The invention relates to an RFID transponder.
RFID transponders or RFID labels or RFID tags are used for identifying and/or tracking various objects. The RFID transponders are read at a distance by RFID readers.
However, every now and then arises a problem that the maximum reading distance should be extended.
Viewed from a first aspect, there can be provided an RFID transponder, comprising an antenna, comprising a radiating element or elements, a parasitic radiating element or elements, said radiating element being matched to create a first polarization vector to be excited, said parasitic radiating element being arranged to sweep round the antenna at proximity of the radiating element so that the parasitic element is extending on two to all sides of the radiating element, and the parasitic radiating element being matched to create a second polarization vector to be excited, the second polarization vector being perpendicular to the first polarization vector.
Thereby an RFID transponder that allows for greater read distances in typical UHF RFID systems may be achieved.
The RFID transponder is characterised by an antenna, comprising a radiating element or elements, a parasitic radiating element or elements, said radiating element being matched to create a first polarization vector to be excited, said parasitic radiating element being arranged to sweep round the antenna at proximity of the radiating element so that the parasitic element is extending on two to all sides of the radiating element, and the parasitic radiating element being matched to create a second polarization vector to be excited, the second polarization vector being perpendicular to the first polarization vector. Some other embodiments are characterised by what is stated in the other claims. Inventive embodiments are also disclosed in the specification and drawings of this patent application. The inventive content of the patent application may also be defined in other ways than defined in the following claims. The inventive content may also be formed of several separate inventions, especially if the invention is examined in the light of expressed or implicit subtasks or in view of obtained benefits or benefit groups. Some of the definitions contained in the following claims may then be unnecessary in view of the separate inventive ideas. Features of the different embodiments of the invention may, within the scope of the basic inventive idea, be applied to other embodiments.
Some embodiments illustrating the present disclosure are described in more detail in the attached drawings, in which
In the figures, some embodiments are shown simplified for the sake of clarity. Similar parts are marked with the same reference numbers in the figures.
The RFID transponder 100 is a layered structure that comprises an antenna 1, a radiating element 2 of the antenna and an IC 4.
Layers of the RFID transponder 100 are typically attached together with suitable adhesive layers and sealed by e.g. a silicone liner.
The antenna 1 and the IC 4 (together with further electronic components, if any) may be arranged to a structural module such as an inlay comprising a dielectric substrate.
The polarisation of the dipole signal excited by the antenna 2 has been shown by arrows A in
A problem with the RFID transponder 100 shown in
Layers of the RFID transponder 100 are typically attached together with suitable adhesive layers and sealed by e.g. a silicone liner.
The RFID transponder 100 may further comprise a spacer layer described above.
The antenna 1, the IC 4 and any further electronic components may be arranged to a structural module such as an inlay comprising a dielectric substrate.
The radiating element 2 has been matched to create a first polarization vector to be excited, shown by arrows A in
In addition, the RFID transponder 100 comprises a parasitic radiating element 3. The parasitic radiating element 3 has been matched for creating a second polarization vector, shown by arrows B, to be excited so that the second polarization vector is perpendicular to the first polarization vector A. In other words, the RFID transponder 100 has a dual polarization.
An advantage of the perpendicular polarization vectors A, B is that the link losses may be substantially minimized. As a result, the reading distance of the RFID transponder 100 is increased.
Another advantage is that if linear reader antennas are used, the RFID transponder 100 is readable in both vertical and horizontal orientation toward the reader antenna. Thus the orientation or position of the RFID transponder 100, or of the object labelled with the RFID transponder 100, does not have any significant role for maximum reading distance.
In the embodiment shown in
In the embodiment shown in
In another embodiment, the parasitic radiating element 3 extends round the antenna 1 at proximity of the radiating element 2 on just two sides of the radiating element 2. In still another embodiment, the parasitic radiating element 3 extends around the antenna 1 at proximity of the radiating element 2 on all sides of the radiating element 2.
According to an aspect, the radiating element 2 may have a general outer shape of an ellipsoid, with or without one or more recess(es), and the parasitic radiating element 3 has an inner edge following the general outer shape of the ellipsoid.
According to another aspect, the radiating element 2 has a general outer shape of a circle, with or without one or more recess(es), and the parasitic radiating element 3 has an inner edge following the general outer shape of the circle.
According to still another aspect, the radiating element 2 has a general outer shape of a square, with or without one or more recess(es), and the parasitic radiating element 3 has an inner edge following the general outer shape of the square.
It is to be noted that there may be not only one but two or even more radiating elements 2 in the RFID transponder 100. Also there may be plurality of parasitic radiating elements 3 in the RFID transponder 100. An advantage is that the efficiency of the radiating elements 2, 3 may be enhanced and the reading distance of the RFID transponder thus extended.
The parasitic radiating element 3 may be coupled to the radiating element 2 by a magnetic (inductive) field, by an electric (capacitance) field, or by a electromagnetic (combination of inductive and capacitance) field. The distance between the radiating elements 2, 3 shall be as small as possible in order to ensure a good coupling between the radiating elements 2, 3. According to an aspect, the maximum distance is about 2 mm.
In an embodiment, the radiating element 2 and the parasitic radiating element 3 are arranged on the same plane surface in the RFID transponder 100. In another embodiment, said elements 2, 3 are arranged on different plane surfaces. For instance, the parasitic element 3 may be arranged on a plane on top of the radiating element 2, or alternatively, on a plane below the radiating element.
In
The parasitic radiating element 3 has an outer edge that follows at least two inner edges of said opening 7, i.e. the inner edge of the radiating element 2.
As shown by the diagram of
Additionally it was measured an RFID transponder comprising a parasitic radiating element 3 that extends on two sides of the radiating element 2, as shown in
Thus one can conclude that RFID transponders according to the invention may be read by a linear polarized reader antenna even the polarization vector of the reader antenna is in angle of 90° compared to the polarization vector of the RFID antenna.
When comparing the diagrams of
Thus an advantage is that RFID transponders according to the invention may be read by a circular polarized reader antenna more far than prior art RFID transponders.
In
The upmost diagram of
The middle diagram of
The lowest diagram of
One can conclude that the performance of RFID transponders according to the invention is immune or at least substantially more immune to the surface material as known RFID transponders. Thus the RFID transponder according to the invention works well on both metal and plastic surfaces. Additionally, the readability of the transponder may be improved when read by a linear polarized reader antenna, because the transponder may receive energy through the parasitic radiating element 3 even if the (main) radiating element 2 is cross-polarizated with respect to the electromagnetic wave of the reader antenna.
The invention is not limited solely to the embodiments described above, but instead many variations are possible within the scope of the inventive concept defined by the claims below. Within the scope of the inventive concept the attributes of different embodiments and applications can be used in conjunction with or replace the attributes of another embodiment or application.
The drawings and the related description are only intended to illustrate the idea of the invention. The invention may vary in detail within the scope of the inventive idea defined in the following claims.
1 antenna
2 radiating element
3 parasitic radiating element
4 IC
6
a-c parasitic subarea
7 opening
8 reader antenna
100 RFID transponder
A 1st polarization vector
B 2nd polarization vector
This application is the National Stage of International Application No. PCT/FI2017/050788, filed Nov. 16, 2017, the contents of which is incorporated by reference herein.
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/FI2017/050788 | 11/16/2017 | WO | 00 |