Computation of Specific Absorption Rate (SAR) Distribution by the Human Eye Due to Mobile Base Station Antennas & Dependency of SAR on Electrical Properties

In Sri Lanka, more base stations are being installed in every part of the country. This may cause a potential danger to public health. The amount of electromagnetic energy absorbed by the body is given by the Specific Absorption Rate (SAR) in W/kg. International regulations specify the maximum acceptable SAR value and field density for public safety. Electric field strengths due to base station antennas are measured in different parts of the country at sites which represent a normally high population during daytime and three frequency bands of 900 MHz, 1800 MHz and 2 GHz are considered. Field strength is measured at 30 locations in main cities in the country. The present exposure levels are found to be below the maximum limits set by the FCC (Federal Communication Commission) guidelines. From among the measured sites, highest is reported at Vavuniya mostly due to the 2 GHz band. Among those five network providers, one particular service provider dominates in all three frequency bands. The SAR values are calculated by using Finite Difference Time Domain (FDTD) method. The maximum SAR for the eye under worst-case conditions is 0.1491 W/kg was observed from Galle and the highest contribution is due to 2 GHz band. The human eye at 2500 MHz was considered to observe how the electrical properties of the tissues affect the electromagnetic energy absorption in an organ. When relative permittivity is perturbed in small percentages with conductivity remaining unchanged; the value of the maximum SAR also changes by small values. However both these cases, when the electrical properties are changed, the location of maximum SAR remains unchanged. It is exactly at the center of the eye.