Differential Touch Sensor Architecture for Low-Noise Screen Sensing
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Solution Overview
Problem
Existing touch sensor panels suffer from high noise levels, which degrade the signal-to-noise ratio (SNR) and affect the performance of touch screens.
Innovation Solution
Implementing a two-dimensional array of touch nodes with differential driving and sensing, optimized routing traces, and a hybrid pattern of interconnections between electrodes, along with a dielectric layer to reduce capacitive coupling and common mode noise, and incorporating a display-noise shield to mitigate electrical interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If capacitive touch sensor panels use conventional single-ended driving and sensing, then the device complexity is reduced, but the signal-to-noise ratio deteriorates due to high noise levels
Solution Approach 1:
The patent segments the touch sensor panel into multiple banks of rows, with each bank having its own dedicated routing tracks. This segmentation allows differential driving and sensing to be implemented independently in each bank, reducing the overall complexity while maintaining high SNR through differential measurement techniques.
Solution Approach 2:
The patent changes the driving and sensing parameters from single-ended to differential mode. By applying complementary drive signals to adjacent column electrodes and using differential sensing for row electrodes, the system achieves noise rejection while maintaining measurement precision through parameter transformation.
2Ease of manufacture
If routing traces are extended to cover the entire touch sensor panel, then the ease of manufacture is improved, but parasitic capacitance increases
Solution Approach 1:
The patent divides the routing traces into separate tracks for different banks of rows. Each routing track serves a specific bank and can be optimized independently for length and placement, reducing parasitic capacitance while maintaining ease of manufacture through modular routing design.
Solution Approach 2:
The patent applies different routing strategies to different regions of the touch sensor panel. Routing traces are optimized locally for each bank, with trace lengths and placements adjusted to minimize parasitic capacitance in each specific region while maintaining overall manufacturability.
3Area of stationary object
If display components are positioned close to touch sensor electrodes, then the area utilization is improved, but electrical interference increases
Solution Approach 1:
The patent introduces a dielectric layer as an intermediary between the display components and the touch sensor electrodes. This dielectric layer acts as a mediator that reduces electrical interference and capacitive coupling while allowing the display and touch sensor to be positioned close together for optimal area utilization.
Solution Approach 2:
The patent converts the potential harmful electrical interference from display components into a beneficial differential measurement opportunity. By using differential sensing, the system can reject common-mode noise and interference, turning the proximity to display components from a liability into an advantage for noise rejection.
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
Enhances the signal-to-noise ratio (SNR) and reduces parasitic capacitance, thereby improving the accuracy and reliability of touch screen operations.
Implementation Method 1
a dielectric layer to reduce capacitive coupling and common mode noise
Implementation Method 2
Differential driving (e.g., using complementary drive signals) and/or differential sensing can reduce noise in the touch and/or display systems of the touch screen
Implementation Method 3
incorporating a display-noise shield to mitigate electrical interference
Data Source
AI summary
Differential driving and/or sensing can reduce noise in a touch screen. In some examples, the touch screen can include column and row electrodes routed vertically in the active area. In some examples, the touch electrodes and/or routing traces can be implemented using metal mesh in first and second metal layers. To improve optical performance, overlapping portions of metal mesh can be designed to provide an appearance of uniform width/area. In some examples, a dielectric layer can have an increased thickness and/or a reduced dielectric constant, and/or metal mesh in the first metal layer can be flooded with a transparent conductive material. In some examples, routing traces can be disposed beneath touch electrodes and/or metal mesh for touch electrodes can be flooded with a transparent conductive material without flooding metal mesh for routing traces. In some examples, touch electrodes can be interleaved within a touch node to improve differential cancelation.