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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.


Schematic diagram and time-frequency diagram (TFD) in the range direction of two operation modes of a multi-sub-band system. (a) Consecutive stepped-frequency mode; (b) non-consecutive stepped-frequency mode.
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f1-sensors-15-15339: Schematic diagram and time-frequency diagram (TFD) in the range direction of two operation modes of a multi-sub-band system. (a) Consecutive stepped-frequency mode; (b) non-consecutive stepped-frequency mode.

Mentions: Currently, the synthetic bandwidth technique can be implemented in two modes. The schematic diagram and time-frequency diagram (TFD) in the range direction of the two modes are shown in Figure 1, where the number of sub-bands is five. In Figure 1a, the system transmits one wide-bandwidth signal or several successive chirp signals, and the transmitted signals are received as successive chirp signals offset by a certain step frequency. This is referred to as the consecutive stepped-frequency approach. The other method is described as non-consecutive stepped-frequency mode and is sketched in Figure 1b, where the transmitted and received signals are composed of several non-consecutive chirps in different sub-bands to avoid range ambiguity.


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)

Schematic diagram and time-frequency diagram (TFD) in the range direction of two operation modes of a multi-sub-band system. (a) Consecutive stepped-frequency mode; (b) non-consecutive stepped-frequency mode.
© Copyright Policy
Related In: Results  -  Collection

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

f1-sensors-15-15339: Schematic diagram and time-frequency diagram (TFD) in the range direction of two operation modes of a multi-sub-band system. (a) Consecutive stepped-frequency mode; (b) non-consecutive stepped-frequency mode.
Mentions: Currently, the synthetic bandwidth technique can be implemented in two modes. The schematic diagram and time-frequency diagram (TFD) in the range direction of the two modes are shown in Figure 1, where the number of sub-bands is five. In Figure 1a, the system transmits one wide-bandwidth signal or several successive chirp signals, and the transmitted signals are received as successive chirp signals offset by a certain step frequency. This is referred to as the consecutive stepped-frequency approach. The other method is described as non-consecutive stepped-frequency mode and is sketched in Figure 1b, where the transmitted and received signals are composed of several non-consecutive chirps in different sub-bands to avoid range ambiguity.

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.