Antenna Layout Near Housing Opening for Low-SAR Wireless Links
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Solution Overview
Problem
Wireless communication apparatuses, such as digital radiography devices, face challenges in maintaining a low Specific Absorption Rate (SAR) value while preventing a reduction in radiant quantity of radio waves due to metallic housing and conductive components near the antenna, which can increase the risk of local heating and cataract formation when high-power electromagnetic waves are absorbed by the human body.
Innovation Solution
The design incorporates a dipole or inverted-F antenna configuration with a coaxial cable as an electric supply unit, where the first regions of the antenna elements are positioned closer to the fixing member and the second regions are closer to the opening, allowing electromagnetic waves to radiate outward, thereby reducing the SAR value and maintaining radio wave intensity by minimizing coupling with the conductive fixing member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If electric power supplied to the antenna is increased to compensate for reduced radiant quantity, then the radiant quantity of radio waves at communication frequency is improved, but the SAR value becomes greater than the limit
Solution Approach 1:
A non-conductive member is introduced as an intermediary between the antenna and the conductive fixing member. This intermediary prevents direct electromagnetic coupling between the antenna and the conductive structure, reducing the harmful interaction that causes both radiant quantity reduction and SAR increase, while allowing the antenna to operate at safe power levels
Solution Approach 2:
The harmful conductive fixing member is extracted or removed from the immediate vicinity of the antenna. By eliminating the conductive structure that causes electromagnetic coupling and energy loss, the antenna can radiate effectively at lower power levels without exceeding SAR limits
2Strength
If a metallic outer housing with conductive members near the antenna is used for size reduction and drop impact resistance, then the device strength and compactness are improved, but the radiant quantity of radio waves at communication frequency is significantly reduced
Solution Approach 1:
A non-conductive member is positioned between the antenna and the metallic housing to prevent electromagnetic coupling. This intermediary allows the metallic housing to provide mechanical strength and protection while preventing it from interfering with the antenna's radiation pattern and efficiency
Solution Approach 2:
The housing structure is designed with different local properties: non-conductive materials or structures are used in the immediate vicinity of the antenna to minimize electromagnetic interference, while conductive metallic housing is used in other areas to provide mechanical strength and protection, creating a spatially differentiated structure that addresses both requirements
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 effectively decreases the SAR value and prevents a reduction in radiant quantity of radio waves at communication frequencies, ensuring safer energy absorption by the human body while maintaining efficient wireless communication.
Implementation Method 1
an antenna 160... adapted to radiate electromagnetic waves outward
Implementation Method 2
when high-power electromagnetic waves emitted by an antenna of a wireless communication apparatus enter a human body and are absorbed by the human body, a temperature of the human body locally rises
Data Source
Figure 1~2
Figure 3~4A
Figure 4B~5B
AI summary
In a wireless communication apparatus according to the present invention, an antenna including an antenna element is disposed at a position closer to an opening of an outer housing than to a fixing member formed of an electric conductor and configured to fix the antenna, and an electric supply unit configured to supply the antenna with electric power and a first region that is positioned on an electric supply unit side of the antenna element are disposed closer to the fixing member than a second region including an open end portion of the antenna element.