Efficient detection and signal parameter estimation with application to high dynamic GPS receiver

• US 4,959,656 A
• Filed: 10/31/1989
• Issued: 09/25/1990
• Est. Priority Date: 10/31/1989
• Status: Expired due to Fees

• Current Assignee: California Institute of Technology
• Original Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Inventors: Kumar, Rajendra
• Primary Examiner(s): Barron, Jr., Gilberto
• Application Number:
  US07/429,734
• Time in Patent Office: 329 Days
• Field of Search: 342/418, 342/357, 342/358, 342/386, 342/352, 329/306-309, 375/80, 375/84, 375/94-96
• US Class Current: 342/418
• 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: H03L 7/087 using at least two phase detectors or a frequency and phase detector in the loop

Abstract

In a system for deriving position, velocity, and acceleration information from a received signal emitted from an object to be tracked wherein the signal comprises a carrier signal phase modulated by unknown binary data and experiencing very high Doppler and Doppler rate, this invention provides combined estimation/detection apparatus for simultaneously detecting data bits and obtaining estimates of signal parameters such as carrier phase and frequency related to receiver dynamics in a sequential manner. There is first stage for obtaining estimates of the signal parameters related to phase and frequency in the vicinity of possible data transitions on the basis of measurements obtained within a current data bit. A second stage uses the estimates from the first stage to decide whether or not a data transition has actually occurred. There is a third stage for removing data modulation from the received signal when a data transition has occurred and a fourth stage for using the received signal with data modulation removed therefrom to update global parameters which are dependent only upon receiver dynamics and independent of data modulation. Finally, there is a fifth stage for using the global parameters to determine the position, velocity, and acceleration of the object.

Claims

1. In a system for deriving position, velocity, and acceleration information from a signal emitted from an object to be tracked wherein the signal comprises a carrier signal phase modulated by unknown binary data and experiencing very high Doppler and Doppler rate, the method of providing the parameters associated with the signal from which the position, velocity, and acceleration information can be derived comprising the steps of:

(a) sampling the signal during multiple sample times within a first binary bit period;

(b) using data from samples obtained during the first binary bit period to determine the phase of the signal just prior to the end of the first binary bit period;

(c) sampling the signal during multiple sample times within a next binary bit period;

(d) using data from samples obtained during the next binary bit period to determine the phase of the signal just after the end of the first binary bit period;

(e) comparing the phase of the signal just after the end of the first binary bit period to the phase of the signal just prior to the end of the first binary bit period;

(f) adjusting the signal data associated with the second binary period to reflect a change in bit status if the phase of the signal just after the end of the first binary bit period is offset from the phase of the signal just prior to the end of the first binary bit period by more than a pre-established threshold amount;

(g) repeating steps (a) through (f) to create modified signal data reflecting the signal in an unmodulated state; and

,

(h) using the modified signal data to estimate the parameters from which the position, velocity, and acceleration information are derived.

2. The method of claim 1 wherein said steps of using data from samples obtained during the first binary bit period to determine the phase of the signal just prior to the end of the first binary bit period and using data from samples obtained during the next binary bit period to determine the phase of the signal just after the end of the first binary bit period each comprises the steps of:

(a) using the data from the samples in a first instance to estimate the phase of the signal;

(b) using an estimate from the first instance to update an estimation algorithm being employed to estimate the phase; and

(c) reusing the data from the samples in a second instance to re-estimate the phase of the signal whereby errors tend to cancel out and an improved estimate of the phase is provided.

3. The method of claim 1 wherein said step of using the modified signal data to estimate the parameters from which the position, velocity, and acceleration information are derived comprises the steps of:

employing an adaptive Hilbert transform in a phase locked loop to estimate the parameters.

4. In a system for deriving position, velocity, and acceleration information from a received signal emitted from an object to be tracked wherein the signal comprises a carrier signal phase modulated by unknown binary data and experiencing very high Doppler and Doppler rate, the method of providing the parameters associated with the signal from which the position, velocity, and acceleration information can be derived comprising the steps of:

(a) first estimating the received signal local (data dependent) parameters over two consecutive bit periods;

(b) detecting a possible jump in the parameters signifying a data transition;

(c) removing detected data transitions from the received signal to create an effectively demodulated signal; and

,

(d) processing the effectively demodulated signal to provide estimates of global (data independent) parameters of the signal related to position, velocity, and acceleration of the object.

5. The method of claim 4 wherein the steps thereof further comprise the steps of:

(a) sampling the signal during multiple sample times within a first binary bit period;

(b) using data from samples obtained during the first binary bit period to determine the phase of the signal just prior to the end of the first binary bit period;

(c) sampling the signal during multiple sample times within a next binary bit period;

(d) using data from samples obtained during the next binary bit period to determine the phase of the signal just after the end of the first binary bit period;

(e) comparing the phase of the signal just after the end of the first binary bit period to the phase of the signal just prior to the end of the first binary bit period;

(f) adjusting the signal data associated with the second binary period to reflect a change in bit status if the phase of the signal just after the end of the first binary bit period is offset from the phase of the signal just prior to the end of the first binary bit period by more than a pre-established threshold amount;

(g) repeating steps (a) through (f) to create modified signal data reflecting the signal in an unmodulated state; and

,

(h) using the modified signal data to estimate the parameters from which the position, velocity, and acceleration information are derived.

6. The method of claim 5 wherein said steps of using data from samples obtained during the first binary bit period to determine the phase of the signal just prior to the end of the first binary bit period and using data from samples obtained during the next binary bit period to determine the phase of the signal just after the end of the first binary bit period each comprises the steps of:

(a) using the data from the samples in a first instance to estimate the phase of the signal;

(b) using an estimate from the first instance to update an estimation algorithm being employed to estimate the phase; and

(c) reusing the data from the samples in a second instance to re-estimate the phase of the signal whereby errors tend to cancel out and an improved estimate of the phase is provided.

7. The method of claim 5 wherein said step of using the modified signal data to estimate the parameters from which the position, velocity, and acceleration information are derived comprises the steps of:

employing an adaptive Hilbert transform in a phase locked loop to estimate the parameters.

8. In a system for deriving position, velocity, and acceleration information from a received signal emitted from an object to be tracked wherein the signal comprises a carrier signal phase modulated by unknown binary data and experiencing very high Doppler and Doppler rate, a combined estimation/detection method for simultaneously detecting data bits and obtaining estimates of signal parameters such as carrier phase and frequency related to receiver dynamics in a sequential manner comprising the steps of:

(a) obtaining estimates of the signal parameters related to phase and frequency in the vicinity of possible data transitions on the basis of measurements obtained within a current data bit;

(b) using the estimates from step (a) to decide whether or not a data transition has actually occurred;

(c) where a data transition has occurred, removing data modulation from the received signal;

(d) using the received signal with data modulation removed therefrom to update global parameters which are dependent only upon receiver dynamics and independent of data modulation; and

,

(e) using the global parameters to determine the position, velocity, and acceleration of the object.

9. The method of claim 8 wherein the steps thereof further comprises the steps of:

(a) sampling the signal during multiple sample times within a first binary bit period;

(b) using data from samples obtained during the first binary bit period to determine the phase of the signal just prior to the end of the first binary bit period;

(c) sampling the signal during multiple sample times within a next binary bit period;

(d) using data from samples obtained during the next binary bit period to determine the phase of the signal just after the end of the first binary bit period;

(e) comparing the phase of the signal just after the end of the first binary bit period to the phase of the signal just prior to the end of the first binary bit period;

(f) adjusting the signal data associated with the second binary period to reflect a change in bit status if the phase of the signal just after the end of the first binary bit period is offset from the phase of the signal just prior to the end of the first binary bit period by more than a pre-established threshold amount;

(g) repeating steps (a) through (f) to create modified signal data reflecting the signal in an unmodulated state; and

,

(h) using the modified signal data to estimate the parameters from which the position, velocity, and acceleration information are derived.

10. The method of claim 9 wherein said steps of using data from samples obtained during the first binary bit period to determine the phase of the signal just prior to the end of the first binary bit period and using data from samples obtained during the next binary bit period to determine the phase of the signal just after the end of the first binary bit period each comprises the steps of:

(a) using the data from the samples in a first instance to estimate the phase of the signal;

(b) using an estimate from the first instance to update an estimation algorithm being employed to estimate the phase; and

,

(c) reusing the data from the samples in a second instance to re-estimate the phase of the signal whereby errors tend to cancel out and an improved estimate of the phase is provided.

11. The method of claim 9 wherein said step of using the modified signal data to estimate the parameters from which the position, velocity, and acceleration information are derived comprises the steps of:

employing an adaptive Hilbert transform in a phase locked loop to estimate the parameters.

12. In a system for deriving position, velocity, and acceleration information from a signal emitted from an object to be tracked wherein the signal comprises a carrier signal phase modulated by unknown binary data and experiencing very high Doppler and Doppler rate, the improvement for providing the parameters associated with the signal from which the position, velocity, and acceleration information can be derived comprising:

(a) first means for sampling the signal during multiple sample times within a first binary bit period;

(b) second means for using data from samples obtained during the first binary bit period to determine the phase of the signal just prior to the end of the first binary bit period;

(c) third means for sampling the signal during multiple sample times within a next binary bit period;

(d) fourth means for using data from samples obtained during the next binary bit period to determine the phase of the signal just after the end of the first binary bit period;

(e) fifth means for comparing the phase of the signal just after the end of the first binary bit period to the phase of the signal just prior to the end of the first binary bit period;

(f) sixth means for adjusting the signal data associated with the second binary period to reflect a change in bit status if the phase of the signal just after the end of the first binary bit period is offset from the phase of the signal just prior to the end of the first binary bit period by more than a preestablished threshold amount;

(g) seventh means responsive to said first, second, third, fourth, fifth, and sixth means for creating a modified signal data reflecting the signal in an unmodulated state; and

,

(h) eighth means for using the modified signal data to estimate the parameters from which the position, velocity, and acceleration information are derived.

13. The apparatus of claim 12 wherein said means for using data from samples obtained during the first binary bit period to determine the phase of the signal just prior to the end of the first binary bit period and said means for using data from samples obtained during the next binary bit period to determine the phase of the signal just after the end of the first binary bit period each comprises;

(a) means for using data from the samples in a first instance to estimate the phase of the signal;

(b) means for using an estimate from the first instance to update an estimation algorithm being employed to estimate the phase; and

,

(c) reusing the data from the samples in a second instance to re-estimate the phase of the signal whereby errors tend to cancel out and an improved estimate of the phase is provided.

14. The apparatus of claim 12 wherein said means for using the modified signal data to estimate the parameters from which the position, velocity, and acceleration information are derived comprises;

an adaptive Hilbert transform disposed in a phase locked loop.

15. In a system for deriving position, velocity, and acceleration information from a received signal emitted from an object to be tracked wherein the signal comprises a carrier signal phase modulated by unknown binary data and experiencing very high Doppler and Doppler rate, the improvement for providing the parameters associated with the signal from which the position, velocity, and acceleration information can be derived comprising:

(a) means for first estimating the received signal local (data dependent) parameters over two consecutive bit periods;

(b) means for detecting a possible jump in the parameters signifying a data transition;

(c) means for removing detected data transitions from the received signal to create an effectively demodulated signal; and

,

(d) means for processing the effectively demodulated signal to provide estimates of global (data independent) parameters of the signal related to position, velocity, and acceleration of the object.

16. In a system for deriving position, velocity, and acceleration information from a received signal emitted from an object to be tracked wherein the signal comprises a carrier signal phase modulated by unknown binary data and experiencing very high Doppler and Doppler rate, combined estimation/detection apparatus for simultaneously detecting data bits and obtaining estimates of signal parameters such as carrier phase and frequency related to receiver dynamics in a sequential manner comprising:

(a) first means for obtaining estimates of the signal parameters related to phase and frequency in the vicinity of possible data transitions on the basis of measurements obtained within a current data bit;

(b) second means for using the estimates from said first means to decide whether or not a data transition has actually occurred;

(c) third means for removing data modulation from the received signal when a data transition has occurred;

(d) fourth means for using the receiving signal with data modulation removed therefrom to update global parameters which are dependent only upon receiver dynamics and independent of data modulation; and

,

(e) fifth means for using the global parameters to determine the position, velocity, and acceleration of the object.