Dielectric Properties of Human Hand Tissue for Handheld Devices Testing

The operation of antennas deployed in mobile terminals is affected by the presence of human tissue in their near-field region. Therefore, testing the antenna performance, when the radiator is located in close vicinity to the user, is of paramount importance for any handset. In order to conduct such a study, knowledge about the dielectric properties of relevant human tissues is needed. In this paper, the results for in vivo measured complex relative permittivity of the dry and wet human hand palm and fingertip of thumb are presented. For the sake of having a broader set of data, the palms of 22 individuals and thumbs of 16 individuals are tested at multiple points. The measurements are conducted over the frequency band of 5-67 GHz by using an open-ended coaxial probe. The single-pole Cole-Cole model is used for fitting the measured results. Furthermore, the fitting parameters for the multi-pole Debye model are extracted by using the Cole-Cole ones. The effect of the difference in the dielectric properties between dry and wet palm on the performance of a dual-element PIFA antenna array (operating in the band of 5.8-7.7 GHz) is numerically studied. Useful finding for antenna designers is that the S-parameters and radiation efficiency of the antennas are insensitive to the change in the complex permittivity of the hand.