| As the 5G market continues to grow and 5G penetrates into everyday life,with about a quarter of the world’s population having access to 5G,adults are exposed to a certain level of electromagnetic pollution when using cell phones.At the same time,social development has led to a significant increase in the use of mobile technology by children.Children with immature central nervous system(CNS)may be exposed to more electromagnetic radiation when using cell phones,which also becomes a safety issue that cannot be ignored and needs to be studied in depth.In order to study the specific absorption rate(SAR)values and temperature field distribution of 5G cell phone antennas on the human head of adults and children,a cell phone model using multi-frequency 5G antennas and a three-layer spherical head model representing the skin layer,cranial layer and brain layer of the head of adults and children are established and simulated in COMSOL simulation software in this paper.The maximum error ratio is2.12%,which is within the allowable error range in engineering applications.Secondly,a planar antenna is designed and the radiation performance is analyzed;finally,the SAR values and temperature field distributions of each layer of the head models of adults and children with different operating frequencies,different distances and different usage of the cell phone antenna are studied.Finally,the SAR values and temperature field distributions of the layers of the head tissue of the adult and child models were investigated at different operating frequencies,distances and usage.The designed antenna with return loss bandwidth(-6 d B)can cover multiple frequency bands such as GSM-900,PCS-1900,N78,N79,etc.,and the return loss of multiple frequency bands is less than-10 d B,which can meet its work in 5G network bands and can realize the demand of backward compatibility to 4G/3G/2G bands.Simulation results show that the closer the cell phone model is to the head model,the larger the SAR value in the brain layer.The maximum SAR value of the brain layer of the adult head model is 0.2124 W/Kg,the maximum SAR value of the brain layer of the child head model is 0.4043 W/Kg,All less than the 2 W/Kg limit specified by ICNIRP;when the radiation time is 30 min and the operating frequency is 1900 MHz,both the adult and child head models are at the maximum SAR value of 0.4043 W/Kg.When the radiation time is 30 min and the operating frequency is 1900 MHz,both the adult and child head models have the highest temperature in the brain layer,37.179 ℃ for adults and 37.173 ℃ for children,with the maximum temperature increase of0.179 ℃ and 0.173 ℃ respectively,which are both much smaller than the 1 ℃ thermal damage limit specified by the ICNIRP standard.When the distance between the antenna and the human head model was increased to 30 mm and the antenna was operated at 4900 MHz,the SAR value of the adult brain layer was 23.9% of the SAR value at a distance of 5 mm;the SAR value of the child brain layer was 8.41% of the SAR value at a distance of 5 mm.There is also a certain degree of reduction in the temperature of the cut surface.That is,the human head absorbs less and less radiated energy when the distance increases,and the radiation hazard of the cell phone antenna to the human body becomes weaker and weaker.Children in the same electromagnetic environment absorb more electromagnetic radiation energy compared to adults,but still lower than the international standard limit value.With the continuous development of mobile communication business,the work carried out in this paper provides a certain basis and reference value for the effects of electromagnetic radiation from cell phones on adults and children,and shows that the distribution of electromagnetic radiation and temperature fields in the head due to 5G cell phone antennas is safe and does not pose a health threat to humans. |
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