# Performance and Requirements of GEO SAR Systems in the Presence of Radio Frequency Interferences
## 4 Performance Evaluation and Discussion: Example of GEO SAR Design
### Impact of Bistatic Scattering RFI  
#### 4.2.1 LEO SAR Bistatic Scattering RFI Case Analysis  
In this part, we analyse the bistatic scattering RFI impacts of LEO SAR on GEO SAR. In Table 4[40; 41; 42; 43; 44; 45], the utilized system parameters of the main L band, C band and X band LEO SAR systems in the simulation are given, including most important parameters about the power and the orbit. It can be noted that the number of the LEO SAR systems is large, because some of the systems are formed by not only a single satellite but many satellites as a constellation. Figure 8: Average transmitted power requirement in the distributed RFI case. Figure 7: Average transmitted power requirements in GEO SAR systems of different working frequencies. (**a**) L band; (**b**) C band; (**c**) X band, to ensure a SINR better than 10 dB. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Frequency** & \multicolumn{2}{c}{**L Band**} & \multicolumn{2}{c}{**C Band**} & \multicolumn{2}{c}{**X Band**} \\ \hline SAR & ALOS-2 & Tandem-L & SAOCOM-1A/B & Sentinel-1A/B & Radarsat-2 & RCM & TanDEM-X/P/A2 & COSMO-Sg/Med & SAR-Lape & KOMPSAT-5 \\ \hline Peak power (W) & 5100 & 3622 & 3100 & 4368 & 2280 & 1600 & 2200 & 7600 & 250 (total) & 1700 \\ Daily cycle of power (V3) & 8 & 4 & 5 & 12 & 12 & 13.75 & 18 & 11 & 35 \\ \hline Orbit period (min) & 98.5 & 99.7 & 97.2 & 98.5 & 100.7 & 96.4 & 95.0 & 2075 (max) & 2075 (assumed) & 95.8 \\ Working time period (min) & 49 & 30 & 5-20 & 25,74 (wave modes) & 28 & 15 & 3 & 2075 (max) & 2075 (assumed) & 2 \\ \hline Satellite number & 1 & 2 & 2 & 2 & 1 & 3 & 3 & 4 & 5 & 1 \\ \hline Average transmitted power (W) & 203 & 44 & 32 & 394 & 76 & 34 & 13 & 167 & 50 & 13 \\ \hline Bandwidth (MHz) & 42 (middle) & 84 & 50 & 100 & 100 & 100 & 150/300 & 400 & 300 (assumed) & 120 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Utilized system parameters of the main LEO SAR (L, C and X bands) in the simulation. The orbits of the ALOS-2 PALSAR, Sentinel-1 A and TerraSAR-X have been used as the examples of L-, C- and X band LEO SAR systems to calculate the occurrence probabilities of non-specular scattering case, specular scattering case and mainlobe to mainlobe specular scattering case by STK software. The analysis result of the occurrence probabilities is provided in Table 5. The occurrence probabilities are obtained based on the orbit simulation of the GEO SAR and the LEO SAR with different periods, which are the repeat orbit cycles of the three systems (14-day, 12-day and 11-day, respectively). For all three considered working frequencies, because the GEO SAR can often'see' the LEO SAR due to its high running orbit, the non-specular scattering case has a high occurrence probability of about 40%. In contrast, due to the strict condition of the occurrence of the specular scattering case, the occurrence probabilities in all working frequencies are very low, less than 0.1%. In fact, the calculation for the specular scattering case gives out the worst case, because the practical occurrence of the specular scattering is also determined by many factors, such as the incidence angle and the type of the scene. As the beam width of the LEO SAR turns smaller with the increasing of the frequency, the occurrence probability decreases further for the X band system compared with the L band or C band systems. Owing to the very little occurrence probability, mainlobe to mainlobe specular scattering case has never happened during the simulation. The average transmitted power requirements in GEO SAR in the presence of the LEO SAR bistatic scattering RFI are shown in Table 5. Some geometry parameters used in the simulation are given in the caption. To analyse the worst case, we consider the received LEO SAR signal is weighted by the envelope of the GEO SAR one dimensional antenna pattern within the integration time. According to their working frequencies, the LEO SAR satellites in Table 5 are classified and used as the input RFI sources.