Robust low-frequency spread-spectrum navigation system

• US 20080088507A1
• Filed: 10/17/2006
• Published: 04/17/2008
• Est. Priority Date: 10/17/2006
• Status: Active Grant

• Current Assignee: UT-Battelle LLC
• Original Assignee: UT-Battelle LLC
• Inventors: Smith, Stephen F., Moore, James A.
• Granted Patent: US 7,626,544 B2
• Time in Patent Office: Days
• US Class Current: 342/386
• CPC Class Codes: G01C 21/1654 with electromagnetic compass
• CPC Class Codes: G01C 21/206 specially adapted for indoor navigation
• CPC Class Codes: G01S 1/042 Transmitters
• 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 19/10 providing dedicated supplementary positioning signals
• CPC Class Codes: G01S 19/18 Military applications
• CPC Class Codes: G01S 19/47 the supplementary measurement being an inertial measurement, e.g. tightly coupled inertial
• CPC Class Codes: G01S 5/0264 at least one of the systems being a non-radio wave positioning system
• CPC Class Codes: G01S 5/10 Position of receiver fixed by co-ordinating a plurality of position lines defined by path-difference measurements , e.g. omega or decca systemsG01S5/12 takes precedence ; beacons and receivers cooperating therewith G01S1/306, G01S1/308

Abstract

Methods and apparatus are described for a navigation system. A process includes providing a plurality of transmitters distributed throughout a desired coverage area; locking the plurality of transmitters to a common timing reference; transmitting a signal from each of the plurality of transmitters. An apparatus includes a plurality of transmitters distributed throughout a desired coverage area; wherein each of the plurality of transmitters comprises a packet generator; and wherein the plurality of transmitters are locked to a common timing reference.

Claims

1. An apparatus comprising:

a plurality of transmitters distributed throughout a desired coverage area;

wherein each of the plurality of transmitters comprises a packet generator;

and wherein the plurality of transmitters are locked to a common timing reference.

2. The apparatus of claim 1, wherein the packet generator further comprises:

an output generating component;

a location generating component coupled to the output generating component;

a system time generating component coupled to the output generating component;

a system data generating component coupled to the output generating component;

and a error correction generating component coupled to the output generating component.

3. The apparatus of claim 1, wherein each of the plurality of transmitters further comprises:

a first code generator coupled to the packet generator;

a second code generator coupled to the packet generator;

a numerically controlled oscillator;

a first pulse shaping component coupled to the first code generator and the numerically controlled oscillator;

a second pulse shaping component coupled to the second code generator and the numerically controlled oscillator;

a DAC converter coupled to the numerically controlled oscillator;

and a RF amplifier coupled to the DAC converter and to an antenna.

4. The apparatus of claim 1, wherein each of the plurality of transmitters further comprises a physically short, vertically polarized antenna.

5. The apparatus of claim 4, wherein the physically short, vertically polarized antenna comprises a wire-antenna array arranged in an inverted-L quadrapole configuration.

6. The apparatus of claim 1, wherein the plurality of transmitters generate highly stable hybrid spread-spectrum waveforms.

7. The apparatus of claim 1, wherein the plurality of transmitters transmit in the 80-120 kHz frequency range.

8. The apparatus of claim 7, wherein the plurality of transmitters transmit a signal split into a 80-90 kHz band and a 110-120 kHz band.

9. The apparatus of claim 1, further comprising:

a receiver comprising;

an RF amplifier coupled to an antenna;

a bandpass filter coupled to the RF amplifier;

an ADC converter coupled to the bandpass filter;

a numerically controlled oscillator coupled to the ADC converter;

a first and a second mixer/multiplier coupled to the numerically controlled oscillator;

a first programmable delay register and downsampling component coupled to the first mixer/multiplier;

a second programmable delay register and downsampling component coupled to the second mixer/multiplier;

a first correlator coupled to the first programmable delay register and downsampling component;

a second correlator coupled to the second programmable delay register and downsampling component;

a delay lock loop coupled to the first correlator and the second correlator;

a rectangular to polar converter coupled to the first correlator and the second correlator;

a detector coupled to the rectangular to polar converter;

and a data decoder coupled to the rectangular to polar converter.

10. The apparatus of claim 9, wherein the receiver further comprises:

a ground-wave correlator;

a sky-wave correlator;

and a processing logic component coupled to the ground-wave correlator and the sky-wave correlator.

11. The apparatus of claim 1, wherein the common timing reference is selected from the group comprising a Global Positioning System timing signal;

a highly stable local oscillator;

signals from WWVB, LORAN-C, or OMEGA;

signals from GOES satellites;

signals from CDMA cell-phone base stations;

VLF, LF, or HF standard-frequency broadcast signals;

standard AM broadcasting signals;

international shortwave broadcasting signals; and

analog and digital television broadcasting signals.

12. The apparatus of claim 1, wherein the plurality of transmitters transmit in the 3.3 MHz frequency range.

13. A method comprising:

providing a plurality of transmitters distributed throughout a desired coverage area;

locking the plurality of transmitters to a common timing reference;

transmitting a signal from each of the plurality of transmitters.

14. The method of claim 13, wherein the signal comprises:

location information;

system time information;

system data information;

error-correction information;

and synchronization bits.

15. The method of claim 13, wherein the transmitting a signal generates highly stable hybrid spread-spectrum waveforms.

16. The method of claim 13, wherein the transmitting a signal is done in the 80-120 kHz frequency range.

17. The method of claim 16, wherein the transmitting a signal is done in a 80-90 kHz band and a 110-120 kHz band.

18. The method of claim 13, wherein the transmitting a signal is done using a frequency hopping protocol.

19. The method of claim 13, wherein the transmitting a signal is done using a code-division multiple-access scheme.

20. The method of claim 13, further comprising:

receiving the signal with a receiver;

using the signal to determine the location of the receiver.

21. The method of claim 20, wherein the determining the location of the receiver takes less than one minute.

22. The method of claim 20, wherein the receiving the signal comprises:

receiving a ground-wave component;

receiving a sky-wave component;

correlating the ground-wave component with the sky-wave component to determine the three-dimensional location of the receiver.

23. The method of claim 20, wherein the using the signal to determine the location of the receiver comprises a method selected from the group comprising Kalman filtering, Allan filtering, multidimensional kernels, and iterative techniques based on linearization.

24. The method of claim 20, wherein the using the signal to determine the location of the receiver comprises:

selecting a 2D or a 3D algorithm;

converting coordinates received from transmitters to an earth-centered format;

calculating chord distances;

converting the chord distances to great-circle distances;

correcting for environmental factors;

using a positioning algorithm to determine the receiver location.

25. The method of claim 13, wherein the transmitting a signal is optimized for maximum immunity from pick-up of power line noise.

26. The method of claim 13, wherein the providing a plurality of transmitters comprises deploying the plurality of transmitters outside the area of operations.

27. A method comprising:

providing a plurality of transmitters distributed throughout a desired coverage area;

locking the plurality of transmitters to a common timing reference;

transmitting a signal in the 80-120 kHz frequency range, using a frequency hopping protocol and highly stable hybrid spread-spectrum waveforms, from each of the plurality of transmitters, wherein the signal comprises;

location information;

system time information;

system data information;

error-correction information;

and synchronization bits;

receiving the signal with a receiver;

using the signal to determine the location of the receiver.