Focusing of Ultrahigh Resolution Spaceborne Spotlight SAR on Curved Orbit

Abstract

Aiming to acquire ultrahigh resolution images, algorithms for spaceborne spotlight synthetic aperture radar (SAR) imaging typically confront challenges of curved orbit and azimuth spectral aliasing. In order to conquer these difficulties, a method is proposed in this paper to obtain ultrahigh resolution spaceborne SAR images on a curved orbit, which is composed of the modified RMA (Range Migration Algorithm) and the modified deramping-based approach. The modified RMA is developed to deal with the effect introduced by a curved orbit and the modified deramping-based approach is utilized to handle the problem of azimuth spectral aliasing. In the modified RMA, the polynomial expression of SAR two-dimensional spectrum on a curved orbit is derived with fourth-order azimuth phase history model and series reversion. Then, the singular value decomposition (SVD) is applied to decompose the expression of SAR two-dimensional spectrum numerically in order to acquire coordinates for Stolt interpolation in the scenario of curved orbit. In addition, the modified deramping-based approach is derived by introducing orbital state vectors in order to accommodate the situation of curved orbit in the proposed method. Experiments are implemented on point target simulation in order to verify the effectiveness of the presented method. In experiments, the range and azimuth resolution can achieve 0.15 m and 0.14 m, with focused scene size of 3 km by 3 km.

Special Issue on “Advanced Technology Related to Radar Signal, Imaging, and Radar Cross-Section Measurement”

“…After a very careful peer-review process, a total of 32 papers were accepted. These works include SAR/ISAR [2][3][4][5][6][7][8][9], polarimetry [10][11][12], MIMO [13,14], direction of arrival (DOA)/direction of departure (DOD) [13][14][15], sparse sensing [5,14,16], ground-penetrating radar (GPR) [17][18][19], through-wall radar [20,21], coherent integration [22,23], clutter suppression [24,25], and meta-materials, among others [26][27][28][29][30][31]. All of these accepted papers are the latest research results and are expected to be further advanced, applied, and diverted.…”

A Vehicle Target Recognition Algorithm for Wide-Angle SAR Based on Joint Feature Set Matching

“…Synthetic Aperture Radar (SAR) has excellent imaging ability, which can obtain high-resolution image under bad weather conditions. The research on SAR includes imaging, target detection, target recognition, time-frequency analysis, and many other aspects [1][2][3][4][5][6][7][8]. The research on Automatic Target Recognition (ATR) of SAR started around 1990 [9][10][11].…”

Image Formation of Azimuth Periodically Gapped SAR Raw Data with Complex Deconvolution

“…The development and advancement of Synthetic Aperture Radar (SAR) improve humans' abilities to obtain more abundant information for target surveillance with high resolution images and videos [1][2][3][4][5][6][7][8][9]. Along with the development process of SAR, the stability of missing or gapped raw data attracts research interest due to new mission requirements, sensor geometries, jamming, or interference that cause sparse and irregular sampling [10].…”