Algenti Lala, Bexhet Kamo, Olimpjon Shurdi,Vladi Kolici Faculty of InformationTechnology

1. Analysis and evaluation of SAR & influence of metallic objects in the electromagnetic field nearby the MS device Algenti Lala, Bexhet Kamo, Olimpjon Shurdi,Vladi Kolici Faculty of InformationTechnology Tirane, Albania

2. Outline SAR represents the ratio of the power absorbed by the human tissues This paper describes a way of measuring SAR, approximated by the technique of the near field The impact of the metallic jewelry in the face is investigated based on the absorbed energy from the human head, from the radiation of a PDA (personal data assistant) In this simulation are been used simple and complex models of manikin heads and the evaluations of the FD-TD are checked against DASY4 standards

3. Introduction The local SAR can be easily related to the electric field, and to the conductivity and density according to the formula: This way the average SAR can be measured by integrating the local SAR in a given unit The reduction of testing time can be done by reducing the measurements points The principe of the SAR measurements in the near field is to measure the electrical field in a plain surface inside the manikin, and to build the electrical field by the mean of diffusion and reflection scheme As we know only two tangential components of the electrical field are needed to build the three field components necessary to calculate the SAR

4. Our Purpose The testing cell phone is switched in the CW (continuous wave) mode through a simulator BTS and the signal transmitted by it is used as a reference for the network analysing. The testing was performed in two bands GSM900 and GSM1800MHz WE are looking to find an optimum for the numerical electromagnetic approximation of the used manikin. We are also looking to select the approximate sources. The finite domain time difference FDTD in the area of the head is used to examine the absorption when the metallic pins are in the manikin’s head. The excitation was done by using a mono-pole in a conductive box in the side of the manikin’s head.

5. The simulation For the use of the FDTD method are used the perfectly matched layers (PML) geometrically escalated for the limit condition in the net of nodes. The PML is 8 cells thick an is normally positioned 12 cells away from the head. The Yee Cells used in this simulation are in the dimensions 2mm. In the FDTD method the metallic rings are modeled by using Yee cells with the copper conductivity. For the simulation is use a dipole half wavelength ( λ/2 dipole ) in 1.8GHz The used dipoles are oriented as per the Z axis. Description of field quantities on a rectangular 3D grid (YEE cell) The worst case was holding a PDA 100mm from the eyes. The dipole 100mm from the eye was near 80mm from the nose

6. The simulation In this simulation are used two models of the heads. Manikin 1: is in a cubical shape. This manikin is composed of a homogenous cube .The complexity and calculations are significantly reduced. Manikin 2 : is a SAM manikin defined by the IEEE 1528- 2003 CENELEC 50361 and IEC 62209 standards.

7. Results for variable dimensions of the ring and the distance from the cubic manikin The maximum of 1-g SAR is matched when is used a ring with a perimeter almost equal to the 1 wave length The rings very close to the cover of the manikin have smaller effect. The maximal effect is meet at the distance from the ring to the cover is 12mm, and the perimeter 1 wave length This combination amplifies the 1-g SAR 7.4 times. This way from 0 .5 [W/Kg] in 3.7 [W/kg]

8. Measurements and simulations with the second manikin at 1.8GHz The method of measurement is illustrated in this figure together with the geometry of the dipole and the ring near the manikin’s eyebrow. The figure shows that the ring is in contact with the eyebrow and the rest of the ring is in a variable distance from the head

9. Measurements and simulations with the second manikin at 1.8GHz This figure show the results of the distribution of the SAR difference, caused by a ring with the diameter 60 mm. The biggest difference is noticed in the area of the nose, and eyes, and the norms of the absorption are unchanged in the area in the back of the head.

10. Conclusions In this paper are studied the effects of the metallic jewellery on the specific norms of absorption in the head as caused by the electromagnetic radiation from mobile telephones. It was noticed that 1-g SAR was growing to an average 5 times when the metallic jewellery were positioned between the RF source and manikin. The rings that were in contact with the surface of the manikin, where the EM field created by the ring was higher, had the tendency to resonate for sizes less than the perimeter due to the fact that the contact with the head caused the ring to act as dielectric. This means that the jewellery small in size (that are more common to be used daily) have higher impacts specially if they have some specific geometrical forms.

11. Conclusions The FDTD methods with escalated models of a manikin’s head was used to check the effects of the metallic parcels in the norms of absorption of the energy from mobile telephones. The measurements with the presence of the manikin and of the metallic particells in them showed that the metals increase ± 20 dB the absorbed energy near the eyes as cause of the depolarising effects, amplifying effects and isolating effects. The ring increases the norms of absorption in the nose, and decreases the norms in the back, under and above the nose. As conclusion we can state that the jewellery must have big sizes in order to resonate in 1.8GHz. This way the effects are limited and must be evaluated in the future experiments for heads of manikins of different models and wave sources emitting waves in different frequencies

12. The End