Performance and Requirements of GEO SAR Systems in the Presence of Radio Frequency Interferences

Abstract

Geosynchronous Synthetic Aperture Radar (GEO SAR) is a possible next generation SAR system, which has the excellent performance of less than one-day revisit and hundreds of kilometres coverage. However, Radio Frequency Interference (RFI) is a serious problem, because the specified primary allocation frequencies are shared by the increasing number of microwave devices. More seriously, as the high orbit of GEO SAR makes the system have a very large imaging swath, the RFI signals all over the illuminated continent will interfere and deteriorate the GEO SAR signal. Aimed at the RFI impact in GEO SAR case, this paper focuses on the performance evaluation and the system design requirement of GEO SAR in the presence of RFI impact. Under the RFI impact, Signal-to-Interference-plus-Noise Ratio (SINR) and the required power are theoretically deduced both for the ground RFI and the bistatic scattering RFI cases. Based on the theoretical analysis, performance evaluations of the GEO SAR design examples in the presence of RFI are conducted. The results show that higher RFI intensity and lower working frequency will make the GEO SAR have a higher power requirement for compensating the RFI impact. Moreover, specular RFI bistatic scattering will give rise to the extremely serious impact on GEO SAR, which needs incredible power requirements for compensations. At last, real RFI signal behaviours and statistical analyses based on the SMOS satellite, Beidou-2 navigation satellite and Sentinel-1 A data have been given in the appendix.

Formation Design for Single-Pass GEO InSAR Considering Earth Rotation Based on Coordinate Rotational Transformation

“…To design formation SAR according to an application, we need to establish the relationship between baseline and orbital elements. Similar to (2), the baseline in the ECF coordinate system can be expressed as:…”

“…An obvious way to obtain a SAR formation with relatively stable baselines is to minimize the error shown in (13) by numerical optimization. This method, however, has two disadvantages: (1) the computation complexity is considerable; (2) it is difficult to find out a general rule of formation that satisfies the performance requirements. In this section, we propose a GEO InSAR formation design method based on the Minimum Along-track Baseline Criterion (MABC).…”

“…Geosynchronous synthetic aperture radar (GEO SAR) is a spaceborne SAR system operating at geosynchronous orbit with a height of about 36,000 km [1,2]. Compared with the traditional low Earth orbit SAR (LEO SAR), GEO SAR has the advantages of a short revisit period (several hours to one day) and extensive coverage (imaging swath wider than 2000 km).…”

GRFT-Based Moving Ship Target Detection and Imaging in Geosynchronous SAR

“…where A C = A rm exp(j4π(r 0 − r 0 )/λ). Based on (13), (15), and (16), (20) can be rewritten as (21), the difference ofv r andv a will cause the GRFT responses changed.…”

“…be observed within the range of every 1.5-2.5 h per day [14]. Thus, GEO SAR has great advantages in ship surveillance over vast ocean area.Currently, there are growing interests for GEO SAR, which are mainly concentrated on system design and mission planning [15][16][17][18][19][20][21], imaging algorithms [22][23][24][25], ionospheric effects and compensation [26][27][28], and deformation retrieval [29][30][31]. However, there are rarely related researches on detection and imaging of moving ships.Obviously, due to high time resolution and wide swath coverage, GEO SAR has great potential in monitoring moving ships.…”