Abstract-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.

Abstract-The interaction between a dipole antenna, representing a simplified model of a mobile terminal, and a homogeneous spherical model of the human head is examined. The Finite Difference Time Domain (FDTD) method is utilized, to calculate the either peak or average value of the Specific Absorption Rate (SAR), corresponding to different distances between antenna and phantom. The variation of the SAR with the distance between the mobile antenna and the human phantom has gained significant attention in the recent literature and is investigated here. An attempt to correlate the computed SAR values with the basic antenna characteristics, such as the standing wave ratio (SWR), reveals that a precise estimation of the level of the SAR can be achieved regarding data acquired from the mobile terminal.

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An optimized planar inverted F antenna (PIFA), used in mobile communications, is proposed in this paper. With the aid of the Genetic Algorithms (GA) optimization technique, a PIFA with a wide impedance bandwidth and a sufficient gain for use in mobile communications is presented. A comparison with results emerging from an application of the Finite Difference Time Domain (FDTD) method is demonstrated.

Abstract-The field conditions inside a vibrating intrinsic reverberation chamber (VIRC) are examined. By the use of the Finite Difference Time Domain (FDTD) method, the field strength in the VIRC is calculated, and an investigation of the field uniformity and the field distribution is performed. The modes inside the cavity are excited by applying an appropriately modulated waveform on a dipoles gap. The use of this kind of waveform enables the study of the field conditions over a wide frequency range. On the contrary, an implementation of the field excitation with an unmodulated carrier would require a simulation of the FDTD method at each frequency of interest. Thus, a considerable reduction in the simulation time is achieved. The results presented, describing the field behavior inside the enclosure, agree with theory to a high degree.