## 2 Numerical Simulations
### Creation of a Flat-Layered Biological Environment in the Form of a Human Forearm Phantom  
For creating the flat-layered structure of the biological medium with dielectric values close to the values calculated in the numerical model, a number of articles were considered with different approaches to make a phantom. One of the most common methods for making a phantom of a biological environment is based on gelatin, deionized water, sunflower oil and dishwashing liquid [21; 22; 23]. The method described in [24], based on the use of graphite, polyurethane and acetone, proved to be the most suitable. The use of graphite makes it possible to more accurately recreate the dielectric properties of biological tissue. Due to the high value of the relative permittivity for the layers being created, the resulting phantom structure is more durable, less susceptible to external influences. Table 2 shows the values for each of the layers.  
Each of the layers was made separately, in accordance with the data in Table 2. In this case, it was decided to neglect the fat layer due to its low relative permittivity and extremely small thickness (0.5 mm). The properties of each of the layers obtained were checked on a special installation [25].  
Figure 9: Dependence of voltage standing wave ratio on frequency.  
Based on the results of measurements of the dielectric properties of the obtained layers on this installation, graphs of the dependences of the real and imaginary parts of the relative permittivity of the layers on the frequency were built (Figure 10).The obtained electrophysical properties of the experimentally created layers are very close to the values calculated mathematically during modeling. The difference lies in the more linear plots for the experimentally created layers. Then they were selected for further experimental studies of two probes.  
Flat blood materials with glucose values of 0, 4, 5.3, 7.5 mmol/L were also measured separately. The results are shown in Figure 11.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Material**} & **Polyuret. HP40** & **Two-Comp. Polyuret./** & **Graphite,** & **Acetone,** \\  & **\%** & **\%** & **\%** & **\%** & **mL/100 g** \\ \hline Skin & 30 & 30 & 32.3 & 7.7 \\ Blood 0 mmol/L & 30 & 30 & 33.8 & 6.2 \\ Blood 4 mmol/L & 30 & 30 & 30.2 & 9.8 \\ Blood 5.3 & 30 & 30 & 29 & 11 \\ mmol/L & 30 & 30 & 27.1 & 12.9 \\ Muscle & 33.7 & 33.7 & 25.8 & 6.8 \\ Bone & 40 & 40 & 15.6 & 4.4 \\ \hline \hline \end{tabular}
\end{table}
Table 2: The calculated data on the components for the phantom.  
Figure 10: Frequency dependence of the real (**a**) and imaginary (**b**) parts of the relative permittivity of the created biological layers.  
For blood, one can notice a high similarity in the obtained values of the real part of the relative permittivity for various glucose concentrations in the case of theoretical modeling and the created layers of biological tissue (Figure 4). The values of the relative permittivity for the theoretical graphs and those obtained by measuring the phantoms are different, but the values between the different concentrations coincide with the theoretical ones. In the case of the imaginary part of the relative permittivity, the behavior of the curves is similar to the theoretical ones, but the experimental data are larger by about 5 relative units in their values.