Moving platform position determination system and method
View Patent ↗A system and method for determining a position of a moving platform are provided. The method includes transmitting a carrier signal from one of the moving platform and a stationary platform, receiving a received signal at the other of the moving and stationary platforms, deriving a frequency shift between the carrier signal and the received signal, and calculating the apparent closing velocity using the frequency shift and a frequency of the carrier signal.
1. A method for determining a position of a moving platform, the method comprising:
transmitting a carrier signal from one of the moving platform and a stationary platform;
receiving a received signal at the other of the moving and stationary platforms;
deriving a frequency shift between the carrier signal and the received signal; and
calculating the apparent closing velocity using the frequency shift and a frequency of the carrier signal;
wherein calculating the apparent closing velocity comprises using the equation:
f
d
(
t
)
=
f
c
v
c
(
t
)
c
+
f
m
+
n
(
t
)
wherein fd(t) represents the frequency shift, fc represents a center frequency of the carrier signal, c represents a speed of radio propagation, fm is a constant frequency offset between local oscillators at the transmitter and the receiver system, n(t) represents a measurement noise and vc(t) represents the apparent closing velocity.
2. The method of claim 1 , wherein determining the position of the moving platform comprises monitoring the closing velocity over a period of time.
3. The method of claim 1 , wherein the apparent closing velocity is characterized by a measured shape described by cos(θ(z)), wherein z represents the distance that the moving platform has traveled and θ represents a location-varying angle.
4. The method of claim 3 , further comprising determining a course of the moving platform by comparing the measured shape to a plurality of stored shapes.
5. The method of claim 4 , wherein the comparing comprises using sequential statistical methods.
6. The method of claim 1 , wherein deriving the frequency shift comprises analyzing a frequency spectrum corresponding to the received signal.
7. The method of claim 1 , wherein deriving the frequency shift comprises generating a spread spectrum of the received signal.
8. The method of claim 7 , wherein generating a spread spectrum further comprises generating a spectral line at twice the frequency of a Doppler shift of the received signal.
9. The method of claim 8 , wherein the Doppler shift is determined using a center frequency of the received signal.
10. The method of claim 9 , wherein the center frequency of the received signal is determined by homodyning the spread spectrum of the received signal.
11. The method of claim 1 , wherein the stationary platform comprises a plurality of stationary platforms.
12. A method for determining a position of a moving platform, the method comprising:
transmitting a carrier signal from one of the moving platform and a stationary platform;
receiving a received signal at the other of the moving and stationary platforms;
deriving a frequency shift between the carrier signal and the received signal; and
calculating the apparent closing velocity using the frequency shift and a frequency of the carrier signal; wherein the stationary platform comprises a transmitter coupled to a railway track.
13. The method of claim 12 , wherein the transmitter is coupled to a turnout on the railway track.
14. The method of claim 1 , wherein the stationary platform comprises a mobile communication platform base station.
15. The method of claim 1 , wherein the stationary platform comprises a broadcast station.
16. The method of claim 1 , wherein the stationary platform comprises a cellular network station.
17. A method for determining a position of a moving platform, the method comprising:
transmitting a carrier signal from one of the moving platform and a stationary platform;
receiving a received signal at the other of the moving and stationary platforms;
deriving a frequency shift between the carrier signal and the received signal; and
calculating the apparent closing velocity using the frequency shift and a frequency of the carrier signal; wherein the moving platform is a locomotive.
18. The method of claim 1 , wherein the carrier signal comprises radio frequency signals.
19. A system for determining a position of a moving platform, the system comprising:
a transmitter configured for transmitting a carrier signal from one of the moving platform and a stationary platform;
a receiver system configured for receiving a received signal from the other of the moving and stationary platforms, the receiver system further comprising:
a processor configured for:
(i) deriving a frequency shift between the carrier signal and the received signal;
(ii) calculating the apparent closing velocity angle using the frequency shift and a frequency of the carrier signal, wherein the processor is configured for deriving the apparent closing velocity using the equation:
f
d
(
t
)
=
f
c
v
c
(
t
)
c
+
f
m
+
n
(
t
)
wherein fd(t) represents the frequency shift, fc represents a center frequency of the carrier signal, c represents a speed of radio propagation, fm is a constant frequency offset between local oscillators at the transmitter and at the receiver system, n(t) represents a measurement noise and vc(t) represents the apparent closing velocity.
20. The system of claim 19 , wherein the processor is further configured for determining the position of the moving platform by monitoring the apparent closing velocity over a period of time.
21. The system of claim 19 , wherein the processor is further configured to characterize the apparent closing velocity by a measured shape described by cos(θ(z)), wherein z represents the distance that the moving platform has traveled and θ represents a location-varying angle.
22. The system of claim 21 , wherein the processor is further configured for determining a course of the moving platform by comparing the measured shape to a plurality of stored shapes.
23. The system of claim 22 , wherein processor is configured for comparing the measured shape to a plurality of stored shapes using sequential statistical methods.
24. The system of claim 19 , wherein the transmitter is coupled to the stationary platform and the processor is configured to derive the frequency shift by analyzing a frequency spectrum of the received signal.
25. The system of claim 19 , wherein the processor is configured for the deriving the frequency shift by generating a spread spectrum of the received signal.
26. The system of claim 25 , wherein the processor further comprises a spread spectrum system configured for generating a spectral line at twice the frequency of a Doppler shift of the received signal.
27. The system of claim 26 , wherein the Doppler shift is determined using a center frequency of the received signal.
28. The system of claim 27 , wherein the center frequency of the received signal is determined by homodyning the spread spectrum of the received signal.
29. The system of claim 19 , wherein the carrier signal comprises radio frequency signals.
30. The system of claim 19 , wherein the stationary platform comprises a plurality of stationary platforms.
31. A system for determining a position of a moving platform, the system comprising:
a transmitter configured for transmitting a carrier signal from one of the moving platform and a stationary platform;
a receiver system configured for receiving a received signal from the other of the moving and stationary platforms,
the receiver system further comprising:
a processor configured for:
(i) deriving a frequency shift between the carrier signal and the received signal;
(ii) calculating the apparent closing velocity angle using the frequency shift and a frequency of the carrier signal, wherein the stationary platform comprises a transmitter coupled to a railway track.
32. The system of claim 31 , wherein the transmitter is coupled to a turnout on the railway track.
33. The system of claim 19 , wherein the stationary platform comprises a mobile communication platform base station.
34. The system of claim 19 , wherein the stationary platform comprises a broadband station.
35. The system of claim 19 , wherein the stationary platform comprises a cellular network base station.
36. A system for determining a position of a moving platform, the system comprising:
a transmitter configured for transmitting a carrier signal from one of the moving platform and a stationary platform;
a receiver system configured for receiving a received signal from the other of the moving and stationary platforms, the receiver system further comprising:
a processor configured for:
(i) deriving a frequency shift between the carrier signal and the received signal;
(ii) calculating the apparent closing velocity angle using the frequency shift and a frequency of the carrier signal, wherein the moving platform comprises a locomotive.
37. The system of claim 19 , wherein the receiver system is coupled to the moving platform.
38. The system of claim 19 , wherein the receiver system is coupled to the stationary platform.
39. A system for determining a position of a moving platform, the system comprising:
means for transmitting a carrier signal from one of the moving platform and a stationary platform;
means for receiving a received signal at the other of the moving and stationary platforms;
means for deriving a frequency shift between the carrier signal and the received signal;
means for calculating the apparent closing velocity using the frequency shift, a frequency of the carrier signal;
wherein the means for calculating the apparent closing velocity shift comprising using the equation:
f
d
(
t
)
=
f
c
v
c
(
t
)
c
+
f
m
+
n
(
t
)
wherein fd(t) represents the frequency shift, fc represents a center frequency of the carrier signal, c represents a speed of radio propagation, fm is a constant frequency offset between local oscillators at the transmitter and at the receiver system, n(t) represents a measurement noise and vc(t) represents the apparent closing velocity.
40. The system of claim 39 , determining the position of the moving platform further comprises means for monitoring the apparent closing velocity over a period of time.
41. The system of claim 39 , wherein the means for calculating the apparent closing velocity comprises means for characterizing the apparent closing velocity by a measured shape described by cos(θ(z)), wherein z represents the distance that the moving platform has traveled and θ represents a location-varying angle.
42. The system of claim 41 , further comprising means for determining a course of the moving platform by comparing the measured shape to a plurality of stored shapes.
43. The system of claim 39 , wherein the means for deriving the frequency shift comprises means for analyzing a frequency spectrum corresponding to the received signal.
44. The system of claim 39 , wherein the means for deriving the frequency shift comprises means for generating a spread spectrum of the received signal.
45. The system of claim 44 , wherein the means for generating the spread spectrum further comprises means for generating a spectral line at twice the frequency of a Doppler shift of the received signal.
46. A system for determining a position of a moving platform, the system comprising:
a transmitter configured for transmitting a modulated carrier signal;
a receiver system configured for demodulating a received carrier signal, the receiver system further comprising a processor configured for
deriving a frequency shift between the carrier signal and the received signal,
calculating an apparent closing velocity using the frequency shift of the received signal relative to a center frequency of the transmitted carrier signal, and
estimating the position of the moving platform by monitoring the apparent closing velocity over a period of time.
47. The system of claim 46 , wherein the processor is configured for calculating the apparent closing velocity using the equation:
f
d
(
t
)
=
f
c
v
c
(
t
)
c
+
f
m
+
n
(
t
)
wherein fd(t) represents the frequency shift, fc represents a center frequency of the carrier signal, c represents a speed of radio propagation, fm is a constant frequency offset between local oscillators at the transmitter and at the receiver system, n(t) represents a measurement noise and vc(t) represents the apparent closing velocity.
48. The system of claim 47 , wherein the processor is further configured to characterize the apparent closing velocity by a measured shape described by cos(θ(z)), wherein z represents the distance that the moving platform has traveled and θ represents a location-varying angle.
49. The system of claim 48 , wherein the processor is further configured for determining a course of the moving platform by comparing the measured shape to a plurality of stored shapes.
50. The system of claim 49 , wherein processor is configured for comparing the measured shape to a plurality of stored shapes using sequential statistical methods.
51. The system of claim 46 , wherein the transmitter is coupled to the stationary platform and the processor is configured to derive the frequency shift by analyzing a frequency spectrum of the received signal.
52. The system of claim 46 , wherein the processor is configured for the deriving the frequency shift by generating a spread spectrum of the received signal.
53. The system of claim 52 , wherein the processor further comprises a spread spectrum system configured for generating a spectral line at twice the frequency of a Doppler shift of the received signal.
54. The system of claim 53 , wherein the processor is further configured for determining the Doppler shift by using a center frequency of the received signal.
55. The system of claim 54 , wherein the center frequency of the received signal is determined by homodyning the spread spectrum of the received signal.
56. The system of claim 46 , wherein the moving platform is a locomotive.
57. The system of claim 56 , wherein the stationary platform comprises a plurality of stationary platforms.