Injected Touch Noise Analysis for Capacitive Sense Arrays
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Solution Overview
Problem
Capacitance sensing systems face noise interference from conductive objects, leading to errors in measuring finger positions and touch events, which existing systems struggle to accurately mitigate.
Innovation Solution
The implementation of an injected touch method to simulate a conductive object's presence on the capacitive sense array, allowing the system to compute a noise metric and adjust its operation to reject noise, thereby improving measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If capacitance sensing systems measure capacitance changes to detect touch events, then touch detection capability is improved, but noise interference from conductive objects causes measurement errors
Solution Approach 1:
The system performs a listening scan before the actual touch scan to detect noise characteristics in advance. By measuring noise metrics during the listening scan phase, the system prepares noise rejection parameters before the actual measurement, allowing it to compensate for conductive object interference during the subsequent touch detection phase.
Solution Approach 2:
The system dynamically adjusts measurement parameters based on detected noise characteristics. By analyzing noise metrics from the listening scan, the system modifies its capacitance sensing parameters to optimize measurement accuracy under varying noise conditions, thereby maintaining precision despite the presence of conductive objects.
2Reliability
If the system performs listening scans to detect noise, then noise rejection capability is improved, but additional scanning time is required
Solution Approach 1:
The system implements periodic listening scans at strategically chosen moments before actual touch scans. By scheduling these noise detection scans periodically and efficiently, the system maintains continuous noise rejection capability while minimizing the time overhead, balancing reliability improvement with time constraints.
3Measurement precision
If the system uses injected touch to simulate conductive object presence, then noise metric computation accuracy is improved, but system complexity increases
Solution Approach 1:
The system creates a simplified model (injected touch) that replicates the electrical characteristics of actual conductive objects. By injecting test signals that mimic the capacitance effects of real touches, the system can accurately measure noise metrics without requiring physical test objects or complex measurement setups, thereby improving measurement accuracy while maintaining system simplicity.
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 enables the capacitive sensing system to effectively reject noise and provide accurate touch data by tuning its operation to minimize noise interference, enhancing the reliability of touch position measurements.
Implementation Method 1
Capacitance sensing systems can sense electrical signals generated on electrodes that reflect changes in capacitance. Such changes in capacitance can indicate a touch event
Data Source
AI summary
A processing device configured to induce, during a listening scan of a sense array, an injected touch to produce similar data as would be present during a touch scan of the sense array with a conductive object at a known location on the sense array. The processing device is further configured to compute, using the data, an estimate of a noise metric based on the injected touch.