Adaptive Capacitive Touch Sensor Circuit Noise Reduction
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Solution Overview
Problem
Projected capacitive touch sensors face challenges in accurately detecting multiple touch events and are susceptible to electromagnetic interference, which can result in false touch detections due to common mode noise.
Innovation Solution
The implementation of a projected capacitive touch sensor with an adaptive circuit that includes a direct route and an attenuator route, allowing for amplitude decrease, increase, or phase shift, and a differential circuit to generate a differential signal, along with a processor that adjusts the duty cycle and switches between routes to minimize noise and enhance touch detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a standard capacitive touch sensor uses conventional signal processing without adaptive routing, then the device complexity is low, but the measurement precision deteriorates due to common mode noise and electromagnetic interference causing false touch detections
Solution Approach 1:
The signal processing path is segmented into multiple routes: a direct route that bypasses the attenuator and an attenuated route that passes through the attenuator circuit. The system selectively activates one route based on signal conditions, allowing optimization for different operating scenarios and improving touch detection accuracy without permanently increasing circuit complexity.
Solution Approach 2:
The system dynamically switches between the direct route and the attenuated route based on real-time signal characteristics and noise levels. This dynamic adaptation allows the circuit to optimize its performance for current conditions, improving measurement precision while maintaining manageable complexity through conditional rather than permanent structural changes.
2Reliability
If the sensor processes signals from all columns without selective attenuation, then the device complexity remains low, but the reliability deteriorates due to susceptibility to electromagnetic interference and common mode noise
Solution Approach 1:
The attenuator circuit acts as an intermediary element between the sensor columns and the differential amplifier. By introducing this intermediate component with adjustable attenuation, the system can selectively reduce the impact of noisy signals while preserving useful touch detection signals, thereby improving reliability without requiring complete redesign of the signal processing architecture.
Solution Approach 2:
The system changes the attenuation parameter dynamically by switching between the direct route (zero attenuation) and the attenuated route (non-zero attenuation). This parameter adjustment allows the system to adapt to varying noise conditions and improve reliability for multi-touch detection without permanently complicating the circuit structure.
3Measurement precision
If no adaptive signal adjustment is implemented, then the ease of operation is high, but the measurement precision worsens due to inability to compensate for varying signal amplitudes and noise levels across different touch scenarios
Solution Approach 1:
The system performs self-adjustment by automatically selecting between the direct and attenuated routes based on inherent signal characteristics. The circuit monitors signal conditions and autonomously configures the appropriate signal path without requiring external intervention or complex manual calibration, thereby improving precision while maintaining ease of operation.
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 solution effectively reduces common mode noise and improves the accuracy of touch event detection, enabling reliable multi-touch capabilities while minimizing false positives from electromagnetic interference.
Implementation Method 1
an attenuator circuit for applying an amplitude decrease, an amplitude increase, or a phase shift to the sensor grid's signal
Implementation Method 2
a differential circuit that is configured to generate a differential signal based on an output signal from the adaptive circuit and a signal associated with a second portion of the two or more columns
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
This application relates to a projected capacitive touch sensor. The sensor includes a sensor grid including one or more electrically conductive rows and two or more electrically conductive columns. The sensor further includes an adaptive circuit that receives a signal associated with a first portion of the two or more columns and includes a direct route and an attenuator route, the attenuator route including an attenuator circuit for applying an amplitude decrease, an amplitude increase, or a phase shift to the sensor grid's signal, wherein the adaptive circuit is configured to switch between the direct route and the attenuator route. The sensor further includes a differential circuit that is configured to generate a differential signal based on an output signal from the adaptive circuit and a signal associated with a second portion of the two or more columns.