Satellite and local system position determination

• US 20070109188A1
• Filed: 09/05/2006
• Published: 05/17/2007
• Est. Priority Date: 07/30/2004
• Status: Active Grant

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Novariant Incorporated (Kubota Corporation)
• Inventors: Lawrence, David, Zimmerman, Kurt, Montgomery, Paul, Cobb, H.
• Granted Patent: US 7,385,554 B2
• Time in Patent Office: Days
• US Class Current: 342/357.270
• CPC Class Codes: G01S 1/24 the synchronised signals being pulses or equivalent modulations on carrier waves and the transit times being compared by measuring the difference in arrival time of a significant part of the modulations , e.g. LORAN systems
• CPC Class Codes: G01S 19/25 involving aiding data received from a cooperating element, e.g. assisted GPS
• CPC Class Codes: G01S 19/31 Acquisition or tracking of other signals for positioning
• 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, augmentation of the land-based system is provided by receiving signals from a GNSS. The signals from the land-based positioning system have a code phase accuracy better than one wavelength of a carrier of the signals from the GNSS. Different decorrelation may be used for signals from a satellite than from a land-based transmitter, such as using a digital decorrelator for signals from the satellite and an analog decorrelator for signals from a land-based transmitter. The receivers may include both a GNSS antenna and a local antenna. The phase centers of the two antennas are within one wavelength of the GNSS signals from each other. The local antenna is sized for operation in the X or ISM-bands of frequencies. The GNSS antenna is a patch antenna where the microwave antenna extends away from the patch antenna in at least one dimension.

Claims

1. A system for determining a position from transmitted signals, the system comprising:

a digital de-correlator operable to de-correlate first signals from at least one satellite;

an analog de-correlator operable to de-correlate second signals from at least one land based transmitter; and

a processor operable to determine the position as a function of the outputs of the digital and analog decorrelators.

2. The system of claim 1 wherein the second signals from the at least one land based transmitter have a code phase range accuracy better than one wavelength of a carrier of the first signals from the at least one satellite.

3. The system of claim 1 further comprising:

first and second analog-to-digital converters;

wherein the digital de-correlator comprises;

a first code generator; and

a digital mixer operable to mix a first code output by the first code generator with the first signals output by the first analog-to-digital converter;

wherein the analog de-correlator comprises;

a second code generator; and

an analog mixer operable to mix a second code output by the second code generator with the second signals;

wherein the second analog-to-digital converter is operable to convert the mixed second code and second signals from analog to digital.

4. The system of claim 1 wherein the first signals have a carrier with a wavelength greater than 15 cm, and measurements of the second signals have code phase range accuracy better than 2 cm.

5. The system of claim 1 wherein the second signals have a modulation rate of a code being at least 30 MHz carried in the X-band, ISM band or combinations thereof.

6. The system of claim 1 wherein the second signals have a second code modulation rate at least ten times a first code modulation rate of the first signals.

7. The system of claim 1 wherein the first and second signals are direct-sequence, spread spectrum signals responsive to first and second codes, respectively, the first code different than the second code.

8. The system of claim 1 wherein the first signals have a carrier with a wavelength greater than 15 cm, and measurements of the second signals have accuracy better than one-half wavelength of the carrier of the first signals.

9. A method for determining a position from transmitted signals, the method comprising:

(a) digital de-correlating first signals from at least one satellite;

(b) analog de-correlating second signals from at least one land based transmitter; and

(c) determining the position as a function of the de-correlated first and second signals.

10. The method of claim 9 wherein (a) comprises de-correlating the second signals from the at least one land based transmitter, the second signals having a code phase range accuracy better than one wavelength of a carrier of the first signals from the at least one satellite.

11. The method of claim 9 wherein (a) comprises mixing a first code with the first signals after converting the first signals from analog to digital;

and

wherein (b) comprises mixing a second code with the second signals prior to converting the mixed second code and signals from analog to digital.

12. The method of claim 9 wherein (a) comprises de-correlating the first signals, the first signals having a carrier with a wavelength greater than 15 cm;

and

wherein (b) comprises de-correlating the second signals, the second signals having a better than 2 cm code phase range accuracy.

13. The method of claim 9 wherein (b) comprises de-correlating the second signals, the second signals having a modulation rate of a code being at least 30 MHz carried in the X-band, ISM band or combinations thereof.

14. The method of claim 9 wherein (b) comprises de-correlating the second signals, the second signals have a second code modulation rate at least ten times a first code modulation rate of the first signals.

15. The method of claim 9 wherein (a) and (b) comprise de-correlating direct-sequence, spread spectrum signals responsive to different codes.

16. The method of claim 9 wherein (a) comprises de-correlating the first signals, the first signals having a carrier with a wavelength greater than 15 cm;

and wherein (b) comprises de-correlating the second signals, the second signals having code phase range accuracy better than one-half wavelength of the carrier of the first signals.