Single-Layer Touch Sensor Parasitic Coupling Correction
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Solution Overview
Problem
Single-layer touch sensors with interleaved electrodes suffer from parasitic signal coupling, leading to false touches, inaccuracy, and poor touch-response linearity due to increased capacitive cross-coupling, which limits their functionality and user experience.
Innovation Solution
A method for correcting tail effects in single-layer touch sensors involves determining adjustment values for parasitic signal changes caused by conductive objects, using processing logic to generate adjusted measurements that account for parasitic signal coupling between TX and RX electrodes, thereby improving touch accuracy and linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If trace portions of electrodes are routed tightly together on a single substrate without jumpers, then manufacturing cost is reduced, but capacitive cross-coupling between electrodes increases causing false touches and poor accuracy
Solution Approach 1:
The patent introduces non-conductive spacing structures (spacers) as intermediary elements between closely routed electrode traces. These spacers act as mediators that prevent direct capacitive coupling between adjacent traces while maintaining the cost benefits of single-substrate construction without jumpers.
Solution Approach 2:
The patent extracts the harmful capacitive coupling effect by removing the direct electrical proximity between traces through the use of spacers. This separates the beneficial close routing (for cost reduction) from the harmful coupling (for accuracy degradation).
2Measurement precision
If multiple layers of electrode materials are used on multiple substrates, then capacitive cross-coupling is reduced improving accuracy, but manufacturing cost increases
Solution Approach 1:
The patent transitions from a multi-layer/thick-substrate approach (vertical dimension) to a single-substrate-with-spacers approach (horizontal spacing dimension). This dimensional shift achieves similar coupling reduction through lateral separation rather than vertical layering, reducing manufacturing complexity.
3Device complexity
If electrodes are routed tightly together, then device complexity is reduced, but touch-response linearity deteriorates due to parasitic signal coupling
Solution Approach 1:
Non-conductive spacers are introduced as intermediary elements that maintain consistent spacing between electrode traces. This ensures uniform parasitic coupling characteristics across the sensor array, improving touch-response linearity while preserving the simple single-substrate construction.
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 method effectively corrects parasitic signal changes, enhancing the accuracy and linearity of touch responses, thereby improving the overall performance and user experience of single-layer touch sensors.
Implementation Method 1
Capacitive sensing typically involves scan operations that periodically measure changes in capacitance associated with the capacitive sensor elements to determine a presence, position, and/or movement of a conductive object
Implementation Method 2
this type of sensor construction leads to increased capacitive cross-coupling between the electrodes (e.g., especially in response to a conductive object touch), thereby causing false touches, inaccuracy, and poor touch-response linearity
Data Source
AI summary
A method performs a scan operation for a single-layer sensor array that includes transmit (TX) electrodes and receive (RX) electrodes. The method includes determining whether to include a signal value for an RX electrode in a computation of a slope parameter value for a TX electrode. The method computes an index sum based on an index of the RX electrode when the signal value for the RX electrode is included in the computation of the slope parameter value for the TX electrode. The method computes a signal sum based on the signal value for the RX electrode when the signal value for the RX electrode is included in the computation of the slope parameter value for the TX electrode. The method then computes the slope parameter value for the TX electrode based on the signal sum and the index sum.