Capacitive Sensor Array Reference Electrode Shielding
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Solution Overview
Problem
Proximity and fingerprint sensors are susceptible to noise, particularly when the pattern being sensed covers a large portion of the sensor, leading to degraded signal quality and issues with false acceptance and rejection rates, which existing noise rejection methods like differential measurement and baseline image subtraction fail to adequately address.
Innovation Solution
The use of a fixed reference receiver electrode with conductive shielding and thinner transmitter electrodes proximate to the reference receiver electrode, which reduces sensitivity to pattern features and allows for effective noise rejection while maintaining accurate feature detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a reference receiver electrode is used for noise rejection, then signal quality is improved, but sensitivity to pattern features is reduced
Solution Approach 1:
The patent applies local quality by making the transmitter electrode thickness non-uniform: thinner portions are positioned proximate to the reference receiver electrode to reduce noise sensitivity, while thicker portions are positioned proximate to imaging receiver electrodes to maintain pattern feature detection sensitivity. This localized variation in electrode thickness resolves the contradiction by optimizing different regions for different functions.
2Object-affected harmful factors
If transmitter electrodes are made thinner proximate to the reference receiver electrode, then noise sensitivity is reduced, but signal strength is decreased
Solution Approach 1:
The transmitter electrode is designed with varying thickness: thinner sections near the reference receiver electrode reduce noise sensitivity and unwanted coupling, while thicker sections near imaging receiver electrodes maintain strong signal strength for pattern detection. This local quality variation resolves the contradiction between noise rejection and signal strength.
3Object-affected harmful factors
If differential measurement is used for noise rejection, then common mode noise is reduced, but false acceptance and rejection rates increase
Solution Approach 1:
The patent changes the physical parameter of transmitter electrode thickness to optimize the differential measurement process. By making portions of the transmitter electrode thinner near the reference receiver electrode, the capacitive coupling and noise pickup are reduced, improving the quality of the differential measurement and reducing false acceptance/rejection rates while maintaining common mode noise rejection.
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 configuration improves signal quality and reduces false acceptance and rejection rates in fingerprint and proximity sensing applications by minimizing noise sensitivity and enhancing the ability to distinguish between pattern features.
Implementation Method 1
conductive shielding disposed proximate to the reference receiver electrode
Implementation Method 2
each of the plurality of transmitter electrodes is configured to be driven by sensing signals and each of the plurality of receiver electrodes is configured to receive detected signals corresponding to the sensing signals driven onto the transmitter electrodes
Data Source
AI summary
A sensor array for capacitive sensing includes: a plurality of sensor electrodes, the plurality of sensor electrodes comprising: a plurality of transmitter electrodes and a plurality of receiver electrodes, wherein the plurality of receiver electrodes include a plurality of imaging receiver electrodes and a reference receiver electrode, and wherein each of the plurality of receiver electrodes overlaps with the plurality of transmitter electrodes; wherein each of the plurality of transmitter electrodes is configured to be driven by sensing signals and each of the plurality of receiver electrodes is configured to receive detected signals corresponding to the sensing signals driven onto the transmitter electrodes; and conductive shielding disposed proximate to the reference receiver electrode.