Wireless communication system

• US 20050052287A1
• Filed: 09/06/2002
• Published: 03/10/2005
• Est. Priority Date: 09/13/2001
• Status: Active Grant

• Current Assignee: Tagtec Ltd.
• Original Assignee: Tagtec Ltd.
• Inventors: Davies, Richard Lewis, Taylor, Stephen Russell, Fell, Andrew Jon, Lang, Kenneth John, Whitesmith, Howard William, Sims, Charles Robert
• Granted Patent: US 7,408,456 B2
• Time in Patent Office: Days
• US Class Current: 340/825.720
• CPC Class Codes: G01S 13/751 wherein the responder or reflector radiates a coded signal
• CPC Class Codes: G01S 13/765 with exchange of information between interrogator and responder
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• CPC Class Codes: G06K 7/10079 the collision being resolved in the spatial domain, e.g. temporary shields for blindfolding the interrogator in specific directions
• CPC Class Codes: G08B 13/2417 having a radio frequency identification chip
• CPC Class Codes: G08B 13/2488 Timing issues, e.g. synchronising measures to avoid signal collision, with multiple emitters or a single emitter and receiver
• CPC Class Codes: G08B 25/003 Address allocation methods and details

Abstract

An RFID tag (200) and similar control/sensing unit (300) for a communications system are described. The control/sensing unit has a control element (301) having one or more states, and include an antenna (207) as well as an electrical circuit (201-206) generating a pulse control signal for controlling transmission from the antenna and varying a parameter of the pulse control signal in dependence on the state of the control element (301). Also disclosed is a receiving communication unit in the form of a base unit or system controller for such a communications system, the unit including a receiver (100) for receiving a pulsed RF signal and an electrical circuit (105-106) for detecting a parameter of the pulsed RF signal. An output circuit (107) then produces an output control signal dependent on the detected parameter of the pulsed RF signal.

Claims

1. A communication unit for a communications system, the unit including

a control element having one or more states;

an antenna; and

an electrical circuit generating a pulse control signal for controlling transmission from the antenna and varying a parameter of the pulse control signal in dependence on the state of the control element.

2. A communication unit according to claim 1, wherein

the antenna is a backscatter antenna for reflecting RF radiation impinging thereon;

and

the electrical circuit further includes a modulation element receiving the pulse control signal and modulating the radiation reflected by the backscatter antenna dependent on the control signal and hence the state of the control element.

3. A unit according to claim 1 or claim 2, wherein the control element comprises a manually operable switch.

4. A unit according to claim 1 or claim 2, wherein the control element includes a sensor for sensing one or more physical conditions.

5. A unit according to claim 3 or claim 4, wherein the control element has two operative positions.

6. A unit according to claim 3 or claim 4, wherein the control element has a continuously variable output.

7. A unit according to claim 4, wherein the sensor includes one or more of a movement detector, a light level detector;

a gas detector;

a smoke detector;

a temperature detector;

a sound level detector;

an electromagnetic radiation detector;

a humidity detector;

pressure detector; and

a fluid level detector.

8. A unit according to any of claims 1 to 7, wherein the electrical circuit is also able to vary the length of the repeating signal.

9. A unit according to any of claims 1 to 8, wherein the repeating signal is modulated to transmit binary data from the control unit.

10. A unit according to any of claims 1 to 8, wherein a second repeating output signal is output by the electrical circuit at the same period as the first signal and the time between the first and second signals is adjustable dependent on the state of the control element.

11. A unit according to any of claims 1 to 10, wherein the control signal comprises an output signal output through the antenna.

12. A unit according to any of claims 2 to 10, including

a backscatter antenna;

a modulation element for modulating the radiation reflected by the backscatter antenna; and

wherein the control signal comprises an input to the modulation element.

13. A unit according to claim 1, wherein the unit comprises an RFID tag.

14. A unit according to any of claims 1 to 13, wherein the unit includes a battery for powering the unit.

15. A unit according to any of claims 1 to 13, wherein the unit includes an electromagnetic sensor adapted to receive electromagnetic radiation, and a power supply circuit for converting said radiation into electrical power for powering the unit.

16. A unit according to claim 15, wherein the electromagnetic sensor is an RF sensor adapted to receive RF radiation.

17. A unit according to claim 15, wherein the electromagnetic sensor is a light sensor adapted to receive light radiation.

18. A unit according to any of claims 1 to 13, wherein the unit includes a heat sensor adapted to receive heat, and a power supply circuit for converting the heat into electrical power for powering the unit.

28. A communications system including one or more communications units according to any of claims 1 to 18.

29. A communications system according to claim 28, including a base unit having transmitter comprising an RF loop antenna.

30. A communications system according to claim 28, including a base unit having transmitter comprising a discrete RF antenna.

31. A communications system according to claim 29 or claim 30, wherein said transmitter includes an electrical circuit for modulating the frequency of the transmitted RF radiation.

32. A communications system according to any of claims 29 to 31, wherein the base unit includes an RF receiver for receiving RF radiation and producing an electrical current to power the base unit.

33. A communications system according to any of claims 29 to 32, wherein said transmitter includes an electrical circuit for transmitting digital data from the base unit.

44. A communication unit according to any of claims 1 to 14, wherein the antenna is embedded in or attached to a pad or mat.

45. A communication unit according to any of claims 1 to 14, wherein the antenna is embedded in or attached to an item or furniture, for example a shelf.

19. A receiving communication unit for a communications system, the unit including

a receiver for receiving a pulsed RF signal;

an electrical circuit for detecting a parameter of the pulsed RF signal; and

an output circuit for producing an output control signal dependent on the detected parameter of the pulsed RF signal.

20. A receiving communication unit according to claim 19, wherein the parameter is the period between pulses of the pulsed signal.

21. A receiving communication unit according to claim 19, wherein the parameter is the length of the pulses of the pulsed RF signal.

22. A receiving communication unit according to claim 19, wherein the parameter is the amplitude of the pulsed RF signal.

23. A receiving communication unit according to claim 19, wherein the parameter is the frequency of the pulsed RF signal.

24. A unit according to any of claims 19 to 23, including means for demodulating binary data also transmitted by said RF signal.

25. A unit according to any of claims 19 to 23, wherein the output circuit includes a radio transmitter for transmitting the control signal.

26. A unit according to any of claims 19 to 23, wherein the output circuit includes an infra-red transmitter for transmitting the control signal.

27. A unit according to any of claims 19 to 23, wherein the output control signal is a digital control signal.

34. A communications system according to any of claims 29 to 33, and further including a receiving communication unit according to any of claims 19 to 27, said receiving communication unit communicating with an environmental control system to control at least one parameter of said environmental control system.

35. A communications system according to claim 34, wherein said parameter is one of a lighting circuit control parameter;

an air conditioning circuit control parameter;

a heating circuit control parameter;

a ventilation circuit control parameter;

a humidity circuit control parameter;

an access circuit control parameter; and

a security circuit control parameter.

36. A communications system having

a transmitter arranged to transmit bursts of RF energy at a regular period;

a communications unit having an antenna through which RF energy is received from the transmitter, storage means for storing the energy, an electrical circuit for generating output responses at a period dependent on the amount of energy stored and transmitting the output responses; and

a receiving communications unit having an electrical circuit for receiving the output responses from the communications unit and for detecting the time of receipt of the output responses, determining if a change in the period of receipt of the responses occurs and, if so, generating an output.

37. A system according to claim 36, including plural communications units.

38. A system according to claim 37, wherein each communications unit includes a sensitivity switch for modifying the rate at which RF energy is stored.

39. A system according to any of claims 36 to 38, wherein the communications unit electrical circuit has means for discharging the stored energy and the output responses of the communications unit are generated when the stored energy reaches a given value, whereby the period at which the output responses of the communications unit are generated is determined by the time taken for the stored energy to reduce from its maximum value to the given value.

40. A system according to claim 39, wherein the or each communications unit includes a sensitivity switch for modifying the rate at which RF energy is stored.

41. A system according to claim 39, wherein the or each communications unit includes a sensitivity switch for modifying the rate at which RF energy is discharged.

42. A system according to any of claims 36 to 41, wherein the communications unit electrical circuit includes means for transmitting a coded output signal.

43. A system according to any of claims 36 to 42, wherein the transmitter is arranged to transmit RF energy at a relatively low frequency, the communications unit is arranged to transmit output responses at a relatively high RF frequency, and the receiving communications unit electrical circuit is arranged to detect changes in the strength of the received output responses.