基于橢圓模型與改進(jìn)NLCS的一站固定式大基線雙站SAR成像算法
doi: 10.11999/JEIT161016
基金項(xiàng)目:
國(guó)家自然科學(xué)基金(61301248, 61271214),中國(guó)航天科技創(chuàng)新基金
Improved NLCS Algorithm Based on Ellipse Model for One-stationary Bistatic SAR with Large Baseline
Funds:
The National Natural Science Foundation of China (61301248, 61271214), Chinese Innovation Foundation of Aerospace Science and Technology
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摘要: 在一站固定式雙站SAR成像處理中,該文針對(duì)距離-方位2維空變描述不夠準(zhǔn)確導(dǎo)致成像性能迅速下降的問(wèn)題,提出一種新的橢圓模型精確描述一站固定式大基線雙站SAR的距離-方位空變特性,并基于此推導(dǎo)了改進(jìn)的非線性調(diào)頻變標(biāo)(NLCS)成像算法。在距離向,首先利用相位去斜完成距離去走動(dòng)和多普勒中心矯正,接著對(duì)剩余距離單元徙動(dòng)和距離方位高次耦合項(xiàng)進(jìn)行了去除處理。在方位向,根據(jù)一站固定式雙站SAR的2維空變特性,提出了一種用于描述回波距離-方位空變特性的橢圓模型,基于該模型對(duì)空變的回波方位調(diào)頻率進(jìn)行了分析,并重新推導(dǎo)NLCS算法的方位變標(biāo)函數(shù)和方位壓縮系數(shù)。理論分析與仿真結(jié)果證明,所提出的模型不僅揭示了一站固定式大基線雙站SAR數(shù)據(jù)的2維空變特性,而且對(duì)回波的距離-方位空變給出了更精確的解析式描述,使得基于該模型改進(jìn)的NLCS算法可以獲得更好的成像處理效果。
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關(guān)鍵詞:
- SAR成像 /
- 雙站SAR /
- 一站固定式 /
- 非線性調(diào)頻變標(biāo) /
- 橢圓模型
Abstract: In One-Stationary Bistatic Synthetic Aperture Radar (OS-BiSAR) imaging, imprecise description of 2-D range-azimuth space-variant property usually leads to deterioration of final SAR image rapidly. In order to solve this issue, a new ellipse model is proposed to precisely describe range-azimuth space-variant property of OS-BiSAR with large baseline, and an improved Non-Linear Chirp Scaling (NLCS) algorithm is also derived based on this model. First, a phase de-ramp operation is performed to remove the linear Range Cell Migration (RCM) and Doppler centroid in range frequency domain. Then, the residual RCM and high order range-azimuth coupling terms are removed. Thirdly, a new ellipse model is established to describe range-azimuth space-variant property of OS-BiSAR, and then the azimuth frequency modulation rate of space-variant echo is analyzed. Moreover, azimuth scaling function of NLCS and azimuth compression factors are re-derived. Theoretical analysis and simulation results show that the proposed model not only reveals the property of 2-D azimuth-variant in OS-BiSAR, but also provides a precise analytical expression to depict the 2-D range-azimuth space-variant property of OS-BiSAR. Furthermore, simulation results validate that the improved NLCS algorithm based on this new model has high imaging performance.-
Key words:
- SAR imaging /
- Bistatic SAR /
- One-stationary /
- Non-Linear Chirp Scaling (NLCS) /
- Ellipse model
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