FSS Antenna Substrate for SAR Reduction via Frequency Shifting
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Solution Overview
Problem
Existing methods to reduce the specific absorption rate (SAR) of electromagnetic waves from mobile communication devices often compromise the antenna's performance, either by requiring additional space, deteriorating the antenna's overall performance, or failing to effectively manage the radiation pattern when close to the human body.
Innovation Solution
A structure comprising a dielectric substrate with meandering metal lines, metal patch-shaped structures, and complementary slits is integrated into the antenna's radiation path, creating a frequency response with a pass band and a stop band. This structure adjusts EM wave penetration by shifting the resonance frequency when close to a high dielectric object, such as a human body, to reduce SAR while maintaining the antenna's performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If additional elements (copper strip, filter, dielectric sleeve) are added to reduce SAR value, then the SAR value is reduced, but the overall performance of the original antenna deteriorates
Solution Approach 1:
The patent combines the SAR reduction function with the antenna structure by integrating a frequency selective surface (FSS) directly onto the antenna substrate. The FSS pattern is printed on the same substrate as the antenna elements, creating a unified structure that performs both radiation and SAR reduction functions simultaneously, eliminating the need for separate additional elements that would deteriorate antenna performance
Solution Approach 2:
The frequency selective surface is designed to serve multiple functions: it acts as both a radiation element and a SAR reduction mechanism. The FSS pattern can be configured to provide frequency selectivity, impedance matching, and SAR reduction all within a single integrated structure, allowing one component to perform multiple critical functions
2Object-affected harmful factors
If ferromagnetic material or EBG structure is added to reduce SAR value, then the SAR value is reduced, but the antenna performance deteriorates oppositely
Solution Approach 1:
The patent uses frequency selective surfaces with adjustable geometric parameters (unit cell dimensions, pattern geometry, substrate properties) to control the electromagnetic response. By changing these parameters, the FSS can be tuned to provide SAR reduction at specific frequency bands while maintaining antenna performance, avoiding the use of ferromagnetic materials that cause performance deterioration
3Object-affected harmful factors
If loop antenna structure is used to reduce SAR value, then the SAR value is reduced, but a large space is required
Solution Approach 1:
The patent transitions from three-dimensional loop antenna structures to two-dimensional planar FSS patterns printed on a substrate. This dimensional reduction allows the SAR reduction functionality to be integrated into the planar antenna layout without requiring additional volumetric space, maintaining compact device form factors while achieving SAR reduction
4Object-affected harmful factors
If sensor and switch are added to detect human body proximity and reduce SAR value, then the SAR value is reduced, but the device becomes complicated and requires large space
Solution Approach 1:
The frequency selective surface automatically adjusts its electromagnetic response based on the proximity of the human body through passive coupling effects. The FSS structure inherently senses the dielectric environment and modifies its impedance and resonance characteristics without requiring active sensors, switches, or control circuits, thereby reducing device complexity while maintaining SAR reduction functionality
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 effectively reduces SAR by shifting the EM wave penetration response to a stop band when close to the human body, maintaining the total radiated power and reducing EM wave absorption, thereby meeting regulatory standards and ensuring effective communication.
Implementation Method 1
The structure units consist of a plurality of meandering metal lines, a plurality of metal patch-shaped structures, a plurality of complementary slits, or a combination thereof, to enable the EM wave penetration response of the structure for adjusting the EM wave penetration response to include a pass band and a stop band
Implementation Method 2
enable the EM wave penetration response of the structure for adjusting the EM wave penetration response to include a pass band and a stop band
Data Source
AI summary
A structure for adjusting electromagnetic wave (EM wave) penetration response includes a plurality of structure units and a dielectric substrate with an upper surface and a lower surface. The structure units are disposed on the upper surface and/or the lower surface. The structure unit consists of metal lines or complementary slits so as to enable an EM wave penetration response of the structure to include a pass band and a stop band. The frequency of the stop band is higher than that of the pass band. If a distance between the structure and an object with a high dielectric constant is longer than a predetermined distance, the pass band covers a radiation frequency of an antenna. If the distance between the structure and the object with the high dielectric constant is within the predetermined distance, the stop band covers the radiation frequency of the antenna.