Touch Sensor Common-Mode Suppression With Signal Restoration
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Solution Overview
Problem
Existing touch sensor devices face challenges in effectively mitigating spatial common mode noise, which can lead to incorrect detection of input objects and noise interference, especially from display screens, affecting the accuracy of input detection.
Innovation Solution
A processing system and method that utilize a common mode noise suppression circuit to generate a feedback signal, mitigate spatial common mode noise in capacitive sensor electrodes' signals, and convert this mitigation into digital domain for further processing, allowing for accurate detection of input objects while reducing noise interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If common mode noise suppression is applied to mitigate spatial common mode noise, then noise interference is reduced, but the common mode signal itself is also suppressed along with the noise
Solution Approach 1:
The patent segments the common mode component into two distinct parts: noise (harmful) and signal (useful). By separating these components through differential processing - where the noise path undergoes suppression while the signal path is preserved and restored - the system eliminates noise interference without losing the common mode signal information.
Solution Approach 2:
The patent introduces an intermediary restoration mechanism that recovers the common mode signal after noise suppression. The restoration circuit acts as a mediator that takes the suppressed signal and adds back the appropriate common mode component, ensuring that the useful signal information is preserved while the harmful noise has been removed.
2Object-affected harmful factors
If spatial common mode noise is mitigated in analog domain, then noise interference is reduced, but signal processing complexity increases
Solution Approach 1:
The patent replaces complex digital signal processing operations with simpler analog circuit operations. By performing common mode noise suppression in the analog domain using dedicated circuits rather than complex digital algorithms, the system reduces processing complexity while achieving effective noise mitigation.
3Measurement precision
If feedback signal is used to mitigate spatial common mode, then noise suppression effectiveness is improved, but device complexity increases
Solution Approach 1:
The patent implements a feedback mechanism where the common mode noise estimate is fed back into the signal processing path to continuously suppress noise. This feedback loop improves noise suppression effectiveness by dynamically adjusting to changing noise conditions while maintaining a manageable circuit complexity through efficient feedback architecture.
Data Source
AI summary
A processing system is disclosed. The processing system includes an amplifier configured to generate a feedback signal, including a spatial common mode estimate generated from spatial-common-mode-processed signals. The processing system further includes charge integrators configured to obtain resulting signals from capacitive sensor electrodes, the resulting signals including a spatial common mode. The charge integrators generate the spatial-common-mode-processed signals by mitigating the spatial common mode in the resulting signals using the feedback signal. The processing system also includes a controller configured to obtain digital touch signals by analog-to-digital converting the spatial-common-mode-processed signals, obtain a digital spatial common mode estimate by analog-to-digital converting the spatial common mode estimate, and obtain at least one digital resulting signal by combining at least one of the digital touch signals with the digital spatial common mode estimate.