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首页星载斜视多通道合成孔径雷达数据处理方法
“星载斜视多通道合成孔径雷达数据聚焦” 这篇研究论文详细探讨了星载斜视多通道合成孔径雷达(SAR)数据的聚焦问题。合成孔径雷达是一种利用卫星或飞机等平台在移动中发射和接收雷达信号,通过处理这些信号来生成高分辨率地面图像的技术。在“斜视”模式下,即雷达天线与飞行方向存在较大角度时,星载SAR系统面临着特殊挑战。 文章指出,高斜视角和宽发射脉冲带宽会导致星载斜视SAR数据的多普勒频谱折叠。多普勒频谱折叠是指由于雷达目标的相对运动,使得返回的雷达回波信号在频域内产生了非线性展宽,这增加了在方位向多通道数据重建的复杂性。这种复杂性是由于在斜视模式下,扩展的多普勒带宽所引起的。 针对这一问题,论文提出了一种新的成像算法,该算法旨在有效处理因大斜视角产生的回波特性变化,以实现精确的数据聚焦。这种方法可能涉及到对原始回波信号的预处理、多通道数据同步、多普勒频谱的展开以及方位向的图像重建等多个步骤。通过这些步骤,可以克服多普勒频谱折叠带来的影响,提高合成孔径雷达图像的质量和分辨率。 此外,论文还可能涉及到了实验验证和性能评估,通过对比传统方法和新方法的成像结果,展示新方法在解决星载斜视SAR数据聚焦问题上的优势。这有助于推动未来星载雷达系统的优化设计,尤其是在极端观测条件下保持高分辨率和高精度成像能力。 这篇研究论文对于理解和解决星载雷达系统在斜视模式下遇到的复杂问题具有重要意义,为卫星遥感和地球观测领域的技术进步提供了理论支持。其提出的算法和技术将有助于进一步提升星载SAR系统的性能,特别是在处理宽视场和大角度观测任务时,能够获取更清晰、更准确的地球表面图像。
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Published in IET Radar, Sonar and Navigation
Received on 12th April 2013
Revised on 15th March 2014
Accepted on 21st March 2014
doi: 10.1049/iet-rsn.2013.0332
ISSN 1751-8784
Spaceborne squinted multichannel synthetic aperture
radar data focusing
Pingping Huang
1
, Wei Xu
2
, Shengyang Li
3
1
College of Information Engineering, Inner Mongolia University of Technology, Hohhot 010051, People’s Republic of China
2
Department of Spaceborne Microwave Remote Sensing, Institute of Electronics, Chinese Academy of Sciences,
Beijing 100190, People’s Republic of China
3
Space Star Technology Co. Ltd, Beijing 10086, People’s Republic of China
E-mail: cimhwangpp@163.com
Abstract: This study analyses echo properties of spaceborne squinted multichannel along the track synthetic aperture radar (SAR)
data. The highly squint angle and the large transmitted pulse bandwidth lead to Doppler spectrum back folding in the spaceborne
squinted case. The extended Doppler bandwidth in the squinted mode increases the processing difficulty of azimuth multichannel
data reconstruction. According to echo properties of the spaceborne squinted mode, a new imaging approach for spaceborne
squinted multichannel SAR data focusing is proposed. The key point of this imaging approach is azimuth multichannel data
preprocessing to resolve the aliased Doppler spectrum caused by both azimuth sub-sampling in each azimuth channel and the
highly squint angle. Afterwards, a modified range migration algorithm is taken for consequent equivalent monostatic
spaceborne squinted SAR data focusing. Simulation results on point targets and distributed target are given to validate the
proposed imaging approach.
1 Introduction
For the conventional case of spaceborne synthetic aperture
radar (SAR) systems, the azimuth antenna beam is pointed
nearly perpendicular to the flight path [1]. However, in the
squinted mode, the beam is pointed forward or backward
from the perpendicular position by a squint angle as much
as several tens of degrees. The squinted operation scheme
has the potential to provide information about surface
structure through the measurement of the azimuth angle
dependence of backscatter. Moreover, it could increase the
flexibility with which a designed area on the surface is
imaged for multiple looks with a single pass of the platform
[2, 3]. With the increased squint angle, the final obtained
azimuth resolution becomes worse. The displaced phase
centre multiple azimuth beams (DPCMAB) technique can
improve the azimuth resolution for a fixed total receive
antenna [4–6]. Therefore the spaceborne squinted
multichannel along the track mode becomes a good choice
for both high-resolution imaging and multiple looks with a
single pass of the platform.
In the azimuth multichannel case with the DPCMAB
technique, to generate the uniform sampling of the whole
azimuth received signals, the optimum pulse repetition
frequency (PRF) should be chosen and given as follows [6, 7]
PRF
opt
=
2v
s
N · Dx
(1)
where v
s
is the sensor velocity, Δx is the along-track offset and
N is the number of sub-apertures in azimuth. Such a rigid
selection of the PRF value will be in conflict with the
timing diagram selection. Several reconstruction approaches
[6–9] have been proposed to process azimuth multichannel
raw data to resolve the aliased Doppler spectrum in the case
of azimuth non-uniform sampling. However, these
approaches are directly available under a certain condition
that the processed total Doppler bandwidth is less than the
value of N·PRF.
Unfortunately, the total Doppler bandwidth in the
spaceborne highly squinted mode will exceed the equivalent
azimuth total sampling rate because of the highly squint
angle and the large transmitted pulse bandwidth [10, 11].
As a result, the conventional spectrum reconstruction
algorithm [7–9] and the digital beamforming with
null-steering approach [8, 12 ] cannot be directly applied in
the spaceborne squinted multichannel mode. To resolve this
problem, a novel imaging approach is presented, which
extends the multichannel azimuth data reconstruction ability
of the Doppler spectrum reconstruction algorithm to process
SAR data of the spaceborne squinted multichannel case.
Before azimuth data reconstruction, the variation of the
instantaneous Doppler centroid depending on the range
frequency is removed to reduce the total Doppler
bandwidth. Since range cell migration correction (RCMC)
depends on the instantaneous Doppler frequency in most of
SAR focusing algorithms, targets’ original Doppler history
should be recovered after azimuth multichannel data
reconstruction. Consequently, a traditional spaceborne
processor for the squinted case can be adopted to process
www.ietdl.org
IET Radar Sonar Navig., 2014, Vol. 8, Iss. 9, pp. 1073–1080
doi: 10.1049/iet-rsn.2013.0332
1073
&
The Institution of Engineering and Technology 2014
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