Rebroadcasting method and system for navigation signals

• US 20050242994A1
• Filed: 04/29/2004
• Published: 11/03/2005
• Est. Priority Date: 04/29/2004
• Status: Active Grant

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Integrinautics Corporation (Kubota Corporation)
• Inventors: Cobb, H. Stewart, Lawrence, David G.
• Granted Patent: US 7,310,064 B2
• Time in Patent Office: Days
• US Class Current: 342/386
• CPC Class Codes: G01S 19/11 wherein the cooperating elements are pseudolites or satellite radio beacon positioning system signal repeaters

Abstract

A “synchrolite” or rebroadcasting device allows GPS or GNSS navigation signals received at one or several locations to be processed at a separate location. The signals received by the synchrolite are added to a pilot tone and then encoded with a superimposed spread-spectrum code before being rebroadcast. The superimposed code allows signals from different synchrolites to be distinguished during the navigation process.

Claims

1. A method for rebroadcasting radio signals, the method comprising:

(a) receiving one or more radio signals;

(b) modulating the signals received in step (a) with a spreading code; and

(c) transmitting the group of signals modulated in step (b).

2. The method of claim 1 further comprising:

(d) determining a range from each of the signals transmitted in (c).

3. The method of claim 2 further comprising:

(e) determining a position as a function of time from a group of ranges determined in (d).

4. The method of claim 1 further comprising:

(d) shifting a frequency of the radio signals after (a) and prior to (c).

5. The method of claim 1 wherein (a) comprises receiving ranging signals as the radio signals.

6. The method of claim 5 wherein (a) comprises receiving ranging signals in at least one frequency band.

7. The method of claim 6 wherein (a) comprises receiving ranging signals in at least two frequency bands and wherein (b) comprises modulating the ranging signals of each frequency band with a different spreading code.

8. The method of claim 7 further comprising:

(d) shifting the ranging signals of the at least two frequency bands to a single rebroadcast frequency band;

wherein (c) comprises transmitting at the rebroadcast frequency band, the transmitted signals corresponding to the ranging signals from each of the at least two frequency bands.

9. The method of claim 1 further comprising:

(d) combining the radio signals with a pilot tone prior to (b).

11. The method of claim 5 wherein (a) comprises receiving the ranging signals from a satellite selected from the group of:

a GNSS satellite and a satellite-based GNSS augmentation service.

12. The method of claim 5 wherein (a) comprises receiving the ranging signals from a land-based transmitter.

13. The method of claim 1 wherein (c) comprises intermittently transmitting.

14. The method of claim 5 wherein (a) comprises receiving the ranging signals with a plurality of receive antennas, wherein (b) comprises modulating the ranging signals of each of the plurality of receive antennas with a different spreading code, and wherein (c) comprises combining the plurality of modulated signals from step (b) and transmitting them through a single antenna.

15. The method of claim 14 wherein (a) comprises receiving the ranging signals at a same frequency band at each of the plurality of receive antennas;

further comprising;

(d) shifting the ranging signals to a rebroadcast frequency band;

wherein (c) comprises transmitting at the rebroadcast frequency band the modulated ranging signals for each receive antenna simultaneously.

16. The method of claim 1 wherein (a) comprises receiving the radio signals in a first frequency band, wherein (b) comprises modulating the radio signals with at least two different spreading codes, and wherein (c) comprises separately transmitting the modulated ranging signals for each of the at least two different spreading codes.

17. The method of claim 16 wherein (c) comprises simultaneously transmitting the modulated radio signals from separate antennas, each of the modulated radio signals having a substantially same frequency band.

18. The method of claim 4 further comprising:

(d) calibrating the shifting as a function of the radio signals received in (a).

10. The method of claim 10 further comprising:

(e) modulating the pilot tone prior to (d).

19. A system for rebroadcasting ranging signals, the system comprising:

a first receive antenna;

a first modulator connected with the first receive antenna, the first modulator operable to modulate signals from the first receive antenna with a first spreading code; and

a first transmit antenna connected with an output of the modulator.

20. The system of claim 19 further comprising:

a mixer connected with the first modulator, the mixer operable to shift in frequency the signals from the first receive antenna.

21. The system of claim 19 wherein the first modulator is operable on the signals from the first receive antenna at a first frequency band;

further comprising;

a second modulator operable on other signals at a second frequency band different than the first frequency band, the second modulator operable to modulate the other signals with a different spreading code than for the first modulator;

wherein the first transmit antenna is operable to simultaneously transmit the signals and other signals from the first and second modulators.

22. The system of claim 19 wherein the first modulator is operable on the signals at a first frequency band;

further comprising;

a second receive antenna; and

a second modulator connected with the second receive antenna, the second modulator operable on signals from the second receive antenna at the first frequency band and operable to modulate the signals from the second receive antenna with a different spreading code than for the first modulator;

wherein the first transmit antenna is operable to simultaneously transmit signals from the first and second modulators.

23. The system of claim 19 wherein the first modulator is operable on signals at a first frequency band;

further comprising;

a second modulator operable to modulate the signals as a function of a second spreading code different than the first spreading code; and

a second transmit antenna connected with the second modulator, the second transmit antenna operable to transmit the signals modulated by the second modulator and the first transmit antenna operable to transmit the signals modulated by the first modulator.

24. The system of claim 19 further comprising:

a signal combiner connected between the first receive antenna and the modulator, the signal combiner operable to combine the signals with a pilot tone.

25. A method for receiving rebroadcast ranging signals, the method comprising:

(a) receiving a spread spectrum ranging signal;

(b) despreading the spread spectrum ranging signal as a function of a first spreading code;

(c) despreading an output of (b) as a function of a second spreading code; and

(d) determining a range as a function of an output of (c).

26. The method of claim 25 further comprising:

(e) isolating a pilot tone in the output of (b);

(f) performing (b) as a function of the pilot tone.

27. The method of claim 25 further comprising:

(e) despreading the spread spectrum ranging signal as a function of the a third spreading code different than the first spreading code; and

(f) dispreading an output of (e) as a function-of a fourth spreading code;

wherein (d) comprises determining the range as a function of the output of (c) and an output if (d).

28. A system for receiving rebroadcast ranging signals, the system comprising:

a receive antenna;

a first despreading demodulator connected with the receive antenna, the first despreading demodulator responsive to a first spreading code;

a ranging signal receiver connected with an output of the first despreading demodulator, the ranging signal receiver operable to despread an input signal from the output and determine a range.

29. The system of claim 28 further comprising:

a first filter connected with the despreading demodulator, the first filter operable to isolate a pilot signal from the output of the despreading demodulator, the first spreading code responsive to the pilot signal.

30. The system of claim 28 further comprising:

a second despreading demodulator connected with the receive antenna, the second despreading demodulator responsive to a second spreading code different than the first despreading code.