Booster Antenna Structure for Compact RFID Gain and Bandwidth
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Solution Overview
Problem
Existing RFID tags face challenges in reducing antenna size without compromising antenna gain or frequency range, as smaller antennas tend to deteriorate in performance.
Innovation Solution
The antenna device incorporates a booster antenna with a radiation plate, ground plate, and short wall, featuring cut-out portions to increase current path length, allowing radio waves from the antenna element and booster antenna to be superimposed, thereby enhancing antenna gain while reducing size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the antenna size is reduced, then the RFID tag size is reduced, but the antenna gain deteriorates
Solution Approach 1:
The first antenna element is placed inside the booster antenna structure, creating a nested configuration where a smaller antenna is embedded within a larger radiating structure. This allows the compact first antenna element to benefit from the enhanced radiation properties of the surrounding booster antenna, achieving both size reduction and maintained gain.
Solution Approach 2:
The booster antenna utilizes the thickness direction (z-direction) to create its radiating structure, with the radiation plate and ground plate separated in the thickness direction. This three-dimensional configuration allows the antenna to achieve improved radiation characteristics without increasing the planar area, thus reducing overall antenna footprint while maintaining or improving gain.
2Volume of moving object
If the antenna size is reduced, then the RFID tag size is reduced, but the frequency range deteriorates
Solution Approach 1:
The nested configuration of the first antenna element within the booster antenna creates a composite structure that combines the resonant properties of both elements. This nested arrangement enables the antenna system to support multiple resonant frequencies, thereby expanding the operational frequency range while keeping the overall antenna size compact.
Solution Approach 2:
By utilizing the thickness direction for the booster antenna structure, the design achieves broadband characteristics through the distributed capacitance and inductance created by the separated radiation plate and ground plate. This three-dimensional configuration extends the frequency range without requiring a larger planar area.
3Power
If cut-out portions are added to increase current path length, then antenna gain is enhanced, but device complexity increases
Solution Approach 1:
The radiation plate is segmented by introducing cut-out portions that divide the continuous conductive path into multiple sections. This segmentation increases the effective current path length within the same physical area, thereby enhancing antenna gain without requiring a proportionally larger structure. The segmented design also allows for easier fabrication using standard PCB techniques.
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
This configuration enables a reduction in antenna size while maintaining or improving antenna characteristics, including increased gain over a wide frequency range and stability against material or size changes.
Implementation Method 1
a radiation plate 21 that radiates radio waves
Implementation Method 2
a short wall 23 that short-circuits the radiation plate 21 and the ground plate 22
Implementation Method 3
causing radio waves radiated from the antenna element 10 and radio waves radiated from the booster antenna 20 to be superimposed to increase an antenna gain
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
An antenna device according to the present invention includes a first antenna element, and a second antenna element including a ground plate, a radiation plate provided facing the ground plate, and a short-circuit plate provided on sides of the ground plate and the radiation plate, the radiation plate being configured to radiate radio waves, the short-circuit plate configured to short-circuit the radiation plate and the ground plate. The first antenna element is provided between the ground plate and the radiation plate, and the radiation plate receives radio waves emitted from the first antenna element and radiates the radio waves.