Antenna-Based Capacitance Proximity Sensor for SAR Compliance
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Solution Overview
Problem
Conventional mobile communication devices face challenges in reducing electromagnetic radiation to comply with safety limits, as they lack effective methods to differentiate between human and non-human objects, leading to unnecessary power emission.
Innovation Solution
A proximity sensor system that utilizes the antenna structure as a sensing conductor, coupled with a capacitance sensing circuit and processing circuit, to generate a proximity sensing signal and distinguish between human and non-human objects by setting different threshold values, thereby adjusting the transceiver's power emission accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sensing antennas are configured to both ends of a communication antenna with traditional proximity sensors, then the SAR value can comply with test specification, but the area of layout design is increased and unnecessary power emission occurs
Solution Approach 1:
The patent combines the antenna structure with the sensing conductor function by using the antenna itself as the sensing conductor for capacitance sensing. This integration eliminates the need for separate sensing antennas and traditional proximity sensors, thereby reducing layout area while maintaining SAR compliance through accurate human body detection
Solution Approach 2:
The antenna structure serves dual functions: it acts as both the communication antenna for wireless signal transmission and as the sensing conductor for capacitance-based proximity sensing. This multi-functionality reduces the number of separate components needed, optimizing layout space while ensuring reliable SAR compliance
2Reliability
If traditional proximity sensors are used to detect distance between electronic apparatus and human body, then SAR value can be maintained within safe range, but the device cannot distinguish between human and non-human objects leading to unnecessary power reduction
Solution Approach 1:
The patent utilizes capacitance sensing to detect changes in electrical parameters (capacitance values) that occur when a human body approaches the antenna. By monitoring these parameter changes and comparing them against threshold values, the system can distinguish between human and non-human objects, enabling intelligent power management that reduces emission only when necessary for SAR compliance
3Reliability
If sensing antennas and sensors are used to detect proximity, then radiation power can be adjusted to maintain SAR compliance, but the layout design area is increased
Solution Approach 1:
The patent merges the antenna structure with the sensing conductor function, using the antenna itself for capacitance sensing. This integration eliminates the need for separate sensing antennas and traditional proximity sensors, thereby reducing device complexity and layout area while maintaining SAR compliance
Solution Approach 2:
The antenna structure serves dual functions as both communication antenna and sensing conductor, reducing the number of separate components needed and simplifying the overall sensor structure while ensuring reliable SAR compliance through capacitance-based human body detection
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 solution allows for reduced electromagnetic radiation exposure by accurately determining when a human is using the device, enabling the transceiver to lower power emission only when necessary, thus enhancing user safety and compliance with radiation limits.
Implementation Method 1
a capacitance sensing circuit, coupled to the matching circuit, wherein the capacitance sensing circuit senses a capacitance variation on the antenna structure via the matching circuit and accordingly generates a proximity sensing signal
Data Source
AI summary
A proximity sensor and a mobile communication device thereof are provided. The mobile communication device includes an antenna structure, a matching circuit, a capacitance sensing circuit and a processing circuit. The matching circuit couples to the antenna structure. The capacitance sensing circuit couples to the matching circuit. The capacitance sensing circuit senses a capacitance variation on the antenna structure via the matching circuit and accordingly generates a proximity sensing signal. The processing circuit is coupled to the capacitance sensing circuit to receive the proximity sensing signal. When a signal level of the proximity sensing signal exceeds a first threshold value, an object is determined approaching, and when the signal level of the proximity sensing signal exceeds a second threshold value, a human body is determines approaching. The first and the second threshold value are different.