RFID Tag Coil Transformer Layout for Tire Rubber Interference
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Solution Overview
Problem
RFID tags embedded in rubber products, such as tires, face issues with communication performance degradation due to the presence of carbon black, which affects impedance and permittivity, and are prone to damage from tire expansion and contraction.
Innovation Solution
An RFID tag design featuring a substrate with a pattern coil, housed in a housing, and a coil wound around it, with a coupling transformer configuration that sets low impedance at the primary side and high impedance at the secondary side, allowing for stable attachment to rubber products and maintaining communication sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the RFID tag uses a conventional antenna design embedded directly in rubber product, then the tag can be integrated into the tire structure, but the communication performance degrades due to carbon black affecting impedance and permittivity
Solution Approach 1:
The patent introduces a coupling transformer as an intermediary component between the antenna and the RFID chip. The transformer isolates the antenna from the harmful effects of carbon black in the rubber material, allowing the antenna to maintain its electrical characteristics while still being embedded in the tire. The transformer acts as a buffer that prevents impedance degradation caused by carbon black interference.
Solution Approach 2:
The patent modifies the electrical parameters of the antenna system by using a coupling transformer with specific turns ratios to transform impedance values. This allows the antenna impedance to be matched to the RFID chip input impedance despite the presence of carbon black, thereby maintaining communication performance through parameter transformation rather than direct connection.
2Reliability
If the RFID tag is embedded in tire rubber, then the tag remains attached to the tire, but the tag is damaged due to tire expansion and contraction
Solution Approach 1:
The patent employs flexible printed circuit board (FPC) technology for the antenna substrate, allowing the antenna structure to flex and deform with the tire without breaking. The FPC can withstand the expansion and contraction cycles of the tire while maintaining electrical connectivity, thus preserving both attachment stability and tag durability.
3Reliability
If the coil extension lengths are made equal, then the antenna structure is symmetric and simple to manufacture, but the communication sensitivity decreases
Solution Approach 1:
The patent deliberately creates an asymmetric antenna structure where the first coil extension length differs from the second coil extension length. This asymmetry is optimized to improve communication sensitivity by creating a more effective electromagnetic radiation pattern. The asymmetric design is compensated for in the manufacturing process, making it achievable without excessive complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The RFID tag maintains excellent communication characteristics and durability even when attached to rubber products, despite the presence of carbon black, by utilizing a coupling transformer to stabilize the positional relationship and reduce the impact of tire deformation.
Implementation Method 1
a coupling transformer configuration that sets low impedance at the primary side and high impedance at the secondary side
Implementation Method 2
the coil and the pattern coil constitute a coupling transformer
Data Source
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AI summary
To provide a coil that has satisfactory characteristics even when the coil is used by being attached to or embedded in a tire, the coil forming an RFID tag in combination with a substrate on which an RF chip and a pattern coil connected to the RF chip are mounted. A coil 30 is held in a housing 75 accommodating a substrate 90 and is wound around the substrate 90. A first end of the coil 30 extends from the substrate 90 and forms a first element 50 of an antenna. A second end of the coil 30 extends from the substrate 90 and forms a second element 60 of the antenna. The first element 50 and the second element 60 are arranged in parallel to each other, and the first element 50 has a longer extension length than the second element 60. The coil 30 and a pattern coil 40 form a coupling transformer 20. The number of windings in the coil 30 is smaller than the number of windings in the pattern coil 40.