Positioning system with a sparse antenna array

• US 20050270229A1
• Filed: 04/11/2005
• Published: 12/08/2005
• Est. Priority Date: 07/03/2003
• Status: Active Grant

• Current Assignee: Deere & Company
• Original Assignee: Navcom Technology, Inc. (Deere & Company)
• Inventors: Stephens, Scott Adam
• Granted Patent: US 7,466,262 B2
• Time in Patent Office: Days
• US Class Current: 342/146
• CPC Class Codes: G01S 13/46 Indirect determination of position data
• CPC Class Codes: G01S 13/75 using transponders powered from received waves, e.g. using passive transponders , or using passive reflectors
• CPC Class Codes: G01S 13/876 Combination of several spaced transponders or reflectors of known location for determining the position of a receiver G01S13/874 takes precedence
• CPC Class Codes: G01S 2013/466 by Trilateration, i.e. two antennas or two sensors determine separately the distance to a target, whereby with the knowledge of the baseline length, i.e. the distance between the antennas or sensors, the position data of the target is determined
• CPC Class Codes: G01S 2013/468 by Triangulation, i.e. two antennas or two sensors determine separately the bearing, direction or angle to a target, whereby with the knowledge of the baseline length, the position data of the target is determined
• CPC Class Codes: G01S 3/50 the waves arriving at the antennas being pulse modulated and the time difference of their arrival being measured
• CPC Class Codes: G01S 3/72 Diversity systems specially adapted for direction-finding
• CPC Class Codes: G01S 7/026 involving the transmission of elliptically or circularly polarised waves
• CPC Class Codes: G01S 7/42 Diversity systems specially adapted for radar

Abstract

In one embodiment of a positioning system, a transmit element is configured to transmit at least one electromagnetic pulse having a carrier signal frequency. An antenna array with a plurality of receive elements includes at least two receive elements separated by a spacing more than a half wavelength. Each of the at least two receive elements is configured to receive a return signal over a period of time. The return signal includes a return pulse from an object within a detection area of the system. The wavelength corresponds to the carrier signal frequency of the transmitted pulse. A detector is configured to process the return signal from one receive element and the other receive element so as to isolate the return pulse received at each of the at least two receive elements and thereby determine a position of the object in relation to the system.

Claims

1. A positioning system, comprising:

an antenna array with a plurality of transmit elements including at least two transmit elements separated by a spacing more than a half wavelength and configured to transmit at least one set of electromagnetic pulses substantially simultaneously,

wherein each of the at least two transmit elements is configured to transmit one pulse in the set of pulses, each pulse having a respective carrier signal frequency, and the wavelength corresponds to an average of respective carrier signal frequencies of transmitted pulses from the at least two transmit elements;

a receiver configured to receive a return signal over a period of time, the return signal including at least a first return pulse and a second return pulse from an object within a detection area of the system, wherein the first return pulse corresponds to the transmitted pulse from one transmit element and the second return pulse corresponds to the transmitted pulse from the other transmit element; and

a detector configured to process the return signal so as to isolate the first return pulse and the second return pulse and thereby determine a position of the object in relation to the system,

wherein the detector includes angular resolution logic for determining an angular position of the object in accordance with the spacing between the at least two transmit elements and directional resolution logic for determining a direction of the object in accordance with a difference in arrival times of the first return pulse and the second return pulse at the receiver.

2. The system of claim 1, wherein the pulse from each of the at least two transmit elements is encoded differently.

3. The system of claim 1, wherein the pulse from each of the at least two transmit elements has a different carrier signal phase.

4. The system of claim 1, wherein the pulse from each of the at least two transmit elements has a different carrier signal frequency.

5. The system of claim 1, wherein the transmit elements are omni-directional.

6. The system of claim 1, wherein the transmitted pulse from each of the at least two transmit elements has a polarization and the receiver preferentially receives return signals having the polarization.

7. The system of claim 6, wherein the polarization is selected from the group consisting of linear polarization, elliptical polarization, right-hand elliptical polarization, left-hand elliptical polarization, right-hand circular polarization and left-hand circular polarization.

8. The system of claim 1, wherein the object is a passive reflector.

9. The system of claim 1, wherein the object is an active landmark.

10. The system of claim 1, further comprising a third transmit element that is non-collinear with the first two transmit elements, wherein the third transmit element is configured to transmit a pulse having a respective carrier signal frequency.

11. The system of claim 10, further comprising a fourth transmit element that is not co-planar with other transmit elements, wherein the fourth transmit element is configured to transmit a pulse having a respective carrier signal frequency.

12. A positioning system, comprising:

a transmit element configured to transmit at least one electromagnetic pulse having a carrier signal frequency;

an antenna array with a plurality of receive elements including at least two receive elements separated by a spacing more than a half wavelength, wherein each of the at least two receive elements is configured to receive a return signal over a period of time, the return signal including a return pulse from an object within a detection area of the system and the wavelength corresponds to the carrier signal frequency of the transmitted pulse; and

a detector configured to process the return signal from one receive element and the other receive element so as to isolate the return pulse received at each of the at least two receive elements and thereby determine a position of the object in relation to the system,

wherein the detector includes angular resolution logic for determining an angular position of the object in accordance with the spacing between the at least two receive elements and directional resolution logic for determining a direction of the object in accordance with a difference in arrival times of the first return pulse and the second return pulse at the receive elements.

13. The system of claim 12, wherein the transmit element is omni-directional.

14. The system of claim 12, wherein the transmitted pulse has a polarization and each of the at least two receive elements preferentially receives return signals having the polarization.

15. The system of claim 14, wherein the polarization is selected from the group consisting of linear polarization, elliptical polarization, right-hand elliptical polarization, left-hand elliptical polarization, right-hand circular polarization and left-hand circular polarization.

16. The system of claim 12, wherein the object is a passive reflector.

17. The system of claim 12, wherein the object is an active landmark.

18. The system of claim 12, further comprising a third receive element that is non-collinear with the first two receive elements.

19. The system of claim 18, further comprising a fourth receive element that is not co-planar with other receive elements.