Integrated Touch Screen Common Mode Noise Mitigation
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Solution Overview
Problem
Capacitive touch sensor panels in touch screens experience noise interference from display circuitry, particularly when the sensor panel is proximate to the display, leading to degraded performance due to increased noise levels as the distance between them decreases.
Innovation Solution
The solution involves splitting rows or columns of touch electrodes to stimulate one portion to measure capacitance changes while another portion remains unstimulated to measure noise, allowing for the subtraction of common mode noise from the measurements, and using orthogonal stimulation codes to further reduce noise interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the touch sensor panel is positioned close to the display, then the integration and compactness are improved, but noise interference from display circuitry increases
Solution Approach 1:
The touch sensor panel is divided into multiple portions (first portion and second portion) that can be independently stimulated. This segmentation allows one portion to measure capacitance changes while another measures noise, enabling noise subtraction and improving signal accuracy in the integrated configuration.
Solution Approach 2:
An unstimulated portion of the touch sensor panel acts as an intermediary noise measurement channel. By measuring noise in this unstimulated portion and subtracting it from the stimulated portion, the harmful noise interference is eliminated while maintaining the integrated close-proximity design.
2Reliability
If rows or columns of touch electrodes are split to measure noise, then noise reduction is improved, but device complexity increases
Solution Approach 1:
The touch electrode matrix is segmented into multiple portions within the same rows or columns. This allows the system to maintain the overall simple matrix structure while creating specific measurement channels for noise reduction without requiring completely new electrode layouts.
Solution Approach 2:
The split portions of the touch sensor panel serve multiple functions: some portions function as normal touch sensing electrodes while others function as noise measurement channels. This multi-functionality reduces the need for separate dedicated noise measurement components.
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 effectively eliminates or reduces common mode noise in touch sensor panel measurements, enhancing the accuracy and reliability of touch sensing by isolating noise sources and improving signal clarity.
Implementation Method 1
a first portion of the touch sensor panel can be stimulated to measure changes in capacitance
Data Source
AI summary
Some touch screens can be formed by at least partially integrating touch sensing circuitry into a display pixel stackup. In some examples, noise can be introduced into touch sensor panel measurements, for example, from display data lines of a display device proximate to the touch sensor panel. In some examples, rows or columns of touch electrodes can be split and a first portion of the touch sensor panel can be stimulated to measure capacitance and noise and a second portion of the touch sensor panel can be unstimulated and measure noise. In some examples, both the first and the second portions of the touch sensor panel can be stimulated using orthogonal stimulation codes. In some examples, measurements from the first and/or second portions of the touch sensor panel can be subtracted from measurements from the other portion of the touch sensor panel to eliminate or reduce common mode noise.