Antenna Structure with Multi-Branch SAR Reduction
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Solution Overview
Problem
Conventional antenna structures, such as PIFA, face challenges in reducing the Specific Absorption Rate (SAR) for high-frequency bands like 5G, as the current maximum point of these frequencies is often close to the human body, violating SAR limits due to frequency multiplication effects.
Innovation Solution
The proposed antenna structure includes a ground element and two radiation branches, where the second radiation branch is designed to be shorter than the first, with a current maximum point positioned at the second radiation branch to reduce SAR, and a third radiation branch adjusts impedance matching, optimizing the height and shape to move the current maximum point away from the human body.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional antenna structures (PIFA) are used for high-frequency bands, then communication quality is maintained, but SAR (Specific Absorption Rate) exceeds legal limits due to current maximum point being close to the human body
Solution Approach 1:
The antenna is divided into multiple radiation branches (first radiation branch for low-frequency band, second radiation branch for high-frequency band) with different configurations. Each branch independently handles specific frequency bands, allowing the high-frequency branch to be optimized for SAR reduction without compromising low-frequency performance.
Solution Approach 2:
Different parts of the antenna structure are designed with different properties: the first radiation branch has a first height on the ground element, while the second radiation branch has a second height less than 0.5 times the first height. This local differentiation allows the current maximum point of the high-frequency band to be positioned away from the human body, reducing SAR while maintaining communication quality.
2Object-affected harmful factors
If the antenna structure is modified to reduce SAR by changing radiation branch heights, then SAR compliance is achieved, but impedance matching may be affected
Solution Approach 1:
The third radiation branch is designed to serve multiple functions: it adjusts impedance matching for the high-frequency band while also contributing to the overall antenna radiation pattern. This multi-functionality allows SAR reduction through height optimization without compromising impedance matching performance.
Solution Approach 2:
The antenna design utilizes parameter changes in the radiation branch heights (second height less than 0.5 times the first height, third height from 0.5 to 1 times the first height) to simultaneously achieve SAR reduction and maintain proper impedance matching. The specific height ratios are optimized to balance both requirements.
3Object-affected harmful factors
If multiple radiation branches with different heights are used to reduce SAR, then SAR compliance is achieved, but device complexity increases
Solution Approach 1:
Multiple radiation branches are merged into a single integrated antenna structure sharing a common ground element and signal source connection. This unified design achieves SAR reduction through multiple branches while avoiding the complexity of completely separate antenna systems, as all branches work together as one cohesive antenna unit.
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 design effectively reduces the SAR while maintaining or improving antenna efficiency, ensuring compliance with SAR limits and supporting high-frequency bands without increasing the antenna's total area.
Implementation Method 1
the first radiation branch is excited to generate a low-frequency band, the low-frequency band is from about 2400 MHz to about 2500 MHz
Implementation Method 2
the second radiation branch is excited to generate a high-frequency band, the high-frequency band is from about 5150 MHz to about 5850 MHz
Implementation Method 3
a current maximum point of the high-frequency band is positioned at the second radiation branch, so as to reduce an SAR (Specific Absorption Rate) of the antenna structure operating in the high-frequency band
Data Source
AI summary
An antenna structure includes a ground element, a first radiation branch, and a second radiation branch. The first radiation branch has a first end and a second end. The first end of the first radiation branch is coupled to a signal source. The second end of the first radiation branch is open. The second radiation branch has a first end and a second end. The first end of the second radiation branch is coupled to the signal source. The second end of the second radiation branch is coupled to the ground element. The length of the second radiation branch is substantially equal to that of the first radiation branch.