Adaptive Frequency Selection for Capacitive Touch Noise Immunity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Capacitive touch screens and sensors are prone to noise-induced inaccuracies due to electromagnetic interference from sources like power supplies, radio equipment, and internal noise, leading to false touches and reduced accuracy.
Innovation Solution
An adaptive frequency selection method is employed in the capacitive sensing circuit to shift the sensing frequency passband outside the noise spectrum, using noise listening mechanisms to determine when to change the passband and select the lowest noise frequency for operation, thereby reducing the influence of noise on touch measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed frequency passband is used in the capacitive sensing circuit, then the circuit structure is simple, but the circuit is highly susceptible to noise at specific frequencies leading to false touches
Solution Approach 1:
The patent implements dynamic frequency selection by continuously monitoring noise levels across multiple frequency passbands and switching to the optimal passband with lowest noise. The system transitions from a static fixed-frequency approach to a dynamic adaptive approach where the sensing frequency is adjusted in real-time based on environmental noise conditions, thereby improving noise immunity without requiring complex hardware filtering
Solution Approach 2:
The system changes the operating frequency parameter of the capacitive sensing circuit based on measured noise conditions. By selecting from multiple predefined frequency passbands (e.g., 200-300 kHz, 300-400 kHz, 400-500 kHz) and switching to the one with minimum noise, the system adapts its operational parameters to avoid noisy frequency regions while maintaining simple circuit architecture
2Reliability
If the sensing frequency is changed frequently to avoid noise, then noise immunity improves, but measurement accuracy may deteriorate due to frequency transitions
Solution Approach 1:
The system performs preliminary noise assessment by measuring noise levels in candidate frequency passbands before switching operations. A noise assessment module evaluates the electromagnetic environment across different frequencies and identifies the optimal passband in advance, ensuring that frequency transitions occur only when beneficial and not during active touch detection, thereby maintaining measurement precision
Solution Approach 2:
The system implements a feedback mechanism where touch detection results and noise measurements are continuously monitored. When false touches are detected or noise levels exceed thresholds, the system feeds this information back to the frequency selection logic, which then adjusts the operating frequency accordingly. This closed-loop control ensures accurate touch detection while adapting to noise conditions
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 significantly reduces noise-induced false touches and improves accuracy by rendering the capacitive sensing circuit relatively immune to noise, especially from common sources like chargers and power supplies, while also addressing the presence of water.
Implementation Method 1
capacitive sensing circuit receives a response signal from a touch sense array
Implementation Method 2
The capacitive sensing circuit measures a noise component of the response signal
Data Source
AI summary
A method for improving noise immunity of capacitive sensing circuit associated with a touch sense array is disclosed. The capacitive sensing circuit receives a response signal from a touch sense array. The capacitive sensing circuit measures a noise component of the response signal. When a level of noise of the noise component within a passband of the capacitive sensing circuit is greater than a threshold, the capacitive sensing circuit changes at least one parameter of capacitive sensing circuit to move the passband substantially outside the frequency spectrum of the noise component.