Method and device for improved accuracy of proximity and touch detection in mobile devices
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Solution Overview
Problem
Mobile devices face challenges in accurately detecting proximity to the human body, leading to potential health risks from excessive RF radiation and connectivity issues due to inaccurate proximity sensor readings, which are influenced by environmental factors like temperature and humidity.
Innovation Solution
A capacitive touch sensor system with a capacitive touch controller and sensing element, combined with shielding areas, is used to accurately detect human proximity by canceling environmental capacitance and adjusting for temperature effects, thereby controlling RF power output to comply with safety regulations and maintain connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If proximity detection is performed using capacitive sensing, then touch input functionality is enabled, but false proximity detections occur due to environmental capacitance changes
Solution Approach 1:
The system performs calibration before normal operation to establish a baseline environmental capacitance value. This preliminary action allows the system to distinguish between environmental capacitance changes and actual proximity events, preventing false detections while maintaining touch input functionality.
Solution Approach 2:
The system continuously monitors capacitance changes and compares them against the calibrated baseline, using feedback mechanisms to determine whether a proximity event has occurred. This feedback loop enables accurate differentiation between environmental variations and genuine proximity detections.
2Productivity
If RF power is increased to maintain connectivity, then communication range is improved, but RF radiation exposure exceeds safety limits when device is near human body
Solution Approach 1:
The system uses proximity sensing feedback to dynamically adjust RF power output. When a body part is detected in proximity, the system automatically reduces RF power to comply with SAR safety limits, and increases power when no body part is present, thereby maintaining connectivity while preventing excessive radiation exposure.
3Measurement precision
If proximity sensor accuracy is improved by adding calibration features, then false detections are reduced, but device complexity increases
Solution Approach 1:
The calibration features utilize the existing capacitive touch sensor hardware and controller, making the proximity detection system multi-functional. The same capacitive sensing mechanism serves both touch input and proximity detection purposes, with calibration simply adding a preliminary measurement step rather than requiring separate dedicated hardware.
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 solution enhances the accuracy of proximity detection, reducing RF radiation exposure and ensuring compliance with safety limits while maintaining effective connectivity by accurately adjusting RF power based on human proximity.
Implementation Method 1
A capacitive touch sensor system with a capacitive touch controller and sensing element, combined with shielding areas, is used to accurately detect human proximity by canceling environmental capacitance
Implementation Method 2
combined with shielding areas, is used to accurately detect human proximity by canceling environmental capacitance
Data Source
AI summary
A mobile device has a proximity sensor. A compensation value of the proximity sensor is determined. The compensation value is compared to a reference compensation value to determine validity of the compensation value. A capacitance of the proximity sensor is measured. A value of the capacitance of the proximity sensor is adjusted based on the compensation value. A coefficient defining a relationship between a capacitance of the proximity sensor and a temperature of the mobile device is calculated. A temperature sensor is coupled to the proximity sensor. The temperature of the mobile device is measured. A value of the capacitance of the proximity sensor is adjusted based on the coefficient and the temperature of the mobile device. The adjusted capacitance value is compared to a threshold capacitance value to determine proximity of an object to the mobile device. A radio frequency signal is adjusted by detecting proximity.