Surface-wave transducer device and identification system with such device

• US 6,788,204 B1
• Filed: 03/02/2000
• Issued: 09/07/2004
• Est. Priority Date: 03/15/1999
• Status: Expired due to Fees

• Current Assignee: Nanotron Gesellschaft Fur Mikrotechnik mbH
• Original Assignee: Nanotron Gesellschaft Fur Mikrotechnik mbH
• Inventors: Ianelli, Zbigniew, Koslar, Manfred
• Primary Examiner(s): Lee, Benjamin C.
• Application Number:
  US09/517,339
• Time in Patent Office: 1,650 Days
• Field of Search: 340/572.1, 340/572--57, 340/5.25, 340/5.8, 340/5.2, 340/5.7, 340/10.1, 310/313.R, 333/193, 333/195, 333/150, 333/151, 333/153, 333/156
• US Class Current: 340/572.1
• CPC Class Codes: G06K 19/0675 the resonating marks being of the surface acoustic wave [SAW] kind SAW devices per se H03H9/64
• CPC Class Codes: H03H 9/14555 Chirped transducers H03H9/6406 takes precedence
• CPC Class Codes: H03H 9/44 Frequency dependent delay lines, e.g. dispersive delay lines
• CPC Class Codes: H03H 9/642 SAW transducers details for remote interrogation systems, e.g. surface acoustic wave transducers details for ID-tags remote interrogation systems per se G06K7/10009, G01S13/74
• CPC Class Codes: H04B 5/73 for taking measurements, e.g. using sensing coils
• CPC Class Codes: H04B 5/77 for interrogation
• CPC Class Codes: H04R 23/00 Transducers other than those covered by groups H04R9/00 - H04R21/00 diaphragms for transducers of the distributed-mode type H04R7/045

Abstract

The invention relates to a surface-wave transducer device—also called TAGs—and to identification systems with this device.

DE 42 17 049 discloses a passive surface sensor which can be interrogated in wireless mode. In this context, energy is transmitted by radio to the sensor using an interrogation device, the interrogation being done by means of chirped transmission signals. The sensor has transducers and reflectors. The reflectors reflect the chirp signal in a time-staggered sequence, so that the sensor returns a time-staggered chirp signal to the interrogation device. The reflection principle means that the surface-wave sensor described above (also called SAW—surface acoustic wave—sensor in the following text) has a very high insertion loss of the order of 50 dB, for example. When the chirp signal has been received by an SAW interdigital transducer as the input transducer, this transducer produces a surface wave which propagates on the substrate of the SAW arrangement in the direction of the reflectors. When an SAW is received, each individual reflector element returns a correspondingly reflected SAW to the SAW transducer, which for its part produces an electromagnetic signal from the SAW. However, since each reflector element returns not just one SAW to the SAW transducer, but rather the reflector elements also reflect signals amongst one another, the reflections are inevitably relatively small, and a large part of the energy coming from the SAW transducer is lost in the reflector arrangement, so that only a low output power can be achieved. The problem of “internal reflection” from the reflectors cannot be avoided in principle.

The object of the invention is to provide a surface-wave transducer device which has a low insertion loss, allows a considerably greater interrogation distance than with previously known TAGs, and has an increased bit capacity. The device should enable free programming that is simple to perform. The invention proposes a surface transducer device having the features according to claim 1. Advantageous developments are described in the subclaims.

Surface-wave transducer device comprising the combination of a first transmitter device of the dispersive type and a second transmitter device of the non-dispersive type, comprising a multiplicity of n non-dispersive transducers which can be coded or are coded with an identification code.

Claims

1. Surface-wave transducer device comprising a combination of a first transmitter device of a dispersive type and a second transmitter device of a non-dispersive type, comprising a multiplicity of n non-dispersive transducers which can be coded or are coded with an identification code, characterized in that at least one of the transducers of the non-dispersive type has a positive electrode, a negative electrode, and first connection lines which connect the positive electrode and the negative electrode to respectively two bus lines, further characterized in that at least one electronic switch is situated in at least one of the connection lines.

2. Surface-wave transducer device according to claim 1, characterised in that the n non-dispersive transducers are connected such that, when excited by a signal, they transmit a signal which identifies the surface-wave transducer device.

3. Surface-wave transducer device according to claim 1, characterised in that the distance between adjacent non-dispersive transducers is the same.

4. Surface-wave transducer device according to claim 1, in which the device reacts to an electromagnetic input signal with an output signal, and the output signal is such that it has at least three different logic states.

5. Surface-wave transducer device according to claim 1, characterised in that on receiving a chirp signal the device produces a multiplicity of pulses which are transmitted as output signals successively in time.

6. Surface-wave transmitter device according to claim 1, characterised in that on receiving a chirp signal the device transmits m pulse signals, where n>

=m and m corresponds to the number of n non-dispersive transducers which do not provide any pulse signal.

7. Surface-wave transducer device according to claim 1, characterised in that all the transducers are electrically connected in parallel by means of a programming circuit.

8. Surface-wave transducer device according to claim 1, characterised in that at least one of the n non-dispersive transducers is used as a reference element.

9. Surfacewave transducer device according to claim 1, characterised in that the non-dispersive transducers are arranged only on one side or on both sides of the first transmitter device of the dispersive type.

10. Surface-wave transducer device according to claim 1, characterised in that when an input signal which is a short radio-frequency pulse is received, the dispersive transmitter device converts the signal into a first chirp-type surface wave which propagates in a first direction of the n non-dispersive transducers and, when passing through the non-dispersive transducers, initiates electrical chirp pulses whose superimposition on the two bus lines represents programmed code, whilst over the same period of time the non-dispersive transducers which are likewise excited by the input signal produce a sequence, representing the programmed code, of surface waves whose characteristic is the same as that of the input signal and which propagate in a second direction of the dispersive transmitter device and are converted there into electrical pulses with a chirp-type characteristic which are transmitted synchronously and in phase with the electrical chirp pulses produced by the first chirp-type surface wave of the non-dispersive transducers.

11. Surface-wave transducer device according to claim 1, characterised in that the surface-wave transducer device generates signals which can still be received satisfactorily even at a range of more than 2 m.

12. Surface-wave transducer device according to claim 1, characterised in that a chirp signal, as an input signal, has an approximate duration of 0.5 to 1.5 μ

s, and in that the chirp signal has an approximate frequency bandwidth of 50 to 250 MHz.

13. Surface-wave transducer device according to claim 1, characterised in that a pulse signal which is generated by the first transmitter device of the dispersive type when a chirp signal is received, has a main pulse duration T_SC, wherein $T_{\mathrm{SC}}=\frac{2}{B_3}$

where B is a bandwidth of the chirp signal.

14. Surface-wave transducer device according to claim 1, characterised in that a time between successive pulse signals from the second transmitter device of the non-dispersive type is at least as great as half a duration of a pulse signal generated by the first transmitter device of the dispersive type.

15. Surface-wave transducer device according to claim 1, characterised in that the first transmitter device and the non-dispersive transducer devices are interdigital transducers.

16. Surface-wave transducer device according to claim 1, characterised in that the non-dispersive transducers, when excited by a signal, either produce a signal which is in phase with a reference pulse, or produce a signal which is out of phase with the reference pulse, or produce no signal.

17. Surface-wave transducer device according to claim 1, characterised in that the non-dispersive transducers are programmed or coded by providing a second connection line from one of the two bus lines to a positive or negative electrode of a second non-dispersive transducer, wherein the connection line is bonded.

18. Surface-wave transducer device according to claim 1, further comprising a circuit driver with a memory for controlling the switch, and a power supply device for supplying the circuit driver, the switch, or both the circuit driver and the switch, with energy.

19. Surface-wave transducer device according to claim 1, further comprising a housing including a first, second and third layer arranged one above the other, the first layer and the third layer being a protective layer which has the second layer situated between the first layer and the second layer, the first transmitter device, the non-dispersive transducer devices, and an antenna being formed within the said second layer.

20. Surface-wave transducer device according to claim 1, characterised in that a first set of p non-dispersive transducers is arranged on a first side of the first transmitter device and a second set of q non-dispersive transducers is arranged on a second side of the first transmitter device, in that the first set of p transducers is programmed using a first code and the second set of q transducers is programmed using a second code.

21. The surface-wave-transducer of claim 20, wherein the first code is different from the second code.

22. Surface-wave transducer device according to claim 1, characterised in that the transmitter device of the dispersive type has a programmable length.

23. Surface-wave transducer device according to claim 1, characterised in that the device is coupled to a silicon substrate.

24. Surface-wave transducer device according to claim 1, characterised in that one of the n non-dispersive transducers nearest to the first transmitter device of the dispersive type forms a reference transducer whose first signal is transmitted as a reaction to a second signal from the first transmitter device.

25. Surface-wave transducer device according to claim 1, wherein n>

30.

26. Surface-wave transducer device according to claim 1, characterised in that n-k transducers of the n non-dispersive transducers are programmable or programmed, where k<

=n.

27. Surface-wave transducer device according to claim 1, characterised in that the surface-wave transducer device can be programmed once or a number of times.

28. Surface-wave transducer device according to claim 27, further comprising a control device coupled to a switching matrix for programming the surface-wave transducer device, a program interface, and a storage device which can store one or more identification codes or any desired data sequence, and in that the surface-wave transducer device can be programmed using the stored data.

29. Surface-wave transducer device according to claims 28, characterised in that the first transmitter device of the dispersive type is formed by a combination of a non-dispersive transducer and a dispersive reflector, wherein a surface wave is reflected onto the non-dispersive transducer device, which comprises a number of transducers.

30. Use of a surface-wave transducer device according to claim 1 for remotely identifying goods, people or animals.

31. A surface-wave transducer device according to claim 1, comprising a data source coupled thereto and which transmits data to the device for the said data to be interrogated by an interrogation unit.

32. The surface-wave transducer device of claim 1, wherein a first of the two bus lines is a positive bus line and a second of the two bus lines is a negative bus line.

33. Surface-wave transducer device according to claim 32, characterised in that each non-dispersive transducer has a positive and a negative electrode and that the positive electrode of the n transducers is locally allocated the positive bus line and the negative electrode of the n transducers is locally allocated the negative bus line, and that a desired coding of the surface-wave transducer device is carried out by selecting a second connection line between the positive electrode of the n transducers and the positive bus line, or a third connection line between the negative electrode of the n transducers and the negative bus line.

34. Surface wave transducer device according to claim 32, characterised in that a positive electrode of the transmitter device of the dispersive type is connected to the positive bus line and a negative electrode of the transducer of the dispersive type is connected to the negative bus line.

35. Surface-wave transducer device according to claim 32, characterised in that the device has an antenna device comprising two parts, the first part of the antenna being connected to the positive bus line and the other part being connected to the negative bus line.

36. Surface-wave transducer device according to claim 32, characterised in that the non-dispersive transducers react to a pulse signal with a dual-phase pulse signal, a phase angle of a particular dual-phase pulse signal depending on whether a positive or negative electrode of an appropriate non-dispersive transducer is connected to the positive or negative bus line.

37. Surface-wave transducer device according to claim 32, characterised in that all activated non-dispersive transducers are connected to the positive bus line by a positive electrode of the activated non-dispersive transducers and to the negative bus line by a negative electrode of the activated non-dispersive transducers.

38. Surface-wave transducer device according to claim 32, characterised in that the non-dispersive transducers are programmed or coded by cutting a second connection line between the positive bus line and either a positive or negative electrode of a second non-dispersive transducer, or a third connection line between the negative bus line and either the positive or negative electrode of the second non-dispersive transducer.

39. Surface-wave transducer device according to claim 32, characterised in that each electrode of a non-dispersive transducer has a second and a third connection, wherein the second connection is arranged close to the positive bus line and the third connection is arranged close to the negative bus line.

40. Surface-wave transducer device according to claim 39, characterised in that the transducers of the non-dispersive type are programmed or coded by arranging the non-dispersive transducers to be unconnected to the two bus lines on a bottom plate, and in that the bottom plate has a top plate arranged on it whose side associated with the bottom plate has second connection lines arranged on it which, as desired, connect positive or negative electrodes of the non-dispersive transducers to the positive or negative bus line.

41. The surface transducer of claim 1, wherein the switch is a transistor.

42. The surface-wave transducer of claim 1, wherein the non-dispersive transducers are coded by controlling the switch.

43. Surface-wave transducer device according to claim 1, characterized in that a time between successive pulse signals from the second transmitter device of the non-dispersive type is a multiple of the duration of an individual pulse generated by the first transmitter device of the dispersive type.

44. An identification system comprising:

an interrogator having a receiver unit and a transmitter unit; and

a surface-wave transducer device in communication with the interrogator, the surface-wave transducer device comprising a combination of a first transmitter device of a dispersive type and a second transmitter device of a non-dispersive type, comprising a multiplicity of n non-dispersive transducers which can be coded or are coded with an identification code,

characterized in that the surface wave transducer device has a first set of p non-dispersive transducers on a first side of the dispersive transmitter, and a second set of q non-dispersive transducers on a second side, electrodes of the dispersive transmitter being connected to an antenna and to the two bus lines of the first and of the second set of non-dispersive transducers, in that the first set of non-dispersive transducers is programmed using a first code and the second set of non-dispersive transducers is programmed using a second code,

also characterized in that both the transmitter and receiver units of the interrogator contain a first stage with a same characteristic as the dispersive transmitter, and a second stage with an appropriately inverse characteristic,

further characterized in that the transmitter unit transmits an interrogation signal comprising an up-chirp signal or a down-chirp signal which is received via the antenna and converted by the dispersive transmitter into two surface waves which propagate in opposite directions, one of which surface waves, depending on the chirp characteristic of the interrogation signal, contains a compressed pulse signal, so that only one of the two sets of non-dispersive transducers is excited, whilst, over a same period of time, both sets of non-dispersive transducers, excited by the interrogation signal, each transmit a surface-wave signal, comprising a series, identifying the relevant code, of surface waves, in a direction of the dispersive transmitter, one of the surface-wave signals being compressed in the dispersive transducer and converted into an electrical code signal, which produces an output signal on the two bus lines which, depending on the chirp characteristic of the interrogation signal, either represents the first code or the second code, and is transmitted via the antenna to the receiver unit of the interrogator.

45. The system according to claim 44, characterised in that the interrogator transmits the interrogation signal and receives and analyses a response signal returned by the surface-wave transducer device.

46. The system according to claim 44, characterized in that the interrogator is connected to a data processing system and outputs codes in the output signal received from the surface-wave transducer device at its output.

47. The system according to claim 44, characterized in that the interrogator has means for phase discrimination.

48. The system according to claim 44, characterized in that the interrogation signal is a chirp signal or a radio-frequency pulse.

49. The system according to claim 44 wherein the interrogation signal from the interrogator is a short radio-frequency pulse so that the interrogation signal transmitted by the interrogator and received via the antenna is converted by the dispersive transmitter into two chirp-type surface waves which propagate in opposite directions, have complementary characteristics and which each initiate a code signal having different codings and likewise different chirp characteristics when the first or second set of p or q transducers is reached, so that both sets of non-dispersive transducers each transmit a series, carrying a relevant code, of surface waves in a direction of the dispersive transmitter as a reaction to the interrogation signal, these surface waves being converted by the dispersive transmitter into code signals having different chirp characteristics, which produces an output signal, carrying the two codes, on the two bus lines, which comprises up-chirp pulses, which represent the first code, and down-chirp pulses, which represent the second code, and in that the output signal produced on the two bus lines is transmitted via the antenna to the receiver unit of the interrogator and is converted at the receiver unit by the dispersive stages having complementary characteristics into a first sequence representing the first code, a second sequence representing the second code, or both, of radio-frequency pulses.

50. The system according to claim 44, characterised in that the surface-wave transducer device is an integral component of the system.

51. An identification system comprising:

an interrogator having a receiver unit and a transmitter unit; and

a surface-wave transducer device in communication with the interrogator, the surface-wave transducer device comprising a first transmitter device of a dispersive type, and a second transmitter device of a non-dispersive type comprising a multiplicity of n non-dispersive transducers which are coded with an identification code, characterized in that at least one of the transducers of the non-dispersive type has a positive electrode, a negative electrode, and first connection lines which connect the positive electrode and the negative electrode to respectively two bus lines, further characterized in that at least one electronic switch is situated in at least one of the connection lines.

52. The system of claim 51, wherein the n non-dispersive transducers are configured to transmit a signal which identifies the surface-wave transducer device when excited by a signal.

53. The system of claim 51, wherein a first of the two bus lines is a positive bus line and a second of the two bus lines is a negative bus line.

54. The system of claim 53, wherein each non-dispersive transducer has a positive and a negative electrode and that the positive electrode of the n transducers is locally allocated the positive bus line and the negative electrode of the n transducers is locally allocated the negative bus line, and that a desired coding of the surface-wave transducer device is carried out by selecting a second connection line between the positive electrode of the n transducers and the positive bus line, or a third connection line between the negative electrode of the n transducers and the negative bus lines.

55. The system of claim 51, characterised in that when an input signal which is a short radio-frequency pulse is received, the dispersive transmitter device converts the signal into a first chirp-type surface wave which propagates in a first direction of the n non-dispersive transducers and, when passing through the non-dispersive transducers, initiates electrical chirp pulses whose superimposition on the two bus lines represents programmed code, whilst over the same period of time the non-dispersive transducers which are likewise excited by the input signal produce a sequence, representing the programmed code, of surface waves whose characteristic is the same as that of the input signal and which propagate in a second direction of the dispersive transmitter device and are converted there into electrical pulses with a chirp-type characteristic which are transmitted synchronously and in phase with the chirp pulses produced by the first surface wave of the non-dispersive transducers.

56. The system of claim 51, characterised in that a first set of p non-dispersive transducers is arranged on a first side of the transmitter device of the dispersive type and a second set of q non-dispersive transducers is arranged on a second side of the transmitter device of the dispersive type, in that the first set of p transducers is programmed using a first code and the second set of q transducers is programmed using a second code.

57. The system of claim 56, wherein the first code is different from the second code.