Ultrawideband-Ultrawidebeam Synthetic Aperture Radar – Signal Processing and Applications
Sammanfattning: This dissertation presents practical issues in Ultrawideband – Ultrawidebeam (UWB) Synthetic Aperture Radar (SAR) signal processing and crucial applications developed on UWB SAR. In the context of this dissertation, UWB SAR refers to the SAR systems utilizing large fractional bandwidth signals and synthesizing long apertures associated with wide antenna beamwidths. On one hand, such specific systems give us opportunities to develop unique applications. One the other hand, signal processing for data collected by these systems is very challenging and therefore requires much effort due to their characteristics. In the signal processing part, the tools supporting the UWB SAR system design and evaluation are introduced. They include an Impulse Response Function in UWB SAR imaging (IRF-SAR), azimuth and range resolution equations for UWB SAR, and a definition of UWB SAR quality measurements. Pre-processing, processing and post-processing for UWB SAR are also topics that will be examined in the signal processing part. The processing is here defined by SAR algorithms. With this definition, the pre-processing refers to RFI suppression approaches whereas the post-processing implies apodization or sidelobe control methods. In the application part, Ground Moving Target Indication (GMTI) is selected for study due to its interest to both military and civilian end-users. GMTI developed on UWB SAR relates to the moving target detection by focusing technique which can be combined with the space-time processing such as Displaced Phase Center Antenna (DPCA) and Space-Time Adaptive Processing (STAP).
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