Double-Loop RFID Antenna for Compact Mounting Area
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Solution Overview
Problem
Passive-type RFID tags face challenges in downsizing their antennas while maintaining effective communication distance due to reduced radiation efficiency when the antenna length becomes shorter than the wavelength corresponding to the desired frequency, limiting their applicability in various fields that require either short or extended communication ranges.
Innovation Solution
A double-loop antenna configuration is introduced, where a first loop and a second loop are connected in parallel with IC chip connection parts, and separated by a slit, with both loops having lengths equal to or shorter than one-third of the wavelength corresponding to the desired frequency, functioning as inductors to enhance radiation efficiency and antenna gain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the antenna is downsized to fit small target objects, then the mounting area is reduced, but the radiation efficiency decreases and communicable distance is shortened
Solution Approach 1:
The antenna is divided into multiple loops (first loop and second loop) that are connected in parallel. Each loop has a length equal to or shorter than one-third of the wavelength, allowing the antenna to maintain a compact size while improving radiation efficiency through the combined effect of multiple resonant structures.
Solution Approach 2:
The first loop and second loop are arranged in a nested configuration where the first loop is positioned inside the second loop, and both share common connection points at their ends. This nested structure allows both loops to occupy minimal space while maintaining their individual electromagnetic characteristics.
2Length of moving object
If the antenna length is shortened below one wavelength, then the antenna size is reduced, but the radiation efficiency and communicable distance are compromised
Solution Approach 1:
Instead of using a single long antenna element, the invention segments the antenna into multiple shorter loops, each with length ≤ λ/3. The parallel connection of these loops creates multiple current paths that collectively enhance radiation efficiency despite each individual loop being electrically short.
Solution Approach 2:
Multiple loop antennas are merged by connecting them in parallel at their terminal points. This merging allows the combined structure to achieve better radiation characteristics than a single loop of equivalent total length, as the parallel configuration increases the effective aperture and current distribution.
3Reliability
If multiple loop antennas with different resonant frequencies are connected in parallel, then the VSWR characteristic is improved within the needed bandwidth, but the device complexity increases
Solution Approach 1:
Rather than using completely different loop configurations for bandwidth extension, the invention uses identical or similar loop structures (both loops have length ≤ λ/3) connected in parallel. This approach maintains local uniformity in the antenna design while achieving the desired frequency response characteristics through the parallel combination.
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 extends the communicable distance by approximately 25% while maintaining a compact size, suitable for applications requiring either short or extended ranges, and ensures compatibility with suppressed transmission outputs, such as in environments like hospitals.
Implementation Method 1
both loops having lengths equal to or shorter than one-third of the wavelength corresponding to a desired frequency, functioning as inductors to enhance radiation efficiency and antenna gain
Data Source
AI summary
An antenna includes a first loop, a second loop which encloses an outer side of the first loop and is separated from the first loop by a slit and both end of which are merged with both ends of the first loop, and IC chip connection parts provided in a portion where the first loop and the second loop are merged, wherein a loop length of the first loop and a loop length of the second loop are equal to or shorter than one third of a wavelength corresponding to a desired frequency resonant with an IC chip connected to the IC chip connection parts.