# C-SAR/02 Satellite Polarimetric Calibration and Validation Based on Active Radar Calibrators
## 2 Experimental Site and Data
### Experimental Equipment  
This study mainly utilized the L/S/C-band ARCs and trihedral CRs developed by CASPLOS_CCSI. This ARC can work in three bands, namely L (1.26 GHz), S (3.2 GHz) and C (5.4 GHz), and has the functions of receiving and transmitting. The indicators are  
Figure 1: Equipment distribution.  
shown in Table 1. The structure of the ARC is shown in Figure 2a, and consists of basic units of antenna, servo, and pillar. The antenna of the ARC (Figure 2b) uses different band antennas for signal transmitting and receiving work, in which the L/S-band and C-band antennas are perpendicular to each other in direction; thus, there are differences in the polarization matrices when working in different bands. In this experiment, the frequency band of the ARC [15] was set to the C-band. By adjusting the servo mechanism, the antenna of the active calibrator can be rotated in the elevation direction of \(-80^{\circ}\)\(\leftrightarrow\)\(80^{\circ}\) and azimuth direction of \(-180^{\circ}\)\(\leftrightarrow\)\(+180^{\circ}\). The antenna pointing accuracy was \(\leq\)\(\pm\)0.2\({}^{\circ}\), the nominal radar cross-section (RCS) accuracy was \(\leq\)0.2 dB, and the RCS stability was \(\leq\)0.2 dB. The external battery was used in the wild environment to ensure that the device was timed to work according to the uploaded parameters, where the delay could be adjusted at 1, 2, and 4 us, making the imaging position on the satellite adjustable.  
A photograph of the multi-band ARC is shown in Figure 3. In the default state, the transmitting and receiving antennas of the active calibrator are in the horizontal state (i.e., it receives H-polarization electromagnetic waves and sends out H-polarization electromagnetic waves). By rotating the receiving and transmitting antennas of the ARC [i.e., by changing the values of the angle (\(\theta_{1}\)) between the transmitting antenna and the horizontal plane and the angle (\(\theta_{2}\)) between the receiving antenna and the horizontal plane], the transmitting antenna and receiving antenna of the device were switched between \(0^{\circ}\), \(45^{\circ}\), and \(90^{\circ}\), and different forms of polarization scattering matrices were obtained (Table 2). In addition, the azimuth and elevation angles of the ARC ne  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameters** & **L-Band** & **S-Band** & **C-Band** \\ \hline Center Frequency & 1.26 GHz & 3.2 GHz & 5.4 GHz \\ Maximum Bandwidth & 200 MHz & 120 MHz & 240 MHz \\ Antenna Gain & 12 dB & 19 dB & 24 dB \\ Polarization Crosstalk Isolation & & \(-\)40 dB & \\ RCS Setting & & 35–55 dB (5 dB increments) & \\ Delay Options & & 1, 2, 4 us & \\ RCS Accuracy & & \(\leq\)0.2 dB & \\ \hline \hline \end{tabular}
\end{table}
Table 1: Experimental ARC parameters.  
Figure 2: Basic structure of L/S/C ARC. (**a**) Structure diagram of ARC. (**b**) ARC antenna structural diagram.  
the Satellite-Earth Synchronization experiment so that radar signals could be received and imaged by retransmitting them.  
The experimental CR was a foldable, deployable trihedral CR with right-angle side lengths of 1.4 m, primarily used for polarization calibration validating.