NFC Touchpad Shield Trace for RF Interference Reduction
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Solution Overview
Problem
Existing input devices with integrated NFC antennas face interference from RF communication signals, which affects their operation and the detection of input objects.
Innovation Solution
Incorporating a shield trace between the sensor electrodes and the antenna, ensuring it encompasses regions where the first electrode overlaps the antenna but is absent where the second electrode overlaps, to reduce RF interference while maintaining RF communication functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an antenna is integrated beneath the sensor electrodes for NFC communication, then RF communication functionality is enabled, but RF signals interfere with the operation of the sensor electrodes
Solution Approach 1:
The sensor electrode structure is segmented into multiple electrodes (first electrode, second electrode, third electrode) with different shielding configurations. The first electrode receives full shielding from the shield trace, while the second and third electrodes have reduced or no shielding, allowing each electrode to operate optimally under different RF interference conditions while maintaining NFC communication functionality.
Solution Approach 2:
Different regions of the sensor electrode array are assigned different shielding characteristics. The shield trace is positioned to provide localized shielding protection to specific electrodes based on their sensitivity to RF interference and their functional requirements, creating non-uniform local quality across the sensor array to balance detection accuracy with RF communication performance.
2Object-affected harmful factors
If a shield trace is added between sensor electrodes and antenna, then RF interference is reduced, but device complexity increases
Solution Approach 1:
The shield trace is merged with the existing antenna structure and sensor electrode layout, forming an integrated configuration where the shield trace follows the contour of the antenna and sensor electrodes. This combining approach reduces the need for separate shielding components and simplifies the overall device structure while still providing effective RF interference reduction.
Solution Approach 2:
The shield trace acts as an intermediary element between the antenna and sensor electrodes, providing RF shielding without requiring complete enclosure or complex multi-layer shielding structures. This intermediary approach offers a simplified solution that mediates between the conflicting requirements of RF communication and sensor operation.
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 allows for effective detection of input objects while minimizing RF interference, striking a balance between sensor sensitivity and RF signal propagation.
Implementation Method 1
an antenna disposed beneath the input surface and the plurality of sensor electrodes, the antenna being configured to transmit and receive radio-frequency (RF) communication signals
Implementation Method 2
a plurality of sensor electrodes disposed beneath the input surface and configured to detect an input object in the sensing region
Implementation Method 3
a shield trace disposed between the plurality of sensor electrodes and the antenna, wherein the shield trace encompasses a region in which the first electrode overlaps the antenna
Data Source
AI summary
An input device includes a plurality of sensor electrodes, an antenna, and a shield trace disposed between at least some of the sensor electrodes and the antenna. The antenna may be coupled to a transceiver and may transmit and receive radio-frequency (RF) communication signals. The shield trace may reduce, at least in part, coupling of the RF communication signals from the antenna to the sensor electrodes. The plurality of sensor electrodes may determine a presence, and/or a motion associated with an input object.