Ground Patch Antenna SAR Reduction
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Solution Overview
Problem
The challenge in designing cellular communications devices is to create antennas that provide desired operating characteristics within the limited space while ensuring compliance with specific absorption rate (SAR) and hearing aid compatibility (HAC) requirements, especially for smaller and thinner devices where internal antennas may be closer to the user's ear.
Innovation Solution
A mobile wireless communications device with a dielectric substrate carrying a ground patch electrically connected to a ground plane, positioned to reduce SAR by shielding the user from electromagnetic radiation and providing desired HAC, includes an antenna adjacent the lower end of the substrate and a ground patch partially overlapping the antenna to manage radiation direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If internal antennas are used in smaller and thinner devices, then device size is reduced, but radiation exposure to the user increases making SAR compliance difficult
Solution Approach 1:
A ground patch is introduced as an intermediary element between the antenna and the user's head. This ground patch is positioned on the device housing to intercept and redirect electromagnetic radiation away from the user, thereby reducing SAR exposure while allowing the antenna to remain in a compact internal configuration
Solution Approach 2:
The solution moves the radiation management function from the antenna element itself to a separate ground patch structure on the device housing. This spatial separation allows the antenna to maintain its compact form factor while the ground patch provides SAR reduction in a different dimensional plane
2Object-affected harmful factors
If external antennas are used, then radiation exposure is reduced making SAR compliance easier, but the antenna is prone to damage and loss
Solution Approach 1:
The antenna is nested internally within the device housing rather than being external. This protective nesting shields the antenna from physical damage and loss while the ground patch nested on the housing exterior provides the radiation management function that would traditionally require an external antenna
3Volume of moving object
If antenna elements are placed close to the user's ear, then device size is reduced, but hearing aid compatibility becomes difficult to achieve
Solution Approach 1:
The ground patch serves as a mediator between the internally positioned antenna and the user's head/hearing aid. By positioning the ground patch on the device housing, it intercepts and redirects electromagnetic fields before they reach the user's ear, thereby maintaining hearing aid compatibility while allowing compact antenna placement
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 and enhances hearing aid compatibility by shielding the user from electromagnetic radiation and optimizing antenna placement for reduced radiation exposure.
Implementation Method 1
a ground patch adjacent the front side of the dielectric substrate that is electrically connected to the ground plane and spaced apart from and at least partially overlapping the antenna. The ground patch may advantageously reduce a specific absorption rate (SAR) associated with the device by shielding the user from electromagnetic (EM) radiation generated by the antenna
Data Source
AI summary
A mobile wireless communications device may include a portable housing, a dielectric substrate carried by the portable housing having a front side facing toward a user and a back side opposite the front side, and a ground plane carried by the dielectric substrate. The device may further include at least one circuit carried by the dielectric substrate, and an antenna carried by the dielectric substrate adjacent an end thereof and electrically connected to the at least one circuit. A ground patch may be adjacent the front side of the dielectric substrate that is electrically connected to the ground plane and spaced apart from and at least partially overlapping the antenna.