Exposure Assessment for Wearable Patch Antenna Array at Millimeter Waves

The upcoming deployment of wireless networks and systems operating in the upper part of the microwave spectrum, including millimeter-wave (mmWave) frequencies, motivates user exposure assessment studies at these emerging frequencies. At mmWaves, the power absorption is mainly limited to cutaneous and subcutaneous tissues. Till now, there is no literature consensus on the skin model to employ in computational exposure assessment studies. For these reasons, this work analyses four different models of the most superficial tissues with different degree of details exposed to wearable patch antennas operating at 28 GHz and 39 GHz. The results for the layered models are compared to the homogeneous one. Simulations were performed using the FDTD method, implemented in the Sim4life platform and the exposure was assessed in terms of the absorbed power density averaged over 1 cm2 and 4 cm2 (Sab). The data showed that the homogeneous model underestimates the peak value of Sab obtained for multi-layer models in the stratum corneum (by 8% to 12% depending on the number of layers of the model and the frequency) when the simulated models have the same reflection coefficient. Conversely, there are no substantial differences in the exposure levels between the layered models.