UHF RFID Inlay Antenna Pattern for Permittivity-Stable Matching
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Solution Overview
Problem
RFID inlays experience a decrease in communication distance when attached to attachment targets with varying relative permittivity due to mismatched antenna and IC impedances, particularly when affixed to materials with higher permittivity, leading to wavelength shortening effects.
Innovation Solution
An antenna pattern for UHF-band RFID inlays comprising a first element with a loop portion and emission portion, and a second element operating as a dipole antenna through electromagnetic coupling, with different half wavelengths to maintain communication performance across a wide range of relative permittivities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an antenna pattern is designed for a specific relative permittivity material, then the antenna impedance matches the IC impedance for that material, but the communication distance decreases when affixed to materials with higher relative permittivity due to wavelength shortening effects
Solution Approach 1:
The antenna pattern is divided into multiple independent dipole elements (first element with loop and emission portion, second element) that operate at different resonance frequencies. Each element is designed to compensate for wavelength shortening effects caused by different attachment target permittivities, allowing the antenna to maintain effective communication across various materials.
Solution Approach 2:
The patent employs elements with different half-wavelength dimensions (first length for the emission portion, second length for the second element) to create multiple resonance frequencies. This parameter variation enables the antenna system to adapt to wavelength shortening effects caused by different relative permittivity materials, maintaining impedance matching and communication distance across diverse attachment targets.
2Ease of operation
If the RFID inlay is attached close to the attachment target to be inconspicuous, then the aesthetic requirement is met, but the communication distance becomes lower than designed due to interaction with the attachment target material
Solution Approach 1:
By segmenting the antenna into multiple dipole elements with different resonance characteristics, the system can maintain effective communication distance even when positioned close to the attachment target. The diverse resonance frequencies ensure that at least some elements remain effective despite the proximity to materials with varying permittivity.
Solution Approach 2:
The use of elements with different half-wavelength parameters creates a frequency diversity that compensates for the adverse effects of close proximity to attachment targets. This parameter variation ensures that communication performance is maintained even when the RFID inlay must be positioned inconspicuously close to the target surface.
3Device complexity
If a single dipole antenna is used, then the antenna structure is simple, but the resonance frequency shifts out of the UHF band when attached to materials with higher relative permittivity
Solution Approach 1:
The antenna is segmented into multiple dipole elements (first element comprising loop portion and emission portion, second element) that operate at different resonance frequencies. This segmentation allows the system to maintain at least one resonant frequency within the UHF band across various attachment target materials, improving frequency stability.
Solution Approach 2:
The antenna system functions as a composite structure with multiple elements having different electrical characteristics. The combination of elements with different half-wavelengths creates a system where the overall response remains within the UHF band even when individual element frequencies shift due to attachment target permittivity variations.
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 antenna pattern ensures consistent communication performance by shifting resonance frequencies to maintain operation within the UHF band regardless of the attachment target's permittivity, suppressing decreases in communication distance.
Implementation Method 1
the second element operating as a dipole antenna by electromagnetic coupling with the first element to emit a radio wave whose half wavelength is a second length
Data Source
AI summary
An aspect of the present invention is an antenna pattern used in a UHF-band RFID inlay. The antenna pattern includes a first element and a second element. The first element is formed to include a loop portion and an emission portion. The loop portion includes a pair of electric power supply portions. The emission portion is connected to the loop portion, and extends line-symmetrically from the loop portion. The emission portion operates as a dipole antenna to emit a radio wave whose half wavelength is a first length. The second element is formed apart from the first element. The second element operates as a dipole antenna by electromagnetic coupling with the first element to emit a radio wave whose half wavelength is a second length. The second length is different from the first length.