Capacitance Sensing False Touch Filtering via Adaptive Noise Segmentation
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Solution Overview
Problem
Capacitance sensing systems face challenges in accurately distinguishing touch events from noise, particularly due to external noise sources like chargers and electrical fields, which can lead to erroneous sense events and false touch detections.
Innovation Solution
The implementation of a noise listening circuit that dynamically adjusts filtering based on detected noise levels, using techniques such as median filtering and adaptive jitter filtering to differentiate between common mode and localized noise, thereby enhancing the accuracy of touch event detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If common mode filtering is applied to address internal noise, then noise common to all electrodes is reduced, but external noise localized to specific electrodes cannot be effectively filtered
Solution Approach 1:
The patent segments the electrode array into multiple groups and applies different filtering strategies to each group. Instead of using a single uniform filter, the system divides the sensing area and applies localized filtering to address external noise in specific regions while maintaining global filtering for internal noise, thereby resolving the contradiction between filtering effectiveness and system complexity
Solution Approach 2:
The patent implements local quality by applying different filtering characteristics to different regions of the electrode array. Localized filtering is applied to areas experiencing external noise from chargers or electrical fields, while common mode filtering is applied globally. This differentiated approach allows the system to address specific noise sources without unnecessarily complicating the entire filtering system
2Reliability
If filtering is applied to reduce noise, then false touch events are reduced, but legitimate touch events may be missed or degraded
Solution Approach 1:
The patent applies dynamic filtering by continuously monitoring noise levels and adjusting filter strength and characteristics in real-time. When external noise is detected, the system strengthens localized filtering; when noise levels are low, it reduces filtering intensity to preserve touch sensitivity. This dynamic adaptation allows the system to reject false touches during noisy periods while maintaining accurate touch detection during quiet periods
Solution Approach 2:
The patent changes filtering parameters such as filter coefficient, cutoff frequency, and noise threshold dynamically based on detected noise conditions. By adjusting these parameters in response to environmental noise levels, the system optimizes the balance between false touch rejection and legitimate touch detection accuracy, resolving the contradiction between noise reduction and measurement precision
3Reliability
If noise filtering is intensified to handle external noise sources, then charger noise and electrical field interference are reduced, but processing time and computational load increase
Solution Approach 1:
The patent segments the filtering operation into parallel processing channels, with different filter types applied to different electrode groups simultaneously. This segmentation allows the system to process noise reduction for multiple regions in parallel, reducing overall processing time while maintaining intensive filtering where external noise is detected
Solution Approach 2:
The patent applies partial filtering action by implementing filtering only in regions where external noise is detected, rather than uniformly across the entire electrode array. This selective approach reduces the total computational load and processing time while maintaining effective noise rejection in affected areas, resolving the contradiction between noise rejection capability and processing time
Data Source
AI summary
Apparatuses and methods of false touch filtering are described. One device includes a controller and a capacitance sensing array including multiple sense elements (e.g., intersections of TX and RX electrodes). The controller includes a capacitance sensing circuit coupled to the capacitance sensing array, and a filter circuit coupled to the output of the capacitance sensing circuit. The controller is configured to receive, from the capacitance sensing circuit, data representing capacitances of the sense elements, process the data to identify activated sense elements, and filter the data to remove false touch events based on a spatial relationship of activated sense elements.