IP Library › Granted Patent US 12,228,656
Granted Patent B2
US 12,228,656 · App. 18/195,786 · Granted Feb 18, 2025

Resilient despreading of terrestrial navigation signals

Inventor: Brian G. Agee (San Jose, CA)
G01S19/243G01S19/21G01S19/246H04B1/707H04B7/10H04L27/2636
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Quick Facts
Patent No.
US 12,228,656
App. No.
18/195,786
Granted
Feb 18, 2025
Kind
B2
Abstract

A method and apparatus resiliently despreads terrestrial navigation signals in which the spreading code duration is equal to an underlying baseband symbol rate, including ground beacons based on civil GNSS waveforms, and malicious spoofers. Symbol-rate synchronous channelizers exploit the baseband symbol rate, and means for blindly and resiliently detecting and determining geo-observables of those signals are described. Disclosed techniques can despread signals in arbitrary multipath, and subject to near-far interference in which the relative strength of the interferer is much higher than the despreading gain of the receiver, including near-far tonal and narrowband co-channel interference.

Claims (40)

1. A method performed in a receiver, comprising:

configuring the receiver to select a despreading gain;

providing for symbol-rate synchronous channelizing of a received signal that comprises at least two navigation signals, to produce a plurality of frequency channels;

combining the plurality of frequency channels to produce a combined signal; and

estimating the position of the receiver using the combined signal.

2. The method of claim 1 , wherein the at least two navigation signals comprises a ground-based beacon signal.

3. The method of claim 1 , wherein the interference comprises near-far interference.

4. The method of claim 3 , further comprising employing linear-algebraic combining to remove the near-far interference, wherein the near-far interference is higher than the despreading gain.

5. The method of claim 1 , wherein the despreading gain is a function of the plurality of frequency channels.

6. The method of claim 1 , wherein configuring the receiver to select the despreading gain comprises provisioning the receiver with a predetermined number of degrees of freedom.

7. The method of claim 1 , wherein the symbol-rate synchronous channelizing produces a sufficient number of degrees of freedom to enable the linear-algebraic combining to provide for detection and separation of each of the at least two navigation signals in the presence of arbitrary multipath.

8. The method of claim 1 , wherein the symbol-rate synchronous channelizing produces a number of degrees of freedom that exceeds a total number of navigation signals, spoofers, and tonal interferers.

9. The method of claim 1 , wherein the symbol-rate synchronous channelizing comprises sparse channelization such that the plurality of frequency channels comprises less than a total bandwidth of the at least one navigation signal.

10. The method of claim 1 , wherein the received signal comprises a pilot signal, and the symbol-rate synchronous channelizing provides for a number of degrees of freedom that is sufficient to integrate the pilot signal above noise and interference;

the method further comprising:

integrating the pilot signal above the noise and interference; and

determining geo-observables for the pilot signal.

11. The method of claim 1 , further comprising de-emphasizing any of the plurality of frequency channels that contains excessive non-beacon interference.

12. The method of claim 1 , wherein providing for symbol-rate synchronous channelizing is configured to adapt the plurality of frequency channels in response to a frequency shift in at least one of the at least two navigation signals.

13. An apparatus, comprising:

one or more processors;

memory in electronic communication with the one or more processors; and instructions stored in the memory and executable by the one or more processors to:

configure a receiver to select a despreading gain;

provide for symbol-rate synchronous channelizing of a received signal that comprises at least two navigation signals, to produce a plurality of frequency channels;

combine the plurality of frequency channels to produce a combined signal; and

estimate the position of the receiver using the combined signal.

14. The apparatus of claim 13 , wherein the at least two navigation signals comprises a ground-based beacon signal.

15. The apparatus of claim 13 , wherein the interference comprises near-far interference.

16. The apparatus of claim 15 , further comprising instructions stored in the memory and executable by the one or more processors to employ linear-algebraic combining to remove the near-far interference, and wherein the near-far interference is higher than the despreading gain.

17. The apparatus of claim 13 , wherein the despreading gain is a function of the plurality of frequency channels.

18. The apparatus of claim 13 , wherein the despreading gain is selected by provisioning the receiver with a predetermined number of degrees of freedom.

19. The apparatus of claim 13 , wherein the symbol-rate synchronous channelizing produces a sufficient number of degrees of freedom to enable the linear- algebraic combining to provide for detection and separation of each of the at least two navigation signals in the presence of arbitrary multipath.

20. The apparatus of claim 13 , wherein the symbol-rate synchronous channelizing produces a number of degrees of freedom that exceeds a total number of navigation signals, spoofers, and tonal interferers.

21. The apparatus of claim 13 , wherein the symbol-rate synchronous channelizing comprises sparse channelization such that the plurality of frequency channels comprises less than a total bandwidth of the at least one navigation signal.

22. The apparatus of claim 13 , wherein the received signal comprises a pilot signal, and the symbol-rate synchronous channelizing provides for a number of degrees of freedom that is sufficient to integrate the pilot signal above noise and interference;

the apparatus further comprising instructions stored in the memory and executable by the one or more processors to:

integrate the pilot signal above the noise and interference; and

determine geo-observables for the pilot signal.

23. The apparatus of claim 13 , further comprising instructions stored in the memory and executable by the one or more processors to de-emphasize any of the plurality of frequency channels that contains excessive non-beacon interference.

24. The apparatus of claim 13 , wherein the symbol-rate synchronous channelizing is configured to adapt the plurality of frequency channels in response to a frequency shift in at least one of the at least two navigation signals.

Continuity (8)
Continuation 17479658 · Sep 20, 2021
Continuation 16701144 · Dec 2, 2019
Continuation 15731417 · Jun 5, 2017
Provisional Application 62773605 · Nov 30, 2018
Provisional Application 62773589 · Nov 30, 2018
Provisional Application 62429029 · Dec 1, 2016
Provisional Application 62392623 · Jun 6, 2016
Related Publication 20230296787A1 · Sep 21, 2023
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