Accurate distance measurement using RF techniques

• US 6,859,761 B2
• Filed: 01/16/2001
• Issued: 02/22/2005
• Est. Priority Date: 01/16/2001
• Status: Expired due to Fees

• Current Assignee: AeroScout (US) LLC (Stanley Black & Decker, Inc.)
• Original Assignee: Bluesoft, Ltd.
• Inventors: Berliner, Shlomo, Holzkaner, Uri, Mirodin, Edward, Bensky, Alan
• Primary Examiner(s): Barlow, John
• Assistant Examiner(s): Lau, Tung S
• Application Number:
  US09/759,601
• Publication Number:
  US 20030195723A1
• Time in Patent Office: 1,498 Days
• Field of Search: 702/189, 342/125, 342/42, 342/127, 342/43, 342/387, 342/457, 342/463, 375/347, 375/202, 455/132, 455/33.1, 455/33.4, 370/320, 370/335, 370/342, 370/441, 370/485
• US Class Current: 702/189
• CPC Class Codes: G01S 13/84 for distance determination by phase measurement

Abstract

A system, apparatus, and method for determining the distance between two objects using an indirect propagation delay measurement is disclosed. A frequency hopping scheme (such as the Bluetooth™ technology) is used to measure the relative phase offset of the received signal between the various frequencies. For a given distance between the objects, the phase offset vs. frequency curve is a straight line with the slope dependent upon the measured distance. After the phase of the received signals is detected, the data is plotted on a curve and the slope is calculated.

Claims

1. A wireless communication device, comprising:

a first synthesizer for generating a first radio frequency (RF) signal, the first RF signal including a sequence of carriers;

a transmitter for transmitting the first RF signal;

a receiver for receiving a second RF signal from a remote wireless device phase locked with the first wireless device, the second RF signal including a sequence of carriers corresponding to the carriers of the first RF signal, wherein the frequencies of the corresponding sequence of carriers of the first RF signal are different from the frequencies of the sequence of carriers of the second RF signal;

a second synthesizer for generating a third RF signal, the third RF signal including a sequence of carriers corresponding to the carriers of the first and second RF signals, wherein the phase of the third RF signal is coherent with the phase of the first RF signal, and wherein the frequencies of the sequence of carriers of the second RF signals are the same as the frequencies of the sequence of carriers of the third RF signal;

a phase detector for comparing the phase of each of the carriers of the second RF signal to the phase of each of the corresponding carriers of the third RF signal and generating a sequence of phase offsets; and

a processor for determining distance between the wireless communication device and the remote wireless device by calculating an estimated slope of the sequence of phase offsets relative to the frequencies of the sequence of carriers of the second RF signal, wherein the phase detector generates the phase offsets by producing In-phase (I) and Quadrature (Q) signals by mixing the received second RF signal with the third RF signal, and wherein the processor solves for phase angle Θ

by applying the following relationship;

Θ

=Arctan(Q/I)/2.

2. The wireless communication device according to claim 1, wherein the sequence of carriers produced by the synthesizer are modulated with a modulation signal, and wherein the phase of the modulation signal is coherent with each of the phases of the sequence of carriers of the first RF signal.

3. The wireless communication device according to claim 1, wherein the phase detector comprises:

a first mixer for mixing the sequence of carriers of the third RF signal with the corresponding sequence of carriers of the received second RF signal, wherein the first mixer outputs a sequence of DC in-phase components I;

a phase shifter for shifting the phase of the sequence of carriers of the third RF signal by 90 degrees; and

a second mixer for mixing the sequence of 90 degree phase-shifted carriers with the corresponding sequence of carriers of the received second RF signal, wherein the second mixer outputs a sequence of DC quadrature-phase signals Q, wherein the I and Q components are used to calculate the phase offsets of each of the sequence of carriers of the second RF signal, and wherein the phase offsets are used to calculate the distance between the wireless communication device and the remote wireless device.

4. The wireless communication device according to claim 1, wherein the processor calculates the slope by executing a phase ambiguity algorithm to produce a relative phase offset Φ

among the carrier frequencies of the received second RF signal such that

Φ

(n);

=0 if n=0;

otherwise,

Φ

(n);

=(Θ

_n−

Θ

<sub>n−

1</sub>)+Φ

(n−

1)+π

if Θ

_n−

Θ

<sub>n−

1</sub><

0

Φ

(n);

=(Θ

_n−

Θ

<sub>n−

1</sub>)+Φ

(n−

1) otherwise

where Θ

_n is the phase offset for each carrier of the received second RF signals.

5. The wireless communication device of claim 1, wherein the wireless communication device transmits information to the remote wireless device based on the distance between the wireless communication device and the remote wireless device.

6. The wireless communication device of claim 1, wherein the wireless communication device and the remote wireless device transfer data to each other to complete a commercial transaction.

7. The wireless communication device of claim 1, wherein the wireless communication device determines its location based on the calculated distance from the remote wireless device.

8. The wireless communication device according to claim 1, wherein the phase detector comprises:

a first mixer for mixing the sequence of carriers of the third RF signal with the corresponding sequence of carriers of the received second RF signal, wherein the first mixer outputs a sequence of DC in-phase components;

a phase shifter for shifting the phase of the sequence of carriers of the third RE signal by 90 degrees; and

a second mixer for mixing the sequence of 90 degree phase-shifted carriers with the corresponding sequence of carriers of the received second RF signal, wherein the second mixer outputs a sequence of DC quadrature-phase signals Q, wherein the I and Q components are used to calculate the phase offsets of each of the sequence of carriers of the frequency-converted second RF signal, and wherein the phase offsets are used to calculate the distance between the wireless communication device and the remote wireless device.

9. The wireless communication device according to claim 2, wherein the wireless communication device further comprises:

a local oscillator for generating a reference signal used to synchronize the first and second synthesizer; and

a frequency divider for dividing the reference signal to generate the modulation signal.

10. The wireless communication device according to claim 2, wherein the wireless communication device further comprises:

a local oscillator for generating a reference signal used to synchronize the first and second synthesizers; and

a frequency divider for dividing the reference signal to generate the modulation signal.

11. The wireless communication device of claim 4, wherein the following relationships are used by the processor to calculate the distance between the wireless communication device and the remote wireless device:

D;

=cT, with c;

=3×

10⁸ m/s and T;

=m/2π

, where m is the slope of the relative phase shift (Φ

) v. frequency line and D is the distance between the wireless communication device and the remote wireless device.

12. A wireless communication device, comprising:

a first synthesizer for generating a first radio frequency (RF) signal, the first RF signal including a single carrier having a frequency ft0;

a transmitter for transmitting the first RF signal;

a receiver for receiving a second RF signal from a remote wireless device phase locked with the first wireless device, the second RF signal including a sequence of carriers, wherein the frequencies of the sequence of carriers of the second RF signal are different from ft0;

a second synthesizer for generating a third RF signal, the third RF signal including a sequence of carriers corresponding to the carriers of the second RF signal, wherein the phase of the third RF signal is coherent with the phase of the first RF signal, and wherein the frequencies of the sequence of carriers of the second RF signal are the same as the frequencies of the sequence of carriers of the third RF signal;

a phase detector for comparing the phase of each of the carriers of the second RF signal to the phase of each of the carriers of the third RF signal to generate a corresponding sequence of phase offsets; and

a processor for determining distance between the wireless communication device and the remote wireless device by calculating an estimated slope of the phase offsets relative to the frequencies of the sequence of carriers of the second RF signal, wherein the phase detector generates the phase offsets by producing In-phase (I) and Quadreture (Q) signals by mixing the received second RF signal with the third RF signal, and wherein the processor solves for phase angle Θ

by applying the following relationship;

Θ

=Arctan(Q/I)/2.

13. The wireless communication device according to claim 12, wherein the sequence of carriers produced by the synthesizer are modulated with a modulation signal.

14. The wireless communication device according to claim 12, wherein the processor calculates the slope by executing a phase ambiguity algorithm to produce a relative phase offset Φ

among the carrier frequencies of the received second RE signal such that

Φ

(n);

=0 if n=0;

otherwise,

Φ

(n);

=(θ

_n−

θ

<sub>n−

1</sub>)+Φ

(n−

1)+π

if θ

_n−

θ

<sub>n−

1</sub><

0

Φ

(n);

=(θ

_n−

θ

<sub>n−

1</sub>)+Φ

(n−

1) otherwise

where θ

_n is the phase offset for each carrier of the received second RF signals.

15. The wireless communication device of claim 12, wherein the wireless communication device transmits information to the remote wireless device based on the distance between the wireless communication device and the remote wireless device.

16. The wireless communication device of claim 12, wherein the wireless communication device and the remote wireless device transfer data to each other to complete a commercial transaction.

17. The wireless communication device of claim 12, wherein the wireless communication device determines its location based on the calculated distance from the remote wireless device.

18. The wireless communication device of claim 14, wherein the following relationships are used by the processor to calculate the distance between the wireless communication device and the remote wireless device:

D;

=cT, with c;

=3×

10⁸ m/s and T;

=m/2π

, where m is the slope of the relative phase shift (Φ

) v. frequency line and D is the distance between the wireless communication device and the remote wireless device.

19. A computer readable medium containing program instructions for controlling a wireless communication device and for determining distance between the wireless communication device and a remote wireless device, comprising instructions for:

generating a first radio frequency (RF) signal, the first RF signal including a sequence of carriers;

transmitting the first RF signal;

receiving a second RF signal from a remote wireless device phase locked with the wireless communication device, the second RF signal including a sequence of carriers corresponding to the carriers of the first RF signal, wherein the frequencies of the sequence of carriers of the first RF signal are different from the frequencies of the sequence of carriers of the second RF signal;

generating a third RF signal, the third RF signal including a sequence of carriers corresponding to the carriers of the first and second RF signals, wherein the phase of the third RF signal is coherent with the phase first RF signal, and wherein the frequencies of the sequence of carriers of the second RF signal are the same as the frequencies of the sequence of carriers of the third RF signal;

comparing the phase of each of the carriers of the second RF signal to the phase of each of the corresponding carriers of the third RF signal to generate a sequence of phase offsets;

calculating an estimated slope of the phase offsets relative to the frequencies of the sequence of carriers of the second RF signal, wherein the estimated slope is proportional to the distance between the wireless communication device and the remote device;

mixing the received second RF signal with the third RF signal to produce In-phase (I) and Quadrature (Q) signals;

solving for phase angle Θ

by applying the following relationship;

Θ

=Arctan(Q/I)/2; and

calculating the phase offset based on phase angle θ

.

20. The computer readable medium of claim 19, further comprising instructions for modulating the sequence of carriers produced by the first synthesizer of the wireless communication device with a modulation signal, wherein the phase of the modulation signal is coherent with each of the phases of the sequence of carriers of the first RE signal.

21. The computer readable medium of claim 19, further comprising instructions for:

mixing the sequence of carriers of the third RF signal with the sequence of corresponding carriers of the received second RF signal to generate a sequence of DC in-phase components I;

shifting the phase of the sequence of carriers of the third RF signal by 90 degrees; and

mixing the sequence of 90 degree phase-shifted carriers with the corresponding sequence of carriers of the received second RF signal to generate a sequence of DC quadrature-phase signals Q;

calculating the phase offsets of each of the carriers of the second RF signal using the I and Q components; and

calculating the distance between the wireless communication device and the remote wireless device using the phase offsets.

22. The computer readable medium of claim 19, further comprising instructions for calculating the slope by executing a phase ambiguity algorithm to produce a relative phase offset among the carrier frequencies of the received second RF signal such that

Φ

(n);

=0 if n=0;

otherwise,

Φ

(n);

=(θ

_n−

θ

<sub>n−

1</sub>)+Φ

(n−

1)+π

if θ

_n−

θ

<sub>n−

1</sub><

0

 

Φ

(n);

=(θ

_n−

θ

<sub>n−

1</sub>)+Φ

(n−

1) otherwise

where θ

_n is the phase offset for each carrier of the received second RF signal.

23. The computer readable medium of claim 19, further comprising instructions transmitting information to the remote wireless device based on the distance between the wireless communication device and the remote wireless device.

24. The computer readable medium of claim 19, further comprising instructions transferring data between the wireless communication device and the remote wireless device to complete a commercial transaction based on the distance between the wireless communication device and the remote wireless device.

25. The computer readable medium of claim 19, further comprising instructions for determining the location of the wireless communication device based on the calculated distance from the remote wireless device.

26. The computer readable medium of claim 19, further comprising instructions for transmitting information to the remote wireless device based on the distance between the wireless communication device and the remote wireless device.

27. The computer readable medium of claim 19, further comprising instructions for transferring data to between the wireless communication device and the remote wireless device to complete a commercial transaction based on the calculated distance.

28. The computer readable medium of claim 20, further comprising instructions for:

generating a reference signal used to synchronize the first and second synthesizers; and

dividing the reference signal to generate the modulation signal.

29. The computer readable medium of claim 22, wherein the instructions use the following relationships to calculate the distance between the wireless communication device and the remote wireless device:

D;

=cT, with c;

=3×

10⁸ m/s and T;

=m/2π

, where m is the slope of the relative phase shift (Φ

) v. frequency line and D is the distance between the wireless communication device and the remote wireless device.

30. The computer readable medium of claim 22, wherein the instructions use the following relationships to calculate the distance between the wireless communication device and the remote wireless device:

D;

=cT, with c;

=3×

10⁸ m/s and T;

=m/2π

, where m is the slope of the relative phase shift (Φ

) v. frequency line and D is the distance between the wireless communication device and the remote wireless device.

31. A computer readable medium containing program instructions for controlling a wireless communication device and for determining distance between the wireless communication device and a remote wireless device, comprising instructions for:

generating a first radio frequency (RF) signal, the first RF signal including a single carrier having a frequency ft0;

transmitting the first RF signal;

receiving a second RF signal from a remote wireless device phase locked with the remote wireless device, the second RF signal including a sequence of carriers, wherein the frequencies of the sequence of carriers of the second RF signal are different from ft0;

generating a third RF signal, the third RF signal including a sequence of carriers corresponding to the carriers of the second RF signal, wherein the phase of the third RF signal is coherent with the phase of the first RF signal, and wherein the frequencies of the corresponding sequence of carriers of the second RF signal are the same as the frequencies of the corresponding sequence of carriers of the third RF signal;

comparing the phase of each of the carriers of the second RF signal to the phase of each of the corresponding carriers of the third RF signal to generate a sequence of phase offsets;

calculating an estimated slope of the phase offsets relative to the frequencies of the sequence of carriers of the second RF signal, wherein the estimated slope is proportional to the distance between the wireless communication device and the remote wireless device;

mixing the received second RF signal with the third RF signal to produce In-phase (I) and Quadrature (Q) signals;

solving for phase angle Θ

by applying the following relationship;

Θ

=Arctan(Q/I)/2; and

calculating the phase offset based on phase angle θ

.

32. The computer readable medium of claim 31, further comprising instructions for modulating the sequence of carriers produced by the first synthesizer of the wireless communication device with a modulation signal, wherein the phase of the modulation signal is coherent with each of the phases of the sequence of carriers of the first RE signal.

33. The computer readable medium of claim 31, further comprising instructions for:

mixing the sequence of carriers of the third RF signal with the sequence of corresponding carriers of the received second RF signal to generate a sequence of DC in-phase components I;

shifting the phase of the sequence of carriers of the third RF signal by 90 degrees; and

mixing the sequence of 90 degree phase-shifted carriers with the corresponding sequence of carriers of the received second RF signal to generate a sequence of DC quadrature-phase signals Q;

calculating the phase offsets of each of the carriers of the second RF signal by using the I and Q components; and

calculating the distance between the wireless communication device and the remote wireless device using the phase offsets.

34. The computer readable medium of claim 31, further comprising instructions for calculating the slope by executing a phase ambiguity algorithm to produce a relative phase offset among the carrier frequencies of the received second RF signal such that

Φ

(n);

=0 if n=0;

otherwise,

Φ

(n);

=(θ

_n−

θ

<sub>n−

1</sub>)+Φ

(n−

1)+π

if θ

_n−

θ

<sub>n−

1</sub><

0

Φ

(n);

=(θ

_n−

θ

<sub>n−

1</sub>)+Φ

(n−

1) otherwise

where θ

_n is the phase offset for each carrier of the received second RF signals.

35. The computer readable medium of claim 31, further comprising instructions for determining the location of the wireless communication device based on its calculated distance from the remote wireless device.

36. The computer readable medium of claim 32, further comprising instructions for:

generating a reference signal used to synchronize the first and second synthesizers; and

dividing the reference signal to generate the modulation signal.

37. A method of determining distance between a wireless communication device and a remote wireless device, the method comprising the steps of:

generating a first radio frequency (RF) signal, the first RF signal including a sequence of carriers;

transmitting the first RF signal;

receiving a second RF signal from a remote wireless device phase locked with the wireless communication device, the second RF signal including a sequence of carriers corresponding to the carriers of the first RF signal, wherein the frequencies of the sequence of carriers of the first RF signal are different from the frequencies of the sequence of carriers of the second RF signal;

generating a third RF signal, the third RF signal including a sequence of carriers corresponding to the carriers of the first and second RF signals, wherein the phase of the third RF signal is coherent with the phase first RF signal, and wherein the frequencies of the sequence of carriers of the second RF signal are the same as the frequencies of the sequence of carriers of the third RF signal;

comparing the phase of each of the carriers of the second RF signal to the phase of each of the corresponding carriers of the first of the third RF signal to generate a sequence of phase offsets;

calculating an estimated slope of the phase offsets relative to the frequencies of the sequence of carriers of the second RF signal, wherein the estimated slope is proportional to the distance between the wireless communication device and the remote wireless device;

mixing the received second RF signal with the third RF signal to produce In-phase (I) and Quadrature (Q) signals;

solving for phase angle Θ

by applying the following relationship;

Θ

=Arctan(Q/I)/2; and

calculating the phase offset based on phase angle θ

.

38. The method according to claim 37, further comprising the step of modulating the sequence of carriers produced by the first synthesizer of the wireless communication device with a modulation signal, wherein the phase of the modulation signal is coherent with each of the phases of the sequence of carriers of the first RF signal.

39. The method according to claim 37, further comprising the steps of:

generating a reference signal used to synchronize the first and second synthesizers; and

dividing the reference signal to generate the modulation signal.

40. The method according to claim 37, further comprising the steps of:

mixing the sequence of carriers of the third RF signal with the sequence of corresponding carriers of the received second RF signal to generate a sequence of DC in-phase components I;

shifting the phase of the sequence of carriers of the third RF signal by 90 degrees; and

mixing the sequence of 90 degree phase-shifted carriers with the corresponding sequence of carriers of the received second RF signal to generate a sequence of DC quadrature-phase signals Q;

calculating the phase offsets of each of the carriers of the second RF signal using the I and Q components; and

calculating the distance between the wireless communication device and the remote wireless device using the phase offsets.

41. The method of claim 37, further comprising the step of calculating the slope by executing a phase ambiguity algorithm to produce a relative phase offset among the carrier frequencies of the received second RF signal such that

Φ

(n);

=0 if n=0;

otherwise,

Φ

(n);

=(θ

_n−

θ

<sub>n−

1</sub>)+Φ

(n−

1)+π

if θ

_n−

θ

<sub>n−

1</sub><

0

Φ

(n);

=(θ

_n−

θ

<sub>n−

1</sub>)+Φ

(n−

1) otherwise

where θ

_n is the phase offset for each carrier of the received second RF signals.

42. The method of claim 41, wherein the following relationships are used to calculate the distance between the wireless communication device and the remote wireless device:

D;

=cT, with c;

=3×

10⁸ m/s and T;

m/2π

, where m is the slope of the relative phase shift (Φ

) v. frequency line and D is the distance between the wireless communication device and the remote wireless device.

43. The method of claim 37, further comprising the step of transmitting information to the remote wireless device based on the distance between the wireless communication device and the remote wireless device.

44. The method of claim 37, further comprising the step of transferring data between the wireless communication device and the remote wireless device to complete a commercial transaction based on the distance between the wireless communication device and the remote wireless device.

45. The method of claim 37, further comprising the step determining the location of the wireless communication device based on the calculated distance from the remote wireless device.

46. The method of claim 37, further comprising the steps of:

mixing the sequence of carriers of the third RF signal with the corresponding sequence of carriers of the received second RF signal to generate a sequence of DC in-phase components I;

shifting the phase of the sequence of carriers of the third RF signal by 90 degrees; and

mixing the sequence of 90 degree phase-shifted carriers with the corresponding sequence of carriers of the received second RF signal to generate a sequence of DC quadrature-phase signals Q;

calculating the phase offsets of each of the carriers of the second RF signal by using the I and Q components; and

calculating the distance between the wireless communication device and the remote wireless device using the phase offsets.

47. A method of determining distance between a wireless communication device and a remote wireless device, the method comprising the steps of:

generating a first radio frequency (RF) signal, the first RF signal including a single carrier having a frequency ft0;

transmitting the first RF signal;

receiving a second RF signal from a remote wireless device phase locked with the wireless communication device, the second RF signal including a sequence of carriers, wherein the frequencies of the sequence of carriers of the second are different from ft0;

generating a third RF signal, the third RF signal including a sequence of carriers corresponding to the carriers of the second RF signal, wherein the phase of the third RF signal is coherent with the phase of the first RF signal, and wherein the frequencies of the corresponding sequence of carriers of the second RF signal are the same as the frequencies of the corresponding sequence of carriers of the third RF signal;

comparing the phase of each of the carriers of the second RF signal to the phase of each of the corresponding carriers of the third RF signal to generate a sequence of phase offsets;

calculating an estimated slope of the phase offsets relative to the frequencies of the sequence of carriers of the second RF signal, wherein the estimated slope is proportional to the distance between the wireless communication device and the remote device;

mixing the received second RF signal with the third RF signal to produce In-phase (I) and Quadrature (Q) signals;

solving for phase angle θ

by applying the following relationship;

θ

=Arctan(Q/I)/2; and

calculating the phase offset based on phase angle θ

.

48. The method of claim 47, further comprising the step of modulating the sequence of carriers produced by the synthesizer with a modulation signal.

49. The method of claim 47, further comprising the step of calculating the slope by executing a phase ambiguity algorithm to produce a relative phase offset among the carrier frequencies of the received second RF signal such that

Φ

(n);

=0 if n=0;

otherwise,

Φ

(n);

=(θ

_n−

θ

<sub>n−

1</sub>)+Φ

(n−

1)+π

if θ

_n−

θ

<sub>n−

1</sub><

0

Φ

(n);

=(θ

_n−

θ

<sub>n−

1</sub>)+Φ

(n−

1) otherwise

where θ

_n is the phase offset for each carrier of the received second RF signals.

50. The method of claim 47, further comprising the step of transmitting information to the remote wireless device based on the distance between the wireless communication device and the remote wireless device.

51. The method of claim 47, further comprising the step of transferring data between the wireless communication device and the remote wireless device to complete a commercial transaction based on the distance between the wireless communication device and the remote wireless device.

52. The method of claim 47, further comprising the step determining the location of the wireless communication device based on the calculated distance from the remote wireless device.

53. The method of claim 48, further comprising the steps of:

generating a reference signal used to synchronize the synthesizer; and

dividing the reference signal to generate the modulation signal.

54. The method of claim 49, wherein the following relationships are used to calculate the distance between the wireless communication device and the remote wireless device:

D;

=cT, with c;

=3×

10⁸ m/s and T;

m/2π

, where m is the slope of the relative phase shift (Φ

) v. frequency line and D is the distance between the wireless communication device and the remote wireless device.