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Description
In recent years, wireless communication devices have become widespread. Wireless communication devices used near a human body need to be assessed for human exposure. In the frequency range over 6 GHz, absorbed power density (APD) is used as the basic restriction in the safety guidelines. Recently, the compliance test method based on an APD at frequencies from 6 GHz to 10 GHz has been published as publicly available specification by IEC. This method obtains the APD by using the specific absorption rate (SAR) according to an electric field measurement in a tissue equivalent liquid. The APD measurement using the tissue equivalent liquid is also proposed at 28 GHz. In those SAR and APD measurements, the dielectric properties of tissue equivalent liquid are important for a conservative conformity assessment. In this study, the dielectric property of the planar phantom that can estimate the APD to safety side was considered over 6 GHz. To do that, the APD calculation was conducted in multi-layer model consisting of skin, fat, and muscle using FDTD simulation. Additionally, the APD calculation in the single layer model was also conducted. The single layer model has the dielectric property of the outlier value of the conformity assessment standard below 6 GHz, skin, or the average of the skin, fat, and muscle. From the results of the comparison between multi and single layer model, for conservative conformity assessment, the outlier value and the averaged value can be used below and over 10 GHz, respectively.
