Sensor Electrode Defect Detection via Quadrature Demodulation
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Solution Overview
Problem
Existing sensor electrode arrays in input devices, such as proximity sensor devices, face challenges in detecting defects like open or short circuits during manufacturing and usage, which can affect the accuracy of capacitive proximity sensing.
Innovation Solution
A method involving quadrature demodulation of signals from sensor electrodes to determine in-phase and quadrature-phase responses, allowing for precise detection of defects by analyzing changes in these responses, which indicate phase shifts due to defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional sensing methods are used, then device complexity is reduced, but measurement precision deteriorates due to inability to detect defects
Solution Approach 1:
The patent replaces traditional mechanical or simple electrical sensing methods with quadrature demodulation technology. By using in-phase (I) and quadrature (Q) signal components, the system achieves precise defect detection through signal processing substitution, enabling accurate measurement of sensor electrode responses and identification of open/short circuit defects.
Solution Approach 2:
The patent transforms the sensing approach by changing from direct signal measurement to analyzing phase relationships. By converting the resulting signal into I and Q components through quadrature demodulation, the system detects defects based on phase shifts and amplitude variations, providing precise defect identification while maintaining manageable device complexity.
2Measurement precision
If advanced signal processing is applied, then measurement precision improves, but processing time increases
Solution Approach 1:
The patent employs periodic drive signals to excite the sensor electrodes, enabling quadrature demodulation through synchronized detection. By using periodic reference signals at the same frequency as the drive signal, the system efficiently extracts I and Q components through correlation processing, achieving accurate defect detection without excessive processing time delays.
Solution Approach 2:
The patent creates virtual copies of the drive signal in quadrature phase (0° and 90° phase shifted) to simultaneously measure both in-phase and quadrature components. This copying approach allows parallel processing of multiple signal aspects, improving defect detection accuracy while maintaining efficient processing throughput through simultaneous measurement.
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
Enables effective detection of sensor electrode defects, ensuring the accuracy and reliability of capacitive proximity sensing by identifying and potentially correcting issues before and during device usage.
Implementation Method 1
The capacitive sensing circuit is configured to acquire a first resulting signal from the sensor electrode and apply a quadrature demodulation to the first resulting signal to determine an in-phase response and a quadrature-phase response
Data Source
AI summary
A method for testing a sensor electrode is provided. The method includes acquiring a first resulting signal from a sensor electrode. The method further includes determining an in-phase response and a quadrature-phase response through a quadrature demodulation based on the first resulting signal. The method further includes detecting a defect of the sensor electrode based on the in-phase response and the quadrature-phase response.