Abstract
In this paper, a new Spaceborne Sliding Spotlight Range Sweep Synthetic Aperture Radar (SSS-RSSAR) is proposed to generate a high-resolution image of a Region of Interest (ROI) tilted with respect to the satellite track. Comparing to the traditional Spaceborne Sliding Spotlight Synthetic Aperture Radar (SSS-SAR), the SSS-RSSAR is superior in contributing to less data amount, lighter computational load and hence higher observation efficiency. Unlike the Spaceborne Stripmap Range Sweep Synthetic Aperture Radar (SS-RSSAR) proposed in a previous paper, the SSS-RSSAR not only continuously sweeps the beam in range for the ROI tracking, but also in azimuth to enlarge the synthetic aperture for an improved azimuth resolution. Two aspects of the SSS-RSSAR are focused: system and imaging. For the system part, a Continuous Varying Pulse Interval (CVPI) technique is proposed to avoid the transmission blockage problem by non-uniformly adjusting the pulse intervals based on the geometry. For the imaging part, a Modified Polar Format Algorithm (MPFA) is proposed to accommodate the original polar format algorithm to the echo received with the CVPI technique. Moreover, an integrate system parameter design flow for the SSS-RSSAR is also suggested. The presented approach is evaluated by exploiting the point target simulations.
Highlights
The Spaceborne Synthetic Aperture Radar (SAR) has dozens of operation modes, such as the stripmap mode, ScanSAR mode, TOPS mode, spotlight mode and the sliding spotlight mode, to image regions of interest (ROI) with variant combination of resolutions and swaths [1,2,3,4,5,6,7,8]
If a traditional constant was applied for the SSS-RSSAR, the continuous range-azimuth beam sweeping would lead to slant range variation and inevitably cause the range-azimuth beam sweeping would lead to slant range variation and inevitably the transmission blockage
This study investigated the system design and imaging method for a new SSS-RSSAR that continuously steers its beam in azimuth and in range to generate a ROI-matched Beam Illumination Strip (BIS)
Summary
The Spaceborne Synthetic Aperture Radar (SAR) has dozens of operation modes, such as the stripmap mode, ScanSAR mode, TOPS mode, spotlight mode and the sliding spotlight mode, to image regions of interest (ROI) with variant combination of resolutions and swaths [1,2,3,4,5,6,7,8]. The core the instant Central Beam Slant Range (CBSR), defined as the slant range from the SAR antenna strategy of the CVPI technique is to locate the echo from the ROI at the central part of every PI In this center to the ground beam pointing. For the SSS-RSSAR, the constant carrier frequency and chirp rate will lead to serious spatial variation of the wavenumber and the range wavenumber bandwidth after the MPFA processing will be seriously compressed, leading to a much decreased range resolution To overcome this shortage, a new Parameter-Adjusting (PA) technique is proposed to mitigate the range wavenumber variation by adjusting the carrier frequency and the chirp rate pulse by pulse based on the instant data acquisition geometry.
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