Circular Single-Layer Sensor Electrode Pattern for Wearables
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Solution Overview
Problem
Traditional single-layer sensor patterns, particularly those using a Cartesian grid configuration, are inefficient for capacitive sensing on round shapes such as wearable devices, as they do not effectively utilize the circular geometry, leading to suboptimal performance and increased border area requirements.
Innovation Solution
A circular, single-layer sensor electrode pattern with alternating transmitter and receiver electrodes arranged in a symmetric circular pattern, ensuring each electrode has a uniform surface area and optimized capacitive coupling, allowing for improved absolute and transcapacitive sensing capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Cartesian grid sensor electrode pattern is used, then the sensor can be implemented on flat surfaces, but the sensing performance deteriorates on circular/curved surfaces and the border area increases
Solution Approach 1:
The patent applies curved geometry to the sensor electrode pattern by arranging electrodes in concentric circular rings and radial segments that follow the curvature of the substrate. This circular pattern matches the geometry of wearable devices and curved surfaces, improving capacitive coupling and sensing performance while reducing the border area required for trace routing compared to traditional Cartesian grid patterns.
2Measurement precision
If sensor electrodes are arranged in a circular pattern with alternating transmitter and receiver electrodes, then capacitive sensing performance is improved, but the electrode arrangement complexity increases
Solution Approach 1:
The sensor electrode pattern is segmented into multiple functional zones: an inner circle of electrodes, an outer ring of electrodes, with each electrode further divided into transmitter and receiver segments. This segmentation allows independent control and optimization of capacitive coupling in different regions, improving measurement precision while the modular structure actually simplifies the fabrication process compared to continuous complex patterns.
Solution Approach 2:
The patent employs asymmetric electrode configurations where the inner circle and outer ring have different numbers of electrodes and different spacing arrangements. This asymmetry is optimized to maximize capacitive coupling efficiency in specific directions and regions, improving sensing accuracy for particular gesture types while maintaining overall pattern symmetry for balanced performance.
3Stability of the object's composition
If each sensor electrode is given equal surface area, then sensing uniformity is improved, but the optimization of capacitive coupling in different regions is reduced
Solution Approach 1:
The patent implements local quality optimization by assigning different electrode configurations to different regions: the inner circle electrodes have different spacing and arrangement compared to the outer ring electrodes. Each region's electrode geometry is locally optimized for its specific function while maintaining equal surface area for uniform absolute capacitive sensing. This allows enhanced capacitive coupling efficiency in specific regions without compromising overall sensing uniformity.
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 design enhances capacitive sensing performance along the circular edge, reduces the border area for side trace routing, and minimizes the bonding area with the processing system, resulting in more accurate and efficient input detection on curved surfaces.
Implementation Method 1
a sensing element array comprising a plurality of sensor electrodes that are disposed on a first side of the sensor substrate and are arranged in a symmetric circular pattern
Data Source
AI summary
A circular, single-layer sensor electrode pattern for input devices, such as wearable devices, is described. The sensor electrode pattern features transmitter electrodes and receiver electrodes tiled in alternating fashion, such that each receiver electrode is surrounded by transmitter electrodes. The individual sensor electrodes of the described pattern are designed to provide a substantially uniform electrode area size across the sensor. Additionally, the sensor electrode pattern is arranged to be symmetric across both horizontal and vertical axes. The provided characteristics of the sensor electrode pattern leads to a sensor structure having uniform absolute capacitive sensing measurements for all sensor electrodes as well as uniform transcapacitive sensing measurements for all “pixels.”