Inductively-Coupled Element for Reducing Near-Field Radiation in Mobile Antennas
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Solution Overview
Problem
Current mobile phone antennas fail to meet the hearing aid compatibility standard due to high near-field E-field and H-field strengths in the GSM1800/1900 frequency bands, as they cannot reduce radiation effectively within these bands without altering the antenna structure or size.
Innovation Solution
Incorporating an inductively-coupled element on the circuit board near the ground plane to generate a resonant mode within the 1710–1990 MHz frequency range, reducing surface current and near-field radiation strengths, thereby meeting the hearing aid compatibility standard without changing the antenna's structure or size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the antenna structure is designed for high frequency bands (GSM1800/1900), then the operating bandwidth and far-field radiation efficiency are improved, but the near-field E-field and H-field strengths increase causing failure to meet HAC standard
Solution Approach 1:
An inductively-coupled element is introduced as an intermediary component between the antenna and the ground plane. This element couples inductively to the antenna structure and provides a resonant path that redirects surface currents, thereby reducing near-field radiation while maintaining the antenna's primary function. The inductively-coupled element acts as a mediator that transforms the harmful near-field radiation into a controlled resonant mode.
Solution Approach 2:
The inductively-coupled element is designed with specific inductance and capacitance values to create a resonant circuit at the target frequency range (GSM1800/1900 bands). By adjusting the resonant frequency parameter of this coupled element, the surface current distribution on the ground plane is modified, which directly changes the near-field radiation characteristics and enables HAC standard compliance.
2Reliability
If the antenna structure is modified to reduce near-field radiation, then the HAC standard compliance is improved, but the device complexity increases
Solution Approach 1:
Rather than fundamentally redesigning the antenna structure, a separate inductively-coupled element is added as an auxiliary component. This approach maintains the original antenna design while introducing a additional element that specifically targets the near-field radiation issue, thereby reducing complexity compared to complete antenna redesign.
Solution Approach 2:
The solution separates the antenna function from the near-field radiation control function. The original antenna continues to provide the primary radiation function, while the inductively-coupled element specifically addresses the near-field E-field and H-field strength issues. This functional segmentation allows each component to be optimized independently.
3Object-generated harmful factors
If the inductively-coupled element size is increased to improve resonance effect, then the near-field radiation reduction is improved, but the device size increases
Solution Approach 1:
The inductively-coupled element uses high-value inductors and capacitors to achieve resonance at the target frequency with a compact physical size. By carefully selecting the inductance and capacitance values, the resonant frequency is tuned to the GSM1800/1900 bands while keeping the component dimensions small enough not to increase the overall device size significantly.
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 near-field E-field and H-field strengths by approximately 63% and 72% respectively within the GSM1800/1900 bands, ensuring compliance with the hearing aid compatibility standard without affecting the device's overall size or structure.
Implementation Method 1
generates a resonant mode at a specific frequency within 1710～1990 MHz
Implementation Method 2
inductively-coupled element
Implementation Method 3
reduce the near-field E-field and H-field strengths within the GSM1800/1900 operating bands
Data Source
AI summary
A mobile communication device includes an antenna structure. The antenna structure includes a circuit board. A ground plane is disposed on the second surface of the circuit board and includes a first side edge and a second side edge. An antenna element is disposed on the first surface of the circuit board or placed near the circuit board, and includes a first operating band and a second operating band. A first inductively-coupled element is located near the first side edge of the ground plane, and includes a metal plate and an inductive element. The metal plate is electrically connected to the ground plane through the inductive element. The first inductively-coupled element generates a resonant mode at a specific frequency within the second operating band to reduce a surface current excitation on the ground plane and to reduce near-field E-field and H-field strengths of the mobile communication device within the second operating band.