18 wherein the bank of correlators comprises an extended-range bank of correlators for extracting said radio navigation data from said noise over an extended range of delay error, said correlators processing said radio navigation data and said noise to generate correlator output functions indicative of degree of correlation for each correlator in the extended-range bank between said radio navigation data and a known internal replica signal.
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24. The measurement update unit of claim 18 wherein the radio navigation data comprises Global Positioning System (GPS) data, and wherein the radio navigation data receiver comprises a GPS receiver.
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25. The measurement update unit of claim 18 wherein the line-of-sight error comprises the difference between a measured and an estimated line-of-sight range between the receiver and the external terminals.
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26. A measurement update unit for updating a navigation state and error covariances of the navigation state of a navigation platform based on radio navigation data carried on a radio navigation data carrier signal embedded in noise, said radio navigation data signal being received by a radio navigation data receiver including a bank of correlators for extracting said radio navigation data from said noise over a range of delay error, said correlators processing said radio navigation data and said noise to generate correlator output functions indicative of degree of correlation for each correlator between said radio navigation data and a known replica signal, said correlator output functions being non-triangular M code correlator output functions, said bank of correlators including a prompt correlator for processing radio navigation data signals near the radio navigation data carrier frequency, said measurement update unit comprising:
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a state update unit including a nonlinear filter, said state update unit for updating the navigation state as a function of the prompt correlator output function weighted by state gain functions, the state gain functions being based on a set of correlator moments which are calculated with said nonlinear filter and which represent statistical expectations of nonlinear functions of line-of-sight position error, and an error covariance matrix;
an error covariance matrix update unit for updating the error covariances of the navigation state based on the correlator moments; and
an integrity management unit for maintaining the integrity of the navigation state and the error covariances. - View Dependent Claims (27, 28, 29, 30)
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31. A measurement update unit for updating a navigation state and error covariances of the navigation state of a navigation platform based on radio navigation data embedded in noise, said radio navigation data signal being received by a radio navigation data receiver including a bank of correlators for extracting said radio navigation data from said noise over a range of delay error, said correlators processing said radio navigation data and said noise to generate correlator output functions indicative of degree of correlation for each correlator between said radio navigation data and a known replica signal, said correlator output functions being non-triangular M code correlator output functions, said measurement update unit comprising:
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a state update unit for updating the navigation state as a function of the correlator output functions weighted by state gain functions, the state gain functions being based on a set of correlator moments which are statistical expectations of nonlinear functions of line-of-sight position error variance, a propagation of a previous navigation state and an error covariance matrix;
an error covariance matrix update unit for updating the error covariances of the navigation state based on the correlator moments; and
an integrity management unit for maintaining the integrity of the navigation state and the error covariances. - View Dependent Claims (32, 33, 34, 35, 36, 37, 38)
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39. A method for determining a multidimensional navigation state for a navigation platform based on radio navigation data transmitted by external terminals comprising:
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receiving and amplifying said radio navigation data embedded in noise at a radio navigation data receiver;
extracting said radio navigation data from said noise over a range of delay error at a bank of correlators, said correlators processing said radio navigation data and said noise to generate correlator output functions indicative of degree of correlation for each correlator between said radio navigation data and a known internal replica signal, said correlator output functions being non-triangular M code correlator output functions;
estimating the radio navigation data signal power and noise power from the correlator output functions;
updating the navigation state based on the conditional moments of the navigation state calculated using a set of correlator moments as a function of the estimated radio navigation data signal power and noise power, and the correlator outputs;
calculating said correlator moments, which and represent statistical expectations of nonlinear functions of line-of-sight position errors, with a nonlinear filter. - View Dependent Claims (40, 41, 42, 43, 44, 45, 46, 47, 48, 49)
estimating radio navigation data signal power based on the correlator moments; and
estimating noise power estimator for estimating noise power based on the correlator moments and said signal power estimate.
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50. A method for estimating signal and noise power in a system for determining a multidimensional navigation state for a navigation platform based on radio navigation data embedded in noise, said radio navigation data signal being received by a radio navigation data receiver including a bank of correlators for extracting said radio navigation data from said noise over a range of delay error, said correlators processing said radio navigation data and said noise to generate correlator output functions indicative of degree of correlation for each correlator between said radio navigation data and a known replica signal, comprising:
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calculating correlator moments, which and represent statistical expectations of nonlinear functions of line-of-sight position errors, with a nonlinear filter;
determining radio navigation data signal power based on the correlator moments; and
estimating noise power based on the correlator moments and said signal power estimate;
wherein said correlator moments are calculated according to the equation;
- View Dependent Claims (51, 52, 53, 54, 55, 56, 57)
updating the bias estimate of each correlator according to a smoothing time constant; and
determining the bias estimate as the minimum value of the smoothed bias estimates.
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53. The method of claim 50 wherein said correlator moments each comprise a first conditional moment comprising a conditional mean.
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54. The method of claim 50 wherein the noise power estimate comprises a vector, such that an independent noise power estimate is calculated for each correlator in the correlator bank.
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55. The method of claim 50 wherein the bank of correlators comprises an extended-range bank of correlators for extracting said radio navigation data from said noise over an extended range of delay error, said correlators processing said radio navigation data and said noise to generate correlator output functions indicative of degree of correlation for each correlator in the extended-range bank between said radio navigation data and a known internal replica signal.
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56. The method of claim 50 further comprising generating inertial data indicative of the inertial behavior of the platform and wherein the correlator moments are further calculated as a function of the inertial data.
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57. The method of claim 50 wherein the radio navigation data comprises Global Positioning System (GPS) data, and wherein the radio navigation data receiver comprises a GPS receiver.
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58. A method for updating a navigation state and error covariances of the navigation state of a navigation platform based on radio navigation data transmitted by external terminals and embedded in noise, said radio navigation data signal being received by a radio navigation data receiver including a bank of correlators for extracting said radio navigation data from said noise over a range of delay error, said correlators processing said radio navigation data and said noise to generate correlator output functions indicative of degree of correlation for each correlator between said radio navigation data and a known replica signal, said correlator output functions being non-triangular M code correlator output functions, the method comprising:
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calculating correlator moments, which represent statistical expectations of nonlinear functions of line-of sight position errors, a propagation of a previous navigation state and an error covariances matrix, with a nonlinear filter;
updating the navigation state as a function of the correlator output functions weighted by state gain functions, the state gain functions being based on a set of said correlator moments; and
updating the error covariances of the navigation state based on the correlator moments. - View Dependent Claims (59, 60, 61, 62, 63, 64, 65)
estimating radio navigation data signal power based on the correlator moments; and
estimating noise power based on the correlator moments and said signal power estimate.
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63. The method of claim 58 wherein the bank of correlators comprises an extended-range bank of correlators for extracting said radio navigation data from said noise over an extended range of delay error, said correlators processing said radio navigation data and said noise to generate correlator output functions indicative of degree of correlation for each correlator in the extended-range bank between said radio navigation data and a known internal replica signal.
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64. The method of claim 58 wherein the radio navigation data comprises Global Positioning System (GPS) data, and wherein the radio navigation data receiver comprises a GPS receiver.
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65. The method of claim 58 wherein the line-of-sight error comprises the difference between a measured and an estimated line-of-sight range between the receiver and the external terminals.
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66. A method for updating a navigation state and error covariances of the of a navigation platform based on radio navigation data carried on a radio navigation data carrier signal embedded in noise, said radio navigation data signal being received by a radio navigation data receiver including a bank of correlators for extracting said radio navigation data from said noise over a range of delay error, said correlators processing said radio navigation data and said noise to generate correlator output functions indicative of degree of correlation for each correlator between said radio navigation data and a known replica signal, said correlator output functions being non-triangular M code correlator output functions, said bank of correlators including a prompt correlator for processing radio navigation data signals near the radio navigation data cater frequency, the method comprising:
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updating the navigation state as a function of the prompt correlator output function weighted by state gain functions, the state gain functions being based on a set of correlator moments which are calculated with a nonlinear filter and which represent statistical expectations of nonlinear functions of line-of-sight position error, and an error covariance matrix; and
updating the error covariances of the navigation state based on said state gain functions. - View Dependent Claims (67, 68, 69, 70)
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71. A method for updating a navigation state and error covariances of the navigation state of a navigation platform based on radio navigation data embedded in noise, said radio navigation data signal being received by a radio navigation data receiver including a bank of correlators for extracting said radio navigation data from said noise over a range of delay error, said correlators processing said radio navigation data and said noise to generate correlator output functions indicative of degree of correlation for each correlator between said radio navigation data and a known replica signal, said correlator output functions being non-triangular M code correlator output functions, the method comprising:
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updating the navigation state as a function of the correlator output functions weighted by state gain functions, the state gain functions being based on a set of correlator moments which are statistical expectations of nonlinear functions of line-of-sight position error, a propagation of a previous navigation state, and an error covariance matrix;
updating the error covariances of the navigation state based on the correlator moments; and
maintaining the integrity of the navigation state and the error covariances. - View Dependent Claims (72, 73, 74, 75, 76, 77, 78)
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79. A system for determining a multidimensional navigation state for a navigation platform based on radio navigation data transmitted by external terminals comprising:
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a radio navigation data receiver for receiving and amplifying said radio navigation data embedded in noise;
an extended-range bank of correlators for extracting said radio navigation data from said noise over an extended range of delay error, said correlators processing said radio navigation data and said noise to generate correlator output functions indicative of a degree of correlation for each correlator in the extended-range bank between said radio navigation data and a known internal replica signal;
an estimator for estimating the radio navigation data signal power and noise power from the correlator output functions; and
a measurement update unit including a nonlinear filter, said measurement update unit for updating the navigation state based on a calculation of the conditional moments of the navigation state using a set of correlator moments, the calculation being based on the estimated radio navigation data signal power and noise power and the correlator output functions;
wherein said correlator moments are calculated with said nonlinear filter and represent statistical expectations of nonlinear functions of the line-of-sight position errors, said correlator moments being calculated according to the equation.
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80. A system for determining a multidimensional navigation state for a navigation platform based on radio navigation data transmitted by external terminals comprising:
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a radio navigation data receiver for receiving and amplifying said radio navigation data embedded in noise;
an extended-range bank of correlators for extracting said radio navigation data from said noise over an extended range of delay error, said correlators processing said radio navigation data and said noise to generate correlator output functions indicative of a degree of correlation for each correlator in the extended-range bank between said radio navigation data and a known internal replica signal;
an estimator for estimating the radio navigation data signal power and noise power from the correlator output functions; and
a measurement update unit for updating the navigation state based on a calculation of the conditional moments of the navigation state using a set of correlator moments, the calculation being based on the estimated radio navigation data signal power and noise power and the functions;
wherein said correlator moments represent statistical expectations of nonlinear functions of the line-of-sight position errors and are calculated according to the equation;
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81. A method for determining a multidimensional navigation state for a navigation platform based on radio navigation data transmitted by external terminals comprising:
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receiving and amplifying said radio navigation data embedded in noise at a radio navigation data receiver;
extracting said radio navigation data from said noise over an extended range of delay error at an extended-range bank of correlators, said correlators processing said radio navigation data and said noise to generate correlator output functions indicative of degree of correlation for each correlator in the extended-range bank between said radio navigation data and a known internal replica signal;
estimating the radio navigation data signal power and noise power from the correlator output functions; and
updating the navigation state using a set of correlator moments, the calculation being based on the estimated radio navigation data signal power and noise power, and the correlator output functions; and
calculating said correlator moments, which represent statistical expectations of nonlinear functions of line-of-sight position errors, with a nonlinear filter, said correlator moments being calculated according to the equation;
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82. A method for determining a multidimensional navigation state for a navigation platform based on radio navigation data transmitted by external terminals comprising:
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receiving and amplifying said radio navigation data embedded in noise at a radio navigation data receiver;
extracting said radio navigation data from said noise over an extended range of delay error at an extended-range bank of correlators, said correlators processing said radio navigation data and said noise to generate correlator output functions indicative of degree of correlation for each correlator in the extended-range bank between said radio navigation data and a known internal replica signal;
estimating the radio navigation data signal power and noise power from the correlator output functions; and
updating the navigation state using a set of correlator moments, the calculation being based on the estimated radio navigation data signal power and noise power, and the correlator output functions; and
calculating said correlator moments, which represent statistical expectations of nonlinear functions of line-of-sight position errors, said correlator moments being calculated according to the equation;
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Specification