Directional Capacitive Proximity Sensor with Guard Electrodes
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Solution Overview
Problem
Conventional capacitive proximity-sensing technology fails to distinguish between an object directly above the sensor and objects around it, leading to confusion in applications like mobile phones, where user proximity is misinterpreted, such as touching the screen versus holding the phone to the head.
Innovation Solution
A directional capacitive proximity sensing circuit employing guard electrodes and dual capacitive sensors, where one sensor is positioned above and the other below the guard electrode, allowing for differential capacitance measurement to determine the direction of user proximity, thereby reducing stray capacitance and enhancing accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional capacitive proximity-sensing technology is used, then the sensor can detect the presence of an object, but it cannot distinguish the direction or location of the object relative to the sensor
Solution Approach 1:
The guard electrode is divided into multiple sections (first guard electrode section, second guard electrode section, third guard electrode section) that are coupled to different capacitive sensors. This segmentation allows each sensor to detect capacitance changes in specific directional zones, enabling the system to distinguish whether an object is above or below the sensor array while maintaining a relatively simple overall structure.
2Adaptability or versatility
If a single capacitive sensor is used, then the device structure remains simple, but the sensor cannot differentiate between objects at different positions around it
Solution Approach 1:
The guard electrode structure serves multiple functions: it acts as a shielding electrode to reduce stray capacitance, divides the sensing area into different zones through its segmented sections, and works with multiple capacitive sensors to provide directional detection capability. This multi-functionality allows the system to achieve versatile directional detection without proportionally increasing device complexity.
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 precise differentiation between user proximity above and below the sensor, improving the accuracy of proximity detection and reducing battery consumption by accurately distinguishing between touch screen interactions and head proximity in mobile devices.
Implementation Method 1
first capacitive sensor circuitry operable to sense a first capacitance and produce a first capacitive sensor reading indicative of the sensed first capacitance
Implementation Method 2
allowing for differential capacitance measurement to determine the direction of user proximity, thereby reducing stray capacitance and enhancing accuracy
Data Source
AI summary
A directional capacitive proximity sensor circuit capable of providing directional capacitive proximity sensing includes one or more guard electrodes, a first sensor, and a second sensor. The directional capacitive proximity sensor is installed in a device such that the first sensor is positioned near a first component of the device, and the second sensor is positioned near a second component of the device. The first and second sensors measure a capacitance to detect proximity of a user relative to the respective sensor, wherein the detected proximity is interpreted to determine a direction in which the user proximity is detected relative to the directional capacitive proximity sensor circuit. The guard electrode is provided to mitigate stray capacitance to reduce error in the capacitance measurements obtained by the first and second sensors.