High-Frequency Signal Sensing for Liquid-Resistant Capacitive Touch Panels

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Capacitive touch panels malfunction due to liquid interference, such as water or saline, leading to abnormal operations.

Innovation Solution

A touch sensing system that includes a capacitive touch panel, a controller, and a signal source, where the signal source provides a high-frequency periodical signal to overcome liquid-induced interference by determining the type of liquid and adjusting the scanning strategy accordingly, allowing precise detection of touch inputs despite the presence of liquid.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional capacitive touch panel is used, then it can detect touch inputs through capacitance changes, but it malfunctions when liquid is present on the surface

Engineering Contradiction:

Improvetouch detection reliabilityVSAvoidliquid interference

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the detection parameter from low-frequency capacitance changes to high-frequency periodical signal responses. By applying a high-frequency periodical signal and detecting the response at the same frequency, the system can distinguish between capacitive changes caused by touch and those caused by liquid, thereby maintaining reliability in the presence of liquid

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces a high-frequency periodical signal as an intermediary to mediate between the touch panel and the controller. This signal acts as a carrier that allows the controller to detect touch inputs while filtering out liquid interference, as the liquid does not respond to high-frequency signals in the same way as human touch

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If a high-frequency periodical signal is applied to the controller, then liquid interference is mitigated, but additional signal processing complexity is introduced

Engineering Contradiction:

Improveliquid interference resistanceVSAvoidsignal processing complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent employs periodic action by applying a periodical signal to the controller and detecting responses at the same period. This allows the system to filter out non-periodic or differently-periodic interference from liquids while maintaining simplicity in the detection mechanism through frequency-matched signal injection and detection

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent replaces the conventional direct capacitance measurement mechanism with a signal-based detection mechanism. Instead of directly measuring capacitance changes that are ambiguous in the presence of liquid, the system uses high-frequency signal injection and response detection, substituting a more robust electrical measurement approach

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 accurately determines touch inputs on a capacitive touch panel even with liquid present by using a high-frequency periodical signal, effectively mitigating the interference caused by liquids like water or saline.

Implementation Method 1

A capacitive touch panel is usually used as an input device in an electronic device

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS20250306717A1Touch sensing system and control method thereof

Publication Date: 2025.10.02 ELAN MICROELECTRONICS CORPORATION

AI summary

A touch sensing system includes a capacitive touch panel, a controller, and a signal source. The capacitive touch panel is used for a user to perform inputs. The controller is coupled to the capacitive touch panel, configured to scan the capacitive touch panel. The signal source is configured to provide a periodical signal for coupling to the user, such that the periodical signal can be coupled to the capacitive touch panel via the user.