Fusco Adele, Pepe Antonio, Berardino Paolo, De Luca Claudio, Buonanno Sabatino, Lanari Riccardo
IREA-National Research Council of Italy (CNR) via Diocleziano 328, 80124 Napoli, Italy.
Sensors (Basel). 2019 Jul 29;19(15):3321. doi: 10.3390/s19153321.
We present a new solution for the phase-preserving focusing of synthetic aperture radar (SAR) raw data acquired through the Terrain Observation with Progressive Scan (TOPS) mode. The proposed algorithm consists of a first interpolation stage of the TOPS raw data, which takes into account the Doppler Centroid frequency variations due to the azimuth antenna steering function, and allows us to unfold the azimuth spectra of the TOPS raw data. Subsequently, the interpolated signals are processed by using conventional phase-preserving SAR focusing methods that exploit frequency domain and spectral analyses algorithms, which are extensively used to efficiently process Stripmap and ScanSAR data. Accordingly, the developed focusing approach is easy to implement. In particular, the presented focusing approach exploits one of the available frequency domain Stripmap processing techniques. The only modification is represented by the inclusion, within the 2D frequency domain focusing step, of a spurious azimuth chirp signal with a properly selected azimuthal rate. This allows us to efficiently carry out the TOPS azimuth focusing through the SPECAN method. Furthermore, an important aspect of this algorithm is the possibility to easily achieve a constant and tunable output azimuth pixel size without any additional computing time; this is a remarkable feature with respect to the full-aperture TOPS-mode algorithms available in the existing literature. Moreover, although tailored on Sentinel-1 (S1) raw data, the proposed algorithm can be easily extended to process data collected through the TOPS mode by different radar sensors. The presented experimental results have been obtained by processing real Sentinel-1 raw data and confirm the effectiveness of the proposed algorithm.
我们提出了一种新的解决方案，用于对通过地形观测渐进扫描（TOPS）模式获取的合成孔径雷达（SAR）原始数据进行相位保持聚焦。所提出的算法包括对TOPS原始数据的第一阶段插值，该阶段考虑了由于方位角天线转向功能引起的多普勒质心频率变化，并使我们能够展开TOPS原始数据的方位谱。随后，通过使用利用频域和频谱分析算法的传统相位保持SAR聚焦方法来处理插值信号，这些算法广泛用于高效处理条带图和扫描SAR数据。因此，所开发的聚焦方法易于实现。特别是，所提出的聚焦方法利用了现有的频域条带图处理技术之一。唯一的修改是在二维频域聚焦步骤中包含一个具有适当选定方位率的杂散方位线性调频信号。这使我们能够通过SPECAN方法有效地进行TOPS方位聚焦。此外，该算法的一个重要方面是可以轻松实现恒定且可调的输出方位像素大小，而无需任何额外的计算时间；相对于现有文献中可用的全孔径TOPS模式算法，这是一个显著的特征。此外，尽管该算法是针对哨兵-1（S1）原始数据量身定制的，但可以轻松扩展以处理不同雷达传感器通过TOPS模式收集的数据。通过处理真实的哨兵-1原始数据获得了所呈现的实验结果，证实了所提出算法的有效性。
