Touch Sensor Direct Sequence Spread Spectrum Driving
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Solution Overview
Problem
Existing touch sensor driving methods face challenges in noise immunity and accuracy, particularly in low-frequency noise environments and large-panel applications, where time division processing restricts sample acquisition and multi-line driving methods increase complexity and limit pattern creation within response time.
Innovation Solution
A touch sensor employing a direct sequence spread spectrum technique to modulate driving signals across multiple driving lines, using pseudo-random binary sequences for simultaneous driving and demodulation, which includes a driving unit for signal modulation and a sensing unit for demodulation, amplification, and digital signal processing to enhance noise immunity and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If time division processing is used to sequentially send driving signals to driving lines, then the implementation is simple and demodulation is not required, but the response time is restricted and it is difficult to obtain a large number of samples
Solution Approach 1:
The patent segments the driving signals by assigning unique pseudo-random binary sequences to different driving lines, allowing simultaneous transmission of multiple driving signals without requiring sequential time-division processing. This segmentation approach enables parallel sample acquisition while maintaining implementation simplicity through code-division multiplexing.
Solution Approach 2:
The patent employs periodic pseudo-random binary sequences with specific correlation properties to modulate driving signals on multiple lines simultaneously. The periodic nature of these sequences enables synchronized demodulation and rapid sample acquisition across all driving lines, resolving the contradiction between simple implementation and high productivity.
2Productivity
If multi-line driving method is used to simultaneously send driving signals to multiple driving lines, then a large number of samples can be obtained and noise filtering performance is excellent, but a demodulation circuit is required which increases complexity and area
Solution Approach 1:
The patent uses pseudo-random binary sequences as code copies that can be transmitted simultaneously on multiple driving lines. Each driving line is assigned a unique code copy, and the receiving end can separate and demodulate signals from different lines by correlating with the known code sequences, eliminating the need for complex hardware demodulation circuits.
Solution Approach 2:
The patent replaces the traditional mechanical/electrical demodulation circuit approach with a signal processing approach using pseudo-random code modulation and correlation. This substitution reduces hardware complexity and area while maintaining the ability to simultaneously process multiple driving lines and achieve excellent noise filtering performance.
3Ease of operation
If regular pattern using two different polarities is used in multi-line driving method, then driving signals can be transmitted, but there are restrictions on creation of large types of patterns within a predetermined response time
Solution Approach 1:
The patent changes the fundamental parameter of signal representation from simple two-polarity patterns to multi-level pseudo-random binary sequences. This parameter change enables a vastly increased number of distinguishable signal patterns while maintaining the ability to transmit driving signals, thereby improving pattern creation flexibility without sacrificing transmission capability.
Data Source
AI summary
A touch sensor includes a touch panel including driving lines and sensing lines and having node capacitors between neighboring or overlapping driving lines and sensing lines, a driving unit configured to modulate driving signals using a direct sequence spread spectrum technique or scheme and simultaneously drive two or more of the driving lines using the modulated driving signals, and a sensing unit configured to demodulate the signals from the sensing lines using the direct sequence spread spectrum method and generate demodulated signals.