Theoretical approach of the interaction between a human head model and a mobile handset helical antenna using numerical methods

The interaction of a helical antenna, mounted on a mobile handset, with a human head phantom is investigated in this paper. Using the Genetic Algorithms (GA) technique combined with the Method of Moments (MoM), an optimization of the antenna structure is achieved regarding the input impedance at the operating frequency. The Finite Difference Time Domain (FDTD) method is then applied to simulate the handset's function in the close region of a spherical homogeneous and heterogeneous head phantom. A formula, based on an application of an existing model proposed by Kuster and Balzano for dipole antennas, provides a rather accurate prediction of the induced Specific Absorption Rate (SAR) values in the human head due to the radiating helical antenna. The concept of relating the SAR to the current on the antenna is used in this study to formulate the final expression. Moreover, using the theory of regression, the results of the calculated peak or average SAR are correlated with the distance between the antenna and phantom and with the standing wave ratio (SWR) at the antenna feed point. Thus, the conception that the SAR is indeed related to the antenna operational parameters is reinforced by the outcome of the current study.