Active Noise Cancellation in Simultaneous Display and Touch Sensing
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Solution Overview
Problem
Simultaneous display updating and capacitive sensing in input devices often results in corrupting currents that hinder the ability to detect input objects due to interference between display and sensing signals.
Innovation Solution
A processing system that includes a source driver and an interference remover to drive a source line with a source driver signal and receive resulting signals on a routing trace coupled to a sensor electrode, while removing the interference signal generated by the source driver effects using tunable impedance or digital methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If display updating and capacitive sensing are performed simultaneously, then productivity is improved, but measurement precision deteriorates due to corrupting current interference
Solution Approach 1:
The patent segments the sensing signal into two components: the desired capacitive sensing signal and the corrupting display driver signal. By separately identifying and processing these components, the system can remove the harmful display interference while preserving the useful sensing information, thus maintaining measurement precision during simultaneous operation
Solution Approach 2:
The patent extracts the corrupting current component from the composite sensing signal by measuring the display driver signal characteristics and subtracting this extracted interference component from the total signal. This isolation and removal of the harmful element enables accurate touch detection despite simultaneous display updating
2Productivity
If display driver signal is applied to update display elements, then productivity is improved, but object-generated harmful factors increase due to corrupting current in sensing routing
Solution Approach 1:
The patent converts the harmful corrupting current into a useful component by measuring and characterizing the display driver signal's effect on the sensing routing. This measured interference signal is then used as a reference to subtract the exact amount of corruption from the sensing signal, transforming the previously harmful interference into a known quantity that can be eliminated
Solution Approach 2:
The patent applies preliminary anti-action by measuring the display driver signal characteristics before they fully corrupt the sensing signal, and preparing the compensation signal in advance. The system proactively generates and applies the counter-signal to neutralize the expected interference, preventing rather than merely reacting to the corruption
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
Effectively removes the corrupting current interference, enhancing the accuracy of input object detection by isolating and subtracting the source driver effects from the sensing signals, thereby improving the ability to determine the presence of input objects during simultaneous display and sensing operations.
Implementation Method 1
A routing for a sensor electrode may be capacitively coupled to a routing for a sub-pixel
Data Source
AI summary
Techniques for removing display-based corrupting components from a capacitive sensing signal when display and capacitive sensing is performed at or nearly at the same time. A routing carrying display related signals (e.g., a source signal for sub-pixel updating) may induce a corrupting current into a routing for carrying capacitive sensing signals. This corrupting current would reduce the ability to determine presence of an input object via the sensing signal. Therefore, the corrupting signal is effectively removed from a signal received from a sensor electrode when driven for sensing. The corrupting component may be removed either in analog or digitally. In analog, the corrupting component is removed via a tunable capacitance. Digitally, a corrupting component is calculated as an impulse response convolved with the source driver voltage. This corrupting component is then subtracted from a digital value output by the sensing circuitry to obtain a “clean” value.