Active Pen Signal Processing via Under-Sampling and Demodulation
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Solution Overview
Problem
Capacitive touch screens experience reduced signal-to-noise ratio and touch precision due to interference signals, leading to potential failure in identifying active pen signals and causing point jumps.
Innovation Solution
The method involves an active pen sending an excitation signal to a touch screen, which under-samples and demodulates the signal to calculate touch coordinates, thereby improving signal processing precision and reducing noise interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the capacitive touch screen receives signals via a coupled capacitor with an open electrical field, then the active pen can be used for touch input operations, but interference signals are easily coupled resulting in reduced signal-to-noise ratio and decreased touch precision
Solution Approach 1:
The patent converts the harmful interference signals into beneficial information by using them as reference signals for correlation processing. The interference signals that were previously causing noise are now used to improve signal detection accuracy through cross-correlation operations, transforming the harmful coupling effect into a useful reference for signal processing
Solution Approach 2:
The patent introduces correlation processing as an intermediary mechanism between the received signal and the touch coordinate determination. This intermediary process separates the useful active pen signal from interference by comparing the received signal with known reference signals, effectively filtering out harmful interference while preserving the intended touch information
2Reliability
If conventional sampling methods are used to process the excitation signal, then the signal can be processed, but the sampling frequency is high resulting in increased power consumption and cost
Solution Approach 1:
The patent changes the sampling frequency parameter from conventional high values to a lower value that is sufficient for the specific application. By analyzing the actual signal characteristics and interference patterns, the patent determines that a reduced sampling frequency maintains processing reliability while significantly lowering power consumption and system cost
Solution Approach 2:
The patent applies partial sampling action by selectively sampling at critical moments rather than continuous high-rate sampling. The correlation processing enables the system to extract sufficient information from partial samples, avoiding the excessive power consumption of continuous high-frequency sampling while maintaining signal processing reliability
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 approach enhances the signal-to-noise ratio, reduces sampling frequency, lowers costs, and decreases power consumption while preventing noise frequency bands with severe interference.
Implementation Method 1
The principle of the active pen is that the capacitive touch screen receives a signal sent by the active pen via a coupled capacitor
Data Source
AI summary
A method for processing a signal from an active pen, and an active pen and a touch screen thereof are provided. The method includes: under-sampling a received excitation signal from the active pen with a predetermined sampling frequency to obtain a digital signal of the excitation signal from the active pen, and demodulating the digital signal of the excitation signal from the active pen to obtain a demodulated signal; and calculating touch coordinates according to an amplitude and a phase of the demodulated signal, and outputting the touch coordinates. Embodiments of the present application are intended to improve the signal processing precision of the active pen and improve the signal-to-noise ratio.