Multi-channel Capacitive Touch Sensing via Non-orthogonal Spreading Codes
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Solution Overview
Problem
Conventional liquid crystal display touch panels face issues such as long touch reaction times, low scan rates, and noise interference, which affect touch control chip operations and increase costs and thickness, making it difficult to reduce die size and cost.
Innovation Solution
A multi-channel sensing system utilizing a transceiver with a spreading code generator and modulator to emit non-orthogonal spreading signals through emitting electrodes, which are converted into coupled signals by capacitive coupling, allowing for effective determination of touch events without the need for additional noise-reducing mechanisms, using an invertible matrix and its inverse for demodulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an insulating material is disposed between the ITO sensor and the display panel to block noise, then noise interference is reduced, but cost and thickness of the apparatus are increased
Solution Approach 1:
The patent extracts and removes the insulating material layer from the conventional touch panel structure. Instead of adding noise-blocking materials between the ITO sensor and display panel, the invention uses a different approach that eliminates the need for this additional layer, thereby reducing cost and thickness while maintaining noise rejection capability through the capacitive coupling sensing mechanism
Solution Approach 2:
The patent replaces the physical mechanical barrier (insulating material layer) with an electrical field-based sensing mechanism. By using capacitive coupling to detect touch events directly through the display panel, the system substitutes the need for physical noise-blocking structures with an electromagnetic field-based detection approach that inherently rejects noise
2Productivity
If conventional touch sensing uses sequential scanning of sensing lines, then circuit design is simplified, but touch reaction time is long and scan rate is low
Solution Approach 1:
The patent implements continuous touch sensing by maintaining constant voltage on all sensing lines simultaneously rather than sequentially scanning them. The capacitive coupling mechanism allows all sensing lines to continuously monitor touch events across the entire panel, eliminating dead time between scans and achieving real-time touch detection with maximum scan rate
Solution Approach 2:
The patent merges the functions of multiple sensing lines into a unified capacitive coupling detection system. By using the display panel's pixel electrodes as both display elements and sensing elements through capacitive coupling, the system combines display and touch sensing functions, allowing simultaneous monitoring of all channels without sequential scanning delays
3Measurement precision
If amplifier is added to amplify the coupled voltage for touch detection, then touch sensitivity is improved, but die size and cost are increased
Solution Approach 1:
The patent implements a self-service sensing mechanism where the capacitive coupling between the touch object and the pixel electrodes directly generates detectable voltage changes on the sensing lines. The system uses the touch event itself to generate the sensing signal without requiring external amplification, as the coupled voltage naturally reaches sufficient levels for detection through the high-capacitance coupling mechanism
Solution Approach 2:
The patent makes the pixel electrodes serve dual functions as both display elements and sensing elements. The same pixel electrodes used for display also act as capacitive sensors for touch detection, eliminating the need for separate sensing structures and amplifiers. This multi-functionality reduces component count, die size, and cost while maintaining high touch detection sensitivity
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 reduces touch reaction time, eliminates the need for SNR enhancement mechanisms, and lowers power consumption while maximizing resource use, offering flexibility and cost-effectiveness by enabling multiple emitting electrodes to be driven simultaneously and resisting noise interference.
Implementation Method 1
the spreading signals are converted into coupled signals by capacitive coupling
Data Source
AI summary
A multi-channel sensing system and operating method thereof are disclosed. The multi-channel sensing system includes a transceiver, emitting electrodes, and a receiving electrode. The transceiver includes a spreading code generator and a modulator. The spreading code generator generates a non-orthogonal spreading code through an invertible matrix and then the modulator modulates a data signal to spreading signals according to the non-orthogonal spreading code. The emitting electrodes, corresponding to sensing channels respectively, emit the spreading signals at the same time to pass through corresponding sensing channels respectively, and the spreading signals are converted into coupled signals by capacitive coupling. The receiving electrode receives the coupled signals and generates a received signal according to the coupled signals.