Spread Spectrum Touch Detection for Interference Rejection
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Solution Overview
Problem
Electromagnetic interferences significantly affect the accuracy of touch detection in electronic devices, such as mobile phones and tablets, due to their reliance on weak electrical signals, which are vulnerable to noise from natural and artificial sources.
Innovation Solution
A touch detection method and system that employs spread spectrum technology to improve location detection accuracy by generating a spectrum-spread signal, outputting it to the touch screen's driving terminal, and performing a de-spread spectrum process on the coupled signal received from the response terminal to obtain a touch detection signal, while using a sliding-correlation de-spread spectrum with a step size constrained by capacitor time constants to enhance anti-interference capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If weak electrical signals are used for touch detection, then the device can operate with low power consumption, but the detection accuracy is severely affected by electromagnetic interference
Solution Approach 1:
The patent changes the signal parameter from weak electrical signals to spread spectrum signals with wider bandwidth. By transforming the signal into the frequency domain and spreading it across a wider spectrum, the system achieves better interference rejection while maintaining low power consumption characteristics.
2Device complexity
If conventional electrical signals are used for touch detection, then the system is simple to implement, but electromagnetic interference from wireless communication, LCD, and charger severely affects detection performance
Solution Approach 1:
The patent introduces spread spectrum modulation as an intermediary layer between the touch detection system and electromagnetic interference. This intermediary transforms the signal in a way that makes it resistant to conventional electromagnetic interferers, effectively isolating the detection system from environmental noise.
Solution Approach 2:
The patent moves the touch detection signal from the time domain to the frequency domain through spread spectrum modulation. By expanding the signal into the frequency domain across a wider bandwidth, the system gains the ability to filter out narrowband electromagnetic interferers while maintaining detection capability.
3Object-affected harmful factors
If spread spectrum technology is applied to touch detection, then anti-interference ability is enhanced, but the system complexity increases due to additional modulation and demodulation processes
Solution Approach 1:
The patent implements a universal spread spectrum signal processing approach that can be applied to various touch detection scenarios. The same modulation and demodulation processes work for different touch types and environmental conditions, providing multi-functional interference resistance without requiring separate systems for each application.
Data Source
AI summary
Some embodiments of the present invention provide a touch detection method and system. The touch detection method comprises: performing a spread spectrum process on a driving signal to generate a spectrum-spread signal; outputting the spectrum-spread signal to a driving terminal of a touch screen; receiving, from a response terminal of the touch screen, a coupled signal formed by coupling the spectrum-spread signal received by the driving terminal to the response terminal; and performing a de-spread spectrum process on the coupled signal to obtain a touch detection signal. Employing the embodiments of the present invention, an accuracy of a detection of a location on the touch screen can be improved by a spread spectrum technology, so as to enhance an anti-interference ability of a touch-controlled device.