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Subject to the low pulse repetition frequency (PRF), or under sampling, grating-lobes will appear at azimuth in synthetic aperture radar (SAR) imagery. In this paper, the presence of particular ring-shaped grating-lobes (RSGLs) in circular SAR (CSAR) imagery is first reported as much as the authors know. Characteristics of RSGLs are analysed in detail, including the radius, the width and the amplitude...
Due to the reference signal based on the fixed reference range is used in the range migration (RM) algorithm, the RM algorithm is not available to process an airborne squint-mode spotlight synthetic aperture radar (SAR) data. Thus, a modified RM algorithm is developed, which can be applied on processing large scene squinted-mode spotlight SAR data without division. Based on the squint-mode spotlight...
This paper presents a new airborne squint-mode spotlight SAR data focusing algorithm based on a two-step processing strategy that combines the advantages of the efficiency of spectral analysis (SPECAN) algorithm and the precision of wavenumber domain (WD) algorithm. The first step of the proposed algorithm implements a modified SPECAN processing to the range compressed echo signal. This operation...
As current airborne SAR systems aiming to produce SAR imagery at resolution less than 0.1 m, attaining ultrawideband signal become a difficult problem. Synthetic bandwidth based on frequency-stepped chirps is an available method to achieve this type of ultra-wideband signal, the advantage of which is the reduction of the instantaneous bandwidth and sampling rate requirements of the radar system. This...
One problem in SAR processing is degradation of the spatial resolution owing to uncorrected motion errors. Several reconstruction algorithms with motion error correction have been developed. In this paper, an efficient motion compensation method via the known motion error information is proposed. The effects of motion error in spotlight SAR imaging by the range migration algorithm (RMA) is analyzed...
As compared to the high frequency squinted mode SAR, it is more difficult to processing the low frequency highly squinted SAR. In this paper, we present an extended wavenumber domain algorithm and study its application on low frequency highly squinted SAR imaging. The expressions of squinted SAR in wavenumber domain are deducted in detail, and the Stolt interpolation method in 2D frequency domain...
The phase gradient autofocus (PGA) technique has been proved to be a superior method for higher order autofocus. However, given the different nature of P-band ultra-wideband synthetic aperture radar (UWB SAR) imagery and very low signal-to-clutter ratio in the data, conventional PGA algorithm usually fail to yield robust focusing result on raw data without distortion. We proposed the modified PGA...
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