Analog decorrelation of ranging signals

• US 20060022869A1
• Filed: 07/30/2004
• Published: 02/02/2006
• Est. Priority Date: 07/30/2004
• Status: Active Grant

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Integirnautics Corporation
• Inventors: Cobb, H. Stewart, Zimmerman, Kurt R.
• Granted Patent: US 7,339,524 B2
• Time in Patent Office: Days
• US Class Current: 342/458
• CPC Class Codes: G01S 11/02 using radio waves G01S19/00 takes precedence
• CPC Class Codes: G01S 19/11 wherein the cooperating elements are pseudolites or satellite radio beacon positioning system signal repeaters
• CPC Class Codes: G01S 19/18 Military applications
• CPC Class Codes: G01S 19/31 Acquisition or tracking of other signals for positioning
• CPC Class Codes: G01S 19/34 Power consumption
• CPC Class Codes: G01S 19/44 Carrier phase ambiguity resolution; Floating ambiguity; LAMBDA [Least-squares AMBiguity Decorrelation Adjustment] method
• CPC Class Codes: G01S 19/46 the supplementary measurement being of a radio-wave signal type

Abstract

In a local positioning system, a receiver is adapted for receiving signals from a land-based transmitter. The receiver includes an analog decorrelator for decorrelating the transmitted spread spectrum signals. A down converter connected with an antenna may be spaced away from other portions of the receiver. The down converter down converts received ranging signals and provides them to the remotely spaced receiver portions. A signal line connecting the down converter to the receiver may be operable to transmit any two or more of a reference signal provided to the down converter, the down converted intermediate frequency signals provided to the receiver, and power provided to the down converter. The receiver may be positioned adjacent to or as part of a land-based transmitter. By determining positions of two or more antennas, the location of the associated transmitter is determined.

Claims

1. A method for determining a range to a transmitter, the method comprising:

(a) receiving time-slotted spread spectrum signals from the transmitter;

(b) decorrelating the spread spectrum signals in an analog domain; and

(c) determining the range as a function of the decorrelated signals.

2. The method of claim 1 wherein (b) comprises decorrelating the spread spectrum signals in the analog domain as a function of different codes corresponding to different time slots with a same decorrelator.

3. The method of claim 1 wherein (a) comprises receiving the spread spectrum signals having a code modulation rate of at least 30 MHz.

4. The method of claim 1 wherein (a) comprises receiving at least four sets of spread spectrum signals in a respective at least four time slots, each of the at least four time slots being less than about 0.20 milliseconds.

5. The method of claim 1 wherein (b) comprises decorrelating the signals with a single analog channel for signals from a plurality of transmitters.

6. The method of claim 1 further comprising:

(d) converting the decorrelated signals into digital signals; and

(e) tracking the decorrelated signals with separate digital channels for each of the time slots;

wherein (c) comprises determining the range as a function of the tracking from at least one of the separate digital channels.

7. The method of claim 6 wherein (c) comprises determining a position as a function of ranges from a plurality of transmitters corresponding to a plurality of the time slots.

8. The method of claim 1 wherein (a) comprises receiving X-band signals from land based transmitters.

9. The method of claim 1 wherein (a) comprises receiving ISM-band signals from land based transmitters.

10. The method of claim 1 further comprising:

(d) down converting the received spread spectrum signals prior to (b).

11. The method of claim 1 wherein (a) comprises receiving the spread spectrum signals from a plurality of transmitters, each transmitter associated with a detection code and a tracking code and each transmitter associated with at least one time slot.

12. The method of claim 11 wherein (c) comprises determining the range as a function of differential phase measurements of the detection code and the tracking code.

13. The method of claim 11 wherein the detection code and the tracking code are the same.

14. The method of claim 11 wherein the detection code and the tracking code are different.

31. The method of claim 1 wherein (b) comprises decorrelating the signals from a plurality of transmitters with first and second analog channels, where the first analog channel is for measuring a detect signal and the second analog channel is for measuring a track signal.

15. A system for determining a range to a transmitter, the system comprising:

an antenna;

an analog mixer connected with the antenna, the analog mixer operable to mix signals received by the antenna with each of a plurality of replica spread spectrum codes;

a switch connected with the analog mixer, the switch operable to select between each of the plurality of replica spread spectrum codes as a function of time; and

a processor operable to determine the range to the transmitter as a function of mixed signals output from the analog mixer.

16. The system of claim 15 wherein the analog mixer comprises a balanced mixer.

17. The system of claim 15 further comprising a down-converter between the antenna and the analog mixer.

18. The system of claim 15 wherein the replica spread spectrum codes have a modulation rate of at least 30 MHz.

19. The system of claim 15 wherein the switch comprises a multiplexer operable to switch between all of the plurality of replica spread spectrum codes within at least about one millisecond.

20. The system of claim 15 wherein the plurality of replica spread spectrum codes comprising at least four spread spectrum codes, a different one of each of the at least four spread spectrum codes associated with a respective one of the four transmitters.

21. The system of claim 15 further comprising:

an analog-to-digital converter connected with the analog mixer; and

a plurality of separate digital channels, each of the digital channels operable to receive mixed signals responsive to different respective ones of the replica spread spectrum codes.

22. The system of claim 21 wherein the processor is operable to determine a position as a function of ranges from a plurality of transmitters corresponding to the plurality of separate digital channels.

23. The system of claim 15 further comprising:

a plurality of land based transmitters;

wherein the antenna is operable to receive X-band signals from the plurality of land based transmitters.

24. The system of claim 15 further comprising:

a first accumulator operable to accumulate first information responsive to a detection code input as a replica spread spectrum code to the analog mixer; and

a second accumulator operable to accumulate second information responsive to a tracking code input as a replica spread spectrum code to the analog mixer;

wherein the detection and tracking codes correspond to a same transmitter and wherein the processor is operable to initiate tracking as a function of the first information and determine the range as a function of the second information.

25. A method for determining a range to a transmitter, the method comprising:

(a) receiving spread spectrum, X-band signals;

(b) decorrelating the spread spectrum, X-band signals as analog signals; and

(c) determining the range as a function of the decorrelated signals in response to one-way communication of the spread spectrum, X-band signals received in (a).

26. The method of claim 25 wherein (b) comprises decorrelating the spread spectrum, X-band signals as a function of different codes corresponding to different time slots.

27. The method of claim 25 wherein (a) comprises receiving the spread spectrum, X-band signals having a code modulation rate of at least 30 MHz.

28. The method of claim 25 wherein (a) comprises receiving at least four sets of spread spectrum, X-band signals in a respective at least four time slots, each of the at least four time slots being less than 0.20 milliseconds.

29. The method of claim 25 wherein (c) comprises determining a position as a function of ranges from a plurality of land-based transmitters.

30. The method of claim 25 further comprising:

(d) down converting the received spread spectrum signals after (b).