Motion and Doppler Characteristics Analysis Based on Circular Motion Model in Geosynchronous SAR
Motion and Doppler Characteristics Analysis Based on Circular Motion Model in Geosynchronous SAR
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DOI：
10.1109/jstars.2015.2429915
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发表时间：
2016-03
影响因子：
5.5
通讯作者：
T. Zeng;Wei Yin;Zegang Ding;T. Long
中科院分区：
文献类型：
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作者：
T. Zeng;Wei Yin;Zegang Ding;T. Long
地球同步合成孔径雷达(GEO SAR)的多普勒特性无法用传统的线性运动模型(LMM)来解释，并且GEO SAR的工作模式也没有被清楚地说明。为了解决这些问题，基于曲率圆的数学概念提出了圆周运动模型（CMM）。 GEO SAR被认为沿着大多数轨道位置的中心不是地球中心的曲率圆运行。然后，基于坐标测量机推导零多普勒平面的速度，以正确表达多普勒参数并分析GEO SAR的多普勒特性。分析结果表明，GEO SAR的圆周运动引起零多普勒平面的符号变速度，从而产生复杂的多普勒特征。此外，根据运动和多普勒特性，GEO SAR被认为有两种不同的工作模式。当多普勒速率为零或接近零时，GEO SAR类似于部分孔径圆形SAR（CSAR），具有非线性时频关系，导致传统频域成像算法失效。当多普勒速率非零时，GEO SAR 类似于低地球轨道 (LEO) SAR。最后通过计算机模拟验证了本研究的有效性。所提出的 CMM 可以解释 GEO SAR 的复杂多普勒特征。推导的表达式和工作模式分析可以为系统设计和成像提供进一步的方向。
The Doppler characteristics of geosynchronous synthetic aperture radar (GEO SAR) cannot be explained by the conventional linear motion model (LMM), and the work modes of GEO SAR have not been clearly illustrated. To solve these problems, a circular motion model (CMM) is proposed based on the mathematical concept of curvature circle. GEO SAR is considered to run along the curvature circle whose center is not the earth center at most orbital positions. Then, the velocity of the zero-Doppler plane is derived based on the CMM to correctly express the Doppler parameters and analyze the Doppler characteristics of GEO SAR. Analyses results indicate that the circular motion of GEO SAR causes the sign-variant velocity of the zero-Doppler plane, which then induces the complex Doppler characteristics. Furthermore, GEO SAR is considered to work in two different modes according to the motion and Doppler characteristics. When the Doppler rate is zero or near zero, GEO SAR is similar to a partial aperture circular SAR (CSAR) and has a nonlinear time-frequency relationship, which causes the invalidity of the conventional frequency-domain imaging algorithms. When the Doppler rate is nonzero, GEO SAR is similar to the low-earth-orbit (LEO) SAR. Finally, the validity of this study is verified by computer simulations. The proposed CMM can explain the complex Doppler characteristics of GEO SAR. The derived expressions and the work mode analyses can provide further directions for the system design and imaging.