Capacitive Proximity Sensing for RF Power Control 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 fail to properly calibrate amidst environmental changes and human presence.
Innovation Solution
A capacitive touch sensor system with a capacitive touch controller and sensing element, coupled with shielding areas, is used to accurately detect human proximity by isolating environmental capacitance and adjusting RF power output to comply with SAR regulations while maintaining connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If proximity detection sensitivity is increased to detect human body proximity, then health protection from RF radiation is improved, but false detection from environmental factors increases
Solution Approach 1:
A capacitive sensor acts as an intermediary between the RF transmission system and the environment, measuring proximity through capacitance changes caused by human body proximity. This intermediary measurement enables indirect detection that is more accurate and less prone to false positives than direct RF-based detection methods.
Solution Approach 2:
The patent replaces traditional mechanical or direct electromagnetic proximity detection with capacitive sensing, which measures electrical field interactions. This substitution provides more precise measurement of proximity by detecting changes in capacitance caused by the dielectric properties of the human body, thereby improving both health protection and measurement accuracy.
2Object-affected harmful factors
If RF power output is reduced to comply with SAR regulations, then health safety is improved, but wireless connectivity performance deteriorates
Solution Approach 1:
The system dynamically adjusts RF power output based on real-time proximity measurements from the capacitive sensor. When the human body is detected in proximity, RF power is reduced to comply with SAR regulations. When no body is present, RF power is increased to maintain optimal wireless connectivity. This dynamic adaptation resolves the contradiction by making the system flexible rather than static.
Solution Approach 2:
The patent changes the RF power parameter based on proximity conditions. By monitoring capacitance changes and translating them into proximity determinations, the system adjusts the RF transmission power parameter accordingly, ensuring both health compliance and connectivity performance are optimized for current conditions.
3Ease of operation
If environmental capacitance is included in calibration, then sensor responsiveness is improved, but proximity detection accuracy deteriorates
Solution Approach 1:
The patent extracts and separates environmental capacitance from the total capacitance measurement. By identifying and removing the environmental baseline capacitance component, the system isolates only the capacitance changes caused by human body proximity. This extraction process improves measurement precision while maintaining sensor responsiveness to actual proximity events.
Solution Approach 2:
The system performs preliminary calibration to establish a baseline environmental capacitance value before actual proximity detection begins. This preliminary action captures environmental factors that are then subtracted from subsequent measurements, ensuring that only changes caused by human proximity are detected. This approach maintains responsiveness while eliminating false positives from environmental variations.
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 power when near the body to prevent excessive radiation and ensuring reliable connectivity by effectively differentiating human presence from environmental factors, thus addressing both health and functionality concerns.
Implementation Method 1
A capacitive touch sensor system with a capacitive touch controller and sensing element, coupled with shielding areas, is used to accurately detect human proximity by isolating environmental capacitance
Implementation Method 2
A capacitive touch sensor system with a capacitive touch controller and sensing element, coupled with shielding areas, is used to accurately detect human proximity by isolating 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.