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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.


Upper limit of the timing error versus the slant-range resolutions for X-band and C-band SAR systems employing the synthetic bandwidth technique.
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f4-sensors-15-15339: Upper limit of the timing error versus the slant-range resolutions for X-band and C-band SAR systems employing the synthetic bandwidth technique.

Mentions: Next, the requirement on timing accuracy is analysed according to the phase errors introduced by the timing error. By Equation (9), we can see that the timing error between the subsystems will lead to a signal phase error, which increases with frequency. The image quality will be reduced if the phase error exceeds 0.25π within the constructed bandwidth [2]. Figure 3 shows the maximum phase errors within the bandwidth caused by different timing errors for X-band and C-band SAR systems employing the synthetic bandwidth technique with a slant-range resolution of 0.25 m, which is the requirement of future applications, such as the TerraSAR Next Generation [13]. As shown by Figure 3, the phase error becomes larger with the increase of timing errors. To limit the phase error under 0.25π, the timing error should be less than 12.6ps and 21.2ps for X-band and C-band SAR systems, respectively. Figure 4 illustrates the upper limit value of timing error for different slant range resolutions. It can be seen that if the synthetic bandwidth technique is applied, the upper limit value of timing error required is at the ps level, which is a rather strong requirement on the consistency of the subsystems [14].


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)

Upper limit of the timing error versus the slant-range resolutions for X-band and C-band SAR systems employing the synthetic bandwidth technique.
© Copyright Policy
Related In: Results  -  Collection

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

f4-sensors-15-15339: Upper limit of the timing error versus the slant-range resolutions for X-band and C-band SAR systems employing the synthetic bandwidth technique.
Mentions: Next, the requirement on timing accuracy is analysed according to the phase errors introduced by the timing error. By Equation (9), we can see that the timing error between the subsystems will lead to a signal phase error, which increases with frequency. The image quality will be reduced if the phase error exceeds 0.25π within the constructed bandwidth [2]. Figure 3 shows the maximum phase errors within the bandwidth caused by different timing errors for X-band and C-band SAR systems employing the synthetic bandwidth technique with a slant-range resolution of 0.25 m, which is the requirement of future applications, such as the TerraSAR Next Generation [13]. As shown by Figure 3, the phase error becomes larger with the increase of timing errors. To limit the phase error under 0.25π, the timing error should be less than 12.6ps and 21.2ps for X-band and C-band SAR systems, respectively. Figure 4 illustrates the upper limit value of timing error for different slant range resolutions. It can be seen that if the synthetic bandwidth technique is applied, the upper limit value of timing error required is at the ps level, which is a rather strong requirement on the consistency of the subsystems [14].

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.