Capacitive Touch System Differential Noise Cancellation
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Solution Overview
Problem
Capacitive touch systems face interference from noise in electronic devices, degrading detection accuracy in applications such as liquid crystal displays.
Innovation Solution
A capacitive touch system and method that perform differential operations between digital components of detection matrices from different receiving electrodes to reduce noise interference, utilizing a drive circuit, encoding and modulation modules, detection and decoding circuits, and subtraction circuits to generate component differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional capacitive sensing is used to detect touch events, then the basic detection function is achieved, but noise from electronic devices degrades detection accuracy
Solution Approach 1:
The patent applies differential sensing that subtracts noise components common to adjacent electrodes, converting the harmful noise into a cancelable common-mode signal. By treating noise as a shared characteristic between neighboring sensors, the system eliminates it through subtraction, transforming the harmful interference into a beneficial filtering mechanism.
Solution Approach 2:
The patent changes the sensing parameter from absolute capacitance measurement to differential capacitance measurement. Instead of measuring the absolute capacitance value at each electrode, the system measures the difference in capacitance between adjacent electrodes, which fundamentally alters how the signal is processed and enables noise rejection through differential calculation.
2Measurement precision
If differential sensing with subtraction circuits is implemented, then noise interference is reduced, but device complexity increases
Solution Approach 1:
The patent merges the differential sensing functionality into the existing capacitive touch sensor array by using adjacent electrodes that already exist in the sensing matrix. Rather than adding completely separate sensing elements, the system combines the signal processing capability with the existing electrode structure, reducing the need for additional hardware components.
Solution Approach 2:
The patent makes the existing electrode pairs serve dual functions: both for normal capacitive sensing and for differential noise rejection. The same electrode array used for detecting touch events also provides the differential pairs needed for noise cancellation, eliminating the need for dedicated reference electrodes or separate noise-canceling sensor arrays.
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
The system effectively reduces noise interference, improving detection accuracy and reliability in capacitive touch systems by subtracting digital components of adjacent electrodes, thereby enhancing the identification of touch events and positions.
Implementation Method 1
Electric field can be generated between the first electrode 91 and the second electrode 92 so as to transfer charges to the second electrode 92
Implementation Method 2
When the conductor is present, the amount of charge transfer between the pair of electrodes can be changed so that it is able to detect whether the conductor is present or not according to a voltage variation
Data Source
AI summary
A capacitive touch system including a drive end, a capacitive sensing matrix and a detection end is provided. The drive end concurrently inputs encoded and modulated drive signals into a plurality of channels of the capacitive sensing matrix within each drive time slot of a frame. The detection end detects a detection matrix of the channels in the frame and decodes the detection matrix to respectively generate a two-dimensional detection vector corresponding to each of the channels. The detection end further calculates a subtraction between components of the two-dimensional detection vectors associated with two receiving electrodes of the capacitive sensing matrix to eliminate interference from noises.