## 3 Results and Discussion
### Microwave Properties
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{\begin{tabular}{c} **Group of** \\ **Samples** \\ \end{tabular} } & \multirow{2}{*}{**Code of Sample**} & \multicolumn{2}{c}{**Dominant Shielding Effectiveness**} & \multirow{2}{*}{\
\begin{tabular}{c} **Deposit of Conductive** \\ **SE, dB** \\ \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} **Surface** \\ **Paste, g/m\({}^{2}\)** \\ \end{tabular} } \\  & & & & \\ \hline \multirow{2}{*}{**I**} & S1C & 15 & 10 & \(2.5\times 10^{-2}\) \\  & S1 PC & 18–19 & 12 & \(4.0\times 10^{-2}\) \\ \hline \multirow{2}{*}{**II**} & S2C & 16–18 & 5 & \(3.5\times 10^{-2}\) \\  & S2 PC & 15–17 & 5 & \(3.2\times 10^{-2}\) \\ \hline \multirow{2}{*}{**III**} & S3C & 15–16 & 14 & \(2.5\times 10^{-2}\) \\  & S3 PC & 15 & 15 & \(2.5\times 10^{-2}\) \\ \hline \multirow{2}{*}{**IV**} & S4C & 18–20 & 6 & \(4.7\times 10^{-2}\) \\  & S4 PC & 17–20 & 7 & \(4.7\times 10^{-2}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 5: EMR shielding effectiveness of investigated fabrics. side of the fabric) covered with conductive paste fabrics can be considered as a thin layer with particular surface conductivity. The surface conductivity values calculated with reference to reflection and transmission measurements are presented in Table 5. It can be seen that calculated \(\sigma\) values strongly correlate with obtained SE values and allow to distinguish the samples with different conductivity, that is complicated using electrostatic parameter--surface resistivity, determined by the method conventional for textile testing. To evaluate the ability of developed coated fabrics to absorb microwaves in radar operating frequency range, their reflection properties were measured (Figure 8) and absorption (A) coefficient calculated based on transmission and reflection measurements results (according to formulas (4) and (6)). The data presented in Table 6 show the contribution of reflection and absorption to the total EMR shielding effectiveness for each tested sample at 12 GHz and 18 GHz respectively. As it is seen from Table 6, for tested samples the combined effect of reflection and absorption determines the shielding properties, but the role of these two parameters is different over the tested frequency range. As the reflection coefficient is more or less frequency depended for all tested samples (Figure 8), their reflectance properties are different over the 2-18 GHz range--reflectance decrease when the frequency increase. The lower reflection coefficients are obtained in the 12-18 GHz range, it means that in this range coated fabrics have the better absorption ability. Moreover, different types of fabric demonstrated different reflection and consequently absorption properties (Table 6). Figure 7: Shielding effectiveness SE, dB of tested fabrics coated with PEDOT:PSS formulation: (**a**)—I group of samples; (**b**)—II group of samples; (**c**)—III group of samples; (**d**)—IV group of samples. The best results were obtained for group II samples (Figure 9)--the contribution of absorption at 18 GHz sought about 52% and 74% respectively for sample without plasma treatment (S2C) and with plasma treatment (S2 PC). For other tested fabrics, no significant difference in reflection and absorption between plasma treated and untreated sample was noticed.