1. Field of the Invention
The present invention relates to a RFID tag, particularly to an RFID tag, which is an RFID tag working in a UHF frequency band, and which can solve the conventional tag-reading problem occurring when an RFID tag is attached to a metallic or liquid object.
2. Description of the Related Art
The radio frequency identification (RFID for abbreviation thereinafter) system is a technology using a radio frequency to automatically identify objects and acquire related data. RFID technology was developed to replace the traditional barcode. RFID technology can uniquely label each of the objects, can read data from and write data into the RFID tags of the objects, and can instantly acquire related information of the objects. In addition to fabrication, logistics, warehousing, and retailing, RFID technology also widely applies to daily living activities, such as security, convenience stores, libraries, public transit, parking tolling, electronic freeway tolling, and medical service. RFID technology is still expanding its application field to bring people safer and easier living.
An RFID system comprises a reader/writer, tags, and an application software. The reader/writer sends out an electromagnetic wave or a magnetic field. The tag receives the electromagnetic wave or magnetic field and converts it into electric power to drive the chip inside the tag. The chip sends a wireless signal containing the identification code to the reader/writer. The reader/writer decodes the wireless signal and sends the decoded signal to the rear-end application software. RFID technology is characterized in the automatic and non-contact identification process, wherein the data exchange between the tag and the reader/writer is realized wirelessly.
According to the frequency bands where RFID systems work, RFID systems may be categorized into the low-frequency type (135 KHz), the high-frequency type (13.56 MHz), the ultra-high-frequency (UHF) type (860-96 OMHz) and the microwave type (2.45 GHz). Table 1 shows the frequency ranges and transmission methods of RFID systems.
The frequency bands of 135 KHz and 13.56 MHz are most frequently used by RFID systems. However, the RFID systems using the abovementioned frequency bands are disadvantaged by a limited transmission distance between the tag and the reader/writer. Extending the frequency band to the UHF or microwave range is a logical approach to achieve a longer transmission distance and a higher transmission rate. For example, an RFID system using a UHF frequency band (860-960 MHz) can have a transmission distance of over 5 m and a transmission rate of over 40 packets per second.
An RFID tag does not transmit information unless its antenna receives the electromagnetic wave sent out by a reader/writer. An RFID signal is likely to retarded by metallic material or interfered with by noise. The induced current in a metallic material will attenuate the electromagnetic field, shorten the read distance, or even interrupt the communication between the tag and the reader/writer. Thus is reduced the identification capability and correctness of an RFID system. The higher the frequency of an electromagnetic wave, the greater the influence of metals. However, metallic materials are often used in electric appliances and food packages, which RFID systems are usually applied to. Besides, water is also an important factor affecting the sensitivity of an RFID system. Water is likely to reduce the receiving capability of an RFID system. The higher the frequency of an electromagnetic wave, the more the electromagnetic energy absorbed by water.
The antenna of RFID systems is intrinsically apt to be influenced by the environment. The common solution is to vary the design of antenna or adopt an active RFID tag. However, both the abovementioned solutions raise the fabrication cost. Some manufacturers, such as TDK, DIADO, NITTA, EMERSON & CUMING, improve electromagnetic wave absorber materials to solve the influences of metallic or liquid factors. Most of the electromagnetic wave absorber materials only function for the electromagnetic wave below 13.56 MHz. For the influence in the UHF frequency, the solution of some manufacturers is redesigning the antenna, such as the UHF antenna of Mitsubishi, Toppan, and Fujitsu.
For example, a U.S. patent of U.S. Pat. No. 7,205,898 adopts an electromagnetic wave absorption approach to improve the read distance of an RFID system. The prior art adopts a multi-layer electromagnetic wave absorber material emphasizing the magnetic permeability and dielectric permittivity thereof, wherein a first layer contacting the RFID tag adopts a titanium dioxide material, and a second layer adopts a magnetic powder consisting of iron carbonyl, nickel zinc ferrite and magnet and having a magnetic permeability of 1.5-1.7 and a dielectric permittivity of 1.5-32.
At present, most of the RFID systems are still hard to apply to a metallic object or a container containing a water-based liquid. Few of the products can do it, but they overcome the problem via redesigning the antenna or adopting a thicker electromagnetic wave absorber material, which increases the cost. Therefore, the present invention proposes an effective and low-cost electromagnetic wave absorber material to overcome the problem of RFID technology.
The primary objective of the present invention is to provide a UHF RFID tag, wherein a foamed layer and a magnetic layer are arranged in between a tag and a metallic/non-metallic layer and function as an electromagnetic wave absorber material to prevent from environmental interference on the reader/writer.
Another objective of the present invention is to provide a UHF RFID tag, which is an RFID tag working in a UHF frequency band, and which can solve the conventional tag-reading problem occurring when an RFID tag is attached to a metallic or liquid object.
The present invention proposes a UHF RFID tag, which comprises: a tag, a foamed layer, and a magnetic layer. The foamed layer is a foamed polymeric material having a density of 10-100 kg/m3 and a permittivity of 1-1.5. The foamed layer may be a single-layer structure, a multi-layer structure, or a single-layer structure having a gradient density. The foamed layer contacts the tag.
The magnetic layer may be a single-layer structure, a multi-layer structure, or a single-layer structure having a gradient density of magnetic powder. The magnetic layer contacts another side of the foamed layer. The magnetic layer has a magnetic permeability of 2-10. The magnetic layer consists of a magnetic powder and a rubber/plastic material, wherein the magnetic powder has a weight percent of 65-95%, and the rubber/plastic material has a weight percent of 5-35%. The magnetic powder has a thickness of 0.1-3 mm, and the particles of the magnetic layer have a shape of a platelet, a lens or a spheroid.
When a metallic or non-metallic layer interferes with the signal of an RFID tag, the foamed layer and magnetic layer of the present invention can make the RFID reader has a longer read distance.
Below, the embodiments are described in detail in cooperation with the attached drawings to make easily understood the objectives, technical contents, characteristics and accomplishments of the present invention.
The present invention proposes a UHF RFID tag, which is an RFID tag working in a UHF frequency band, and which can solve the conventional tag-reading problem occurring when an RFID tag is attached to a metallic or liquid object. Refer to
Refer to
In this embodiment, the foamed layer 20 is made of a foamed polymeric material having a density of 10-100 kg/m3 and a permittivity of 1-1.5. The polymeric material is selected from the group consisting of a foamed PE/EVA (Polyethylene/Ethylene Vinyl Acetate) board, a foamed CR/EPDM/NBR (Chloroprene Rubber/Ethylene Propylene Diene Monomer/Nitrile Butadiene Rubber) board, a foamed PS (Polystyrene) board, a foamed rubberplastic board, a foamed conductive board, and a foamed anti-electrostatic board. The polymeric material may also be a combination of the abovementioned materials.
In this embodiment, the magnetic layer 24 consists of a magnetic powder and a rubber/plastic material. The magnetic layer 24 has a magnetic permeability of 2-10. The magnetic powder has a weight percent of 65-95%, and the rubber/plastic material has a weight percent of 5-35%. The magnetic layer is made of an iron powder, a cobalt powder, a nickel powder or a powder of an alloy containing the abovementioned metals. The magnetic powder has a thickness of 0.1-3 mm. In the present invention, the particles of the magnetic powder have a shape of a platelet, a lens or a spheroid. In this embodiment, the particles of the magnetic powder have a shape of a platelet. The platelet particles of the magnetic powder have a diameter of 5-35 μm and a thickness of 0.05-0.25 μm. In the present invention, each of the abovementioned foamed layer and magnetic layer has at least one layer. In the abovementioned embodiment, the foamed layer and magnetic layer are both single-layer structures. In the present invention, both the foamed layer and magnetic layer may be multi-layer structures. In other words, the foamed layer 20 has several foamed layers, and the magnetic layer 24 has several magnetic layers.
Refer to
In this embodiment, both the first foamed layer 32 and the second foamed layer 34 are made of a foamed polymeric material. The first foamed layer 32 has a permittivity of 1-1.1 or 1-1.2, and the second foamed layer 34 has a permittivity of 1-1.5. The first foamed layer 32 has a density of 10-50 kg/m3, and the second foamed layer 34 has a density of 50-100 kg/m3. The polymeric material is selected from the group consisting of a foamed PE/EVA (Polyethylene/Ethylene Vinyl Acetate) board, a foamed CR/EPDM/NBR (Chloroprene Rubber/Ethylene Propylene Diene Monomer/Nitrile Butadiene Rubber) board, a foamed PS (Polystyrene) board, a foamed rubberplastic board, a foamed conductive board, and a foamed anti-electrostatic board. The polymeric material may also be a combination of the abovementioned materials.
In this embodiment, the magnetic layer 24 consists of a magnetic powder and a rubber/plastic material. The magnetic layer 24 has a magnetic permeability of 2-10. The magnetic powder has a weight percent of 65-95%, and the rubber/plastic material has a weight percent of 5-35%. The magnetic powder is made of an iron powder, a cobalt powder, a nickel powder or a powder of an alloy containing the abovementioned metals. The magnetic layer has a thickness of 0.1-3 mm. In the present invention, the particles of the magnetic powder have a shape of a platelet, a lens or a spheroid. In this embodiment, the particles of the magnetic powder have a shape of a platelet. The platelet particles of the magnetic powder have a diameter of 5-35 μm and a thickness of 0.05-0.25 μm.
Refer to
In this embodiment, the UHF RFID tag 12 of the present invention comprises: a tag 18, a first foamed layer 32, a second foamed layer 34, a first magnetic layer 36 and a second magnetic layer 38. The first foamed layer 32 and the second foamed layer 34 are arranged in between the tag 18 and the magnetic layer 24. The first foamed layer 32 and the second foamed layer 34 are joined together with a glue 26. The first magnetic layer 36 and the second magnetic layer 38 are also joined together with the glue 26. The tag 18 is joined to the first foamed layer 32 with a double-sided adhesive tape 22. The second foamed layer 34 is joined to the first magnetic layer 36 with the glue 26. The second magnetic layer 38 is joined to a metallic/non-metallic layer 28 with the double-sided adhesive tape 22.
In this embodiment, both the first foamed layer 32 and the second foamed layer 34 are made of a foamed polymeric material. The first foamed layer 32 has a permittivity of 1-1.1 or 1-1.2, and the second foamed layer 34 has a permittivity of 1-1.5. The first foamed layer 32 has a density of 10-50 kg/m3, and the second foamed layer 34 has a density of 50-100 kg/m3. The polymeric material is selected from the group consisting of a foamed PE/EVA (Polyethylene/Ethylene Vinyl Acetate) board, a foamed CR/EPDM/NBR (Chloroprene Rubber/Ethylene Propylene Diene Monomer/Nitrile Butadiene Rubber) board, a foamed PS (Polystyrene) board, a foamed rubberplastic board, a foamed conductive board, and a foamed anti-electrostatic board. The polymeric material may also be a combination of the abovementioned materials.
In this embodiment, each of the first magnetic layer 36 and the second magnetic layer 38 consists of a magnetic powder and a rubber/plastic material. The first magnetic layer 36 has a magnetic permeability of 2-5, and the second magnetic layer 38 has a magnetic permeability of 6-10. The magnetic powder has a weight percent of 65-95%, and the rubber/plastic material has a weight percent of 5-35%. The magnetic powder is made of an iron powder, a cobalt powder, a nickel powder or a powder of an alloy containing the abovementioned metals. The magnetic layer has a thickness of 0.1-3 mm. In the present invention, the particles of the magnetic powder have a shape of a platelet, a lens or a spheroid. In this embodiment, the particles of the magnetic powder have a shape of a platelet. The platelet particles of the magnetic powder have a diameter of 5-35 μm and a thickness of 0.05-0.25 μm.
In a still further embodiment, the foamed layer 20 has a gradient density. In other words, the density varies from low to high. The low-density side of the foamed layer 20 is joined to the tag 18, and the high-density side is joined to the magnetic layer 24. Similarly, the magnetic layer 24 may also have a gradient magnetic powder density. In other words, the density of the magnetic powder varies from low to high. The low-density side of the magnetic layer 24 is joined to the foamed layer 20, and the high-density side is joined to the metallic/non-metallic layer 28.
Refer to
The embodiments described above are only to exemplify the present invention but not to limit the scope of the present invention. Therefore, any equivalent modification or variation according to the shapes, structures, characteristics and spirit of the present invention is to be also included within the scope of the present invention.
Number | Date | Country | Kind |
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097118246 | May 2008 | TW | national |
097120241 | May 2008 | TW | national |