Microwave tolerant RFID tag
By designing conductor arrays and fluid pressure-controlled antenna structures in RFID tags, the damage caused by microwave radiation is solved, and the functionality and safety in a microwave environment is achieved, suitable for reuse and recycling.
Patent Information
- Application Number
- CN202311852870.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-29
- Publication Date
- 2025-07-01
AI Technical Summary
Existing RFID tags are prone to damage in microwave ovens, cannot withstand repeated microwave radiation, pose a risk of explosive evaporation or chip explosion, and lose functionality during reuse or recycling.
An RFID tag is designed in which the conductor array is encapsulated by an insulating material envelope, the conductors are spaced apart and electrically contacted by the environmental pressure of the outer wall, and the fluid pressure in the antenna chamber can separate the conductors to isolate the electrical contact and reduce microwave energy absorption.
Effectively reduces the damage to RFID tags by microwave energy, ensures that it remains functional in the microwave environment, avoids the risk of explosive evaporation or chip explosion, and is suitable for reuse and recycling.
Smart Images
Figure CN120235178A_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to a radio frequency identification (RFID) tag capable of withstanding microwave radiation. Background Art
[0002] RFID tags generally include an integrated circuit chip having a memory for storing information and an antenna for wireless communication, and the integrated circuit chip is encapsulated together in an envelope. RFID tags are used to provide identification information in response to a radio frequency interrogation signal, and the radio frequency interrogation signal can also provide power to operate passive RFID tags. RFID tags attached to food or its packaging have a wide and expanding application in aspects such as ensuring food safety, tracking in the supply chain, contactless payment, and packaging recycling. In these applications, RFID tags can be exposed to microwaves. In a specific application - namely, a microwave oven equipped with an internal RFID tag reader that controls the microwave oven based on data read from the RFID tag, such microwave exposure is inevitable.
[0003] The disadvantage is that if an old RFID tag is irradiated in a microwave oven, the old RFID tag is prone to damage. In some cases, an old RFID tag can withstand microwaves in a microwave oven for about five minutes and still have satisfactory performance, although repeated exposure can cause cumulative damage sufficient to render the RFID tag inoperative. For applications where food packaging is reusable or should be identified during recycling, the RFID tag should allow repeated microwave exposure while maintaining functionality. On the other hand, even for single-use scenarios, it is important to reduce the likelihood of dangerous failures caused by microwave energy absorption, which can also occur, for example, due to explosive evaporation of the metal constituting the antenna or explosion of the chip. Therefore, there is a need to develop an RFID tag that is more resistant to microwave radiation. The object of the present invention is to address this need, or more generally, to provide an improved RFID tag. Summary of the Invention
[0004] According to a first aspect of the present disclosure, there is provided an RFID tag, comprising:
[0005] an RFID chip;
[0006] a plurality of first conductors spaced apart from each other in a first array having the shape of at least a portion of the antenna;
[0007] a plurality of second conductors spaced apart from each other in a second array having the shape of at least a portion of the antenna;
[0008] An envelope containing an insulating material, the envelope containing the RFID chip, the plurality of first conductors, and the plurality of second conductors, the envelope comprising: a first inner surface, an outer wall of flexible material disposed outside the first inner surface, a communication channel, and a fluid reservoir for containing a fluid;
[0009] Wherein, the outer wall substantially covers the first inner surface and has a second inner surface disposed opposite to the first inner surface, such that the first inner surface and the second inner surface define an antenna chamber;
[0010] The communication channel extends between the fluid reservoir and the antenna chamber to effect fluid communication therebetween;
[0011] Wherein, the plurality of first conductors are fixed on the first inner surface, and the plurality of second conductors are fixed on the second inner surface,
[0012] The outer wall is pushed inward by ambient pressure to press the plurality of second conductors into electrical contact with the plurality of first conductors and thereby form at least a portion of the antenna;
[0013] The fluid pressure in the antenna chamber tends to move the outer wall outward, such that the plurality of second conductors are separated from the plurality of first conductors.
[0014] Preferably, the first inner surface and the second inner surface are planar, and the plurality of first conductors and the plurality of second conductors are flat members having respective planar attachment surfaces fixed to the respective first inner surface and the second inner surface, wherein the planar adjacent surfaces are opposite to the planar attachment surfaces. Preferably, the flat members are substantially rectangular.
[0015] The shape of each of the first and second arrays may be linear or arcuate, or a combination of substantially planar shapes including linear and arcuate lengths, including triangular, square, spiral, figure-eight, or zigzag.
[0016] Preferably, the spacing between adjacent conductors of one of the first conductors and the second conductors is arranged to be opposite to the corresponding opposite conductor of the other of the first conductors and the second conductors, such that the opposite conductors span a corresponding interval in the spacing. Alternatively, at least one pair of opposite conductors may span two or more spaces.
[0017] Preferably, the fluid is a gas and the ambient pressure provides the main force by which the outer wall is pushed inward, and the gas pressure in the fluid reservoir is lower than the ambient pressure. Preferably, the outer wall has a degree of elasticity such that it makes a smaller contribution to the force pushing the outer wall inward.
[0018] Preferably, the first conductor and the second conductor comprise metal, and the gas substantially does not include components that oxidize the metal or otherwise chemically react with the metal. For example, when the gas includes nitrogen or carbon dioxide, low-cost metals such as copper and aluminum can be used for the conductors.
[0019] Preferably, at least a portion of the antenna includes two arms of substantially equal length forming the poles of a dipole, wherein the first conductor and the second conductor are pressed together to form the two arms, the two arms are arranged end-to-end, and the RFID chip is connected between the two arms and supported on an adjacent pair of conductors of one of the first conductor and the second conductor.
[0020] Preferably, the antenna chamber is elongate, and the pair of conductors is disposed at a position close to the center, and the center position is substantially equidistant from the longitudinal opposite ends of the antenna chamber.
[0021] Preferably, the pair of conductors is disposed near a center position that is substantially equidistant from the periphery of the outer wall.
[0022] Preferably, the envelope includes a laminate, the laminate includes an outer sheet having a recess formed therein and an inner sheet through which the communication channel extends, wherein the recess and the inner sheet define the fluid reservoir, and the inner sheet and the outer sheet are laminated together.
[0023] Preferably, the inner wall and the outer wall include a film of a first polymer.
[0024] Preferably, the inner sheet and the outer sheet include a second polymer having a stiffness greater than that of the first polymer.
[0025] Accordingly, the present invention provides an RFID tag that is effective and efficient in operational use and has an overall simple design that minimizes manufacturing costs. Advantageously, it has been found that dividing the antenna into spaced-apart conductors in this way reduces the absorption of microwave energy that causes RFID tag failure, which is believed to be achieved by limiting the amount of charge that can accumulate on the surface of the conductors compared to the amount of charge that may accumulate along the length of a conventional antenna. BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Embodiments of the present disclosure will be described hereinafter by way of example with reference to the drawings.
[0027] Figure 1 is a schematic top view of an RFID tag according to a preferred embodiment of the present disclosure.
[0028] Figure 2 and 3 is along Figure 1Schematic cross-sectional views of line XX, showing the RFID tag in the working state and the non-working state, respectively. Detailed implementation
[0029] Reference Figure 1 and 2 , the RFID tag 10 includes an RFID chip 11 and an antenna 12, which are encapsulated together in an envelope 13 made of insulating material. The antenna 12 can be in a linear form, and the envelope 13 can have a generally rectangular prism shape elongated in the longitudinal direction of the antenna 12. In an embodiment, the RFID tag 10 can be an active RFID tag including an internal power source such as a battery (not shown).
[0030] The antenna 12 is a component of a first conductor 14a-d and a second conductor 15a-d. The first conductor 14a-d and the second conductor 15a-d can be flat metal sheets with substantially the same thickness. In a first array 16 having a linear shape of the antenna 12, the first conductors 14a-d are generally coplanar and spaced apart from each other. In a second array 17 having a linear shape of the antenna 12, the second conductors 15a-d are generally coplanar and spaced apart from each other. Therefore, the antenna 12 is an elongated component formed by maintaining electrical contact between the first conductor 14a-d and the second conductor 15a-d. In the preferred laminated structure shown, the replaceable antenna should adopt a planar shape, such as formed by connected coplanar straight lines and arcs. The present invention is not limited to the linear antenna shown.
[0031] As Figure 3 shown, the first conductors 14a-d can be fixed on the planar first inner surface 19 of the envelope 13, and the second conductors 15a-d are fixed on the planar second inner surface 20 disposed opposite to the first inner surface 19, such that the first and second inner surfaces 19, 20 define an antenna chamber 21. The second inner surface 20 is located on an outer wall 22 disposed outside the first inner surface 19, Figure 3 showing an outwardly displaced outer wall 22, which expands the antenna chamber 21 (in a schematically represented manner) and separates the first conductor and the second conductors 14a-d, 15a-d, thereby placing the RFID tag in the non-working state. The chip 11 can be located at a central position substantially equidistant from the longitudinal opposite ends 23, 24 of the antenna chamber 21, or at a position such that it is substantially equidistant from the periphery 18 of the outer wall 22.
[0032] The envelope 13 can be a laminated structure, which includes two polymer laminates: a laminate material 26 including an outer wall 22 bonded to an inner wall 27, and a block 25 including an inner sheet 28 bonded to an outer sheet 29, which are respectively in Figure 2 and 3It is separately arranged as shown by the dashed line. Block 25 and the laminated structure 26 are also laminated together and joined at the planar interface 35. At the interface 35, as well as at other interfaces within block 25 and the laminated structure 26, an adhesive layer, such as a coating or a separate adhesive sheet, can be provided for joining these layers, which is not shown in the drawings. The inner wall 22 and the outer wall 27 can be films of relatively flexible polymers such as polyester, while the inner sheet 28 and the outer sheet 29 can be formed of relatively hard polymers such as polypropylene.
[0033] Block 25 includes a fluid reservoir 30. The fluid reservoir 30 can be made by a recess formed in the outer sheet 29. The outer sheet 29 is generally enclosed by the inner sheet 28. Thus, the fluid reservoir 30 can have a planar inner surface formed by the inner sheet 28. The recess can be in the form of a substantially rectangular prism and is manufactured by molding the outer sheet 29.
[0034] At least one connecting channel 31 extends laterally through the inner sheet 28 and the inner wall 27 and through the interface 35 to connect the fluid reservoir 30 to the antenna chamber 21. The bonding between the layers 22, 27, 28, 29 of the envelope 13 is airtight. A gas such as nitrogen fills the fluid reservoir 30, the antenna chamber 21, and the connecting channel 31 and is at a pressure below atmospheric pressure. To achieve this, the lamination process can be carried out in an environment containing a negative-pressure gas, including bonding the outer sheet 29 to the inner sheet 28 and bonding the block 25 to the laminated structure 26. The peripheral edges of the inner wall 22 and the outer wall 27 are joined together to form the antenna chamber 21. Thus, in the normal operating state as shown in Figure 2 the outer wall 22 is pushed inward by the ambient pressure to press the second conductors 15a-d into electrical contact with the first conductors 14a-d, thereby forming the antenna 13.
[0035] It should be understood that the drawings are schematic. For example, the first conductors and the second conductors 14a-d, 15a-d are relatively thin, with a thickness of approximately micron level, while the inner wall 22 and the outer wall 27 can have a thickness of approximately dozens of microns. Therefore, in Figure 2 the normal operating state as shown, only a very small volume of gas exists in the antenna chamber 21. In a two-stage manufacturing process, first, a layer of conductor film is deposited on the inner wall 22 and the outer wall 27, and then the first conductors and the second conductors 14a-d, 15a-d can be manufactured by chemical etching. The first conductors and the second conductors 14a-d, 15a-d can be manufactured by chemical etching and then deposited on the inner wall and the outer wall 22, 27 and fixed in place by adhesive bonding. Block 25 can be relatively thick, such as the outer layer 29 is about 2 mm thick and the inner layer 28 is about 1 mm thick. In this way, block 25, which is also composed of rigid materials, provides stability and the main structure of the envelope 13.
[0036] The first and second conductors 14a-d, 15a-d may have a generally rectangular profile and be arranged in two arrays such that the spaces in one array are spanned by the conductors in the other array. For example, a space 32 is provided between adjacent first conductors 14a and 14b. The space 32 is spanned by the second conductor 15b. In the operating state, the opposite ends of the second conductor 15b are pressed into electrical contact with the first conductors 14a and 14b.
[0037] The antenna 12 includes two arms 33, 34 of substantially equal length. The arm 33 includes the first conductors 14a and 14b in contact with each other and the second conductors 15a and 15b in contact with each other. The arm 34 includes the first conductors 14c and 14d in contact with each other and the second conductors 15c and 15d in contact with each other. Thus, the two arms 33, 34 form a dipole, and they are coaxial and arranged end-to-end, with the RFID chip 11 connected therebetween. The RFID chip 11 is supported on two adjacent first conductors 14b, 14c and is connected to the two adjacent first conductors 14b, 14c by flip-chip bonding using anisotropic conductive adhesive.
[0038] When the RFID tag 10 is irradiated with microwaves in its normal operating state, the current induced in the antenna 12 can be dissipated as heat, which tends to be absorbed by the gas in the antenna chamber 21, causing the gas to expand. The increased internal pressure causes the antenna chamber 21 to expand, preferably deflecting the relatively flexible outer wall 22 outward and drawing gas from the reservoir 30 into the antenna chamber 21. When the outer wall 22 undergoes maximum deflection near its center, the relatively low gas pressure is sufficient to initially move the second conductors 15b and 15c out of electrical contact with the first conductors 14b and 14c, respectively, thereby electrically and thermally isolating the chip 11 from the antenna 12. The relatively high gas pressure in the antenna chamber 21 tends to further move the outer wall 22 outward, thereby separating all the second conductors 15a-d from all the first conductors 14a-d. In the case where all the second conductors 15a-d are separated from all the first conductors 14a-d, substantially less microwave energy is absorbed by the RFID tag 10. Additionally, when the gas temperature in the antenna chamber 21 sufficiently drops, the ambient pressure acts to push the outer wall 22 inward, restoring the electrical contact between the conductors and thus restoring the normal operation of the antenna 12 and the RFID tag 10.
[0039] The foregoing has described the aspects of the present disclosure only by way of example, and it should be understood that modifications and additions can be made thereto without departing from its scope.
Claims
1. An RFID tag, characterized in that, Comprising: An RFID chip; A plurality of first conductors spaced apart from each other in a first array having the shape of at least a portion of an antenna; A plurality of second conductors spaced apart from each other in a second array having the shape of at least a portion of the antenna; An envelope containing an insulating material, the envelope containing the RFID chip, the plurality of first conductors, and the plurality of second conductors; the envelope includes: a first inner surface, an outer wall of flexible material disposed outside the first inner surface, a communication channel, and a fluid reservoir for containing a fluid; Wherein the outer wall substantially covers the first inner surface and has a second inner surface disposed opposite the first inner surface, such that the first inner surface and the second inner surface define an antenna chamber; The communication channel extends between the fluid reservoir and the antenna chamber to effect fluid communication therebetween; and Wherein the plurality of first conductors are fixed to the first inner surface, and the plurality of second conductors are fixed to the second inner surface, The outer wall is pushed inward by ambient pressure to press the plurality of second conductors into electrical contact with the plurality of first conductors and thereby form at least a portion of the antenna, The fluid pressure in the antenna chamber tends to move the outer wall outward, such that the plurality of second conductors are separated from the plurality of first conductors.
2. The RFID tag according to claim 1, characterized in that, Wherein, The first inner surface and the second inner surface are planar, and the plurality of first conductors and the plurality of second conductors are flat members having planar attachment surfaces fixed to corresponding ones of the first inner surface and the second inner surface; wherein, the planar adjacent surfaces are opposite the planar attachment surfaces.
3. The RFID tag according to claim 1, characterized in that, Wherein, The spacing between adjacent conductors of one of the first conductor and the second conductor is set to be opposite a corresponding relative conductor of the other of the first conductor and the second conductor, such that the relative conductors span a corresponding gap in the spacing.
4. The RFID tag according to any one of claims 1 to 3, characterized in that, Wherein, The fluid is a gas and the ambient pressure provides a major force by which the outer wall is pushed inward, and the gas pressure in the fluid reservoir is lower than the ambient pressure.
5. The RFID tag according to any one of claims 1 to 3, characterized in that, Wherein, The first conductor and the second conductor include a metal, and the gas substantially does not include components that oxidize the metal or otherwise chemically react with the metal.
6. The RFID tag according to any one of claims 1 to 3, characterized in that, Wherein, At least a portion of the antenna includes two arms of substantially equal length forming the poles of a dipole; wherein, the first conductor and the second conductor are pressed together to form the two arms, the two arms are arranged end-to-end, and the RFID chip is connected between the two arms and supported on an adjacent pair of conductors of one of the first conductor and the second conductor.
7. The RFID tag according to claim 6, characterized in that, Wherein, The antenna chamber is elongated, and the pair of conductors is disposed at a position close to the center; the center position is substantially equidistant from the longitudinal opposite ends of the antenna chamber.
8. The RFID tag according to claim 6, characterized in that, Wherein, The pair of conductors is disposed near a center position that is substantially equidistant from the periphery of the outer wall.
9. The RFID tag according to any one of claims 1 to 3, characterized in that, Wherein, The envelope includes a laminate, the laminate including an outer sheet having a recess formed therein and an inner sheet through which the communication channel extends; wherein the recess and the inner sheet define the fluid reservoir, and the inner sheet and the outer sheet are laminated together.
10. The RFID tag according to claim 9, wherein, Wherein, The inner wall and the outer wall include a film of a first polymer.
11. The RFID tag according to claim 10, characterized in that, Wherein, The inner sheet and the outer sheet include a second polymer having a stiffness greater than that of the first polymer.