Abstract
Sliding spotlight mode is a novel synthetic aperture radar (SAR) imaging scheme with an achieved azimuth resolution better than stripmap mode and ground coverage larger than spotlight configuration. However, its raw signal simulation of extended scenes may not be efficiently implemented in the two-dimensional (2D) Fourier transformed domain. This article presents a novel sliding spotlight raw signal simulation approach from the wide-beam SAR imaging modes. This approach can generate sliding spotlight raw signal not only from raw data evaluated by the simulators, but also from real data in the stripmap/spotlight mode. In order to obtain the desired raw data from conventional stripmap/spotlight mode, the azimuth time-varying filtering, which is implemented by de-rotation and low-pass filtering, is adopted. As raw signal of extended scenes in the stripmap/spotlight mode can efficiently be evaluated in the 2D Fourier domain, the proposed approach provides an efficient sliding spotlight SAR simulator of extended scenes. Simulation results validate this efficient simulator.
Highlights
The spotlight synthetic aperture radar (SAR) mode can improve azimuth resolution by increasing the synthetic aperture time, and its azimuth beam is steered during the whole acquisition time
The major drawback of such configuration is that azimuth beam pointing always at the same area limits the extension of the illuminated area in azimuth
The sliding spotlight mode allows a comprise between azimuth resolution and azimuth extension of imaged scene [1,2,3], and it can be described as using a virtual rotation center which is further away from the radar than the imaging scene [4]
Summary
The spotlight synthetic aperture radar (SAR) mode can improve azimuth resolution by increasing the synthetic aperture time, and its azimuth beam is steered during the whole acquisition time. Azimuth varying band-pass filter (BPF) could be adopted for extracting the desired signals from the raw data in the wide-beam imaging modes and set others to zero This filter should just accommodate the Doppler centroid varying rate and be independent of the slant range, and it can efficiently be implemented by de-rotation operation and BPF. Antenna azimuth beam points along a fixed direction with respect to the flight path, while azimuth beam is steered during the whole acquisition interval in the spotlight mode. The equivalent azimuth beam steering introduces a Doppler centroid rate as follows krot
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