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

Abstract

Today, with the contribution of the new generation of communication technologies, many smart devices are produced. Almost every electronic device, including smart phones, smart watches, wireless headphones, tablets, emits some form of radiation. While most of this electromagnetic radiation is harmless, some of it can have potential health effects, depending on the frequency of use over long periods of time and in close usage. Specific Absorption Rate is a measure of how much human body tissue absorbs energy when the body is exposed to radiation. This measurement helps determine whether a device is safe for regular use. The SAR value may vary depending on the antenna and schematic design of the smartphone. To support high band requirements for 5G smartphones, more RF antennas required to be added in PCB design. When designing smartphones, designers also need to design proximity-grip sensors that accurately meet the industry's Specific Absorption Rate (SAR) requirements. In this study, the effects of proximity and grip sensors used in smartphones on LTE and 5G NR SAR values are investigated. During these measurements, a combination of Grip and Proximity Sensors were alternately turned on and off. Although the proximity sensor and grip sensor are not mainly used to optimize SAR values, it is foreseen that they may have indirect effects on SAR. In this context, SAR measurements were made in 3D environment for different frequencies. As a result of this study, it was observed that the grip-proximity sensors used in smartphones significantly reduce the SAR value and transfer less energy to the users in close range use. The effect of using the proximity sensor on the SAR rate was measured to be approximately 8%, while the effect of using the Grip Sensor was observed to be approximately 10%.

Keywords

• Smartphone
• Proximity Sensor
• Grip Sensor
• Specific Absorption Rate (SAR)
• Long Term Evolution (LTE)
• 5G New Radio

References

1. Aly, A., & Piket-May, M. (2014). FDTD Computation for Sar Induced in Human Head Due to Exposure to EMF from Mobile Phone. Advanced Computing: An International Journal, 5, 01-12. https://doi.org/10.5121/acij.2014.5601
2. Diao, Y., Rashed, E. A., & Hirata, A. (2020). Assessment of absorbed power density and temperature rise for nonplanar body model under electromagnetic exposure above 6 GHz. Physics in medicine and biology, 65(22), 224001. https://doi.org/10.1088/1361-6560/abbdb7
3. Guraliuc, A. R., Zhadobov, M., Sauleau, R., Marnat, L., & Dussopt, L. (2017). Near-Field User Exposure in Forthcoming 5G Scenarios in the 60 GHz Band. IEEE Transactions on Antennas and Propagation, 65(12, 1), 6606–6615. https://doi.org/10.1109/TAP.2017.2754473
4. Hamed, T.B., & Maqsood, M. (2018). SAR Calculation & Temperature Response of Human Body Exposure to Electromagnetic Radiations at 28, 40 and 60 GHz mmWave Frequencies. Progress in Electromagnetics Research M, 73, 47-59. https://doi.org/10.2528/PIERM18061102
5. Jeladze, V., Nozadze, T., Petoev-Darsavelidze, I., & Partsvania, B. (2019). Mobile phone antenna-matching study with different finger positions on an inhomogeneous human model. Electromagnetic biology and medicine, 38(4), 297–306. https://doi.org/10.1080/15368378.2019.1641721
6. Koukiou, G. (2024). SAR Features and Techniques for Urban Planning—A Review. Remote Sensing, 16(11), 1923. https://doi.org/10.3390/rs16111923
7. Li, K., Sasaki, K., Watanabe, S., & Shirai, H. (2019). Relationship between power density and surface temperature elevation for human skin exposure to electromagnetic waves with oblique incidence angle from 6 GHz to 1 THz. Physics in medicine and biology, 64(6), 065016. https://doi.org/10.1088/1361-6560/ab057a
8. Morelli, M. S., Gallucci, S., Siervo, B., & Hartwig, V. (2021). Numerical Analysis of Electromagnetic Field Exposure from 5G Mobile Communications at 28 GHZ in Adults and Children Users for Real-World Exposure Scenarios. International Journal of Environmental Research and Public Health, 18(3), 1073. https://doi.org/10.3390/ijerph18031073

9. Morgado, A., Huq, K. M. S., Rodriguez, J., & Mumtaz, S. (2018). A survey of 5G technologies: regulatory, standardization and industrial perspectives. Digital Communications and Networks, 4(2), 87-97. https://doi.org/10.1016/j.dcan.2017.09.010
10. Nakae, T., Funahashi, D., Higashiyama, J., Onishi, T., & Hirata, A. (2020). Skin temperature elevation for incident power densities from dipole arrays at 28 GHz. IEEE Access, 8, 26863-26871. https://doi.org/10.1109/ACCESS.2020.2970219
11. Neufeld, E., Carrasco, E., Murbach, M., Balzano, Q., Christ, A., & Kuster, N. (2018). Theoretical and numerical assessment of maximally allowable power-density averaging area for conservative electromagnetic exposure assessment above 6 GHz. Bioelectromagnetics, 39(8), 617–630. https://doi.org/10.1002/bem.22147
12. Rappaport, T.T., Sun, S., Mayzus, R., Zhao, H., Azar, Y., Wang, K., Wong, G.N., Schulz, J.K., Samimi, M., & Gutierrez, F. (2013). Millimeter Wave Mobile Communications for 5G Cellular: It Will Work! IEEE Access, 1, 335-349. https://doi.org/10.1109/ACCESS.2013.2260813
13. Rosenqvist, A., Jones, C. E., Rignot, E., Simons, M., Siqueira, P., & Tadono, T. (2021). A review of SAR observation requirements for global and targeted science applications. In 2021 IEEE International Geoscience and Remote Sensing Symposium IGARSS (pp. 1745-1748). IEEE. https://doi.org/10.1109/IGARSS47720.2021.9553966
14. Sabbah, A.I., Dib, N.I., & Al-Nimr, M.A. (2011). Evaluation of specific absorption rate and temperature elevation in a multi-layered human head model exposed to radio frequency radiation using the finite-difference time domain method. Iet Microwaves Antennas & Propagation, 5, 1073-1080. https://doi.org/10.1049/iet-map.2010.0172
15. Siervo, B., Morelli, M. S., Landini, L., & Hartwig, V. (2018). Numerical evaluation of human exposure to WiMax patch antenna in tablet or laptop. Bioelectromagnetics, 39(5), 414-422. https://doi.org/10.1002/bem.22128
16. Tian, R., Wu, Y. -Q., Lu, M., & Miao, X. -F. (2023). Specific Absorption Rate and Temperature Distributions in the Human Head with Implanted Deep Brain Stimulation Subjected to Mobile Phone Electromagnetic Radiation. Electronics, 12(21), 4389. https://doi.org/10.3390/electronics12214389
17. Wu, T., Rappaport, T. S., & Collins, C. M. (2015). Safe for Generations to Come. IEEE microwave magazine, 16(2), 65–84. https://doi.org/10.1109/MMM.2014.2377587