System and method for locating objects and communicating with the same

• US 8,258,923 B2
• Filed: 12/20/2005
• Issued: 09/04/2012
• Est. Priority Date: 03/14/2005
• Status: Active Grant

• Current Assignee: Santa Mionica Semiconductor
• Original Assignee: Alfred E. Mann Foundation For Scientific Research
• Inventors: Schulman, Joseph H., Karr, Lawrence J.
• Primary Examiner(s): Nguyen, Nam V
• Application Number:
  US11/885,844
• Publication Number:
  US 20080169904A1
• Time in Patent Office: 2,450 Days
• Field of Search: 340/8.1, 340/7.22, 340/7.21, 340/10.1, 340/10.4, 342/70, 342/118, 235/384
• US Class Current: 340/8.1
• CPC Class Codes: B60R 2325/205 Mobile phones
• CPC Class Codes: B60R 25/00 Fittings or systems for preventing or indicating unauthorised use or theft of vehicles locks for vehicles E05B77/00-E05B85/00
• CPC Class Codes: B60R 25/33 of global position, e.g. by providing GPS coordinates
• CPC Class Codes: G08B 21/0244 System arrangements wherein the alarm criteria uses signal delay or phase shift

Abstract

An object locator system utilizes a microtransponder (12) that is used in association with an object to be located. A remote locator (10) transmits an encoded signal in which is embedded an identification code associated with the object to be located. The microtransponder (12) receives the encoded transmitted signal and processes such signal utilizing fast fourier transform techniques. The microtransponder (12) correlates the transformed received signal with a fast fourier transformed version of an identification code associated with the microtransponder (12) and upon detection of a correlation, transmits an acknowledgement signal to the remote locator (10). The remote locator (10) determines the distance to the microtransponder (12) based upon the round trip time from transmission of the coded signal to the microtransponder (12) to the receipt of the acknowledgement signal.

Claims

1. A method for locating a transponder (MT) with a remote locator (RL), the method comprising:

selecting an identification code (ID Code) for transmission from the RL to at least one MT, wherein each of the at least one MT has a specific associated ID Code;

generating, at a predetermined carrier frequency, a transmission signal for transmission by the RL, the transmission signal comprising;

a first pattern that is transmitted over a first transmission interval, wherein the selected ID Code is encoded within the first pattern;

transmitting the transmission signal from the RL for reception by the MT at a first time;

receiving the transmission signal from the RL by the MT to provide a received signal;

correlating, by FFT processing at the predetermined carrier frequency, the received signal with an ID Code stored in the MT to detect the presence of the selected ID Code in the received signal;

upon detection of the selected ID Code in the received signal, generating an acknowledgement signal;

transmitting the acknowledgement signal, at the predetermined carrier frequency, from the MT to the RL;

said selected ID Code being encoded in the acknowledgement signal;

receiving the acknowledgement signal from the MT by the RL at a second time;

correlating, by FFT processing at the predetermined carrier frequency, the received acknowledgement signal with the selected ID Code stored in the RL to detect the presence of the selected ID Code in the acknowledgement signal; and

upon detection of said selected ID Code in the acknowledgement signal, determining a distance between the RL and the MT as a function of an elapsed time between the first time and the second time.

2. The method of claim 1, wherein the step of generating a transmission signal further comprises:

providing a carrier; and

modulating the carrier as a function of the selected ID Code to thereby generate the transmission signal.

3. The method of claim 2, wherein the modulating step comprises the step of modulating the carrier by the selected ID Code by utilizing at least one of:

a multi-phase shift keying (MPSK) pattern, a binary-phase shift keying (BPSK) pattern, and a quadrature phase shift keying (QPSK) pattern.

4. The method of claim 1, wherein transmitting the transmission signal from the RL to the MT comprises:

transmitting the transmission signal by the RL at a first power level during a first time period; and

wherein transmitting the acknowledgement signal from the MT to the RL comprises transmitting the acknowledgement signal at a second power level during a second time period.

5. The method of claim 4, wherein the first power level is at least an order of magnitude greater than the second power level.

6. The method of claim 4, wherein the second time period is at least one order of magnitude greater than the first time period.

7. The method of claim 1, wherein the step of correlating the received signal further comprises the step of processing the received signal from the RL to provide an in phase signal and a quadrature phase signal.

8. The method of claim 7, wherein the step of processing the received signal further comprises the step of mixing the received signal from the RL with a first sinusoidal signal at the carrier frequency, said first sinusoidal signal having a first phase angle to thereby provide an in phase product and mixing the received signal from the RL with a second sinusoidal signal at the carrier frequency, said second sinusoidal signal having a second phase angle 90 degrees shifted with respect to the first phase angle to thereby provide a quadrature phase product.

9. The method of claim 8, further comprising the step of analog to digital conversion of the in phase product and the quadrature phase product to provide a digital representation of each product and further storing each product in a memory.

10. The method of claim 9, further comprising the step of generating a Fast Fourier Transform (FFT) of each product stored in the memory.

11. The method of claim 10, further comprising the step of complex conjugate multiplying the FFT of each product with either of:

(1) a pre-computed FFT of an ID Code associated with an MT or (2) the FFT of an ID Code of an MT and providing thereby a vector representing such multiplication.

12. The method of claim 11, further comprising the step of generating the inverse FFT of said vector, wherein the existence of a large spike occurring within the inverse FFT relative to other spikes therein, indicates a match between the ID Code in the received transmission signal from the RL and the ID Code of the MT.

13. The method of claim 12, further comprising the step of transmitting an acknowledgement signal from the MT to the RL subsequent to detecting the existence of a match between the ID Code in the received transmission signal from the RL and the ID Code of the MT.

14. The method of claim 13, wherein the steps of:

generating a Fast Fourier Transform (FFT) of each product stored in the memory;

complex conjugate multiplying the FFT of each product with either of;

(1) a pre-computed FFT of an ID Code associated with an MT or (2) the FFT of an ID Code of an MT and providing thereby a vector representing such multiplication, is undertaken on a bin by bin basis.

15. The method of claim 13, further comprising the step of receiving the transmitted acknowledgement signal by the RL.

16. The method of claim 15, further comprising the step of correlating the received acknowledgement signal with the ID Code of the target MT stored in the RL.

17. The method of claim 7, wherein the step of correlating the received acknowledgement signal by the RL further comprises the step of mixing the received acknowledgement signal from the MT with a first sinusoidal signal at the carrier frequency, said first sinusoidal signal having a first phase angle to thereby provide an in phase product and mixing the received acknowledgement signal from the MT with a second sinusoidal signal at the carrier frequency, said second sinusoidal signal having a second phase angle 90 degrees shifted with respect to the first phase angle to thereby provide a quadrature phase product.

18. The method of claim 17, further comprising the step of analog to digital conversion of the in phase product and the quadrature phase product related to the received acknowledgement signal to provide a digital representation of each product and further storing each product in a memory.

19. The method of claim 18, further comprising the step of generating a Fast Fourier Transform (FFT) of each product related to the received acknowledgement signal stored in the memory.

20. The method of claim 19, further comprising the step of complex conjugate multiplying the FFT of each product related to the received acknowledgement signal with either of:

(1) a pre-computed FFT of an ID Code associated with the target MT or (2) the FFT of an ID Code of the target MT and providing thereby a vector representing such multiplication.

21. The method of claim 20, further comprising the step of generating the inverse FFT of said vector relating to the received acknowledgement signal, wherein the existence of a large spike occurring within the inverse FFT relative to other spikes therein, indicates a match between the ID Code in the received acknowledgement signal from the MT and the ID Code of the MT stored in the RL.

22. The method of claim 21, wherein the steps of:

generating a Fast Fourier Transform (FFT) of each product stored in the memory;

complex conjugate multiplying the FFT of each product with either of;

(1) a pre-computed FFT of an ID Code associated with an MT or (2) the FFT of an ID Code of an MT and providing thereby a vector representing such multiplication, is undertaken on a bin by bin basis, the bins arranged in succession order, each bin having a bin number related to the position of such bin in the succession.

23. The method of claim 22, wherein the bins have a predetermined time duration, the method further comprising the steps of:

identifying the bin in which the large spike occurs;

identifying the bin number of the bin in which the spike occurs;

multiplying the bin number by the predetermined bin time duration to provide a round trip time;

subtracting a predetermined time delay, if any, from the round trip time to provide a corrected round trip time;

multiplying the corrected round trip time by the speed of light to thereby determine the round trip distance; and

dividing the round trip distance by two to thereby determine the distance between the RL and the MT.

24. The method of claim 23, further comprising the step of providing a directional antenna for use in conjunction with the RL to determine the position of the MT relative to the RL.

25. The method of claim 23, wherein the predetermined time delay is 0.0 seconds.

26. The method of claim 1, further comprising the step of providing a MT having a lateral dimension of no greater than about 7 mm and a longitudinal dimension of no greater than about 70 mm.

27. The method of claim 1, further comprising the step of providing a MT having a volume of no greater than about 2700 mm³.

28. An object locator system configured for operation utilizing FFT processing at a predetermined carrier frequency, the system comprising:

a microtransponder (MT) for use in association with the object to be located and responsive to a received coded signal comprising;

a MT receiver circuit adapted to recognize the received coded signal when it correlates with an identification code (ID Code) associated with such MT and trigger a response thereto, said MT receiver circuit including means to correlate the received coded signal with the ID Code of such MT by the use of FFT processing at the predetermined carrier frequency;

a transmitter circuit adapted to transmit at the predetermined carrier frequency an acknowledgment signal after detection of the triggered response; and

a remote locator (RL) for determining the distance between the RL and said object comprising;

a RL transmitter adapted to transmit at the predetermined carrier frequency a coded signal for transmission to the MT;

a RL receiver circuit adapted to receive the acknowledgement signal; and

a time measurement circuit adapted to measure the round trip time between the transmission of the coded signal by the RL and receipt of the acknowledgment signal, whereby the distance between the MT and RL is a function of the time between the transmission of the coded signal and receipt of the acknowledgment signal.

29. The object locator system of claim 28, wherein the RL transmitter circuit comprises:

a carrier frequency signal generator adapted to generate a carrier frequency signal at the predetermined frequency;

a storage device adapted to store a coded signal associated with a MT, the storage device having an output providing a data pattern representing the coded signal; and

a modulator circuit coupled to the output of the storage device and the carrier frequency signal generator and adapted to provide a coded output signal representing the carrier frequency signal being modulated in accordance with said data pattern.

30. The object locator system of claim 29, wherein the modulating circuit is adapted to perform at least one of:

multi-phase shift keying (MPSK), binary-phase shift keying (BPSK), and a quadrature phase shift keying (QPSK).

31. The object locator system of claim 29, wherein the MT receiver circuit is adapted to process a received coded signal to provide two output signals in quadrature phase relationship comprising an in phase signal and a quadrature phase signal.

32. The object locator system of claim 31, wherein the MT circuit receiver further comprises:

an analog to digital (A/D) converter adapted to provide a digital representation of the in phase signal and the quadrature phase signal;

a random access memory adapted to store the digital representation of the in phase signal and the quadrature phase signal;

a Fast Fourier Transform (FFT) circuit coupled to the random access memory and adapted to generate a FFT of the digital representation of the in phase signal and the quadrature phase signal;

a multiplier circuit adapted to complex conjugate multiply the FFT of the digital representation of the in phase signal and the quadrature phase signal with a pre-computed FFT associated with an ID Code relating to a target MT or the FFT of an ID Code associated with a target MT, the multiplication providing thereby a resultant multiplication vector; and

an inverse FFT circuit adapted to transform said resultant multiplication vector, wherein the existence of a large pulsatile signal relative to other pulsatile signals within the transformed vector indicates a match between the received coded signal and the ID Code associated with the target MT.

33. The object locator system of claim 32, wherein the MT transmitter circuit is adapted to transmit an acknowledgement signal upon the detection of the existence of a large pulsatile signal relative to other pulsatile signals within the transformed vector.

34. The object locator system of claim 33, wherein the MT transmitter circuit comprises:

a carrier signal generator adapted to generate a carrier signal at the predetermined frequency;

a storage device adapted to store a coded signal associated with the MT, the storage device having an output providing a data pattern representing the coded signal; and

a MT modulator circuit coupled to the output of the storage device and the carrier signal generator and adapted to provide a coded output signal representing the carrier signal being modulated in accordance with said data pattern.

35. The object locator system of claim 34, wherein the MT modulating circuit is adapted to perform at least one of:

multi-phase shift keying (MPSK), binary-phase shift keying (BPSK), and a quadrature phase shift keying (QPSK).

36. The object locator system of claim 34, wherein the RL receiver circuit is adapted to process a received coded signal to provide two output signals in quadrature phase relationship comprising an in phase signal and a quadrature phase signal.

37. The object locator system of claim 36, wherein the RL receiver circuit further comprises:

an analog to digital (A/D) converter adapted to provide a digital representation of the in phase signal and the quadrature phase signal;

a random access memory adapted to store the digital representation of the in phase signal and the quadrature phase signal;

a Fast Fourier Transform (FFT) circuit coupled to the random access memory and adapted to generate a FFT of the digital representation of the in phase signal and the quadrature phase signal;

a multiplier circuit adapted to complex conjugate multiply the FFT of the digital representation of the in phase signal and the quadrature phase signal with a pre-computed FFT associated with an ID Code relating to a target MT or the FFT of an ID Code associated with a target MT, the multiplication providing thereby a resultant multiplication vector, said multiplication being undertaken on a bin by bin basis, the bins arranged in succession order, each bin having a bin number related to the position of such bin in the succession; and

an inverse FFT circuit adapted to transform said resultant multiplication vector, wherein the existence of a large pulsatile signal relative to other pulsatile signals within the transformed vector indicates a match between the received coded signal and the ID Code associated with the target MT, the bins arranged in succession order, each bin having a bin number related to the position of such bin in the succession.

38. The object locator system of claim 37, wherein the time measurement circuit further comprises circuitry adapted to:

identifying the bin in which the large spike occurs;

identifying the bin number of the bin in which the spike occurs;

multiplying the bin number by a predetermined bin time duration to provide a round trip time;

subtracting a predetermined time delay, if any, from the round trip time to provide a corrected round trip time;

multiplying the corrected round trip time by the speed of light to thereby determine the round trip distance; and

dividing the round trip distance by two to thereby determine the distance between the RL and the MT.

39. The object locator system of claim 28, wherein the MT is sized to have a lateral dimension of no greater than about 7 mm and a longitudinal dimension of no greater than about 70 mm.

40. The object locator system of claim 28, wherein the MT is sized to have a volume of no greater than about 2700 mm³.

41. The object locator system of claim 28, wherein the MT includes at least one physiologic sensor adapted for monitoring selected physiological parameters and wherein the MT transmitter is adapted to transmit signals corresponding to such physiological sensors to the RL.

42. The object locator system of claim 41, wherein said physiological parameters comprise at least one of:

surrounding ambient temperature;

heart rate;

blood pressure;

glucose level; and

breathing rate.

43. The object locator system of claim 28, wherein the MT further comprises a motion detector and wherein the MT is adapted to transmit movement information associated with the MT to the RL.

44. The object locator system of claim 43, wherein the motion detector comprises an accelerometer.

45. The object locator system of claim 28, wherein the MT comprises stimulation circuitry for stimulating a nerve or muscle in an object in response to a correlated received coded signal.

46. The object locator system of claim 28, wherein the MT further comprises sensing circuitry for sensing an electrical signal associated with neuromuscular activity in said object, wherein said electrical signal is transmitted to the remote locator.

47. The object locator system of claim 28, wherein the MT further comprises a sound-activated unit for receiving and/or recording and/or transmitting sound, wherein the sound transmission is effected through an information signal used in association with the acknowledgement signal to the RL.

48. The object locator system of claim 47, further comprising a speaker associated with the MT for providing an audio message to the object from the RL.

49. The object locator system of claim 28, wherein the RL receiver circuit further comprises an antenna configured to transmit and receive radio waves.

50. The object locator system of claim 49, wherein the RL receiver antenna comprises a directional antenna adapted to identify the position of the MT relative to the RL.

51. The object locator system of claim 28, wherein the RL includes circuitry to transmit a plurality of signals being coded to match different ones of a plurality of objects, wherein an acknowledgement signal is transmitted by an MT when a received coded signal matches the ID Code associated with such MT.

52. The object locator system of claim 28, wherein the RL further comprises a global positioning system (GPS) circuit, including a GPS signal antenna, adapted to receive global positioning satellite (GPS) signals and obtain thereby the current MT position, the MT configured to transmit such current MT position to the remote locator.

53. An object locator system, comprising:

at least one location transceiver adapted to be connected to or implanted in an object to be located, wherein the location transceiver comprises a broadband receiver and a low power broadband encoded signal transmitter; and

a finder transceiver for communicating with the location transceiver, wherein the finder transceiver comprises a high power broadband encoded transmitter and a broadband receiver;

wherein the location transceiver periodically operates in a receive mode for a first predetermined length of time and in a sleep mode for a second predetermined period of time; and

wherein the finder transmitter periodically transmits a relatively high power encoded signal for a third predetermined length of time, wherein the third predetermined length of time is at least as long as the first predetermined length of time.

54. The system of claim 53, wherein the high power encoded signal comprises at least one identification (ID) code associated with the location transceiver.

55. The system of claim 54, wherein in response to reception of the at least one ID code from the finder transceiver, the location transceiver provides an encoded signal comprising appropriate acknowledgement information for the finder transceiver when the received ID code matches that associated with the location transceiver.

56. The system of claim 55, wherein upon reception of all or part of the finder transceiver transmitted signal, said location transceiver schedules operation in the receive mode during transmission of the encoded signal by the finder transceiver so as to capture at least one complete encoded signal containing the ID code.

57. The system of claim 55, wherein the finder transceiver transmitted signal is transmitted in a series of repeating intervals wherein the signal received by the location transceiver during the receive mode, is used by the location transceiver to determine the anticipated occurrence of a following series of repeating intervals.

58. The system of claim 57, wherein the location transceiver includes circuitry to determine the anticipated occurrence of a following series of repeating intervals, to cause the location transceiver to go into a sleep mode and then into the receive mode prior to the anticipated arrival of a following series of repeating intervals.

59. The system of claim 53, wherein the location transceiver is sized to have a lateral dimension of no greater than about 7 mm and a longitudinal dimension of no greater than about 70 mm.

60. The system of claim 53 wherein the location transceiver is sized to have a volume of no greater than about 2700 mm³.

61. A method for locating a transponder with a transceiver, the method comprising:

selecting an identification code (ID Code) stored in the transceiver, for transmission from the transceiver to at least one transponder, wherein each of the at least one transponder has a specific associated ID Code;

generating a transmission signal at a predetermined carrier frequency for transmission by the transceiver, wherein the transmission signal includes the selected ID Code;

transmitting the transmission signal from the transceiver for reception by the transponder at a first time;

receiving the transmission signal from the transceiver by the transponder to provide a received signal;

correlating, utilizing Fast Fourier Transform processing at the predetermined carrier frequency to correlate in the time domain, the received signal with an ID Code stored in the transponder to detect the presence of the selected ID Code in the received signal;

upon detection of the selected ID Code, generating an acknowledgement signal by the transponder;

transmitting the acknowledgement signal from the transponder to the transceiver;

receiving the acknowledgement signal from the transponder by the transceiver at a second time; and

determining a distance between the transceiver and the transponder as a function of an elapsed time between the first time and the second time.

62. The method of claim 61, wherein the step of receiving the acknowledgement signal by the transceiver includes correlating, utilizing Fast Fourier Transform processing at the predetermined carrier frequency, the acknowledgement signal with the ID Code stored in the transceiver to detect the presence of the selected ID Code in the acknowledgement signal.

63. The method of claim 62, wherein the steps of correlating further includes correlating utilizing inverse Fast Fourier Transforms.