## 3 Experiments and Results  
### Unidirectional Probe  
To confirm the simulation and experimental verification, a near-field probe was made. A copper tube with a diameter of 6 mm was taken as a basis. The diameter of the probe itself was 100 mm (in accordance with the dimensions described in [18]). Figure 12 (left) shows a photograph of the manufactured probe in the form of a loop vibrator. The probe was powered from the input of a symmetrical dipole. Figure 11: Frequency dependence of the real (**a**) and imaginary (**b**) parts of the relative permittivity of biological tissues such as blood. To take S-parameters, we used a PNA-L NetworkAnalyzer vector network analyzer from Agilent Technologies, which has a frequency band of 0.01-40 GHz. This equipment allows high speed measurements (4 to 9 us per point) and accuracy. The manufactured installation is shown in Figure 12 (right). A metal circle 2 mm thick and 160 mm in diameter was used as a reflective plate, which corresponds to the dimensions in the simulation  
When examining the reflected signal of a unidirectional probe, an identical setup was used with the addition of a metal plate at a distance corresponding to the distance in the simulation (Figure 5). Experimental measurements were carried out on four samples of the material. The structure of each consisted of 4 layers with electrophysical values of the dermis, muscles, bone and blood layer. The first three layers (dermis, muscles, bone) in these samples were the same; only the layer with blood parameters for different glucose concentrations changed: 0 mmol/L, 4 mmol/L, 5.3 mmol/L, 7.5 mmol/L. The measurements were carried out on four samples of the material. The measurement took place in two stages: registration of a signal without a sample to remove background noise and registration of S11 parameters with samples. The data obtained after the background subtraction is presented in Figure 13. The results, as in the case of modeling, have a similar pattern of change. Considering the entire measured range of 2-10 GHz, a large number of resonant amplitudes can be observed. The resonances that are closest to the simulation are in the frequency range 2-2.4 GHz and at a frequency of 5 GHz. The amplitude at 9 GHz differs significantly from the simulation values in region 2 (Figure 7). The values of the amplitude at a frequency of 5 GHz, obtained during simulation, differ slightly from the values obtained during experimental measurements with phantoms. A detailed study of the first band 2-2.4 GHz (Figure 14) shows differences in both amplitude and frequency at different glucose concentrations. Figure 12: Microwave near-field copper tube probe and experimental setup for a unidirectional probe. Figure 13: Frequency dependence of the reflected signal from the unidirectional probe for various glucose concentrations. Frequency range 2–10 GHz. Comparison of the measured data for different glucose concentrations was carried out in amplitude at a frequency of 2.235 GHz. This frequency is the minimum for a concentration of 7.5 mmol/L. The data for each concentration are presented in Table 3. Also, in Table 3, the frequency values at resonance deviation are presented for each concentration. Using the data presented in Table 3, the amplitude sensitivity of the probe was calculated. It was 1 dB/(mmol/L) with a concentration change from 4 to 7.5 mmol/L. A sensitivity of 2 dB/(mmol/L) is achieved when the concentration changes from 0 to 4 mmol/L. Such a spread in sensitivity in amplitude is associated with a high deviation of the error at a concentration of 0 mmol/L. Such a measurement error at a low glucose concentration (0 mmol/L) is associated with an increased value of the imaginary part of the relative permittivity, as well as due to the compositional structure of the layer. The frequency sensitivity of the probe was also calculated, which was 4.34-5 MHz/(mmol/L) for a concentration range of 4-7.5 mmol/L.