Antenna Design Reducing SAR via Parasitic Element Coupling

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Solution Overview

Problem

Manufacturers of cellular and wireless devices face challenges in meeting the Federal Communications Commission (FCC) Specific Absorption Rate (SAR) limits while maintaining sufficient RF transmission power for device performance.

Innovation Solution

The use of a primary antenna element coupled with one or more parasitic antenna elements, electromagnetically coupled via a dielectric, to spread out RF energy and reduce SAR hotspots, thereby reducing the Specific Absorption Rate near the device surface for a given transmit power.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If conventional antenna designs are used, then RF transmission power can be maintained at sufficient levels, but SAR exceeds FCC limits

Engineering Contradiction:

ImproveSARVSAvoidRF transmission power

Core Design Contradiction:

Object-affected harmful factorsVSPower

Solution Approach 1:

The antenna system is divided into a primary antenna element and one or more parasitic antenna elements. The primary element is connected to the RF energy source, while the parasitic elements are electromagnetically coupled to the primary element but not directly connected to the source. This segmentation allows the RF energy to be distributed across multiple elements, reducing the SAR hotspot concentration that would occur with a single conventional antenna element.

Inventive Principle:

Principle #1Segmentation

2Productivity

If RF transmission power is increased to ensure acceptable device performance, then device performance improves, but SAR exceeds FCC limits

Engineering Contradiction:

Improvedevice performanceVSAvoidSAR

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces spatial distribution as an additional dimension for RF energy management. By arranging multiple parasitic antenna elements at different positions and orientations around the primary element, the system distributes RF energy across multiple spatial dimensions rather than concentrating it in a single direction or location. This dimensional expansion allows maintaining high total transmit power for device performance while reducing peak SAR values through spatial dispersion.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 achieves a significant reduction in SAR by distributing RF energy, resulting in a 50% reduction in SAR measurements across various RF frequencies without degrading antenna performance.

Implementation Method 1

Each parasitic antenna element is electromagnetically coupled to the primary antenna element (e.g., via an intervening dielectric) to create one or more additional SAR hotspots

Methodology Applied

Scientific EffectElectromagnetic coupling: Electromagnetic Induction

Implementation Method 2

Each parasitic antenna element is electromagnetically coupled to the primary antenna element (e.g., via an intervening dielectric)

Methodology Applied

Scientific EffectDielectric: Dielectric

Data Source

PatentUS9812773B1Antenna design for reduced specific absorption rate

Publication Date: 2017.11.07 AMAZON TECH INC

AI summary

An antenna for use in portable wireless devices is described for which SAR is significantly reduced relative to conventional antenna designs for the same transmit power. The antenna includes a primary antenna element and one or more parasitic antenna elements. Each parasitic antenna element is electromagnetically coupled to the primary antenna element so as to spread out the RF energy associated with SAR hotspots.