The effect of jewellery and the human hand on SAR and antenna performance

This thesis investigates the effect of the human hand and metallic jewellery items worn on the human head and hand on SAR and on the antenna radiation patterns at 900 and 1900 MHz. The field excitation is provided by means of a A./4 monopole antenna on top of a metal box to emulate a simple handset. A planar inverted 'F' antenna (PIFA) is also used for comparison with the monopole. This thesis presents a detailed parametric study utilizing computer simulations via the Transmission Line Matrix (TLM) method and measurements from the DASY 4 SAR measurement system. Two different head and hand geometries are considered. Firstly a homogenous spherical head and block-hand were used in the simpler simulation, while the more realistic head and hand models were employed for the detailed study. The hand models include fingers which allow the metallic jewellery rings to be examined. The human hand has a significant effect on Specific Absorption Rate (SAR) and on the antenna pattern due to energy absorption and possible reflection at the hand dielectric boundary. In addition, the effects of different sizes, orientation, and distance of the metallic loop-like jewellery items relative to the antenna have been investigated. The metallic rings worn on the hand tend to reduce the SAR and could also alter the antenna radiation performance. The wrist worn bangle has very little effect on the results at the frequencies tested due to its position that is relatively far away from the handset antenna. The earrings could significantly influence the SAR and the radiation patterns, but the effects varied depending on the earring's diameter, its position relative to the head, the frequency and the type of antenna in use. The effect of the combination of the hand, the earring and the finger ring only show minor difference on the SAR values and on the antenna radiation patterns. Measurements of the effects of the hand and metallic jewellery items on SAR were performed inside a Standard anthropomorphic model (SAM) head phantom. A novel liquid hand phantom with realistic fingers has been manufactured, which allow the effect of metallic ring to be further investigated. Measurement results support the simulation results.