Simplified models of the human body to study the wearable antennas

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In recent years we have seen a marked increase in interest in systems such WBAN (ang. Wireless Body Area Network). They allow min. for long-term monitoring of vital signs and assessment of the physical condition of man in a way that minimally restricts the user's convenience. Designing such systems require the performance of computer simulations of RF energy from the human body and to carry out measurements to verify them. In this process model is used to assess the human body its influence on the antenna and radio link. Due to the high cost of available physical models and the problem with selecting the perfect counterpart numerical seeks to replace their simplified structures Replicated averaged electrical parameters of the body. The development of simplified models requires assumptions geometry resulting from the observation of the human body or the information contained in the literature. A valuable tip is also a simulation using available numerical models of heterogeneous mapping the different tissues of the human body. The process of designing the model is to select the simplified mapping, the geometry of the construction of the body part by dividing them into layers according to their electrical parameters. The work was presented project bilayer simplified models of the human body to measure the input impedance of the antenna nasobnych. An exemplary model of human will is shown in Figure 1. The testing and verification of the proposed design is selected dipole antenna fitted to operate at a frequency of 2.45 GHz. Physical counterpart of the proposed numerical model consists of a two-layer thin-walled container into which fluids are poured on the electrical parameters close to various tissues of the human body. The paper used for this purpose water, glycerol 99.6% denatured ethyl alcohol and vegetable oil products. The verification results obtained in the simulation was carried out using the position designed to measure the input impedance of the antenna near the human body model or. For this purpose, the device is made for changing the position of the antenna to the model with an accuracy of 0.5mm. To support the measurement process was written computer application in C #, responsible for the control of both the location of the antenna and circuitry ZVB14 analyzer from Rohde & Schwarz. It allows you to record the detuning of the antenna impedance (WFS) on your computer for a defined frequency range and the distance from the antenna model. In order to compare the obtained results the script was written in Matlab wykreślający dependence on the detuning of the antenna impedance from its distance.

The resulting work results allow to positively evaluate the proposed simplified models of the human body both numeric and physical. Their properties allow a significant reduction simulations give results comparable to the exact model of the tissue. The materials have allowed significantly reduce the cost associated with the purchase of dedicated fluids for electrical parameters close to the average values ​​for the tissues of the human body.

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