WO2012074378A1

WO2012074378A1 - Rfid transponder

Info

Publication number: WO2012074378A1
Application number: PCT/NL2011/000079
Authority: WO
Inventors: Jan Saeys
Original assignee: Ique Rfid Technologies B.V.
Priority date: 2010-12-01
Filing date: 2011-11-30
Publication date: 2012-06-07
Also published as: NL1038416C2

Abstract

Transponder, for a ear tag for example, comprising a transponder chip (6) and a thereto connected planar antenna configuration that is arranged onto a disc-shaped support layer (7), which antenna configuration comprises one or two elongated end capacities (9) which are directly or indirectly connected to the transponder chip and which have a course that is substantially coaxial with, or at least substantially similar to, the outer shape of the disk-shaped support layer and/or substantially follow the outer shape of the disk-shaped support layer. Meandering shortening coils (10) and a impedance matching circuit (11) are provided in the connections between the transponder chip and the end capacities (9). The transponder carrier wave frequency is preferably between 0.5 and 1.5 GHz. The disc-shaped support preferably has a diameter of about 25 mm.

Description

Title: RFID Transponder DESCRIPTION The invention relates to a transponder, comprising a transponder chip and an antenna configuration connected thereto. Such a transponder can be part of or connected to an identification device, for example being shaped as an ear tag, in particular for animals. However, many alternative applications are conceivable, such as for example an identification device for dustbins, for implementing waste collection using "diftar". Diftar stands for differentiated tariffs wherein the amount of waste collected per household is recorded. The more waste is disposed by a citizen the higher the waste disposal tax will be. Conversely, improved sorting and less disposing waste results in a reduced disposal tax. Hereinafter in particular will be aimed at the implementation of the transponder as part of an ear tag, a first embodiment for which the transponder is developed.

An ear tag is a label that can be attached to one or both ears of an animal. Ear tags are used to identify inter alia cows, goats, sheep, etc. Ear tags can be provided with visually perceptible features. Ear tags can also be provided with RFID tags or transponders wherein such features are stored. Such (information) features can be readout by RFID readers. The stored information typically comprises of an Animal Identification Number that is assigned to the animal. The Animal Identification Number can be used, among others, to keep track of the life cycle (including slaughter data) of the animal. For example, geographical data of the animal can be tracked and stored. Also, other relevant information about the animal such as vaccination, disease, etc. can be recorded. For example, the information can be stored in a central database.

Such ear tags provided with a transponder are generally known. For example such a transponder is known from NL1008540, where an electronic ear tag for identifying animals is disclosed having a housing and a transponder incorporated in the housing. Information about the animal is stored within the transponder, which data can be readout by means of an electromagnetic field. The known transponders posses large dimensions and are not suitable for UHF carrier wave frequencies. For that reason, still widely use is made of small ear tags, which are only visually readable. Such ear tags consist for example of two disc-shaped elements of which one element is provided with a sharp "piercing" element, which is pressed through the ear of the animal shortly after its birth, and subsequently is pressed into the second disc-shaped element positioned on the other side of the ear. The two elements are snapped together by means of a protrusion provided upon the piercing element.

The present invention aims to provide an ear tag, or an identification device for another application, that is small, but nevertheless is provided with a transponder, in particular a UHF transponder. Such ear tags have, among others, the following requirements:

- The ear tag must be small because, for example, two day old piglets already have them inserted into the ear;

- The ear tag must be able to withstand the temperature of the furnace in the slaughterhouse, where the hairs are burned-off after slaughter, making insertion of new ear tags in the slaughterhouse no longer necessary;

- The antenna of the transponder must be provided with a large sensitivity, omni-directional and polarization-independent, ensuring a large and reliable reading range and simultaneous reading-out of different ear tags irrespective of the direction and polarization of the radio signal used for readout, and mainly irrespective of the orientation (attitude) of the transponder (antenna) with regard to the direction of that radio signal;

- The antenna must be suitable for UHF, in other words for carrier wave frequencies in the range of 300 MHz - approximately 3 GHz;

- The antenna must be shaped in such a way that there is room for an opening for the piercing element.

From WO2010/063287-A (BR TECHNIK) a transponder is known suitable for use as an ear tag, comprising a communication chip and a planar antenna configuration connected thereto, the antenna configuration being arranged upon a disk-shaped support layer provided with a central opening. The proposed antenna configuration is very simple and is mainly formed by a planar ring, which acts as a dipole, which ring is interrupted by an air gap. The communications chip is soldered at a suitable location onto the planar antenna ring having both connections on either sides of the air gap. The antenna is very robust, due to its great simplicity although, however, the transmission properties are rather mediocre. Also from WO2006/045162-A (VAN WIJK) a transponder is known suitable for use as an ear tag, comprising a communication chip and connected thereto an antenna configuration, which is not planar, but is provided with an (non-planar) antenna coil. In compliance with these and other requirements and in achieving the objectives, the invention provides for a transponder, in particular but not exclusively, for an ear tag or identification device,

comprising a transponder chip and a thereto connected planar antenna configuration that is arranged onto a disc-shaped support layer, which antenna configuration comprises one or two elongated end capacities, which are directly or indirectly connected to the transponder chip and which have a course that is substantially coaxial with, or at least substantially similar to, the outer shape of the disk-shaped support layer and/or substantially follow the outer shape of the disk-shaped support layer. In this patent application by the term end capacities of the antenna configuration is meant: electrical conductors of a dipole antenna where with, using a receiver, signals are received (irradiated) or where with, using a transmitter, signals are emitted (radiated).

Due to the curved shape of the end capacities, which follow the curved shape of the disc-shaped support layer, is achieved that the transponder is disc-shaped and thereby can be provided with a compact shape, resulting in an increased wearing comfort and extended applicability. Moreover the antenna obtains an omni-directional and polarization-independent sensitivity by the circular end capacities, resulting in a large and reliable reading range and in being able to readout the ear tags to a large extend independent of the direction and polarization of the radio signal and to a large extend independent of the orientation (attitude) of the transponder (antenna) with regard to the direction of the radio signal.

Preferably the width of the end capacities is substantially constant on at least a substantial portion of their operational length.

To reduce the diameter of the disc-shaped antenna preferably the shortening coils are provided in the connections between the transponder chip and the end capacities. Preferably the shortening coils are meander-shaped comprising one or more back-and- forth sections having a course that is substantially coaxial with, or at least substantially similar to, the outer shape of the disc-shaped support layer. In this way the shortening coils can be in the right way provided onto the available disk area. The width of the shortening coils preferably is substantially constant on at least the greater part of their operational length.

With regard to the antenna quality, the best results are achieved when the shortening coils are always with one outer end connected to one outer end of the end capacity.

Preferably an (also) planar impedance matching circuit is included in the connection between the transponder chip and the end capacities, the impedance matching circuit is arranged as an matching transformer to adjust the characteristic impedance of the transponder chip to that of the antenna configuration and vice versa.

Preferably the disc-shaped support layer comprises a substantially coaxial opening for a piercing element. The dimensions of respectively the antenna configuration and the impedance matching circuit are preferably chosen such that the transponder is suitable for a transponder carrier wave frequency between 0.5 and 1.5 GHz, preferably between 700 MHz and 1 GHz, more particularly between 800 and 900 MHz. The substantially disc-shaped support has a diameter between 20 and 30 mm, preferably of about 25 mm.

It is noted that from US2007/0200782-A (OMROM) a transponder is known having a planar antenna configuration, which comprises two end capacities that are connected to the transponder chip by means of meandering shortening coils and an impedance matching circuit, essentially identical to the antenna configuration of the invention. Due to the elongated, rectangular shape of the support layer and the corresponding shape of the end capacities (radiating parts) this antenna does not possess an antenna sensitivity that is nearly equal for all directions (omni-directional sensitivity). Nor has the antenna a uniform sensitivity to radio signals having different polarization directions. Moreover the transponder of US2007/0200782 is not compact and robust and therefore not suitable for use with smaller animals. In contrast, the invention provides for a transponder that is compact and animal friendly due to its curved circular shape, and that has a more extensive application area than the well-known transponder from US2007/0200782 and also has a higher sensitivity than the known disk-shaped transponder from WO2010/063287. These advantages are obtained by applying an improved antenna configuration, provided with end capacities, (preferably) shortening coils and an impedance matching circuit which, due to the (in practice preferred) design of the transponder being adapted to the disk shape, is compact and robust, but also appears to be very insensitive for differences in the direction of the radio signals to be received and for differences in the polarization of the radio signals to be received.

Hereinafter the invention will be further discussed by means of some embodiments, with reference to a few figures.

Figures la and lb show two embodiments of an ear tag with a transponder as shown in Figure 2;

Figure 2 shows a preferred embodiment of a transponder that is suitable for an ear tag as shown in Figure la or lb;

Figuur 3 shows the electrical equivalent-circuit diagram of the transponder shown in Figure 2.

Figures la and lb both show an ear tag with fastening means to attach the ear tag to an ear. In both figures the ear tag comprises a first disc-shaped element 1 and a second disc-shaped element 2, wherein the first element 1 is provided with a piercing element 3 that is intended for pressing through the ear. On the other side of the ear the piercing element is received and locked into the second element 2, thereby attaching the ear tag inextricably (inseparably) into the ear. In the first element 1 (Figure la) or the second element 2 (Figure lb) a RFID transponder configuration is incorporated, symbolically represented by a RF wave front 4. The components 1, 2 and 3, for example, are manufactured by means of injection moulding of a suitable thermoplastic. During the injection moulding process, the first element 1 (Figure la) or the second element 2 (Figure lb) can be provided with the transponder, including a chip and an antenna configuration. Such a transponder can be supplied to the injection moulding process in the form of an, for example, (substantially disk-shaped) support foil, whereupon the chip and the (planar) antenna configuration have previously been fitted by means of an appropriate process.

Figure 2 shows a preferred embodiment of a transponder 5 suitable for an ear tag as shown in Figure la or lb, in particular for incorporation in or attachment to the discshaped elements 1 and 2. The transponder 5 comprises a transponder chip 6 and an antenna configuration connected thereto, wherein the antenna configuration on its outside is limited by a substantially circular outer boundary. The transponder is mounted onto a disc-shaped support foil 7 comprising a lead-through hole 8 for conducting through the piercing element 3 or a (not shown) piercing tool by means of which the ear tag is applied. The antenna configuration comprises a dipole having at both ends an end capacity 9, which are largely responsible for the electrical sensitivity of the antenna and therefore possess a relatively large surface. The end capacities 9 have a shape, which essentially follows the outer boundary of the antenna configuration. In the shown embodiment, the outer edges of the end capacities 9 in fact form the outer boundaries of the antenna configuration.

The antenna configuration further comprises two shortening coils 10, positioned between the transponder chip 6 and (always on one end of) the end capacities 9. Each shortening coil 10 has a meandering shape, including back-and-forth sections that essentially have a circular course, essentially around the centre point of the circular outer boundary of the antenna configuration and/or essentially around (the centre) of the central opening 8. The transponder chip 6 and the antenna configuration are interconnected by means of an impedance matching circuit 11. The purpose is twofold. Firstly the impedance matching circuit 11 is arranged as a compensation coil (with an inductive reactance obviously) to compensate for the (in fact undesirable) capacitive reactance of the transponder chip in order to increase the antenna efficiency. Furthermore, the impedance matching circuit 11 is arranged as a matching transformer for adjusting the characteristic capacitance of the transponder chip (for example 35 Ω) to those of the antenna configuration (for example 50 Ω) and vice versa. That impedance matching is the result of the selection of terminals 12 where the antenna is connected to the impedance matching circuit 11. This will be shown more clearly from the equivalent- circuit diagram as shown in Figure 3. The impedance matching circuit 11 is planar, as well as the entire antenna configuration.

The dimensions and design of the antenna configuration as shown in Figure 2 are such that the transponder is suitable for receiving and (encrypted with the corresponding, in the transponder programmed digital ID code of the animal concerned) sending back (carrier wave) signals between 0, 5 and 1.5 GHz, preferably between 700 MHz and 1 GHz, more particularly between 800 and 900 MHz. The respectively substantially circular outer boundary and the substantially disc-shaped support are provided with a diameter between 20 and 30 mm, preferably about 25 mm.

Finally, Figure 3 shows the electrical equivalent-circuit diagram of the transponder shown in Figure 2. The antenna shown is particularly suited as a ViA-dipole antenna. In this figure can be seen that the end capacities 9 and the shortening coils 10 are connected to the impedance matching circuit 11 by means of terminals 12. As already mentioned the impedance matching circuit 11 serves as compensation for the (imaginary) capacitive reactance of the transponder chip 6. Moreover, an impedance transformation is accomplished by means of connecting the antenna to the terminals 12, while the transponder chip is connected to points 13, wherein the circuit 11 partly acts as an autotransformer achieving an impedance transformation of (for example) 35 Ω to 50 Ω and vice versa. With respect to the shown ViA-term in figure 3 it is further noted that this is a denomination of the (half) electrical wavelength, which is about 300 mm at a frequency of about 1 GHz. By using the shortening coils 10 and end capacities 9, the geometric distance of the antenna configuration, as shown in Figure 2, is about 10- fold reduced, so that the outer diameter of the antenna configuration has a value between about 20 and 30 mm.

Claims

1. Transponder, comprising a transponder chip (6) and a thereto connected planar antenna configuration that is arranged onto a disc-shaped support layer (7), which antenna configuration comprises one or two elongated end capacities (9) which are directly or indirectly connected to the transponder chip and which have a course that is substantially coaxial with, or at least substantially similar to, the outer shape of the disk-shaped support layer and/or substantially follow the outer shape of the disk-shaped support layer.

2. Transponder according to claim 1, wherein the width of the end capacities (9) is substantially constant on at least a substantial portion of their operational length.

3. Transponder according to any one of the preceding claims, wherein shortening coils (10) are provided in the connections between the transponder chip and the end capacities (9).

4. Transponder according to claim 3, wherein the shortening coils (10) are meander-shaped comprising one or more back-and-forth sections having a course that is substantially coaxial with, or at least substantially similar to, the outer shape of the disc-shaped support layer.

5. Transponder according to any one of the preceding claims 3 - 4, wherein the width of the shortening coils (10) is substantially constant on at least the greater part of their operational length.

6. Transponder according to any one of the preceding claims 3 - 5, wherein the shortening coils (10) are always with one outer end connected to one outer end of the end capacity (9).

7. Transponder according to any one of the preceding claims, wherein a planar impedance matching circuit ( 11) is included in the connection between the transponder chip (6) and the end capacities (9).

8. Transponder according to claim 7, wherein the impedance matching circuit (11) is arranged as an matching transformer to adjust the characteristic impedance of the transponder chip (6) to that of the antenna configuration and vice versa.

9. Transponder according to any one of the preceding claims, wherein the discshaped support layer (7) comprises a substantially coaxial opening (8).

10. Transponder according to any one of the preceding claims, arranged for a transponder carrier wave frequency between 0.5 and 1.5 GHz, preferably between 700 MHz and 1 GHz, more particularly between 800 and 900 MHz.

11. Transponder according to any one of the preceding claims, wherein the substantially disc-shaped support has a diameter between 20 and 30 mm, preferably of about 25 mm.

12. Identification device, comprising a transponder according to any one of the preceding claims.

13. Identification device according to claim 12, arranged as ear tag, in particular for animals.