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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.


Synthesis results with different time error between sub-bands. (a) Impulse response function with linear component of the phase errors; (b) impulse response function with constant component of the phase errors; (c) impulse response width (IRW) versus time error; (d) peak side-lobe ratio (PSLR) versus time error.
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f2-sensors-15-15339: Synthesis results with different time error between sub-bands. (a) Impulse response function with linear component of the phase errors; (b) impulse response function with constant component of the phase errors; (c) impulse response width (IRW) versus time error; (d) peak side-lobe ratio (PSLR) versus time error.

Mentions: In order to analyse the effect of the two phase error components induced by the timing error, simulations are performed with the parameters listed in Table 1. The impulse response function is shown in Figure 2. The deterioration of the profile is obvious, and the compression result becomes worse with the increase of timing errors. Figure 2a shows that the linear component splits the response and results in symmetric raised side-lobes, which correspond to the deviation of the compressed positions of the signals in different sub-bands. In another case, the asymmetric side-lobes illustrated in Figure 2b demonstrate that the constant component belongs to the class of high order phase errors, which is consistent with our earlier analysis. In Figure 2c,d, the impulse response widths (IRWs) (normalized to the theoretical value) and the peak side-lobe ratio (PSLR) with respect to the timing error are provided. It can be seen that even a nanosecond timing error can degrade the compression quality.


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)

Synthesis results with different time error between sub-bands. (a) Impulse response function with linear component of the phase errors; (b) impulse response function with constant component of the phase errors; (c) impulse response width (IRW) versus time error; (d) peak side-lobe ratio (PSLR) versus time error.
© Copyright Policy
Related In: Results  -  Collection

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

f2-sensors-15-15339: Synthesis results with different time error between sub-bands. (a) Impulse response function with linear component of the phase errors; (b) impulse response function with constant component of the phase errors; (c) impulse response width (IRW) versus time error; (d) peak side-lobe ratio (PSLR) versus time error.
Mentions: In order to analyse the effect of the two phase error components induced by the timing error, simulations are performed with the parameters listed in Table 1. The impulse response function is shown in Figure 2. The deterioration of the profile is obvious, and the compression result becomes worse with the increase of timing errors. Figure 2a shows that the linear component splits the response and results in symmetric raised side-lobes, which correspond to the deviation of the compressed positions of the signals in different sub-bands. In another case, the asymmetric side-lobes illustrated in Figure 2b demonstrate that the constant component belongs to the class of high order phase errors, which is consistent with our earlier analysis. In Figure 2c,d, the impulse response widths (IRWs) (normalized to the theoretical value) and the peak side-lobe ratio (PSLR) with respect to the timing error are provided. It can be seen that even a nanosecond timing error can degrade the compression quality.

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.