Dynamic Frequency Selection for Touch Panel Noise Mitigation
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Solution Overview
Problem
Capacitive touch sensing systems are hindered by noise signals from sources like CCFLs and AC/DC chargers, which distort touch signals and interfere with proper measurement.
Innovation Solution
A touch panel sensor system that includes a sensor to detect capacitance changes, a drive module generating periodic and constant voltage signals, and a measuring module to measure noise, allowing for frequency adjustment to minimize interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a touch panel sensor system operates at a fixed frequency, then the system structure is simple, but background noise from external sources (CCFLs, AC/DC chargers) distorts touch signals and interferes with proper measurement
Solution Approach 1:
The patent implements dynamic frequency selection by measuring background noise at multiple candidate frequencies and selecting the frequency with the lowest noise level. The system transitions from a fixed-frequency operation to a dynamic frequency adaptation mechanism, where the operating frequency is adjusted based on real-time noise measurements to optimize touch signal detection accuracy
Solution Approach 2:
The system changes the operating frequency parameter based on measured noise characteristics. By measuring background noise at different frequencies and selecting the optimal frequency, the system dynamically adjusts the frequency parameter to minimize interference from external noise sources while maintaining simple measurement procedures
2Measurement precision
If the system measures background noise at multiple frequencies to find the optimal operating frequency, then touch signal measurement accuracy improves, but the measurement time and processing complexity increase
Solution Approach 1:
The system performs preliminary noise measurements at multiple candidate frequencies during system initialization or idle periods before actual touch detection begins. This preliminary action allows the system to pre-determine the optimal operating frequency, so that during active touch detection, no additional time is lost for frequency selection
Solution Approach 2:
The noise measurement and frequency selection process is implemented periodically rather than continuously. The system measures background noise at intervals, updates the optimal frequency selection, and maintains operation at that frequency until the next periodic update, reducing overall measurement time while maintaining accuracy
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 detects and mitigates background noise, ensuring accurate touch signal measurement by identifying and adjusting the operating frequency to reduce interference.
Implementation Method 1
a sensor configured to detect a change in capacitance associated with a touch upon a touch panel
Data Source
AI summary
A touch panel sensor system that can dynamically measure noise and automatically switch to a frequency with minimal noise is described. The touch panel sensor system includes a sensor configured to detect a change in capacitance associated with a touch upon a touch panel. The system also includes a drive module configured to generate a drive signal having a first waveform characteristic (e.g., signal having a periodic waveform characteristic) during a first phase (e.g., sensor phase) and a second drive signal having a second waveform characteristic (e.g., constant voltage signal) during a second phase (e.g., noise detection phase). The first and second drive signals are configured to drive the sensor. The system also includes a measuring module coupled to the sensor that is configured to measure noise having the first waveform characteristic (e.g., periodic waveform characteristic) during the second phase.