Abstract
The synthetic bandwidth technique is an effective method to achieve ultra-high range resolution in an SAR system. There are mainly two challenges in its implementation. The first one is the estimation and compensation of system errors, such as the timing deviation and the amplitude-phase error. Due to precision limitation of the radar instrument, construction of the sub-band signals becomes much more complicated with these errors. The second challenge lies in the combination method, that is how to fit the sub-band signals together into a much wider bandwidth. In this paper, a novel synthetic bandwidth approach is presented. It considers two main errors of the multi-sub-band SAR system and compensates them by a two-order PGA (phase gradient auto-focus)-based method, named TRPGA. Furthermore, an improved cut-paste method is proposed to combine the signals in the frequency domain. It exploits the redundancy of errors and requires only a limited amount of data in the azimuth direction for error estimation. Moreover, the up-sampling operation can be avoided in the combination process. Imaging results based on both simulated and real data are presented to validate the proposed approach.
Highlights
Synthetic aperture radar (SAR) is a powerful active remote sensing system with all-time and all-weather observation ability to form two-dimensional high-resolution images [1,2,3]
To demonstrate the performance and effectiveness of the proposed method for multi-sub-band signal construction, results based on both simulated data and three-sub-band raw data collected through a real system are provided
It can be seen that the impulse response function has deteriorated seriously with the side lobes raised and asymmetric, which means that impulse response width (IRW), peak side-lobe ratio (PSLR) and integrated side-lobe ratio (ISLR) cannot meet the imaging requirement any more
Summary
Synthetic aperture radar (SAR) is a powerful active remote sensing system with all-time and all-weather observation ability to form two-dimensional high-resolution images [1,2,3]. A time-domain method was proposed by [11] in which the sub-band signal is required to be up-sampled first to avoid aliasing. This will increase the computational load significantly, given the required pre-processing steps, including frequency shift, phase correction and time shift.
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