## 2 Materials and Methods
### Radar Cross Section (RCS) of the Drone's Blade  
This section investigates the forward-scattering radar cross section (FS RCS) for the different materials that are used to fabricate the drone's blade at various plane wave incident angles, \(\varphi\). The paper assumes the drone could fly in three different directions while crossing the satellite-ground station FS baseline, which are cruising horizontally, flying vertically and flying sideways. All the positions will affect the electromagnetic signal illuminating the drone and, thus, its FS RCS. The EM simulation of the drone blade was conducted by using a computer simulation technology (CST) on a commercial DJI Phantom drone's blade.  
The two different blade materials considered were i. perfect electrical conductor (PEC) and ii. plastic, where most of the drone's blade was made by these materials. The size of the blade follows the typical size of the commercial Phantom drone's blade model. Theoretically, parameters  
Figure 1: DVB-S-based passive FSR geometry.  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline Centre frequency (\(\mathrm{f_{c}}\)) & 11 GHz \\ Effective isotropic radiated power (EIRP) \(P_{T}G_{T}\) & 57 dBW \\ Transmitter range (\(\mathrm{R_{rx}}\)) & 35,921 km \\ Receiver range (\(\mathrm{R_{rx}}\)) & 1–100 m \\ Receiver bandwidth (\(\mathrm{B_{rx}}\)) & 24 MHz \\ Signal bandwidth (\(\mathrm{B_{s}}\)) & 36 MHz \\ Min. antenna gain (Ga) & 36 dBi \\ Low noise block (LNB) gain \(G_{L}\) for Ku-band & 55–65 dB \\ Noise temp. of Rx sys (Ts) & 300 K \\ Boltzmann constant (\(K\)) & \(1.38\times 10^{-23}\) J/K \\ Ku-band prop. loss (\(\mathrm{L_{p}}\)) & 0.2 dB \\ \hline \hline \end{tabular}
\end{table}
Table 3: The DVB-S Measat3 parameters.  
influencing the RCS performance include the target physical geometry, material, target external features, radar transmitting frequency, plane wave incident angle, \(\varphi\) and the bistatic angle (\(\beta\)) [36].  
Figure 2 illustrates the blade orientations towards the E-field direction. The blade orientation was defined by their positions in XYZ coordinates. For this case, a linear polarization plane wave with plane normal (x = \(-\)1, y = 0, z = 0) and electrical field vector (x = 0, y = -1, z = 0) was used to transform the blade orientation. The blade was positioned along the x-axis for the E-field to be in the direction of the \"blade-face\", as in Figure 2a.  
The blade was then rotated 90\({}^{\circ}\) along the z-axis for the blade to face-up for the \"blade-edge\" faced the E-field direction, as in Figure 2b, and also rotated another 90\({}^{\circ}\) along the y-axis for the \"blade-tip\" to face the direction of E-field, as in Figure 2c. The RCS representation on the Cartesian and Polar coordinates for both materials and the three different blade orientations are illustrated in Figure 3.  
From Figure 3, the bistatic RCS was appreciable at the FS mode (\(\varphi\) = 180\({}^{\circ}\)) irrespective of the material and the orientation of the blades. This further revealed the RCS enhancement capability of the FSR geometry, which, in turn, may improve the performance of the system. In summary, Table 4 presents the magnitude and direction of the RCS main lobe and other essential parameters achieved.  
It describes that the PEC material, with the blade face facing the E-field direction at a Centre frequency of 11.725 GHz, yields the highest bistatic RCS of 0.877 dBm\({}^{2}\). Similarly, for the plastic materials, the highest RCS value is \(-\)49.7 dBm\({}^{2}\) at 183\({}^{\circ}\) of the main lobe's direction. A similar effect will be expected to be achieved during the detection due to the direction of illumination of the DVB-S signal to the normal flying drone. The look angle is expected to be in the direction of the blade face.  
Figure 2: E-field facing the direction of the blade’s (**a**) Face (**b**) Edge (**c**) Tip.