Segmented Shield for Wearable RFID Antenna Stability
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Solution Overview
Problem
Wearable communication devices face performance variability due to changes in skin permittivity and conductivity, leading to inconsistent read ranges and resonance shifts when in close proximity to the human body.
Innovation Solution
A shielded antenna design featuring a spiral antenna with a segmented shield comprising electrically isolated conductive segments, which reduces the impact of skin permittivity and conductivity variations by minimizing resonant frequency shifts and maintaining reliable performance across different hydration conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a continuous shield is used on the antenna, then electromagnetic shielding effectiveness is improved, but the resonant frequency shifts significantly and quality factor decreases
Solution Approach 1:
The continuous shield is divided into multiple electrically isolated conductive segments separated by gaps. This segmentation allows the shield to maintain electromagnetic shielding effectiveness while reducing the impact on resonant frequency stability and quality factor, as the gaps prevent excessive loading on the antenna resonance.
Solution Approach 2:
Different regions of the antenna are shielded with varying segment densities and gap sizes optimized for local electromagnetic interference protection while maintaining overall resonant frequency stability. The shield structure is tailored locally to balance shielding effectiveness with minimal impact on antenna performance.
2Ease of operation
If the antenna is placed next to the human body for wearable applications, then portability and usability are improved, but performance variability increases due to skin permittivity and conductivity changes
Solution Approach 1:
The segmented shield structure reduces sensitivity to variations in skin permittivity and conductivity by minimizing resonant frequency shifts, thereby maintaining consistent communication performance when the antenna is worn on the human body.
Solution Approach 2:
The shield parameters (segment dimensions, gap sizes, spacing) are optimized to minimize the impact of nearby dielectric materials such as human skin, maintaining stable resonant frequency and quality factor across varying physiological conditions.
3Object-affected harmful factors
If shield segments are placed close together for better shielding, then electromagnetic shielding effectiveness is improved, but quality factor reduction increases
Solution Approach 1:
The shield is segmented with optimized gap sizes and segment spacing that balance electromagnetic shielding effectiveness with minimal quality factor reduction. The segmentation creates a trade-off curve where sufficient shielding is achieved while limiting energy losses.
Solution Approach 2:
The electrical parameters of the shield segments (conductivity, dimensions, spacing) are optimized to achieve the desired shielding effectiveness while minimizing the reduction in antenna quality factor, balancing shielding performance with energy efficiency.
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 shielded antenna maintains consistent performance and reduces resonant frequency shifts by less than 5% when placed adjacent to the human body, ensuring reliable near-field communication regardless of skin moisture or perspiration levels.
Implementation Method 1
The shield reduces a free-space quality factor of the antenna by less than about 40% at the resonant frequency
Implementation Method 2
the resonant frequency of the RFID tag shifts by less than about 5%
Implementation Method 3
at least one pair of adjacent conductive segments defines an electrically insulative gap therebetween
Data Source
AI summary
A shielded antenna (100) includes a spiral antenna (110) and a shield (120) disposed on the spiral antenna. The spiral antenna comprises a plurality of substantially concentric loops. The shield comprises a plurality of electrically isolated electrically conductive segments forming a regular pattern, such that in a top plan view, at least one segment overlaps a portion of at least two loops, and at least one pair of adjacent conductive segments defines an electrically insulative gap therebetween.