Abstract
Adaptive sliding receive-window (ASRW) technique was usually introduced in airborne squint synthetic aperture radar (SAR) systems. Airborne squint spotlight SAR varies its receive-window starting time pulse-by-pulse as a function of range-walk, namely, the linear term of range cell migration (RCM). As a result, a huge data volume of the highly squint spotlight SAR echo signal can be significantly reduced. Because the ASRW technique changes the echo-receive starting time and Doppler history, the conventional image algorithm cannot be employed to directly focus airborne squint spotlight ASRW-SAR data. Therefore, a fast image-formation algorithm, based on the principle of the wave number domain algorithm (WDA) and azimuth deramping processing, was proposed for accurately and efficiently focusing the squint spotlight ASRW-SAR data. Azimuth deramping preprocessing was implemented for eliminating azimuth spectrum aliasing. Moreover, bulk compression and modified Stolt mapping were utilized for high-precision focusing. Additionally, geometric correction was employed for compensating the image distortion resulting from the ASRW technique. The proposed algorithm was verified by evaluating the image performance of point targets in different squint angles. In addition, a detailed analysis of computation loads in the appendix indicates that the processing efficiency can be greatly improved, e.g., the processing efficiency could be improved by 17 times in the 70-deg squint angle by applying the proposed image algorithm to the squint spotlight ASRW-SAR data.
Highlights
In order to deal with the varying receive-window starting times in airborne squint spotlight adaptive sliding receive-window (ASRW)-Synthetic aperture radar (SAR), a fast image-formation algorithm is presented for highly precise focusing of the ultrahigh-resolution (e.g., 0.1 m) airborne squint spotlight ASRW-SAR data
Bulk compression and modified Stolt mapping are utilized for precise focusing
Geometric correction is implemented to remove the effect of the varying receive-window starting time by the ASRW technique
Summary
Synthetic aperture radar (SAR) plays a significant role in remote sensing.[1,2,3] Recently, airborne squint spotlight SAR has become one of the most important topics in microwave remote sensing, as it has the advantages of illuminating a particular area within a single pass of the platform by foreword/backward-squinted antenna and providing higher azimuth resolution by operating at a spotlight mode.[4,5] squint spotlight SAR currently has significant applications in intelligence surveillance, security monitoring, target detection, etc.[6,7]. The adaptive sliding receive-window (ASRW) technique was introduced for effectively reducing RCM in a -squinted airborne spotlight SAR system. In this system, its receive-window starting time varies pulse-by-pulse as a function of range-walk, namely, the linear term of RCM. A fast image-formation algorithm for ultrahigh-resolution airborne squint spotlight ASRW-SAR was proposed based on the principle of WDA and the azimuth deramping technique. A presentation of the process flow of the fast image-formation algorithm was given, which was proven to focus the ultrahigh-resolution airborne squint spotlight ASRW-SAR data accurately and efficiently
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