The present invention relates to an RFID transponder, which includes a case, a radiator, and a ground element, as opposed antenna elements, a ground plane intended to be set against the base at a distance from the radiator, and an electrical chip component, and in which the ground plane is on the first plane and the radiator is on the second plane, at a distance from the first plane, and in which the chip component is connected to the radiator and the ground element, and further in which the said radiator, ground element, and chip component are installed on a special foil. The invention also relates to a blank for the transponder. Here, the term RFID transponder refers mainly to a UHF-range passive transponder equipped with an RFID chip, but other applications too may be considered. Such RFID transponders operate using so-called backscatter technology. In this connection, reference is also made to so-called micro-strip antennae.
A passive RFID transponder is a small device comprising an antenna, microcircuit, and memory, which uses backscattering to transmit the contents of its memory when it receives a transmission command from a reading device and the reading device illuminates it with a radio signal. A passive transponder has no battery, but instead draws its operating power from the radio signal transmitted to it by the reader. The transmission of power and information between the transponder and the reader can take place with the aid of a magnetic field, an electric field, or a radiating radio signal. Active transponders have a battery and somewhat simpler operation, as power transmission is not needed.
Patent application publication US2004/0005754 A1 discloses one ‘smart label’ construction and a method for manufacturing it. Though the example in the publication concerns an inductively connecting RFID transponder, the same type of construction can also be applied to transponders operating at a radio frequency, which latter have a substantially greater range than the former. In the publication, polycarbonate, polyolefin, polyester, polyethylene terephthalate (PET), polyvinylchloride (PVC), and acrylonitrile/butadiene-styrene copolymer are presented as materials of the base web.
A challenge in RFID transponders operating in the UHF range is to make them operate reliably even on conductive surfaces. This is because the electrical properties of the antenna also depend on the properties of the installation surface. The effect of the base can be reduced sufficiently by equipping the transponder with a separate conductive shielding plane, above which the antenna is raised slightly. Another possibility is to use so-called PIFA (Planar Inverted F-antenna) antennae, in which the ground element of the antenna is formed of a sufficiently large surface area below the radiator. The totality is then less sensitive to the properties of the base and the transponder can generally be made to function on a conductive surface.
The manufacture of an PIFA antenna is difficult and expensive, particularly relating to the vias, due to the complexity of the construction. VTT (the Technical Research Centre of Finland) has published a basic solution (WO 2006/120287A1) for a so-called PAFFA antenna, which is intended to solve the problems relating to PIFA antennae. According to the abstract of the publication, a special folding technique in the antenna base is used to replace the vias of a PIFA antenna.
The present invention is intended to create a mechanical solution for reliably supporting the structures of an RFID transponder. The characteristic features of the transponder according to the invention are stated in the accompanying Claims 1. A blank for the transponder according to the invention is presented in Claim 9.
The invention can be applied to both RFID transponders equipped with a separate ground plane, and to transponders equipped with a newer PAFFA-type antenna structure. In one embodiment, the folded foil is supported on a special spacer piece, which keeps the planes of the foil at a distance to each other. In a second embodiment of the invention, the foil is supported directly on the side walls of the case. The solution applies generally to an antenna structure for a two-terminal antenna connection. A PAFFA antenna structure comprises a ground plane on the first surface, at least one transmission line on the second surface, connected to the ground plane through a fold in the edge of the antenna structure, in which case the fold acts as the primary source of the magnetic field, an insulator layer arranged between the first and second surface, and an electronic component, in which there is a two-terminal antenna, connected to the antenna structure. According to the solution, the electronic component is attached to the second surface of the antenna structure and connected from one of the antenna terminals to the transmission line and from the other terminal to either a second transmission line or to the fold.
Other embodiments and benefits of the invention are described hereinafter, in connection with examples of applications, which are shown in the accompanying drawings, in which
a-1c show the construction and assembly of one RFID transponder according to the invention,
a and 2b show a second assembly of the RFID transponder, and
a-3c show a blank for an RFID transponder, manufactured using the injection moulding technique, and its assembly.
In the embodiment of
In the foil 20, there is a first part 20b, a fold 20a, and a second part 20c. When the foil 20 is folded on top of the frame 18 according to
In this case, the foil 20, together with its insulation, folded to its final form, forms an RFID transponder with advantageous electrical properties. The length of the radiator is approximately λ/4 (ε=1, i.e. the air gap). At the example of a frequency of 867 MHz, the vertical-angle length from the free end of the radiator 12 to the middle of the transmission line 19 is 66 mm in the example according to the figure, in which the gap between the planes is 4 mm. It should be noted that the chip 16 is attached to the ground element 14 over a considerably shorted conductor length than λ/4. In this electrical application, the chip 16 is attached to the edge of the radiator at a point that corresponds to the impedance of the chip. In this relation, the location of the chip does not greatly affect the resonance frequency. According to
The assembly of
According to
In the above, air is used between the planes. It is also possible to use a circuit-board material, or preferably plastic, which acts at the same time as the body of the transponder, as an intermediate substrate.
Number | Date | Country | Kind |
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20065279 | Apr 2006 | FI | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/FI2007/050218 | 4/24/2007 | WO | 00 | 10/9/2008 |