Adjustable Biquad Noise Filter for Touch Screen Signal Integrity
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Solution Overview
Problem
Mutual capacitance type touch screen devices face challenges in accurately filtering noise from touch sensors due to varying noise ranges across different products, leading to the need for specific noise filters for each product, which complicates the removal of erroneous charge variations and affects touch coordinate calculation accuracy.
Innovation Solution
A touch screen device equipped with a noise filter that can adjust its pass band by varying resistance values, allowing it to change the center frequency and pass band width, utilizing a biquad bandpass filter design with fully differential or single-ended configurations, enabling optimal noise removal for different touch scenarios, such as those caused by human touch or pens.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a fixed noise filter is used for each product, then noise removal is optimized for that specific product, but device complexity increases and adaptability decreases
Solution Approach 1:
The noise filter is designed with adjustable parameters including variable resistance values and variable capacitance values that can be dynamically changed based on different product requirements. This allows a single filter design to adapt to multiple products with different noise characteristics, eliminating the need for separate fixed filters for each product while maintaining optimal noise removal performance.
Solution Approach 2:
The invention changes the electrical parameters of the noise filter (resistance and capacitance values) to match different noise ranges of various touch screen products. By adjusting these parameters, the same filter hardware can be optimized for different products, reducing complexity while preserving measurement precision.
2Reliability
If different noise filters are used for different products, then noise removal performance is optimized, but manufacturing complexity and inventory requirements increase
Solution Approach 1:
The noise filter is designed as a universal component that can serve multiple products with different noise characteristics. By incorporating adjustable resistance and capacitance elements, a single filter design fulfills multiple product-specific requirements, simplifying manufacturing processes and reducing inventory complexity while maintaining reliable noise removal performance across different products.
3Adaptability or versatility
If the pass band is fixed, then the filter design is simpler, but it cannot adapt to different touch scenarios such as human touch or pen touch
Solution Approach 1:
The pass band of the noise filter is made dynamic through adjustable resistance and capacitance values. This allows the filter to adapt its frequency response characteristics to match different touch scenarios (human touch, pen touch, etc.) while maintaining a manageable adjustment complexity through systematic parameter selection.
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
The adjustable noise filter minimizes noise in touch sensors, improves signal-to-noise ratio, and enhances the accuracy of touch coordinate calculations by optimizing the pass band and width for specific touch conditions, reducing errors and improving overall touch screen performance.
Implementation Method 1
A touch screen device equipped with a noise filter that can adjust its pass band by varying resistance values, allowing it to change the center frequency and pass band width, utilizing a biquad bandpass filter design
Data Source
AI summary
A touch screen device includes a touch screen panel including Tx lines, Rx lines, and touch sensors formed at crossings of the Tx lines and Rx lines; a Tx driving circuit for supplying a driving pulse to the Tx lines; and an Rx driving circuit for sampling charge variations of the touch sensors, which are received through the Rx lines, and converting the received charge variations into touch raw data, wherein the Rx driving circuit includes: a noise filter that removes noise of signals received from the Rx line; an integrator that accumulates the charge variations passing through the noise filter; a sampling circuit that samples the accumulated charge variation of the integrator; and an analog to digital converter that converts the charge variation sampled by the sampling circuit into the touch raw data, the noise filter being a biquad bandpass filter including variable resistors and variable capacitors.