Tunable Antenna Grounding Rings for Wireless Charging Interference
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Solution Overview
Problem
Electronic devices with compact wireless circuitry face challenges in achieving efficient antenna performance and wireless charging efficiency due to interference and limited bandwidth, as radio-frequency signals can induce currents on coil structures, leading to signal losses.
Innovation Solution
The implementation of antenna grounding ring structures formed from concentric ring-shaped traces on a flexible printed circuit, which couple antenna currents to the ground traces on a sensor board, preventing signal losses and allowing the ground traces to form part of the antenna, while a switchable inductor adjusts the antenna bandwidth and effective electrical length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ground traces are extended to form part of the antenna to maximize antenna volume, then antenna efficiency bandwidth is improved, but wireless charging efficiency is impaired due to current interference between antenna and coil structures
Solution Approach 1:
The grounding system is segmented into multiple grounding rings at different frequencies. The first grounding ring operates at the antenna resonant frequency to provide grounding for antenna currents, while the second grounding ring operates at the wireless charging frequency to provide grounding for coil currents. This segmentation allows each grounding ring to independently handle its designated frequency without interfering with the other, thus maximizing antenna efficiency while preserving wireless charging efficiency.
Solution Approach 2:
Different grounding rings are provided with different local qualities optimized for their respective frequencies. The first grounding ring is designed with characteristics suitable for antenna grounding (e.g., specific impedance, size, and positioning relative to the antenna), while the second grounding ring is designed with characteristics suitable for wireless charging coil grounding. This local quality differentiation ensures optimal performance for each function without compromise.
2Reliability
If antenna resonating element is made larger to increase efficiency bandwidth, then antenna performance is improved, but device compactness is reduced
Solution Approach 1:
The antenna grounding system utilizes the vertical dimension by stacking multiple grounding rings at different heights above the sensor board. The first grounding ring is positioned at a first height and the second grounding ring is positioned at a second height, creating a three-dimensional grounding structure. This dimensional approach allows the antenna to achieve larger effective electrical length and broader efficiency bandwidth without increasing the planar footprint, thus maintaining device compactness while improving antenna performance.
3Reliability
If coil structures include ferrite structures to improve wireless charging efficiency, then charging performance is improved, but antenna efficiency is reduced due to signal loss from induced currents
Solution Approach 1:
The grounding system is segmented into multiple grounding rings at different frequencies. The first grounding ring operates at the antenna resonant frequency to provide grounding for antenna currents, while the second grounding ring operates at the wireless charging frequency to provide grounding for coil currents. This segmentation allows each grounding ring to independently handle its designated frequency without interfering with the other, thus maximizing antenna efficiency while preserving wireless charging efficiency.
Solution Approach 2:
The multiple grounding rings act as intermediaries between the antenna/coil structures and the sensor board ground. The first grounding ring mediates antenna currents, providing a controlled path to ground that prevents unwanted induction into the ferrite structures. The second grounding ring mediates coil currents for wireless charging. These intermediary grounding structures decouple the antenna and coil systems, allowing ferrite structures to enhance wireless charging without causing antenna signal loss.
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 maximizes antenna volume and efficiency bandwidth without impairing wireless charging efficiency, enhancing antenna performance across various frequency bands, including LTE band B71.
Implementation Method 1
Antenna currents at the first frequency (e.g., in a lower frequency resonant mode of the antenna) may be coupled onto the ring-shaped traces by near-field capacitive coupling
Implementation Method 2
The coil structures may receive wireless charging signals at a second frequency that is less than the first frequency through the rear housing wall
Data Source
AI summary
An electronic device may include a rear housing wall, antenna resonating element, sensor board, and grounding ring. The grounding ring may couple antenna currents from the resonating element onto a ground trace on the sensor board. A switchable inductor may couple the grounding ring to the ground traces. The switchable inductor may be used to tune a frequency response of the antenna in a cellular low band. Additionally or alternatively, an inductor may couple the resonating element to the ground traces or other portions of an antenna ground. This inductor may serve to extend the effective length of the antenna resonating element in the cellular low band to compensate for dielectric loading by the rear housing wall, such as in examples where the rear housing wall is formed from zirconia.