Multiplexed Capacitive Sensing for Touch Detection Throughput
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Solution Overview
Problem
Existing touch detection systems face challenges in increasing the signal-to-noise ratio and efficiently transmitting multiplexed signals across multiple transmitter electrodes, which affects the accuracy and reliability of positional information determination for input objects.
Innovation Solution
A processing system coupled with transmitter and receiver electrodes that simultaneously drives multiple transmitter electrodes with distinct digital codes, allowing for demodulation and determination of positional information by decoding the resulting signals, utilizing multiplexing schemas like code division multiplexing or orthogonal frequency division multiplexing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple transmitter electrodes are driven sequentially one at a time, then the signal-to-noise ratio is maintained, but the throughput and efficiency of touch detection are reduced
Solution Approach 1:
The patent combines multiple transmitter electrode drive operations into a single time period by simultaneously driving multiple transmitter electrodes with different codes. This merging of operations increases throughput while the code-based separation maintains signal integrity and signal-to-noise ratio through mathematical independence of the codes.
Solution Approach 2:
The patent segments the drive signal for each transmitter electrode into distinct codes that are mathematically independent from each other. This segmentation allows multiple electrodes to be driven simultaneously without interference, as each electrode's signal can be independently identified and processed at the receiver端 through correlation with its specific code.
2Productivity
If multiple transmitter electrodes are driven simultaneously with the same signal, then the throughput is increased, but the ability to determine positional information accurately is degraded
Solution Approach 1:
The patent segments the drive signal into distinct codes for each transmitter electrode, where each code is mathematically independent. This segmentation enables the receiver to distinguish which transmitter electrode produced which signal component, preserving the ability to accurately determine positional information even when multiple electrodes are driven simultaneously.
Solution Approach 2:
The patent applies local quality by assigning different codes to different transmitter electrodes. Each electrode has its own unique code signature, allowing the receiver to identify the specific electrode location corresponding to each received signal component, thereby maintaining measurement precision while enabling simultaneous multi-electrode operation.
3Productivity
If more transmitter electrodes are driven in parallel, then the throughput increases, but the complexity of signal demodulation and processing increases
Solution Approach 1:
The patent segments the overall signal into code-specific components, where each transmitter electrode is assigned a unique code. The receiver processes signals by correlating with each code independently, which simplifies the processing complexity compared to other multiplexing schemes. The mathematical independence of codes allows for efficient demodulation even as the number of parallel electrodes increases.
Data Source
AI summary
Embodiments of the invention generally provide an input device that simultaneously transmits a multiplexed signal across two or more transmitter electrodes used in touch detection. The multiplexed includes two or more component signals that are transmitted on respective electrodes (or channels). The component signals are then decoded and correlated to indicate a positional location of an input object. Various multiplexing schemas—e.g., code division multiplexing, frequency division multiplexing, orthogonal frequency division multiplexing, and the like—may be used to generate the multiplex signal and then demultiplex the received results.