Concurrent Imaging Mode Applied to High Resolution Wide Swath SAR Imaging

Abstract

Synthetic aperture radar (SAR) is gradually becoming mainstream for imaging of the Earth’s surface due to its all-weather day-and-night functionality. Its increasing image quality tied to the capabilities of polarimetry, interferometry, and tomography turns it into a very attractive technology for a continuous monitoring of global phenomena (such as glacier retreat, deforestation, and sea ice coverage), surveillance, farming and numerous other applications. Therefore, imaging wide swaths with high resolution (HRWS) is a key line of research for the future generation of SAR systems. One of the recently proposed techniques to increase imaging capability and flexibility is the concurrent imaging mode. This mode allows for simultaneous acquisitions of two areas by increasing the pulse repetition frequency and interleaving the transmission and reception of both modes in a pulse-to-pulse manner. Due to intrinsic system limitations, this technique applied to current operational systems, such as the German satellite TerraSAR-X, comes along with strong trade-offs in terms of limited swath width and increased ambiguity levels. In this Master’s thesis, multiple techniques are investigated to improve the concurrent mode within the scope of the next generation of SAR systems. Given that those systems are still under development and there is no strict restriction on what is available, a vast range of technologies and possibilities are analyzed in this work, such as orthogonal frequency division multiplexing (OFDM), frequency scanning (F-Scan), and displaced phase centers antenna (DPCA) technique. F-Scan is shown to comply well with the requirements, achieving significant improvements not only in range performance but also in scene size, all of this under a relatively simple and inexpensive system. Finally, global performance simulations and improvement predictions are carried out within the framework of the upcoming German X-Band HRWS mission, which is planned to use F-Scan operationally.