Abstract
The effects of antenna dielectric substrate materials on the specific absorption rate (SAR) towards the human head are presented in this investigation. The variation of radiation efficiencies of antenna due to different substrate materials are also analyzed and discussed in the close vicinity of head model. An E-shaped planar inverted-F antenna (PIFA) is used as internal handset antenna in this analysis with five different dielectric substrate materials-Bakelite, FR4 glass epoxy, Rogers R04003, Taconic TLC and RT Duroid. Moreover, different thicknesses of each substrate are considered in the experimental setup. The studied cell phone is located beside a specific anthropomorphic (SAM) head phantom in a position of actual handset use. The finite-difference time-domain (FDTD) method with the lossy-Drude model is utilized in this study by using CST Microwave Studio. The SAR values and radiation efficiencies are calculated for two global system for mobile (GSM) frequency band at 900 MHz and 1800 MHz. The results show that the SAR values are affected due to the variation of substrate materials and its thickness. PIFA with RT Duroid substrate is found to be better over all other substrates, which results lower SAR values to the human head in both GSM frequency bands. In addition, the substrate materials affect the SAR values much more at 900 MHz than that of at 1800 MHz. On the other hand, the antenna radiation efficiencies are not affected significantly, but they show small variation at lower and upper frequency bands due to different substrate materials.