Modeling a complex antenna on a handheld telephone close to human tissue

Design-development and performance evaluation of antennas on handheld telephones can be done experimentally or numerically. Numerical modeling approach or a combination of experiment and numerical modeling, offer many advantages compared with purely experimental approach, which has been often used till now. However, modeling poses many challenges and in order to be considered reliable has to be verified. In this work, modeling of an antenna consisting of two helices is verified by a comparison with measurements made in the laboratory of the handset manufacturer, and by use of two different computer codes. The numerical method used in this investigation is the finite difference time domain (FDTD). A comparison of the measured (in manufacturer´s laboratory) electric and magnetic field in four planes at distances 1-4 cm from the antenna with the computed values shows agreement within 15% (which corresponds to the uncertainty in measurements). This agreement is for two operational positions of the antenna in free space. Performance of the handset antenna in the vicinity of the user´s head is evaluated. Investigations include the input impedance, far-field radiation pattern and power deposited in the human tissue. The influences of the ear shape and various positions of the handset with respect to the user´s head have been evaluated