HF RFID Antenna Magnetic Coupling Stabilization
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Solution Overview
Problem
In communication systems, particularly in HF-bands like 13.56 MHz-band RFID, physical contact failures due to assembly issues and positional variations lead to antenna characteristic variations and interference with surrounding components.
Innovation Solution
An antenna device with a conductor member and a feed element featuring a first coil magnetically coupled to a second coil, integrated with terminal electrodes and a capacitor, forming a resonance circuit, which reduces magnetic coupling influence from external components and stabilizes antenna characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If physical contact connection is used between RFID IC chip and antenna, then electrical connection can be established, but contact failure occurs due to friction or positional deviation
Solution Approach 1:
The patent replaces the mechanical contact connection system with a magnetic coupling system. The RFID IC chip and antenna are electrically connected through magnetic coupling between coils, eliminating physical contact portions. This substitution of mechanical connection with magnetic field coupling resolves the contradiction by providing reliable electrical connection without friction or contact wear, while eliminating sensitivity to positional deviations.
2Reliability
If magnetic coupling is used to establish electrical connection, then physical contact failure is avoided, but coupling degree varies due to coil position variation
Solution Approach 1:
The patent applies parameter changes by introducing a magnetic shielding plate with specific magnetic permeability between the coils and surrounding components. This changes the magnetic field distribution parameters, concentrating magnetic flux between the coils and reducing the effect of positional variations. The shielding plate's magnetic properties are selected to optimize coupling stability, thereby resolving the contradiction between avoiding contact failure and maintaining stable coupling degree.
3Ease of operation
If magnetic coupling is used, then electrical connection is established without physical contact, but stray capacitance varies with coil position causing antenna characteristic variation
Solution Approach 1:
The patent introduces a magnetic shielding plate as an intermediary component between the coils and surrounding components. This shielding plate mediates the magnetic field interaction, preventing direct coupling between the coils and surrounding components that would cause variable stray capacitance. By positioning the shielding plate strategically, the patent stabilizes the magnetic field path and eliminates the harmful effect of position-dependent stray capacitance, thus maintaining stable antenna characteristics while preserving the ease of magnetic coupling assembly.
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 solution significantly reduces antenna characteristic variations and interference by maintaining consistent magnetic coupling within an insulating stacked body, enhancing radiation efficiency and flexibility in layout without requiring additional components for stray field reduction.
Implementation Method 1
a first coil connected to a feed circuit, a second coil magnetically coupled to the first coil
Implementation Method 2
the conductor member, the capacitor, the first coil constitute a resonance circuit. a capacitance of the capacitor and an inductance of the first coil are determined such that a resonance frequency of the resonance circuit is a communication frequency or close to the communication frequency
Data Source
AI summary
An antenna device includes a conductor surface in which an opening having an open edge portion in communication with the outside is provided, a feed element including a first coil connected to the feed element and a second coil magnetically coupled to the first coil, a first mounting portion disposed in the open edge portion and connected to a first end of the second coil, and a second mounting portion disposed in the open edge portion in a state isolated from the first mounting portion and connected to a second end of the second coil. The first mounting portion and the conductor surface are directly or indirectly conducted to each other, and the second mounting portion and the conductor surface are directly or indirectly conducted to each other. A loop is defined around the opening through the first mounting portion, the second mounting portion, and the second coil.