Abstract
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}× 4.86{{varvec{lambda}}}_{0} × 0.036{{varvec{lambda}}}_{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.
Highlights
In this paper three different multi stub antenna arrays at 27–29.5 GHz are designed
To appraise the exposure some parameters use by standard institutes such as Specific Absorption Rate (SAR), power density (PD), and the Skin Surface Temperature Elevation
Duo to the probable hazards on human health in actual conditions, many assesments about field exposure are conducted by software simulations and exprimental environments. In13, for the determination of SAR, the human body tissues are modeled in one and three layer and a four-element array of rectangular patch antenna as an exposure source have been modeled by the CST softawre
Summary
As it can be seen reflection coeffcient, isolation and insertion loss are in acceptable range and the observed deviation from the theoritical values are due to high frequency range of operation which leads to higher microstrip line loss (conductor, dielectric and radiation losses)[18,19,20]. The details of the design procedure for each of the single elements and the results (simulation and fabrication) of them are reported in21 All of these antennas have end-fire patterns and acceptable measurmant performance but are not applicable in 5G systems due to low gain values as the single element. The number of antenna array elements are 2 N owing to 2N-way is beneficial structure for designing a power divider with minimum losses.
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