Branched Capacitive Position Sensor for Larger Sensing Arrays
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Solution Overview
Problem
Existing 2D capacitive touch sensors face challenges in increasing sensor area without adding more sense channels, which leads to increased size, thickness, and cost, while maintaining resolution and accuracy, especially when integrated with display screens.
Innovation Solution
The design incorporates sense electrodes with branches extending towards adjacent electrodes, reducing capacitive coupling and allowing for a larger sensor area with fewer sense channels, utilizing a two-layer electrode construction with drive and sense electrodes on opposing sides of a substrate, and employing resistive elements to improve linearity and scalability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the sensor area is increased by adding more sense channels, then the sensing coverage is improved, but the device size, thickness, and cost increase
Solution Approach 1:
The sense electrodes are segmented into multiple branches that extend towards adjacent drive electrodes. Each branch independently senses capacitive coupling with its adjacent drive electrode, allowing a single sense electrode to function as multiple sensing points. This segmentation enables increased sensor area without proportionally increasing the number of sense channels, as one sense electrode with multiple branches replaces what would traditionally require multiple separate sense electrodes.
2Ease of manufacture
If traditional sense electrode arrangement is used, then manufacturing is simpler, but capacitive coupling between adjacent electrodes increases causing noise
Solution Approach 1:
The sense electrode branches are designed with asymmetric geometry, extending preferentially towards adjacent drive electrodes rather than uniformly in all directions. This asymmetric arrangement creates directional sensitivity where the branches primarily sense coupling with nearby drive electrodes while minimizing coupling with other sense electrodes. The asymmetric design maintains manufacturing simplicity by using standard electrode fabrication processes while effectively reducing noise through geometric optimization.
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 approach enables a larger sensor area without increasing sense channels, maintaining resolution and accuracy, and providing a thinner, more cost-effective solution suitable for display integration with improved optical transmission and noise attenuation.
Implementation Method 1
capacitive position sensor... based on capacitive proximity sensing techniques... detecting a disturbance in a capacitive coupling of sensor electrodes caused by the proximity of a pointing object
Data Source
AI summary
A capacitive position sensor has a two-layer electrode structure. Drive electrodes extending in a first direction on a first plane on one side of a substrate. Sense electrodes extend in a second direction on a second plane on the other side of the substrate so that the sense electrodes cross the drive electrodes at a plurality of intersections which collectively form a position sensing array. The sense electrodes are provided with branches extending in the first direction part of the way towards each adjacent sense electrode so that end portions of the branches of adjacent sense electrodes co-extend with each other in the first direction separated by a distance sufficiently small that capacitive coupling to the drive electrode adjacent to the co-extending portion is reduced. Providing sense electrode branches allow a sensor to be made which has a greater extent in the first direction for a given number of sense channels, since the co-extending portions provide an interpolating effect. The number of sense electrode branches per drive electrode can be increased which allows a sensor to be made which has ever greater extent in the first direction without having to increase the number of sense channels.