GNSS line bias measurement system and method

• US 20060244656A1
• Filed: 04/15/2005
• Published: 11/02/2006
• Est. Priority Date: 04/15/2005
• Status: Active Grant

• Current Assignee: Novariant Incorporated (Kubota Corporation)
• Original Assignee: Novariant Incorporated (Kubota Corporation)
• Inventors: Lawrence, David Gary, Zimmerman, Kurt, Cobb, Henry Stewart, Montgomery, Paul Yalden
• Granted Patent: US 7,489,270 B2
• Time in Patent Office: Days
• US Class Current: 342/357.290
• CPC Class Codes: G01S 19/04 providing carrier phase data
• CPC Class Codes: G01S 19/44 Carrier phase ambiguity resolution; Floating ambiguity; LAMBDA [Least-squares AMBiguity Decorrelation Adjustment] method

Abstract

A number of solutions for deriving the line bias are disclosed. Some of these solutions utilize signal processing and judicious selection of the frequency plan used in the position detection systems to either enable the derivation of the line bias, or make the measurements insensitive to line bias. In other examples, the present invention utilizes measurement schemes for deriving the line bias and enabling a position detection system to process line bias information in order to find a position solution

Claims

1. A differential carrier phase position detection system, comprising:

one or more antennas for receiving carrier signals;

a receiver for determining position information for the one or more antennas in response to a clock signal and intermediate frequency signals from the antennas;

at least one antenna adapter module for interfacing between a first one of the antennas and the receiver and generating the intermediate frequency signal in response to the carrier signals and the clock signal; and

at least one antenna communications path for transmitting the clock signal to the antenna adapter module and for transmitting the intermediate frequency signal to the receiver, said system providing phase measurements of the carrier signals that are substantially independent of delay in the antenna communications path.

2. A system as claimed in claim 1, wherein the intermediate frequency signal is approximately one half the frequency of the carrier signals.

3. A system as claimed in claim 1, wherein the first one of the antennas is remote from the receiver.

4. A method for rendering a differential carrier phase position detection system substantially insensitive to line bias, the method comprising:

receiving carrier signals at one or more antennas;

generating a clock signal and transmitting the clock signal to a first one of the antennas;

generating an intermediate frequency signal in response to the carrier signals and the clock signal at the first one of the antennas;

transmitting the intermediate signal to a receiver; and

determining position information at the receiver for the antennas, position information for the first one of the antennas being generated in response to the clock signal and the intermediate frequency signal from the first one of the antennas.

5. A method as claimed in claim 4, the intermediate signal is approximately one half a frequency of the carrier signals.

6. A method as claimed in claim 4, further comprising locating the first one of the antennas remote from the receiver.

7. A differential carrier phase position detection system having line bias compensation, the system comprising:

antennas for receiving carrier signals;

a receiver for determining position information for the antennas in response to a clock signal and an intermediate frequency signal from the antennas;

at least one antenna adapter module for interfacing between a first one of the antennas and the receiver and generating the intermediate frequency signal in response to the carrier signals and the clock signal, and generating a compensation signal;

at least one antenna communications path for transmitting the clock signal to the antenna adapter module and for transmitting the intermediate frequency signal and the compensation signal to the receiver; and

a line bias compensation module for determining a correction to a phase of the intermediate frequency signal in response to the compensation signal, the correction being used by the receiver to determine the position information.

8. A system as claimed in claim 7, wherein the at least one antenna adapter module generates the compensation signal as a harmonic tone at an integer multiple of the frequency of the clock signal, said compensation signal being transmitted on the at least one antenna communications path.

9. A system as claimed in claim 7, wherein the line bias compensation module determines the delay in response to a measure of a fractional phase of the compensation signal.

10. A system as claimed in claim 7, wherein a relationship between a frequency of the intermediate frequency signal f_IF, carrier signals f_RF, and the compensation signal f_TF is:

f_IF−

(f_RF−

f_IF) is approximately equal to 2 n f_TF;

where n is an integer.

11. A system as claimed in claim 7, wherein a frequency of the intermediate frequency signal and the compensation signal are both less than 650 MHz.

12. A method for compensating for line bias in a differential carrier phase position detection system, the method comprising:

receiving carrier signals at antennas;

generating a clock signal and transmitting the clock signal to a first one of the antennas;

generating an intermediate frequency signal in response to the carrier signals and the clock signal at the first one of the antennas;

generating a compensation signal at the first one of the antennas;

transmitting the intermediate signal and the compensation signal to a receiver; and

determining position information at the receiver for the antennas, position information for the first one of the antennas being generated at least in response to the intermediate frequency signal and the compensation signal from the first one of the antennas.

13. A method as claimed in claim 12, further comprising determining a delay in the transmission of the intermediate frequency signal in response to a measure of a fractional phase of the compensation signal.

14. A system as claimed in claim 12, wherein a relationship between a frequency of the intermediate frequency signal f_IF, carrier signals f_RF, and the compensation signal f_TF is:

f_IF−

(f_RF−

f_IF) is approximately equal to 2 n f_TF;

where n is an integer.

15. A specified-delay antenna communications cable for a position detection system, the communications cable for connecting an antenna to a receiver that uses a delay of the communications cable to determine position information for the antenna, the cable comprising an indication of a length and/or signal delay associated with the cable.

16. A cable as claimed in claim 15, wherein the delay of the communications cable is determined using time or frequency domain reflectometry.

17. A cable as claimed in claim 15, wherein the delay of the communications cable is determined by transmitting signals at a multiple frequencies through the cable.

18. A cable as claimed in claim 15, wherein the delay of the communications cable is determined in a factory, which delay is entered into the position detection system.

19. A cable as claimed in claim 15, wherein the delay of the communications cable is entered into the position detection system by an operator.

20. A cable as claimed in claim 15, wherein the delay of the communications cable is determined in a factory and stored with the cable, which delay is entered into the position detection system automatically.

21. A cable as claimed in claim 15, wherein the delay is stored in a memory device with the cable.

22. A cable as claimed in claim 15, wherein the position detection system comprises a cable delay measurement system that measures the delay of the communications cable.

23. A cable as claimed in claim 15, further comprising thermal sensitivity information that relates the delay of the cable to temperature.

24. A cable as claimed in claim 23, wherein the cable includes a temperature detector for generating temperature information for the communications cable.

25. A method for using communications cable for a carrier phase position detection system, the method comprising:

measuring a delay of the communications cable;

providing delay information characterizing the delay with the cable; and

entering the delay information into the carrier phase position detection system.

26. A method as claimed in claim 25, further comprising providing thermal sensitivity information that relates the delay of the cable to temperature with the cable.

27. A cable as claimed in claim 26, further comprising detecting a temperature of the cable and updating the delay information in response to the temperature and the thermal sensitivity information.

28. A cable as claimed in claim 25, wherein the delay information is entered automatically.

29. A differential carrier phase position detection system having line bias compensation, the system comprising:

antennas for receiving carrier signals;

a receiver for determining position information for the antennas in response to a clock signal and carrier signal information from the antennas;

a communications cable connecting the receiver to at least one of the antennas to transmit the carrier signal information to the receiver; and

a communications cable delay detector for determining a delay of the communications cable by transmitting test signals over the communications cable.

30. A system as claimed in claim 29, wherein the communications delay detector determines the delay transmitting time domain reflectometry test signals over the communications cable and using time domain reflectometry to determine the delay.

31. A system as claimed in claim 29, wherein the communications delay detector determines the delay by transmitting the test signals at a multiple frequencies through the cable.

32. A system as claimed in claim 29, wherein the communications cable delay detector provides delay information characterizing the delay to the receiver, which determines the position information in response to the delay information.

33. A differential carrier phase position detection system having line bias compensation, the system comprising:

antennas for receiving carrier signals;

a communications cable connecting the receiver to at least one of the antennas to transmit the carrier signal information to the receiver;

a temperature detector for detecting changes in temperature that indicate changes in a temperature of the communications cable;

a line bias module for using temperature information from temperature detector to determine a delay of the communications cable; and

a position solution module for determining position information for the antennas in response to carrier signal information from the antennas and the delay of the communications cable.

34. A system as claimed in claim 33, wherein the line bias module relates changes in temperature to changes in the delay of the communications cable.

35. A system as claimed in claim 33, wherein the line bias model stores information relating changes in temperature to changes in delay.

36. A method for determining position of an antenna with a carrier phase receiver, the method comprising:

receiving carrier signals at the antenna;

transmitting a clock signal to the antenna over a communications cable from the receiver;

detecting a temperature of the communications cable;

transmitting carrier signal information from the antenna to the receiver;

relating the temperature of the communications cable to changes in delay of the communications cable; and

the receiver determining a position of the antenna in response to the carrier signal information and the changes in delay of the communications cable.

37. A method as claimed in claim 36, further comprising a second antenna.

38. A method as claimed in claim 37, wherein the step of determining the position comprises determining a relative position of the antennas.

39. A method as claimed in claim 36, wherein the carrier phase receiver is a differential carrier phase receiver.

40. A method as claimed in claim 36, further comprising relating changes in temperature to changes in the delay of the communications cable.

41. A method as claimed in claim 36, wherein the step of determining the temperature comprises detecting an ambient temperature.

42. A method for determining the relative position of a first antenna and a second antenna, the first antenna being connected to a receiver via a cable, the method comprising:

measuring a delay associated with the cable by sending a signal from the receiver to the first antenna; and

determining the relative position of the first and second antennas from the delay.

43. The method of claim 42, wherein the signal is reflected back to the receiver from the first antenna.

44. The method of claim 42, wherein the signal is modified at the first antenna.

45. The method of claim 44, wherein the modified signal is retransmitted to the receiver from the first antenna.

46. The method of claim 42 further comprising sweeping through a plurality of frequencies and measuring corresponding delays associated with the frequencies.

47. A method for determining the relative position of a first antenna and a second antenna, the first antenna being connected to a receiver via a cable and the second antenna connected to the receiver via a second cable, the method comprising:

a. generating differential carrier phase measurements between the first and second antennas by

i. transmitting signal information bi-directionally between the receiver and the first and second antennas;

ii. measuring phases of at least some of said signal information for the first and second antennas; and

iii. subtracting phases for the second antenna from phases for the first antenna;

b. calculating the relative position of the first and second antennas from the differential carrier phase measurements generated in step a.

48. The method of claim 47, wherein the first and second antennas are configured to receive GNSS signals.

49. The method of claim 47, wherein the step of transmitting signal information comprises:

transmitting a clock signal from the receiver to the first and second antennas; and

transmitting an intermediate frequency from the antennas to the receiver.

50. The method of claim 47, wherein the step of transmitting signal information comprises:

transmitting a clock signal from the receiver to the first and second antennas; and

transmitting a down-converted GNSS signal from the antennas to the receiver.

51. The method of claim 50, wherein the step of transmitting the down-converted GNSS signal comprises down-converting a received GNSS signal to substantially half the frequency at which it was received at the first and second antennas.

52. The method of claim 47, wherein the step of transmitting signal information further comprises transmitting a first compensation signal from the first antenna to the receiver and a second compensation signal from the second antenna to the receiver.

53. The method of claim 52 wherein the first compensation signal and the second compensation signal are a harmonic of the clock signal.