Capacitive Sensor Electrode Timing and Routing for Display Crosstalk
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Solution Overview
Problem
Cross-talk interference between sensor electrodes and display elements in capacitive sensing devices affects the accuracy of input detection, as signals from display elements can interfere with capacitive sensing, leading to incorrect detection or non-detection of input objects.
Innovation Solution
The solution involves driving sensor electrodes and display elements in a manner that prevents overlap, with sensor electrodes being driven ahead of or staggered relative to display elements, and routing configurations that minimize capacitive coupling, thereby reducing cross-talk and interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If sensor electrodes and display elements are driven simultaneously, then display updating and capacitive sensing can occur at the same time, but cross-talk interference occurs between the two signals
Solution Approach 1:
The patent applies preliminary action by driving sensor electrodes before display elements in a staggered sequence. The sensor electrode is activated in advance during a sensing phase, then the display element is activated afterward during a display update phase. This temporal separation ensures that the sensor electrode is already in its sensing state when the display element is driven, preventing cross-talk interference while enabling simultaneous operation of both functions.
2Device complexity
If routing traces are positioned close to sensor electrodes, then device layout is simplified, but capacitive coupling and cross-talk increase
Solution Approach 1:
The patent extracts the routing trace from the immediate proximity of the sensor electrode by positioning it in a separate, non-overlapping region. The routing trace is routed through a different spatial path that avoids close coupling with the sensor electrode, thereby reducing parasitic capacitive coupling. This extraction maintains electrical connectivity while eliminating the harmful capacitive interaction between the routing trace and sensor electrode.
3Speed
If display elements are driven at high frequency, then display refresh rate increases, but cross-talk with sensor electrodes worsens
Solution Approach 1:
The patent uses preliminary action by establishing the sensor electrode's sensing state before the display element is driven, even when display refresh rate is high. The sensor electrode is activated in advance during a dedicated sensing window, allowing the system to maintain high display refresh rates while ensuring the sensor electrode is already in its sensing state before the display update begins, thus preventing cross-talk.
Solution Approach 2:
The patent implements periodic action by using a staggered driving sequence where sensor electrodes and display elements are driven in alternating periodic phases. Within each display refresh cycle, the sensor electrode is driven first during a sensing phase, then the display element is driven during a display update phase. This periodic staggering maintains high refresh rates while preventing overlap between sensor and display driving signals.
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 allows for simultaneous capacitive sensing and display updating without significant cross-talk, improving the accuracy of input detection and reducing the overall time required for both processes.
Implementation Method 1
the first sensor electrode comprises a first display electrode of a display, the first display electrode configured for updating display pixels of the display and for capacitive sensing
Data Source
AI summary
A processing system, input device, and method are provided for reducing interference in a capacitive sensing system. The processing system generally includes a sensor module configured to drive a first sensor electrode of a plurality of sensor electrodes with a first sensing signal during a first time period, wherein the first sensor electrode comprises a first display electrode of a display, the first display electrode configured for updating display pixels of the display and for capacitive sensing. The input device also includes a display driver configured to drive a first display line of display elements within the display with a display update signal during a second time period. The first time period at least partially overlaps with the second time period. Further, the first display line of display elements does not overlap the first sensor electrode.