Positioning system with co-polarized and cross-polarized mapping

• US 7,427,945 B2
• Filed: 04/11/2005
• Issued: 09/23/2008
• Est. Priority Date: 07/03/2003
• Status: Active Grant

• Current Assignee: Deere & Company
• Original Assignee: Navcom Technology, Inc. (Deere & Company)
• Inventors: Stephens, Scott Adam
• Primary Examiner(s): ALSOMIRI, ISAM A
• Application Number:
  US11/103,962
• Publication Number:
  US 20050225482A1
• Time in Patent Office: 1,261 Days
• Field of Search: 342/5, 342/126, 342/146, 342/188, 342/191, 342/463
• 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 13/89 for mapping or imaging
• 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 7/026 involving the transmission of elliptically or circularly polarised waves
• CPC Class Codes: G01S 7/41 using analysis of echo signal for target characterisation; Target signature; Target cross-section

Abstract

A local positioning system using co-polarized and cross-polarized radar mapping is provided. In one embodiment of the method, at least a first electromagnetic pulse having a first polarization is transmitted. A first return signal preferentially having the first polarization is received over a respective period of time. The first return signal is processed so as to isolate a first return pulse corresponding to an object within a radar detection area of the positioning system. At least a second electromagnetic pulse having the first polarization is also transmitted. A second return signal preferentially having a second polarization is received over a respective period of time. The second return signal is processed so as to isolate a second return pulse corresponding to the object. A characteristic of the object is determined in accordance with a relative signal strength of the first return pulse and the second return pulse.

Claims

1. A method of determining position performed by a mobile local positioning system, comprising:

transmitting at least a first electromagnetic pulse having a carrier signal frequency and a first polarization from a mobile device;

receiving a first return signal over a respective period of time, wherein the first return signal includes at least a first return pulse from a landmark having a known position within a radar detection area of the positioning system, and the receiving includes preferentially receiving signals having the first polarization;

processing the first return signal so as to isolate the first return pulse from the first return signal;

transmitting a second electromagnetic pulse having the carrier signal frequency and the first polarization from the device;

receiving a second return signal over a respective period of time, wherein the second return signal includes a second return pulse from the landmark within the radar detection area of the positioning system, and the receiving includes preferentially receiving signals having a second polarization;

processing the second return signal so as to isolate the second return pulse from the second return signal;

determining a range to and a characteristic of the landmark in accordance with a relative signal strength of the first return pulse and the second return pulse; and

determining a position of the mobile device based on the range to the landmark.

2. The method of claim 1, wherein the first polarization is right-hand circular polarization and the second polarization is left-hand circular polarization.

3. The method of claim 1, wherein the first polarization is left-hand circular polarization and the second polarization is right-hand circular polarization.

4. The method of claim 1, further comprising using a same polarized antenna for both the transmitting and receiving.

5. The method of claim 1, wherein transmitting from the device uses one transmitter and receiving in the device uses a plurality of receivers.

6. The method of claim 1, wherein transmitting from the device uses a plurality of transmitters and receiving in the device uses one receiver.

7. The method of claim 1, wherein the landmark is an active landmark.

8. The method of claim 1, wherein the landmark is a passive reflector.

9. The method of claim 1, wherein the characteristic of the landmark is a roughness of at least one surface of the landmark.

10. A mobile local positioning system, comprising:

a mobile device configured to transmit at least a first electromagnetic pulse having a carrier signal frequency and a first polarization, to receive a first return signal including at least a first return pulse from a landmark having a known position, located within a radar detection area of the positioning system, over a respective period of time, to process the first return signal so as to isolate the first return pulse from the first return signal, to transmit at least a second electromagnetic pulse having the carrier signal frequency and the first polarization, to receive a second return signal including a second return pulse from the landmark over a respective period of time, to process the second return signal so as to isolate the second return pulse from the second return signal, and to determine a range to and a characteristic of the landmark in accordance with a relative signal strength of the first return pulse and the second return pulse,

wherein the device preferentially receives the first return signal having the first polarization and the second return signal having a second polarization; and

the mobile device is configured to determine a position of the mobile device based upon the range to the landmark.

11. The positioning system of claim 10, wherein the first polarization is right-hand circular polarization and the second polarization is left-hand circular polarization.

12. The positioning system of claim 10, wherein the first polarization is left-hand circular polarization and the second polarization is right-hand circular polarization.

13. The positioning system of claim 10, wherein the landmark is an active landmark.

14. The positioning system of claim 10, wherein the landmark is a passive reflector.

15. The positioning system of claim 14, in which the passive reflector is selected from the group consisting of a dihedral and a corner cube.

16. The positioning system of claim 10, the device further including at least one circularly polarized antenna.

17. The positioning system of claim 10, the device further including at least one polarizing antenna, wherein the device uses the polarizing antenna to transmit and to receive.

18. The positioning system of claim 10, the device further including a transmitter and a plurality of receivers, wherein the device transmits using the transmitter and the device receives using the plurality of receivers.

19. The positioning system of claim 10, the device further including a plurality of transmitters and a receiver, wherein the device transmits using the plurality of transmitters and the device receives using the receiver.

20. The positioning system of claim 10, the device further including a processor, wherein the processor processes the first return signal so as to isolate the first return pulse, processes the second return signal so as to isolate the second return pulse and determines the characteristic of the landmark in accordance with the relative signal strength of the first return pulse and the second return pulse.

21. The positioning system of claim 10, the device further including a processor, a memory and at least one program module, the at least one program module containing instructions for:

isolating the first return pulse from the first return signal;

isolating the second return pulse from the second return signal; and

determining the characteristic of the landmark in accordance with the relative signal strength of the first return pulse and the second return pulse.

22. The positioning system of claim 10, wherein the characteristic of the landmark is a roughness of at least one surface of the landmark.