DE102012211188A1 - Condition monitoring with RFID - Google Patents

Abstract

A signaling device based on a transponder has an RFID chip with two connections that are connected to two antenna segments. Furthermore, the connections are connected to two conductors with a length of (2n + 1) × λ / 4 or (2n) × λ / 4, where λ is the line wavelength of the signal sent or received by the RFID chip and n is an integer positive number is. The ends of the conductors can be short-circuited by a switching element. This makes it possible to control an RFID chip without a separate control input and to separate the switching element from the antenna segments.

Description

Technical area

The invention relates to an arrangement with an RFID transponder for non-contact monitoring of electrical and mechanical conditions. In particular for monitoring the position of an object or a mechanical component.

State of the art

For non-contact monitoring of a switching state of a switch discloses the US 2005/0242957 A1 an arrangement with an RFID chip, in which the supply line to the antenna is closed or interrupted by a mechanical switch. When the switch is closed, the RFID chip responds to requests from a reader, while it does not react when the switch is open. Thus, the switching state of the switch can be determined in a simple manner without contact.

Another solution for non-contact monitoring of mechanical conditions discloses the US 2011/0156905 A1 , Here a two-part security tag is disclosed, wherein the first part contains the RFID chip and the second part contains the associated antenna. Only when both parts are brought into electrical contact with each other, the RFID chip can respond to requests from the reader. Thus, the mechanical state can be determined here as well.

The solutions based on RFID chips disclosed here all have the disadvantage that they only work reliably with proper mechanical contact in the circuit between antenna and RFID chip. In addition, the switching contact is integrated directly into the current path between the RFID chip and the antenna.

In the EP 1 732 242 A2 Another embodiment of a non-contact status inquiry is disclosed. Here, the capacity, which is connected to an antenna, is changed by a mechanical state change. This can then be determined by a remote transceiver. By this arrangement, a plurality of states can be detected. The disadvantage of this arrangement is the relatively high mechanical and electrical effort.

Presentation of the invention

The invention has for its object to improve the known from the prior art systems for contactless condition monitoring to the effect that they are reliable, precise and robust, which are to be produced at the same time at low cost in large quantities.

This object is achieved by a device according to claim 1 or 2. Advantageous embodiments of the invention are specified in the subclaims.

According to the invention, a signaling device has an RFID chip with at least two terminals for connecting antenna segments, or an antenna segment and a ground plane. Advantageously, the RFID chip has exactly two connections. Preferably, at least one antenna segment is connected to one of the terminals. Particularly preferably, two antenna segments are connected to two terminals. The antenna segments are used for transmitting or receiving electromagnetic radiation. The RFID chip together with at least one antenna segment forms a transponder, also called an RFID tag. Furthermore, a conductor for connection to a switching element is connected to at least one terminal of the RFID chip. Preferably, a conductor is connected to two terminals of the RFID chip for connection to a switching element. The conductor has a length which preferably corresponds to an integer multiple of a quarter of the line wavelength λ of the signal transmitted or received by the RFID chip. The length of the conductor is particularly preferably λ / 4 or λ / 2.

In a preferred embodiment of the invention, an antenna segment is connected to each of the two terminals of the RFID chip, and a conductor is connected to a first end parallel thereto. The second ends of the two conductors are connected to a switching element. The switching element may for example be a mechanical switching contact or a capacitive switching element. A capacitive switching element preferably has two flat conductors, which are brought close to each other for switching, so that a high capacity exists between these conductors. It may also be two parallel conductors, which are capacitively connected to each other by a third, overlying conductor. Furthermore, it is preferred if the length of the two conductors is at a quarter of the line wavelength of the signal transmitted or received by the RFID chip. Thus, an interruption between the two second ends of the conductor is transformed into a short circuit at the location of the RFID chip. Thus, the RFID chip can neither transmit nor receive high-frequency signals. Only when a short circuit between the two second ends of the conductor is generated by the switching element, this is transformed into an idle at the location of the RFID chip, so that the RFID chip can transmit and receive high-frequency energy by means of the antenna segments and thus can communicate with the outside world. This deactivates the transponder or tag. Such a configuration according to the invention allows a switching element to be mounted remotely from the RFID chip and also away from the antenna segments. Thus, the radiation characteristic of the antenna segments is no longer influenced by the switching element, as would be the case in the prior art.

By this embodiment of the invention, the circuit complexity for the realization of a switchable transponder is substantially reduced. It is no longer required transponder chip with a switching or control input. Nevertheless, it is of course possible to provide further inputs or outputs to the RFID chips.

In a further advantageous embodiment of the invention, the length of the conductor is λ / 2. Thus, substantially the impedance at the second ends of the conductors is transformed to the first ends of the conductors. In this case, a short circuit is preferably provided at the second ends of the conductors. Furthermore, advantageously, a switching element in the middle of the conductor, that is mounted at a distance of λ / 4 to the RFID chip. If this switching element is now open, the short circuit at the second ends of the conductors is transformed into a short circuit on the RFID chip and thus prevents the transmission and reception of high-frequency energy by the RFID chip. If the switching element is closed, a short circuit occurs at the point λ / 4 corresponding to half the length of the conductor, which in turn is transformed into an open circuit on the RFID chip, thereby enabling transmission and reception of high-frequency energy by the RFID chip.

In a further advantageous embodiment of the invention, at least one, preferably both conductors, each having a first end connected to the RFID chip and connected to a second end with an antenna segment. The length of the at least one conductor between the RFID chip and the at least one antenna segment is preferably λ / 2. It is furthermore preferred if a switching element is present at the position λ / 4, that is to say at half the conductor length. If the switching element is opened, the impedance of the antennas transforms via the λ / 2 conductor directly to the RFID chip. If now the switching element is closed at the position λ / 4, then a short circuit to the ends of the conductor is transformed in each case at the location of the RFID chip and the antenna segments, so that a transmission and reception of high-frequency energy are not possible.

Another aspect of the invention relates to the combination of antenna segments and leads. Thus, two lines, which are preferably the same length with a length n x λ / 4, connected to a first end to the RFID chip and a second end to a switching element. By the switching element, the two lines can be connected to each other, so that there is a short circuit through which a transmission or radiation of electromagnetic energy is impossible. Only with an open switching element, this is again possible because the lines can now work as antenna segments.

The function of the various embodiments of the invention is shown here for the sake of clarity on a symmetrical arrangement. So two conductors and two antenna segments are connected to the RFID chip. The two conductors form a line here. In principle, however, an asymmetrical arrangement is possible. In such a case, only one conductor and one antenna segment is connected to the RFID chip. The RFID chip is further galvanically or capacitively connected to a ground plane, which is preferably a good conductive metallic surface. In this case, the ground plane could be considered as a second antenna segment. Again, the conductor forms a line over the ground plane. The switching element is then switched between the conductor and the ground plane. All embodiments shown here are optionally symmetrical or asymmetric executable.

The antenna segments described here can also consist of several parts. Characteristic of one of the antenna segments described here is that it is connected to a terminal of the RFID chip.

The embodiments described herein, which by way of example relate to a length of the conductors of λ / 4, can also be realized with (2n + 1) × λ / 4 conductor lengths, where n is an integer positive number ≥ 0. The λ / 2 embodiments described herein are also feasible with conductor lengths of n × λ / 2.

Shortening elements and / or extension elements can also be used. This allows the use of geometrically shorter and / or longer conductors than would be the case without shortening elements and / or extension elements. A shortening element may for example be an inductive component, which is connected in series with a conductor. This component increases the electrical length of the conductor, so that now a geometrically shorter conductor can be used. An extension element may for example be a capacitive component, which in series with a Head is switched. Such a component reduces the electrical length of the conductor, so that a geometrically longer conductor can be used. A capacitive switching element could simultaneously be used as an extension element or shortening element. As a result, the switching point is then preferably at a specific capacity, so that the RFID chip is deactivated at a larger capacity and at a smaller capacity. In arrangements with a conductor, a shortening element and / or extension element is preferably connected in series with the one conductor. In arrangements with two conductors, a shortening element and / or extension element is preferably connected in series with each of the two conductors. The shortening elements and / or extension elements can be used at any position. For example, they can be connected between the transponder and the line. But you can also be provided in the line or at the end of the line. It is also possible in principle to connect shortening elements or extension elements parallel to the lines.

The advantage of using RFID tags for a signaling device is that it is not necessary (regardless of whether a passive or an active tag is used) at the location of the sensor, i. to ensure a power supply at the location where the RFID tag is located. This opens up a very reasonably priced, universally mountable and electrically neutral possibility of object monitoring.

In contrast to the applications in which the presence of objects is checked by means of (passive) RFID tags, whether a day is still in the range of the reader (eg theft protection in weapon cabinets, picture galleries or jewelery displays) allows the use of the signaling device disclosed here also to detect smallest displacements of two objects against each other. The displacement need only be large enough to operate the switching element.

A particular advantage of the invention is that the switching element can be discontinued from the antenna. The conductors can therefore be made thin, space-saving and inconspicuous. Due to the spatial separation of switching element and RFID chip or antennas, the antennas, preferably together with the RFID chip can be arranged to a place where favorable transmission or reception conditions exist, while the switching element, for example, on a metallic support plate or in a shielded Environment can be arranged. An application example would be the use as monitoring contact of a metallic door or a metallic window frame. Thus, the switching element can be mounted on the metallic window frame or on the door while the antenna can be remotely mounted together with the RFID chip in a location of more favorable radiation conditions.

The signaling device disclosed here opens up a variety of possibilities in the field of building and property security, the control of shut-off valves, faucets or valves, the control of covers for food packages, tanks, containers of industry, the positioning of objects, etc.

Below are some examples of use of the signaling device shown:
To secure the building, the antenna and short-circuit cable can be placed in the immediate vicinity of closed windows and doors. A reader is placed in the room so that all tags can be read while idle. There is a query of all tags in a fixed time interval. If the door or window is opened, there will be an open circuit on the line, which will be transformed into a short circuit on the RFID chip so that the tag can no longer be read. An alarm can now be triggered. This is a cost effective alternative to building security, which manages without the installation of power supplies for the door and window sensors. A reader can check many windows and doors.

As an electronic seal document envelopes can be secured with an RFID tag, so that when opening the switching element preferably permanently open and the antenna is shorted. This can be done, for example, by tearing off a short-circuit line which is used instead of the switching element. Hereby, for example, in police use, apartment doors can be secured with an RFID tag, so that the tag is destroyed when it penetrates and this is reported by a reader in the apartment (preferably with a mobile radio interface). The application of this principle is also possible in the food industry when it comes to determining whether a package (e.g., beverage cartons, bottles) or even a container has already been opened. This provides a higher level of security than with conventional seals, abuse can be reported immediately.

An accurate relative positioning of two objects can be achieved in that an RFID tag can only be read by a reading device when the capacitive switching element is close to the coupling surfaces. In this case, by varying the transmission power of the reading device, the accuracy of the positioning can even be increased. It can also be made accurate adjustments.

By the signaling device objects in displays, museums, etc. can be secured or monitored in a general form. Bicycles can also be stored in bicycle garages or shops. For example, the front wheel short-circuits the connecting line or opens it. Here already a small shift from the rest position can be detected. A pure theft monitoring can also be done by conventional checking if the tag is in the reading area.

For remote maintenance, for example, the proper seating of a lid or cover (e.g., gully) or the opening of an emergency exit may be checked by the function of the tag if the chip is shorted by displacement of the contact over the line. It can be determined whether a faucet, a shut-off valve, a gas cylinder or a slider has been opened. As a result, a particularly simple and cost-effective remote monitoring is possible. A single reader can monitor many valves and store the information e.g. via radio modem to a control center. This method can also be used in electrically critical environments such as chemical plants since the day is passive. By the signaling device can be done with little effort monitoring in explosion-proof areas. Likewise, it can be checked at a gas station by the fuel pump, whether a gas cap was properly closed again after refueling.

Description of the drawings

The invention will now be described by way of example without limitation of the general inventive idea by means of embodiments with reference to the drawings.

1 schematically shows the invention;

2 shows an arrangement with a capacitive switching element.

3 shows a further embodiment of a capacitive switching element.

4 shows an embodiment of a capacitive coupler 3 ,

5 shows a further embodiment of the invention with λ / 2 conductors

6 shows an embodiment with antenna segments, which are connected via the conductor with the RFID chip.

7 shows a variant with capacitive switching element.

8th shows an arrangement with antenna segments, which are connected to each other via a switching element.

9 shows an embodiment according to the preceding figure, but with a capacitive switching element.

10 shows a further variant of the invention with a ground plane.

11 shows an embodiment with a shortening element.

12 shows an embodiment with an extension element.

In 1 the invention is shown schematically. An RFID chip 10 has a first connection 11 and a second connection 12 , With the first connection 11 are a first antenna segment 21 as well as a first leader 31 with a first end 36 connected. Furthermore, with the second connection 12 a second antenna segment 22 and a second conductor 32 with a first end 38 connected. A switching element 40 is with the second end 37 of the first leader 31 and the second end 39 of the first leader 32 connected. The switching element can now connect, that is a short circuit between the second ends 37 . 39 the leader 31 . 32 produce. Preferably, the length of the ladder 31 . 32 each λ / 4, that is a quarter of the line wavelength of the signal, which is transmitted or received by the RFID chip. Will now through the switching element 40 a connection between the second ends 37 . 39 the leader 31 . 32 made this short circuit transforms into an open circuit at the first ends 36 . 38 the leader 31 . 32 , Thus, the RFID chip can transmit and receive electromagnetic energy by means of the antenna segments and communicate with a reading device. Will now through the switching element 40 the connection between the second ends 37 . 39 the leader 31 . 32 interrupted, there arises an idle, which in turn in a short circuit at the first ends 36 . 38 the leader 31 . 32 is transformed. This short circuit short-circuits both the RFID chip and the antenna segments, thus preventing the transmission or reception of electromagnetic energy. The RFID chip is thus deactivated. The antenna segments are shown here by way of example as planar conductors, wherein the conductor width at the RFID chip is narrow and widens with increasing distance. In principle, however, other forms of antenna segments are possible.

In 2 is an embodiment with a capacitive switching element 50 disclosed. This may, for example, have planar capacitive elements, which by moving in the direction 51 be reduced or enlarged in their capacity. Thus, with a large capacity, a closed switching element with a short circuit at the second ends 36 . 38 the leader 31 . 32 be approximated, which in turn to an idle at the first ends 36 . 38 the leader 31 . 32 and thus leads to the RFID chip. By a large distance of the capacitive surfaces, an idle can be approximated, which in turn leads to a short circuit on the RFID chip, so that it is then deactivated.

In 3 a further embodiment of a capacitive switching element is shown, in which two coupling surfaces 52 . 53 through a coupler 54 capacitive coupled with each other. By a movement of this coupler 54 near the coupling surfaces 52 and 53 As a result, the capacitance and thus the impedance increases and generates a short-circuit-like state, while removal of the coupling surfaces results in a low capacitance corresponding to a higher impedance with an open-circuit-like state.

In 4 is an embodiment of a capacitive coupler according to 3 shown in detail. Here is the coupler 54 designed as an electrically conductive plate, which by a movement 51 in the vicinity of the capacitive coupling surfaces 52 and 53 on an insulated support leads to a capacitive coupling of these surfaces.

In 5 another embodiment of the invention with two λ / 4 conductors is disclosed. Here is the connections 11 . 12 of the RFID chip a pair of conductors 31 . 32 connected with a length λ / 4. These conductors have a switching element at the second ends 40 , Furthermore, at the second end of the first conductor 31 and / or at the second end of the second conductor 32 a third leader 34 and / or fourth conductor 35 connected, which continues with a short circuit 33 is completed. The short circuit at the second ends 33 is also transformed via the two λ / 4 conductors into a short circuit at the position of the RFID chip.

Will now through the switching element 40 generates a short circuit at the position λ / 4, so it is transformed into an idle at the location of the RFID chip, whereby the RFID chip is activated.

In 6 an embodiment of the invention is shown, in which the antenna segments 21 . 22 over the ladder 31 . 32 with the connections 11 . 12 of the RFID chip are connected. The length of the conductors here is preferably λ / 2, so that the impedance of the antenna segments to the location of the RFID chip 10 transformed. Furthermore, it is preferable in the middle of the conductor, that is, at the position λ / 4, a switching element 40 arranged. By a short circuit on this switching element, the energy flow between the antenna and RFID chip can now be interrupted.

In 7 a variant with a capacitive switching element according to the previous embodiment is disclosed.

In 8th a further advantageous embodiment of the invention is shown, in each case a first conductor 26 with the first connection 11 of the RFID chip and a second conductor 27 with the second connection 12 the RFID chip is connected. The two conductors are with their second ends with a switching element 40 connected. Here, the two conductors can take over the function of antennas, unless they are connected or short-circuited by the switching element. Thus, by a short circuit of the switching element 40 who is a connection of the two conductors 26 and 27 causes each other, the transmission or the reception of high-frequency energy are prevented, while by opening the connection between the two conductors, the transmission or the reception of high-frequency energy is enabled.

9 shows an embodiment similar to the previous figure, wherein the switching element by a capacitive switching element 50 is replaced.

In the 10 is shown a further variant of the invention. In the previous illustrations of the invention, reference has been made to a symmetrical embodiment with two antenna segments and two conductors. This variant now shows an asymmetrical embodiment. Here is just one antenna segment to a port 11 of the RFID chip 10 connected. Furthermore, there is only one conductor 31 with a first end 36 with the first connection 11 of the RFID chip 10 connected. The second end 37 of the leader 31 is with a switching element 40 connected. Furthermore, the RFID chip with a second connection 12 with a ground plane 28 connected. Also connected to this ground plane is the switching element 40 , The second connection 12 The RFID chip can optionally be a connection pad and / or the substrate and / or another suitable connection point of the RFID chip. The unbalanced arrangement shown here acts in principle the same as the symmetrical arrangements shown above. Therefore, in principle, all the symmetrical arrangements shown here can be realized correspondingly asymmetrically.

In the 11 is an embodiment with a shortening element 41 shown. This can be, for example, an inductive component, preferably a conductor loop. This results in a shorter geometric length of the conductor 31 needed.

In the 12 is a further embodiment with an extension element 42 shown. The reducing element may for example be a capacitive component. This allows the conductor 31 be geometrically extended, for example, to produce a greater distance from the switching element.

LIST OF REFERENCE NUMBERS

10

RFID chip

11, 12

connections

13

Direction of movement of the RFID chip

21, 22

antenna segments

23, 24

coupling pads

26, 27

ladder

28

ground plane

31, 32, 34, 35

ladder

33

short circuit

36, 37

Ends of the first conductor

38, 39

Ends of the second conductor

40

switching element

41

shortening element

42

extension element

50

capacitive switching element

51

movement direction

52, 53

coupling surfaces

54

coupler

60

carrier

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 2005/0242957 A1 [0002]
• US 2011/0156905 Al [0003]
• EP 1732242 A2 [0005]

Claims (12)

Signaling device comprising an RFID chip ( 10 ) with at least one first connection ( 11 ) and a second connection ( 12 ), wherein a first antenna segment ( 21 ) to the first connection ( 11 ) and a second antenna segment ( 22 ) to the second port ( 12 ), characterized in that a first conductor ( 31 ) with a first end ( 36 ) to the first connection ( 11 ) and a second conductor ( 32 ) with a first end ( 38 ) to the second port ( 12 ) is connected, wherein at least one switching element ( 40 . 50 ) with a second end ( 37 ) of the first leader ( 31 ) and a second end ( 39 ) of the second conductor ( 32 ) connected is. Signaling device comprising an RFID chip ( 10 ) with at least one first connection ( 11 ) and a second connection ( 12 ), wherein an antenna segment ( 21 ) to the first connection ( 11 ) and a ground plane ( 28 ) to the second port ( 12 ), characterized in that a first conductor ( 31 ) with a first end ( 36 ) to the first connection ( 11 ) is connected, wherein at least one switching element ( 40 . 50 ) with a second end ( 37 ) of the first leader ( 31 ) and the ground plane ( 28 ) connected is. Signaling device comprising an RFID chip ( 10 ) with at least one first connection ( 11 ) and a second connection ( 12 ), wherein a first antenna segment ( 21 ) to the first connection ( 11 ) and a second antenna segment ( 22 ) to the second port ( 12 ), characterized in that a first conductor ( 31 ) between the first antenna segment ( 21 ) and the first connection ( 11 ) as well as a second conductor ( 32 ) between the second antenna segment ( 23 ) and the second port ( 12 ), wherein at least one switching element ( 40 . 50 ) with the first conductor ( 31 ) and the second conductor ( 32 ) connected is. Signaling device comprising an RFID chip ( 10 ) with at least one first connection ( 11 ) and a second connection ( 12 ), wherein an antenna segment ( 21 ) to the first connection ( 11 ) and a ground plane ( 28 ) to the second port ( 12 ), characterized in that a first conductor ( 31 ) between the first antenna segment ( 21 ) and the first connection ( 11 ), wherein at least one switching element ( 40 . 50 ) with the first conductor ( 31 ) and the ground plane ( 28 ) connected is. Device according to one of the preceding claims, characterized in that the length of the first conductor ( 31 ) and / or second conductor ( 32 ) (2n + 1) × λ / 4, where λ is the line wavelength of the signal transmitted by the RFID chip, and n is an integer positive number. Device according to one of claims 1-4, characterized in that the length of the first conductor ( 31 ) and / or second conductor ( 32 ) n × λ / 2, where λ is the line wavelength of the signal transmitted by the RFID chip and n is an integer positive number. Device according to one of the preceding claims, characterized in that the at least one switching element ( 40 ) is a galvanic contact. Device according to one of the preceding claims, characterized in that the at least one switching element ( 50 ) is a capacitive element. Device according to claim 5, characterized in that at the second end ( 37 ) of the first leader ( 31 ) and / or at the second end ( 39 ) of the second conductor ( 32 ) a third conductor ( 34 ) and / or fourth conductor ( 35 ), which continues to be short-circuited ( 33 ) is completed. Device according to claim 1 or 2, characterized in that the first conductor ( 26 ) is identical to the first antenna segment and / or the second conductor ( 27 ) is identical to the second antenna segment. Device according to one of the preceding claims, characterized in that at least one shortening element ( 41 ) is provided and the geometric length of at least one conductor is shortened compared to an embodiment without shortening element. Device according to one of the preceding claims, characterized in that at least one extension element ( 42 ) is provided and the geometric length of at least one conductor is extended relative to an embodiment without extension element.

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