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A Synthetic Bandwidth Method for High-Resolution SAR Based on PGA in the Range Dimension.

Li J, Chen J, Liu W, Wang P, Li C - Sensors (Basel) (2015)

Bottom Line: The synthetic bandwidth technique is an effective method to achieve ultra-high range resolution in an SAR system.Furthermore, an improved cut-paste method is proposed to combine the signals in the frequency domain.Imaging results based on both simulated and real data are presented to validate the proposed approach.

View Article: PubMed Central - PubMed

Affiliation: School of Electronic and Information Engineering, Beihang University, Beijing 100191, China. lijincheng_buaa@163.com.

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.

No MeSH data available.


Results of real SAR imaging without strong point target: (a) imaging result of sub-band signal; (b) imaging result of reconstruction with relative calibration; (c) imaging result of reconstruction of first-order TRPGA; (d) imaging result of reconstruction of two-order TRPGA.
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f10-sensors-15-15339: Results of real SAR imaging without strong point target: (a) imaging result of sub-band signal; (b) imaging result of reconstruction with relative calibration; (c) imaging result of reconstruction of first-order TRPGA; (d) imaging result of reconstruction of two-order TRPGA.

Mentions: To show the improvement further, quantitative analysis is performed on the point target circled in Figure 9b–d. The range profiles are shown in Figure 9e in which the Taylor window is applied to suppress the pulse side lobe in image formation. From Figure 9e, it can be seen that the side lobe of the point target is suppressed less than 10 dB after implementing the first-order TRPGA, corresponding to the improvement from Figure 9b to c. However, the profile is far below optimal, and further elimination of the residual error is still necessary. The measured value of IRW, PSLR and ISLR after the implementation of the proposed approach is listed in the lower part of Table 2. The IRW after being processed by the TRPGA is 0.196 m, and the first side lobe is below −25 dB, which is consistent with the theoretical results. Figure 10 is the processing results of the SAR image without strong points. The performance in terms of contrast and entropy is shown in Table 2. The enhancement of image quality shows that the TRPGA method works well, demonstrating the robustness of the proposed technique.


A Synthetic Bandwidth Method for High-Resolution SAR Based on PGA in the Range Dimension.

Li J, Chen J, Liu W, Wang P, Li C - Sensors (Basel) (2015)

Results of real SAR imaging without strong point target: (a) imaging result of sub-band signal; (b) imaging result of reconstruction with relative calibration; (c) imaging result of reconstruction of first-order TRPGA; (d) imaging result of reconstruction of two-order TRPGA.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4541834&req=5

f10-sensors-15-15339: Results of real SAR imaging without strong point target: (a) imaging result of sub-band signal; (b) imaging result of reconstruction with relative calibration; (c) imaging result of reconstruction of first-order TRPGA; (d) imaging result of reconstruction of two-order TRPGA.
Mentions: To show the improvement further, quantitative analysis is performed on the point target circled in Figure 9b–d. The range profiles are shown in Figure 9e in which the Taylor window is applied to suppress the pulse side lobe in image formation. From Figure 9e, it can be seen that the side lobe of the point target is suppressed less than 10 dB after implementing the first-order TRPGA, corresponding to the improvement from Figure 9b to c. However, the profile is far below optimal, and further elimination of the residual error is still necessary. The measured value of IRW, PSLR and ISLR after the implementation of the proposed approach is listed in the lower part of Table 2. The IRW after being processed by the TRPGA is 0.196 m, and the first side lobe is below −25 dB, which is consistent with the theoretical results. Figure 10 is the processing results of the SAR image without strong points. The performance in terms of contrast and entropy is shown in Table 2. The enhancement of image quality shows that the TRPGA method works well, demonstrating the robustness of the proposed technique.

Bottom Line: The synthetic bandwidth technique is an effective method to achieve ultra-high range resolution in an SAR system.Furthermore, an improved cut-paste method is proposed to combine the signals in the frequency domain.Imaging results based on both simulated and real data are presented to validate the proposed approach.

View Article: PubMed Central - PubMed

Affiliation: School of Electronic and Information Engineering, Beihang University, Beijing 100191, China. lijincheng_buaa@163.com.

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.

No MeSH data available.