Mobile Proximity Sensing With Capacitance Compensation and RF Control
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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 differentiate between environmental capacitance and human presence.
Innovation Solution
A capacitive touch sensor system with a shielding area and a capacitive touch controller that cancels environmental capacitance, allowing for precise detection of human proximity by isolating the capacitance attributable to the user, thereby adjusting RF power output to comply with safety regulations and maintain connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If proximity detection is performed using environmental capacitance sensing, then human presence can be detected, but environmental capacitance interference causes inaccurate detection results
Solution Approach 1:
The patent extracts and removes the environmental capacitance component from the total capacitance measurement. The capacitive touch controller separately identifies and subtracts the environmental capacitance (C_env) from the total measured capacitance (C_total) to obtain the user-proximity capacitance (C_user). This extraction process eliminates the harmful environmental interference and isolates the relevant proximity signal.
Solution Approach 2:
The patent introduces an intermediary reference capacitance measurement mechanism. A reference capacitor or reference sensing area is used to measure the environmental capacitance separately, which then serves as a mediator to compensate for environmental variations in the main proximity detection. This intermediary measurement allows the system to distinguish between environmental changes and actual proximity events.
2Reliability
If RF power output is increased to maintain connectivity, then communication quality improves, but RF radiation exposure exceeds safety limits when close to user
Solution Approach 1:
The patent implements a feedback control system where the capacitive touch controller continuously monitors proximity conditions and provides real-time feedback to the RF power control. When user proximity is detected through capacitance changes, the system automatically reduces RF power output to comply with SAR limits. This closed-loop feedback ensures connectivity is maintained at safe power levels by dynamically adjusting RF output based on detected proximity conditions.
3Adaptability or versatility
If capacitive sensing is used for both touch input and proximity detection, then device functionality is enhanced, but differentiation between touch and proximity events becomes difficult
Solution Approach 1:
The patent segments the capacitive sensing function into distinct operational modes for touch input and proximity detection. Different sensing areas are designated for different purposes: a first capacitive sensing area for proximity detection and a second capacitive sensing area for touch input. Additionally, different capacitance threshold levels are used to distinguish between proximity events (smaller capacitance change) and touch events (larger capacitance change), enabling the system to differentiate event types despite using the same sensing technology.
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 determining when to reduce RF power when in close proximity to the user.
Implementation Method 1
A capacitive touch sensor system with a shielding area and a capacitive touch controller that cancels environmental capacitance, allowing for precise detection of human proximity by isolating the capacitance attributable to the user
Implementation Method 2
A capacitive touch sensor system with a shielding area
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.