The Effect of Proximity Sensor & Grip Sensor Use on Specific Absorption Rate (SAR) in Smartphones

Abstract

Overview

With the advancement of new-generation communication technologies, the production and ubiquity of smart devices such as smartphones, smart watches, wireless headphones, and tablets have increased. These electronic devices emit various forms of radiation, much of which is considered harmless. However, prolonged and close-range exposure, especially to certain electromagnetic frequencies, may pose potential health risks. Of particular concern is the Specific Absorption Rate (SAR), a critical measure for quantifying the energy absorbed by human tissue during exposure to electromagnetic fields. SAR evaluations are essential for establishing safety standards for device usage.

Findings

• The SAR value varies with the antenna and schematic design of smartphones, especially as more RF antennas are integrated for 5G support.
• Proximity and grip sensors—though not primarily designed for SAR optimization—can have indirect and notable effects on SAR levels.
• This study investigated the combined and individual impacts of these sensors (when alternately turned on/off) on SAR values during LTE and 5G NR operations in a 3D measurement environment, across multiple frequencies.
• The use of grip-proximity sensors in smartphones was found to significantly reduce SAR, i.e., the energy transferred to users during close-range use is lower.
• Specifically, use of proximity sensors reduced SAR by approximately 8%, while grip sensors alone contributed a 10% reduction. Using both sensors together yielded a 5% to 11% reduction depending on frequency.
• The main mechanism for risk reduction is through the sensors' influence on power management and transmission power adjustment based on user proximity and device handling.

Conclusion

The incorporation of proximity and grip sensors can significantly mitigate electromagnetic exposure risks in smartphone users. Their adoption as standard hardware is recommended for all future smartphone designs. It is important to acknowledge that while these sensors reduce SAR, exposure to electromagnetic fields from mobile devices still carries potential health risks, especially with increased use of higher-frequency bands and newer communications standards (e.g., 5G).