Capacitive Touch Keyboard Multi-Frequency Sensing Against Noise
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Solution Overview
Problem
Capacitive touch systems face interference from noise in electronic devices, degrading detection accuracy, particularly in applications like LCDs, due to voltage variations detected by detection circuits.
Innovation Solution
A capacitive touch system and method that utilize frequency division multiplexing to input mixed signals with multiple driving frequencies, reducing noise interference, power consumption, and detection interval by modulating drive signals and decoding detection matrices to generate two-dimensional detection vectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional capacitive sensing with single frequency drive signal is used, then device structure is simple, but noise interference degrades detection accuracy
Solution Approach 1:
The patent segments the detection process by using multiple driving frequencies instead of a single frequency. Each frequency component can be independently analyzed to detect touches while filtering out noise that typically occurs at specific frequency ranges. The detection circuit processes signals at different frequencies separately, allowing noise rejection while maintaining detection accuracy.
Solution Approach 2:
The patent changes the frequency parameter of the drive signal from a single fixed frequency to multiple varying frequencies. By modulating the drive signal with different frequencies and analyzing the response at each frequency, the system can distinguish between actual touch signals and noise based on their frequency characteristics, thereby improving detection accuracy in noisy environments.
2Measurement precision
If multiple driving frequencies are used to reduce noise interference, then detection accuracy improves, but device complexity increases
Solution Approach 1:
The patent employs periodic modulation of drive signals at multiple frequencies in a structured sequence. By using periodic actions with known frequency patterns, the system can systematically analyze responses at each frequency point. This structured approach manages complexity by providing a predictable signal pattern that simplifies the processing and analysis of multiple frequency components compared to using arbitrary frequencies.
3Productivity
If conventional single-frequency drive signal is used, then power consumption is higher, but detection interval is longer
Solution Approach 1:
The patent implements continuous multi-frequency drive signals that simultaneously excite multiple frequency responses. This continuous action at multiple frequencies allows the detection circuit to gather information about touches across different frequency bands concurrently, reducing the total detection time. The system processes multiple frequency components in parallel rather than sequentially, improving detection speed while the efficient signal design minimizes power consumption.
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
The approach enhances detection accuracy, reduces power consumption, and shortens detection intervals by effectively filtering noise and improving signal quality in capacitive touch systems, particularly in touch panels and keyboards.
Implementation Method 1
Electric field can be generated between the first electrode 91 and the second electrode 92 so as to transfer charges to the second electrode 92
Implementation Method 2
When the conductor is present, the amount of charge transfer between the pair of electrodes can be changed so that it is able to detect whether the conductor is present or not according to a voltage variation
Data Source
AI summary
A capacitive touch system including a drive end, a capacitive touch sensing device and a detection end is provided. The drive end inputs a modulated drive signal into an input channel of the capacitive sensing device, wherein the modulated drive signal includes a plurality of driving frequencies. The detection end detects a detection signal of an output channel of the capacitive sensing device and generates a two-dimensional detection vector corresponding to each of the driving frequencies. The capacitive touch system includes a touch panel or a touch keyboard.