Radio tracking system and method of operation thereof

Claims

I claim:

1. A method for determining where at least one radio frequency transmitter is located with respect to a set range measured from a radio frequency receiver comprising:

periodically transmitting an identification code which identifies each radio frequency transmitter with a radio frequency carrier modulated with a subcarrier with the subcarrier being modulated with the identification code; and

in response to receiving each radio frequency carrier determining if an identification code of one of the at least one radio frequency transmitter is contained therein, calculating an integral of a received signal strength indicator of each radio frequency carrier determined to contain an identification code of one of the at least one radio frequency transmitter, computing an average of the calculated integrals which is updated to include newly calculated integrals only when each newly calculated integral differs from the computed average of the calculated integrals by less than a function of the average of the calculated integrals so as to exclude from the computation of the average of the calculated integrals newly calculated integrals which differ from the average of the calculated integrals by more than the function, comparing the average of the calculated integrals to a numerical value representing the set range and generating an alert when the comparison reveals that at least one of the at least one radio frequency transmitter is outside the set range.

2. A method in accordance with claim 1 wherein:

the at least one radio frequency transmitter transmits an alert to the radio frequency receiver as part of the radio frequency carrier containing the identification code to cause the radio frequency receiver to signal a user of the radio frequency receiver that a user of the at least one radio frequency transmitter is transmitting a change in status of the user of the at least one radio frequency transmitter.

3. A method in accordance with claim 1 further comprising:

using an omnidirectional antenna to receive the radio frequency carrier transmitted by each radio frequency transmitter which is used to calculate the average of the calculated integrals; and

after generation of the alert using a directional antenna to receive transmissions of the radio frequency carrier containing the identification code identifying the radio frequency transmitter from which the identification codes were transmitted which caused generation of the alert and in response to the radio frequency receiver being moved by a user the radio frequency receiver displaying a magnitude of the integral of each successively received signal strength indicator generated in response to reception of transmissions of the radio frequency carrier containing the identification code of the radio frequency transmitter from which the identification codes were transmitted which caused the generation of the alert to permit a user of the radio frequency receiver to locate a direction, from which a radio frequency carrier containing the identification code of the radio frequency transmitter from which the identification codes were transmitted to generate the alert is received, producing a maximum magnitude of the integral of each successively received signal strength indicator relative to the radio frequency receiver whereby a direction of the radio frequency transmitter which is outside of the set range is determined by the user of the radio frequency receiver relative to the radio frequency receiver.

4. A method in accordance with claim 2 further comprising:

using an omnidirectional antenna to receive the radio frequency carrier transmitted by one of the at least one radio frequency transmitter which contains the alert; and

in response to reception of the alert from one of the at least one radio frequency transmitter using a directional antenna to receive transmissions of the radio frequency carrier containing the identification code identifying the radio frequency transmitter from which the alert was transmitted and in response to the radio frequency receiver being moved by a user displaying a magnitude of the integral of each successively received signal strength indicator generated in response to reception of the radio frequency carrier from the radio frequency transmitter from which the alert was received to permit a user of the radio frequency receiver to locate a direction, from which a radio frequency carrier is received from the radio frequency transmitter transmitting the alert, producing a maximum magnitude of the integral of each successively received signal strength indicator relative to the radio frequency receiver whereby a direction of the radio frequency transmitter which transmitted the alert is determined by the user of radio frequency receiver relative to the radio frequency receiver.

5. A method in accordance with claim 4 further comprising:

each radio frequency transmitter modulates the subcarrier with at least one identification frame group, each identification frame group comprising a plurality of frames with at least one of the plurality of frames of the identification frame group containing bits encoding the identification code of each radio frequency transmitter, a plurality of bits of error correction code in each frame, synchronization information for synchronizing a clock of the radio frequency receiver, and a command field for encoding the alert transmitted to the radio frequency receiver from the user of the radio frequency transmitter transmitting the alert.

6. A method in accordance with claim 1 further comprising:

modulating cycles of the subcarrier with bits encoding the identification code of the radio frequency transmitter which transmitted the received radio frequency carrier with each cycle of the subcarrier being modulated with bits at a plurality of separated angular positions; and wherein

for each radio frequency carrier received from each radio frequency transmitter processing detected individual cycles of the subcarrier to calculate an integral of at least one selected modulated part of each of the individual cycles, numerically comparing each of the calculated integrals with a plurality of stored numerical ranges which ranges each represent one of a plurality of possible numerical values that the selected part may encode to identify a stored range numerically including the calculated integral, substituting for the at least one selected part of each of the cycles the one of the plurality of numerical values representative of the identified stored range including the calculated integral with each numerical value encoding one bit of the identification code of the radio frequency transmitter and decoding the plurality of numerical values to produce the identification code of the radio frequency transmitter.

7. A method in accordance with claim 6 wherein:

the processing of the detected individual cycles of the subcarrier includes calculating the integral by taking a plurality of samples of each selected modulated part of each of the individual cycles with each sample having a numerical value and each sample is compared with a range of numerical values representing a valid sample which should be included within the calculation of the integral and when the comparison reveals that the sample value is outside the range of numerical values, the compared sample value is replaced with a value which is a function of the sample values adjacent the sample value which is replaced.

8. A method in accordance with claim 7 wherein:

the compared sample value is replaced with a value which is an average of at least one sample value which precedes the compared sample value and at least one sample value which succeeds the compared sample value.

9. A method in accordance with claim 2 further comprising:

modulating cycles of the subcarrier with bits encoding the identification code of the radio frequency transmitter which transmitted the received radio frequency carrier with each cycle of the subcarrier being modulated with bits at a plurality of separated angular positions; and wherein

for each radio frequency carrier received from each radio frequency transmitter processing detected individual cycles of the subcarrier to calculate an integral of at least one selected modulated part of each of the individual cycles, numerically comparing each of the calculated integrals with a plurality of stored numerical ranges which ranges each represent one of a plurality of possible numerical values that the selected part may encode to identify a stored range numerically including the calculated integral, substituting for the at least one selected part of each of the cycles the one of the plurality of numerical values representative of the identified stored range including the calculated integral with each numerical value encoding one bit of the identification code of the radio frequency transmitter and decoding the plurality of numerical values to produce the identification code of the radio frequency transmitter.

10. A method in accordance with claim 9 wherein:

the processing of the detected individual cycles of the subcarrier includes calculating the integral by taking a plurality of samples of each selected modulated part of each of the individual cycles with each sample having a numerical value and each sample is compared with a range of numerical values representing a valid sample which should be included within the calculation of the integral and when the comparison reveals that the sample value is outside the range of numerical values, the compared sample value is replaced with a value which is a function of the sample values adjacent the sample value which is replaced.

11. A method in accordance with claim 10 wherein:

the compared sample value is replaced with a value which is an average of at least one sample value which precedes the compared sample value and at least one sample value which succeeds the compared sample value.

12. A method in accordance with claim 3 further comprising:

modulating cycles of the subcarrier with bits encoding the identification code of the radio frequency transmitter which transmitted the received radio frequency carrier with each cycle of the subcarrier being modulated with bits at a plurality of separated angular positions; and wherein

for each radio frequency carrier received from each radio frequency transmitter processing detected individual cycles of the subcarrier to calculate an integral of at least one selected modulated part of each of the individual cycles, numerically comparing each of the calculated integrals with a plurality of stored numerical ranges which ranges each represent one of a plurality of possible numerical values that the selected part may encode to identify a stored range numerically including the calculated integral, substituting for the at least one selected part of each of the cycles the one of the plurality of numerical values representative of the identified stored range including the calculated integral with each numerical value encoding one bit of the identification code of the radio frequency transmitter and decoding the plurality of numerical values to produce the identification code of the radio frequency transmitter.

13. A method in accordance with claim 12 wherein:

the processing of the detected individual cycles of the subcarrier includes calculating the integral by taking a plurality of samples of each selected modulated part of each of the individual cycles with each sample having a numerical value and each sample is compared with a range of numerical values representing a valid sample which should be included within the calculation of the integral and when the comparison reveals that the sample value is outside the range of numerical values, the compared sample value is replaced with a value which is a function of the sample values adjacent the sample value which is replaced.

14. A method in accordance with claim 13 wherein:

the compared sample value is replaced with a value which is an average of at least one sample value which precedes the compared sample value and at least one sample value which succeeds the compared sample value.

15. A method in accordance with claim 4 further comprising:

modulating cycles of the subcarrier with bits encoding the identification code of the radio frequency transmitter which transmitted the received radio frequency carrier with each cycle of the subcarrier being modulated with bits at a plurality of separated angular positions; and wherein

for each radio frequency carrier received from each radio frequency transmitter processing detected individual cycles of the subcarrier to calculate an integral of at least one selected modulated part of each of the individual cycles, numerically comparing each of the calculated integrals with a plurality of stored numerical ranges which ranges each represent one of a plurality of possible numerical values that the selected part may encode to identify a stored range numerically including the calculated integral, substituting for the at least one selected part of each of the cycles the one of the plurality of numerical values representative of the identified stored range including the calculated integral with each numerical value encoding one bit of the identification code of the radio frequency transmitter and decoding the plurality of numerical values to produce the identification code of the radio frequency transmitter.

16. A method in accordance with claim 15 wherein:

the processing of the detected individual cycles of the subcarrier includes calculating the integral by taking a plurality of samples of each selected modulated part of each of the individual cycles with each sample having a numerical value and each sample is compared with a range of numerical values representing a valid sample which should be included within the calculation of the integral and when the comparison reveals that the sample value is outside the range of numerical values, the compared sample value is replaced with a value which is a function of the sample values adjacent the sample value which is replaced.

17. A method in accordance with claim 16 wherein:

the compared sample value is replaced with a value which is an average of at least one sample value which precedes the compared sample value and at least one sample value which succeeds the compared sample value.

18. A method in accordance with claim 5 further comprising:

modulating cycles of the subcarrier with bits encoding the identification code of the radio frequency transmitter which transmitted the received radio frequency carrier with each cycle of the subcarrier being modulated with bits at a plurality of separated angular positions; and wherein

for each radio frequency carrier received from each radio frequency transmitter processing detected individual cycles of the subcarrier to calculate an integral of at least one selected modulated part of each of the individual cycles, numerically comparing each of the calculated integrals with a plurality of stored numerical ranges which ranges each represent one of a plurality of possible numerical values that the selected part may encode to identify a stored range numerically including the calculated integral, substituting for the at least one selected part of each of the cycles the one of the plurality of numerical values representative of the identified stored range including the calculated integral with each numerical value encoding one bit of the identification code of the radio frequency transmitter and decoding the plurality of numerical values to produce the identification code of the radio frequency transmitter.

19. A method in accordance with claim 18 wherein:

the processing of the detected individual cycles of the subcarrier includes calculating the integral by taking a plurality of samples of each selected modulated part of each of the individual cycles with each sample having a numerical value and each sample is compared with a range of numerical values representing a valid sample which should be included within the calculation of the integral and when the comparison reveals that the sample value is outside the range of numerical values, the compared sample value is replaced with a value which is a function of the sample values adjacent the sample value which is replaced.

20. A method in accordance with claim 19 wherein:

the compared sample value is replaced with a value which is an average of at least one sample value which precedes the compared sample value and at least one sample value which succeeds the compared sample value.

21. A method in accordance with claim 1 wherein:

an amplifier, responsive to each radio carrier modulated with the subcarrier containing the identification of one of the at least one radio frequency transmitter, produces each received signal strength indicator.

22. A method in accordance with claim 21 wherein:

the amplifier is an intermediate frequency amplifier.

23. A method in accordance with claim 2 wherein:

an amplifier, responsive to each radio carrier modulated with the subcarrier containing the identification of one of the at least one radio frequency transmitter, produces each received signal strength indicator.

24. A method in accordance with claim 23 wherein:

the amplifier is an intermediate frequency amplifier.

25. A method in accordance with claim 3 wherein:

an amplifier, responsive to each radio carrier modulated with the subcarrier containing the identification of one of the at least one radio frequency transmitter, produces each received signal strength indicator.

26. A method in accordance with claim 25 wherein:

the amplifier is an intermediate frequency amplifier.

27. A method in accordance with claim 4 wherein:

an amplifier, responsive to each radio carrier modulated with the subcarrier containing the identification of one of the at least one radio frequency transmitter, produces each received signal strength indicator.

28. A method in accordance with claim 27 wherein:

the amplifier is an intermediate frequency amplifier.

29. A method in accordance with claim 5 wherein:

an amplifier, responsive to each radio carrier modulated with the subcarrier containing the identification of one of the at least one radio frequency transmitter, produces each received signal strength indicator.

30. A method in accordance with claim 29 wherein:

the amplifier is an intermediate frequency amplifier.

31. A method in accordance with claim 6 wherein:

an amplifier, responsive to each radio carrier modulated with the subcarrier containing the identification of one of the at least one radio frequency transmitter, produces each received signal strength indicator.

32. A method in accordance with claim 31 wherein:

the amplifier is an intermediate frequency amplifier.

33. A method for determining where at least one radio frequency transmitter is located with respect to a set range measured from a radio frequency receiver comprising:

periodically transmitting an identification code which identifies each radio frequency transmitter with a radio frequency carrier modulated with a subcarrier with the subcarrier being modulated with the identification code; and

in response to receiving each radio frequency carrier determining if an identification code of one of the at least one radio frequency