Specific absorption rate in the presence of conductive metallic objects with close proximity radiating source

Abstract

This thesis identifies and evaluates the effect of human body and conductive metallic objects in the vicinity of portable handheld electronic devices on antenna radiation pattern, antenna performance and Specific Absorption Rate (SAR). The presences of electronic devices in the vicinity of human body especially close to the human sensitive part (when the antenna is left inside the trousers pocket) allow the radiated electromagnetic wave to penetrate inside human tissues. Homogeneous and realistic body models have been considered in the simulation. The excitation is provided by means of a simple dipole and PIFA antennas as the radiating source at four different frequencies (0.4, 0.9, 1.8 and 2.4 GHz). In order to characterize the variation of SAR due to metallic items, the external metallic item and implanted medical item are used and modelled as conducting objects with their sizes chosen in order to coincide with typical sizes available. The results have shown that the presence of human body near to the antenna detuned the resonant frequency and significantly distorted the antenna radiation pattern. Nevertheless, the presence of conductive objects do not have any profound effect on antenna radiation pattern due to their size which is relatively small compared to the size of human body. Additional metallic objects close to the human leg could alter the SAR and the effect varies depending on the size and the position of the objects. In addition, the zip could significantly increase SAR inside the testicle by 50% at 0.9 GHz due to the position of zip that is close to the human sensitive organ. Nevertheless, the presence of conductive medical implant inside the leg could increase the maximum SAR by more than 400 times at 0.4 GHz. However, the medical implant has only minor effect on SAR inside the testicle. The simulation results have been validated through measurement using homogeneous body model at 2.4 GHz.