Alternating Self and Mutual Capacitance Sensing for Touch Noise Reduction
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Solution Overview
Problem
Capacitive touch systems face noise interference issues due to external and internal noise, leading to distorted touch data, ghost points, and incorrect coordinate detection, particularly in handheld devices where power consumption is a concern.
Innovation Solution
A sensing method that alternates between self-capacitance and mutual-capacitance sensing to reduce noise interference, using a control device to configure driving and sensing devices in different modes to detect touch points and calculate coordinates, thereby eliminating noise-affected data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If self-capacitance sensing is used, then the sensing method is simple and can detect correct relative positions, but ghost points are generated causing measurement errors
Solution Approach 1:
The patent divides the sensing process into two distinct modes: self-capacitance sensing mode and mutual-capacitance sensing mode. By segmenting the sensing function and alternating between the two modes, the system can identify and eliminate ghost points while maintaining detection capability, thus resolving the contradiction between simplicity and accuracy.
2Measurement precision
If mutual-capacitance sensing is used, then ghost points are eliminated and correct positions are detected, but the system becomes highly sensitive to noise interference
Solution Approach 1:
The patent implements periodic switching between self-capacitance sensing and mutual-capacitance sensing modes. By periodically alternating between the two sensing methods, the system can identify noise-affected data through comparison and eliminate it, thereby reducing noise sensitivity while maintaining detection accuracy.
3Object-affected harmful factors
If filter circuits are added to reduce noise, then noise interference is decreased, but device complexity and power consumption increase
Solution Approach 1:
The patent replaces the traditional hardware-based filter circuit approach with a software-based method that alternates between self-capacitance and mutual-capacitance sensing modes. By using control logic and data comparison algorithms instead of additional filter circuits, the system achieves noise reduction without increasing hardware complexity or power consumption.
4Object-affected harmful factors
If traditional noise filtering methods are used, then noise is reduced, but system resource consumption and power usage increase
Solution Approach 1:
The patent employs a self-service approach where the system uses its own sensing capabilities in two different modes to identify and eliminate noise-affected data. By comparing results from self-capacitance and mutual-capacitance sensing, the system can detect inconsistencies caused by noise and discard them, achieving noise reduction without requiring additional power-consuming filtering hardware.
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 method improves accuracy and reduces noise-related errors in touch point detection, minimizing the need for filter circuits and system resource consumption, while maintaining low power usage suitable for handheld devices.
Implementation Method 1
a capacitive touch panel uses a capacitance change generated in an electrostatic combination of the arranged transparent electrodes with the touching part of a human body to generate a current or voltage for detecting the coordinate of the touching part
Implementation Method 2
The self-capacitance sensing indicates that a coupled capacitance is generated between a touch object and a conductor line, and a touch occurrence is decided by measuring a capacitance change of the conductor line
Implementation Method 3
the mutual-capacitance sensing indicates that a coupled capacitance is generated between two adjacent conductor lines when a touch occurs
Data Source
AI summary
In a sensing method using self-capacitance and mutual-capacitance alternatively to reduce touch noises, a control device configures a first driving and sensing device and a second driving and sensing device to perform an initialization. The control device configures the first and second driving and sensing devices to perform at least one self-capacitance sensing for producing a first possible touch point range during a first work mode. Then, the control device configures the first and second driving and sensing devices to perform at least one mutual-capacitance sensing for producing a second possible touch point range during a second work mode. The control device determines if there is range conjunction between the first and second possible touch point ranges. The control device produces a possible touch point range conjunction and calculates coordinates of touch points based on the possible touch point range conjunction.