System and method for position determination by impulse radio using round trip time-of-flight

• US 6,611,234 B2
• Filed: 09/18/2001
• Issued: 08/26/2003
• Est. Priority Date: 03/23/1998
• Status: Expired due to Term

• Current Assignee: Humatics Corporation
• Original Assignee: Time Domain Corporation (Humatics Corporation)
• Inventors: Richards, James L., Fullerton, Larry W., Cowie, Ivan A.
• Primary Examiner(s): PHAN, DAO LINDA
• Application Number:
  US09/954,204
• Publication Number:
  US 20020109632A1
• Time in Patent Office: 707 Days
• Field of Search: 342/357.06, 342/463-465, 342/457, 342/458
• US Class Current: 342/458
• CPC Class Codes: G01S 13/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S13/46
• CPC Class Codes: G01S 13/76 wherein pulse-type signals are transmitted
• CPC Class Codes: H04B 1/7183 Synchronisation
• CPC Class Codes: H04B 2001/6908 using time hopping

Abstract

A system and a method for position determination by impulse radio using a first transceiver having a first clock providing a first reference signal and a second transceiver placed spaced from the first transceiver. The system determines the position of the second transceiver. The second transceiver has a second clock that provides a second reference signal. A first sequence of pulses are transmitted from the first transceiver. The first sequence of pulses are then received at the second transceiver and the second transceiver is then synchronized with the first sequence of pulses. A second sequence of pulses are transmitted from the second transceiver. The first transceiver receives the second sequence of pulses and the first transceiver is synchronized with the second sequence of pulses. A delayed first reference signal is generated in response to the synchronization with the second sequence of pulses. A time difference between the delayed first reference signal and the first reference signal is then measured. The time difference indicates a total time of flight of the first and second sequence of pulses. The distance between the first and the second transceiver is determined from the time difference. The direction of the second transceiver from the first transceiver is determined using a directional antenna. Finally, the position of the second transceiver is determined using the distance and the direction.

Claims

1. An impulse radio system, comprising:

a first impulse radio transceiver configured to transmit a first ultra wideband signal;

a second impulse radio transceiver spaced apart from the first impulse radio transceiver and not time synchronized with the first impulse radio transceiver, the second impulse radio transceiver being configured to receive the first ultra wideband signal, the second impulse radio being configured to transmit a second ultra wideband signal responsive to the first ultra wideband signal; and

wherein the first impulse radio transceiver is configured to receive the second ultra wideband signal, the first impulse radio transceiver being configured to determine an elapsed time between the transmission of the first ultra wideband signal and the reception of the second ultra wideband signal indicative of a total time-of-flight of the first and second ultra wideband signals.

2. The system of claim 1, wherein:

the first ultra wideband signal includes a first pulse train having ultra wideband frequency domain characteristics including a center frequency in the GigaHertz (GHz) range and a frequency bandwidth in the GHz range; and

the second ultra wideband signal includes a second pulse train having ultra wideband frequency domain characteristics including a center frequency in the GHz range and a frequency bandwidth in the GHz range.

3. The system of claim 1, wherein:

the first ultra wideband signal includes a first pulse train comprising a first sequence of pulses spaced apart in time; and

the second ultra wideband signal includes a second pulse train comprising a second sequence of pulses spaced apart in time.

4. The system of claim 3, wherein each of the first and second sequences of pulses has a pulse repetition frequency of between 0.7 and 10 megapulses (10⁶) per second.

5. The system of claim 3, wherein at least some of the pulses in each of the first and second sequences of pulses have pulse widths on the order of one nanosecond.

6. The system of claim 1, wherein the first impulse radio transceiver determines a distance between the first and second impulse radio transceivers based at least in part on the elapsed time.

7. The system of claim 6, wherein the distance is determined based on a time difference between

(i) the elapsed time, and

(ii) a delay representing a time difference between the reception of the first ultra wideband signal at the second impulse radio transceiver and the transmission of the second ultra wideband signal from the second impulse radio transceiver, wherein the time difference between the elapsed time and the delay represents the total time-of-flight of the first and second ultra wideband signals.

8. The system of claim 7, wherein a correction factor is used to determine the distance.

9. The system of claim 7, wherein the delay is an estimated delay.

10. The system of claim 9, wherein a correction factor is used to update the delay.

11. The system of claim 6, further comprising:

a direction finding antenna, coupled to the first impulse radio transceiver, for determining an angular direction (φ

) of the second impulse radio transceiver relative to the first impulse radio transceiver,

wherein the first impulse radio transceiver determines a position of the second transceiver based on the distance and the angular direction (φ

).

12. The system of claim 1, wherein the first impulse radio transceiver includes a first clock configured to generate a first clock pulse corresponding to the transmission of the first ultra wideband signal, and a second clock pulse corresponding to the reception of the second ultra wideband signal, and wherein the first impulse transceiver is configured to determine the elapsed time based on the first and second clock pulses.

13. The system of claim 12, wherein the second impulse radio transceiver includes a second clock configured to generate a third clock pulse corresponding to the reception of the first ultra wideband signal, and a fourth clock pulse corresponding to the transmission of the second ultra wideband signal.

14. The system of claim 1, wherein at least one of the first and second impulse radio transceivers is combined with a Global Positioning System (GPS) receiver.

15. The system of claim 1, wherein the second transceiver is installed in a mobile telephone.

16. The system of claim 1, wherein at least one of the first and second ultra wideband signals includes one of amplitude modulation, phase modulation, frequency modulation and time shift modulation.

17. The system of claim 1, wherein at least one of digital data, digitized voice, and analog information is communicated between the first and second impulse radio transceivers via at least one of the first and second ultra wideband signals.

18. An impulse radio system, comprising:

a first impulse radio transceiver including a clock, the clock configured to generate a first clock pulse, the first impulse radio being configured to transmit a first ultra wideband signal responsive to the first clock pulse;

a second impulse radio transceiver spaced apart from the first impulse radio transceiver and configured to receive the first ultra wideband signal, the second impulse receiver being configured to transmit a second ultra wideband impulse signal responsive to the first ultra wideband signal; and

wherein the first impulse radio transceiver is configured to receive the second ultra wideband signal, the clock being configured to generate a second clock pulse responsive to the second ultra wideband impulse signal, the first impulse transceiver being configured to determine an elapsed time between the first and second clock pulses indicative of a total time of flight of the first and second ultra wideband signals.

19. The system of claim 18, wherein the first and second impulse radio transceivers are not time synchronized with each other.

20. In an impulse radio system including a first impulse radio transceiver and a second impulse radio transceiver spaced from the first impulse radio transceiver, a method comprising:

(a) transmitting from the first impulse radio transceiver a first ultra wideband signal;

(b) receiving the first ultra wideband signal at the second impulse radio transceiver;

(c) transmitting, from the second impulse radio transceiver, a second ultra wideband signal responsive to the first ultra wideband signal;

(d) receiving the second ultra wideband signal at the first impulse radio transceiver; and

(e) determining an elapsed time, between the transmission of the first ultra wideband signal and the reception of the second ultra wideband signal, indicative of a total time-of-flight of the first and second ultra wideband signals.

21. The method of claim 20, wherein:

the first ultra wideband signal includes a first pulse train having ultra wideband frequency domain characteristics including a center frequency in the GigaHertz (GHz) range and a frequency bandwidth in the GHz range; and

the second ultra wideband signal includes a second pulse train having ultra wideband frequency domain characteristics including a center frequency in the GHz range and a frequency bandwidth in the GHz range.

22. The method of claim 20, wherein:

the first ultra wideband signal includes a first pulse train comprising a first sequence of pulses spaced apart in time; and

the second ultra wideband signal includes a second pulse train comprising a second sequence of pulses spaced apart in time.

23. The method of claim 22, wherein each of the first and second sequences of pulses has a pulse repetition frequency of between 0.7 and 10 megapulses (10⁶) per second.

24. The method of claim 22, wherein at least some of the pulses in each of the first and second sequences of pulses have pulse widths on the order of one nanosecond.

25. The method of claim 20, further comprising:

(f) determining a distance between the first and second impulse radio transceivers based at least in part on the elapsed time determined in step (e).

26. The method of claim 25, wherein step (f) comprises:

determining the distance between the first and second impulse radio transceivers based on a time difference between

(i) the elapsed time, and

(ii) a delay representing a time difference between the reception of the first ultra wideband signal at the second impulse radio transceiver and the transmission of the second ultra wideband signal from the second impulse radio transceiver, wherein the time difference between the elapsed time and the delay represents the total time-of-flight of the first and second ultra wideband signals.

27. The method of claim 26, wherein a correction factor is used to determine the distance.

28. The method of claim 26, further comprising, prior to step (f):

producing an initial estimate of the delay; and

adjusting the initial estimate of the delay with a correction factor.

29. The method of claim 25, further comprising:

(g) determining an angular direction (φ

) of the second impulse radio transceiver relative to the first impulse radio transceiver; and

(h) determining a position of the second transceiver based on the distance and the angular direction (φ

).

30. The method of claim 20, further comprising:

generating at the first impulse radio transceiver a first clock pulse corresponding to the transmission of the first ultra wideband signal; and

generating at the first impulse radio transceiver a second clock pulse corresponding to the reception of the second ultra wideband signal,

wherein step (e) comprises determining the elapsed time based on the first and second clock pulses.

31. The method of claim 30, further comprising:

generating at the second impulse radio transceiver a third clock pulse corresponding to the reception of the first ultra wideband signal; and

generating at the second impulse radio transceiver a fourth clock pulse corresponding to the transmission of the second ultra wideband signal.

32. In an impulse radio system including a first impulse radio transceiver and a second impulse radio transceiver spaced a known distance from the first impulse radio transceiver, a method for calibrating distance measurements, comprising:

(a) transmitting from the first impulse radio transceiver a first ultra wideband signal;

(b) receiving the first ultra wideband signal at the second impulse radio transceiver;

(c) transmitting, from the second impulse radio transceiver, a second ultra wideband signal in response to the first ultra wideband signal;

(d) receiving the second ultra wideband signal at the first impulse radio transceiver; and

(e) determining an elapsed time representing a time difference between the transmission of the first ultra wideband signal and the reception of the second ultra wideband signal;

(e) producing an estimated delay representing a time difference between the reception of the first ultra wideband signal and the transmission of the second ultra wideband signal;

(f) determining an estimated distance between the first and second impulse radio based on the elapsed time and the estimated delay; and

(g) performing one of

determining an error distance between the estimated distance and the known distance, and

updating the estimated delay based on the known distance.

33. An impulse radio system, comprising:

a first impulse radio transceiver configured to transmit a first ultra wideband signal;

a second impulse radio transceiver spaced apart from the first impulse radio transceiver and not time synchronized with the first impulse radio transceiver, the second impulse radio transceiver being configured to receive the first ultra wideband signal, the second impulse radio being configured to transmit a second ultra wideband signal responsive to the first ultra wideband signal after a delay; and

wherein the first impulse radio transceiver is configured to receive the second ultra wideband signal, the first impulse radio transceiver being configured to determine an elapsed time between the transmission of the first ultra wideband signal and the reception of the second ultra wideband signal, the first impulse radio transceiver being configured to determine a time difference between the elapsed time and the delay indicative of a total time-of-flight of the first and second ultra wideband signals.

34. In an impulse radio system including a first impulse radio transceiver and a second impulse radio transceiver spaced from the first impulse radio transceiver, a method comprising:

(a) transmitting from the first impulse radio transceiver a first ultra wideband signal;

(b) receiving the first ultra wideband signal at the second impulse radio transceiver;

(c) transmitting, from the second impulse radio transceiver, a second ultra wideband signal;

(d) receiving the second ultra wideband signal at the first impulse radio transceiver;

(e) determining an elapsed time between the transmission of the first ultra wideband signal and the reception of the second ultra wideband signal;

(f) determining a delay between the reception of the first ultra wideband signal and the transmission of the second ultra wideband signal; and

(g) determining a difference between the elapsed time and the delay indicative of the total time-of-flight of the first and second ultra wideband signals.

35. The method of claim 34, further comprising:

(h) determining a distance between the first and second impulse radio transceivers based on the time-of-flight.