e interaction between human head model and electromagnetic �eld sources is studied. e head models are composed of one and six layers. e six layers are skin, fat, bone, dura (the outer membrane of brain and spinal cord), CSF (colony stimulating factor), and brain. An antenna as a source of exposure is simulated too. e E-�eld strength distribution in both one-and six-layer human models is shown to estimate the intensity of E-�eld penetration in human head. Like standard models, the antenna is situated near the head model at a distance of 5 mm. e local and average SARs (speci�c absorption rates) are simulated at �00 MHz in both human head models. e results are then compared between the two models. e HFSS soware is used for all the simulations. e paper wants to show that the initial model (one layer) is not a good model, because the real human head tissue is not equivalently modeled. It seems that the values of one-layer model are not reliable, so the paper considers the better and more similar human head model and compares these two models.
In this paper three different multi stub antenna arrays at 27–29.5 GHz are designed. The proposed antenna arrays consist of eight single elements. The structure of feeding parts is the same but the radiation elements are different. The feeding network for array is an eight way Wilkinson power divider (WPD). To guarantee the simulation results, one of the proposed structures is fabricated and measured (namely the characteristics of S11, E-, and H-plane patterns) which shows acceptable consistency with measurement results. The simulation results by CST and HFSS show reasonable agreement for reflection coefficient and radiation patterns in the E- and H- planes. The overall size of the proposed antenna in maximum case is 29.5 mm × 52 mm × 0.38 mm (2.8 $${{\varvec{\lambda}}}_{0}$$
λ
0
× 4.86$${{\varvec{\lambda}}}_{0}$$
λ
0
× 0.036$${{\varvec{\lambda}}}_{0}$$
λ
0
). Moreover, for Specific Absorption Rate (SAR) estimation, a three-layer spherical human head model (skin, skull, and the brain) is placed next to the arrays as the exposure source. The simulation results show that the performance of proposed antennas as low-SAR sources makes them ideal candidates for the safe usage and lack of impact of millimeter waves (mmW) on the human health. In all three cases of SAR simulations the value of SAR1g and SAR10g are below the standard limitations.
Three configurations of compact planar multistub antennas are proposed in the frequency range of 27–29.5 GHz as candidates for the 5G standard frequency band. Each antenna consists of the same feeding part configuration but different structures for the dipole, director, and reflector parts. The feeding part is based on the substrate integrated waveguide (SIW) technology which results in compact size. The TE10 dominant mode is considered in the design procedure by HFSS software simulations. The proposed antennas have been simulated, fabricated, and measured (for S11, E, and H pattern). The simulation and measurement results show reasonable agreement for S11 and radiation patterns of E- and H-planes and impedance bandwidths. Moreover, for specific absorption rate (SAR) estimation, a three-layer human head model (skin, skull, and brain) is placed next to the antennas as the exposure source. The simulation results show the performance of the proposed antennas for low-SAR, which make them good candidates for safe usage concerning the negative impact of millimeter waves (mmWs) on human health. Finally, a comparison table is presented which verifies the compact size of our proposed antennas.
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