Capacitive Multi-Touch Noise Filtering via Dynamic Signal Analysis
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Solution Overview
Problem
Capacitive multi-touch systems face challenges in effectively filtering noise from capacitance signals in touch screens, leading to reduced accuracy and reliability in touch input detection due to variations in noise characteristics and filter bandwidths.
Innovation Solution
A capacitive multi-touch system that includes a touch sensor panel, a front-end circuit, and a digital signal processor, where the digital signal processor analyzes the noise spectrum of a common voltage and selects an appropriate noise filter path based on noise intervals to perform filtering operations, using a combination of digital filters, decimation filters, and moving average filters to optimize noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed noise filter is used for all conditions, then the device complexity is reduced, but the measurement precision deteriorates due to varying noise characteristics
Solution Approach 1:
The patent implements a dynamic filter selection mechanism where the digital signal processor analyzes noise characteristics of the common voltage signal in real-time and automatically selects the most appropriate filter from multiple available filters. This dynamic adaptation allows the system to optimize measurement precision for varying noise conditions without requiring a permanently complex filtering architecture.
Solution Approach 2:
The system changes filtering parameters by selecting different filters based on analyzed noise characteristics. The digital signal processor modifies the filtering operation dynamically by choosing from multiple filters with different characteristics, allowing the system to adapt to varying noise conditions and maintain high measurement precision without permanent system complexity.
2Measurement precision
If multiple noise filters are provided for different noise characteristics, then the measurement precision is improved, but the device complexity increases
Solution Approach 1:
The system performs preliminary noise analysis by having the digital signal processor analyze the noise characteristics of the common voltage signal before selecting a filter. This preliminary action allows the system to prepare the appropriate filter in advance, improving measurement precision while managing complexity through intelligent selection rather than permanent complex architecture.
Solution Approach 2:
The system implements a feedback mechanism where the digital signal processor continuously monitors noise characteristics and uses this information to select the most appropriate filter. This feedback loop allows the system to adapt to changing noise conditions and maintain high measurement precision without requiring all filters to be active simultaneously, thus managing device complexity.
3Speed
If noise filtering is performed without analyzing noise characteristics, then the processing speed is increased, but the reliability deteriorates due to ineffective noise reduction
Solution Approach 1:
The system performs a quick preliminary analysis of noise characteristics using the digital signal processor to identify the appropriate filter. This preliminary action is designed to be computationally efficient, maintaining processing speed while enabling reliable noise reduction by selecting the most suitable filter for current conditions.
Solution Approach 2:
The digital signal processor automatically analyzes noise characteristics and selects the appropriate filter without external intervention. This self-service mechanism ensures that the system maintains both processing speed and reliability by autonomously adapting to noise conditions without requiring complex external control systems.
Data Source
AI summary
A capacitive multi-touch system includes a touch sensor pane, a front-end circuit, and a digital signal processor. The touch sensor panel generates a capacitance signal corresponding to a touch input. The front-end circuit converts the capacitance signal to a sensing channel signal. The digital signal processor receives a common voltage (VCOM) from a display device, calculates a noise interval of two neighboring noise peaks of the common voltage, and performs a noise filtering operation on the sensing channel signal using a noise filter path. The noise filter path is selected from a plurality of noise filter paths based on the noise interval.