# Analysis of the Dihedral Corner Reflector's RCS Features in Multi-Resource SAR
## 4 The RCS Features of the CR Array in Multi-Resource SAR
### The RCS Reduction Difference of CRs with Different Tilt Angles  
In this section, a comparative analysis was conducted on the RCS reduction difference of CRs under TSX and Sentinel data, including observed and modeled results. The observation of the RCS reduction difference helps mitigate the impact of systematic biases caused by CR manufacturing processes or panel dielectric constants, providing a better assessment of RCS reductions induced by the changes of incident angles. Figures 7-10 depict the RCS time series for the triangular CRs and dihedral CRs with 0\({}^{\circ}\), 10\({}^{\circ}\), and 15\({}^{\circ}\) horizontal tilt angles under TSX and Sentinel data. In these figures, the green and blue curves represent the measured RCS results in different orbits. The bottom right corner indicates the deviation angle difference (\(\Delta\beta\)) between the two tracks. The  
Figure 6: (**a,c**) Are the RCS reduction results caused by the deviation angle \(\beta\) in the Sentinel and TSX data; (**b,d**) are the RCS discrepancy between the model and the measured results in the Sentinel and TSX data. terms \(\Delta\sigma\) and \(\Delta\hat{\sigma}\) represent the RCS reduction difference caused by \(\Delta\beta\) from the model calculations and measurements, respectively. The horizontal tilt angle of the triangular CR under investigation is 20\({}^{\circ}\). In the overlapping Sentinel data, there is a deviation angle difference of 6\({}^{\circ}\), leading to a 0.4 dBm and 0.7\(\sim\)0.9 dBm RCS reduction difference in the model and the measurement, respectively. In the TSX data, the deviation angle difference under the ascending and descending orbits is 3\({}^{\circ}\). The RCS reduction difference calculated from the model and the measurement are 0.1 dBm and 0.3\(\sim\)0.4 dBm, respectively. This indicates that the RCS reduction resulting from the deviation angle difference within 6 degrees for the triangular CR is minimal. The discrepancies between the measured and modeled RCS reduction differences under Sentinel and TSX are within the range of 0.5 dBm and 0.3 dBm, respectively. These deviations may be attributed to the thermal noise in the radar system or signal truncation losses caused by sampling. However, the overall small differences indicate a generally high quality of triangular CR. The observed RCS time series results demonstrate the stability and reliability of the triangular CR. Figure 8: The RCS time series of the horizontally placed dihedral reflector under Sentinel (**a**) and TSX (**b**) data. Figure 7: The RCS time series of the triangular CR under Sentinel (**a**) and TSX (**b**) data. Figure 8 illustrates the RCS time series for horizontally placed dihedral CRs. It exhibits large deviation angles under Sentinel and TSX data, reaching up to 12\({}^{\circ}\) and 9\({}^{\circ}\), respectively. The modeled RCS discrepancies are 2.4 dBsm and 2 dBsm, respectively. Based on measurements from the Sentinel data, the \((\Delta\phi)\) by deviation angle differences of DR1 and DR3 show close agreement between the measured and modeled values, ranging from 2.9 to 3.3 dBsm. The measured results indicate that a 12\({}^{\circ}\) deviation angle leads to half energy loss. This highlights the significance of aligning the CR axis with the radar's incident angle during the design of the CR tilt angle. By utilizing the pronounced RCS features of the dihedral CR, crucial standards can be established for identifying targets, such as dihedral reflection structures (e.g., walls), within the overlapping area of Sentinel images. For the TSX data, the measured RCS reduction differences \((\Delta\phi)\) for DR2 and DR3 show negligible deviations from the modeled values, with differences within 0.5 dBsm. However, the measured RCS reduction difference for DR1 reaches 7.1 dBsm. Considering the fluctuation of the RCS time series for DR1 in the descending TSX data, it becomes  
Figure 10: The RCS time series of the dihedral reflector with a tilt angle of 15\({}^{\circ}\) under Sentinel (**a**) and TSX (**b**) data.