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GNSS海面反射信号的三维建模方法

Three-dimensional modeling method of GNSS sea surface reflection signal
QI Yongqiang, ZHANG Bo, YANG Dongkai, ZHANG Yanzhong, ZHANG Jianmin
School of Electronic and Information Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100083, China
Received: 2017-01-16; Accepted: 2017-02-15; Published online: 2017-04-28 15:12
Foundation item: National Natural Science Foundation of China (61171070)
Corresponding author. YANG Dongkai, E-mail: yangdongkai@sina.com
Abstract: In the application of global navigation satellite system-reflection(GNSS-R) technology, the GNSS-R signal simulator is needed to test the reflection signal receiver in order to reduce costs. A modeling method of global navigation satellite system (GNSS) sea surface reflection signal based on the principle of bistatic radar is presented. First, the remote sensing principle of GNSS-R bistatic radar was analyzed. Then, according to the distribution characteristics of the delay and the Doppler frequency on the sea surface, the reflection points of the sea surface were selected, and the area of corresponding reflection units was calculated. Subsequently, the calculation of the scattering coefficient was carried out. Finally, the simulation verification of the multiple combined signals was conducted. The simulation results indicate that the correlation coefficient of the simulated ocean reflection signal's correlation power curve and the theoretical curve of the ZV model is better than 0.92, which can be used to generate the GNSS ocean reflection signal effectively.
Key words: global navigation satellite system (GNSS)     ocean remote sensing     reflection signal     bistatic radar     ZV model

1 GNSS-R双基雷达遥感原理

GNSS-R海洋遥感的原理，是用陆基、机载或星载接收机，接收经海面反射的GNSS信号，可以看作为一种收发分置的L波段雷达系统。基于微波信号散射理论，尤其是利用双基地雷达方程，可分析海面反射信号与GNSS直接信号在频率、相位、强度等参数之间的变化，从而实现海面的微波遥感探测。这也是GNSS海面反射信号建模的理论基础。

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 图 1 GNSS-R海洋遥感示意图 Fig. 1 Schematic diagram of GNSS-R ocean remote sensing

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2 海面反射信号的空间域分析 2.1 延迟和多普勒频率在海面的分布

 图 2 延迟/等多普勒线 Fig. 2 Iso-delay/Doppler lines

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2.2 海面反射点的选取

GNSS-R接收机接收到的海面反射信号是海面一系列散射点反射信号的集合。这就涉及到反射点选取的问题。反射点数越多，计算量就越大，增加实现难度；但是反射点数太少了，就可能不能够正确反映海面特性信息。如何科学合理地选取反射点，是反射信号建模的一个关键。

 图 3 反射信号空间域和时频域的关系 Fig. 3 Relationship between spatial domain andtime frequency domain of reflection signal

 图 4 反射点的映射 Fig. 4 Reflection point mapping

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GNSS-R海洋遥感是利用反射信号的时延多普勒相关功率来反推海洋表面信息的。作为基本的观测量，时延多普勒相关功率的波形是对称的。为保证接收到的海面反射信号相关功率的波形，特征点的选取应满足2个要求：①特征点的分布是较为对称且相对均匀的；②特征点的数量是足够的，且基本无冗余点。

 图 5 海面反射点选取 Fig. 5 Selection of sea surface reflection points
2.3 反射点对应单元的面积计算

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 图 6 反射单元的面积 Fig. 6 Area of reflection unit
3 散射系数计算

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GNSS信号经过海面反射后，信号极化由右旋圆极化变为左旋圆极化。其菲涅耳反射系数[13]

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 图 7 闪烁区的散射系数 Fig. 7 Scattering coefficient of glistening zone
4 海面反射信号的相关处理

 图 8 海面及ZV模型的反射信号相关功率及其顶图 Fig. 8 Reflection signal correlation power and its topview from sea surface and ZV model

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5 结论

1) 反射点的选取不仅符合时延多普勒海面分布的特点，又考虑到相关功率的对称性，且基本无冗余点。

2) 反射单元面积的计算方法是科学合理的，使得能够应用双基雷达方程来计算GNSS海面反射信号的功率。

3) 通过ZV模型和反射信号的相关处理的对比，验证了该建模方法的可行性和有效性。

 [1] ZUFFADA C, LI Z J, NGHIEM S V, et al. The rise of GNSS reflectometry for earth remote sensing[C]//2015 IEEE International Geoscience and Remote Sensing Symposium(IGARSS). Piscataway, NJ: IEEE Press, 2015: 5111-5114. [2] SHAH R, GARRISON J L, GRANT M S. Demonstration of bistatic radar for ocean remote sensing using communication satellite signals[J]. IEEE Geoscience and Remote Sensing Letters, 2012, 9 (4): 619–623. DOI:10.1109/LGRS.2011.2177061 [3] MASHBURN J, AXELRAD P, LOWE S T, et al. An assessment of the precision and accuracy of altimetry retrievals for a Monterey Bay GNSS-R experiment[J]. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 2016, 9 (10): 4660–4668. DOI:10.1109/JSTARS.2016.2537698 [4] SOISUVARN S, JELENAK Z, SAID F, et al. The GNSS reflectometry response to the ocean surface winds and waves[J]. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 2016, 9 (10): 4678–4699. DOI:10.1109/JSTARS.2016.2602703 [5] VALENCIA E, ZAVOROTNY V U, AKOS D M, et al. Using DDM asymmetry metrics for wind direction retrieval from GPS ocean-scattered signals in airborne experiments[J]. IEEE Transactions on Geoscience and Remote Sensing, 2014, 52 (7): 3924–3936. DOI:10.1109/TGRS.2013.2278151 [6] ZHANG Y, TIAN L M, MENG W T, et al. Feasibility of code-level altimetry using coastal BeiDou reflection(BeiDou-R)setups[J]. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 2015, 8 (8): 4130–4140. DOI:10.1109/JSTARS.2015.2446684 [7] CARRENO-LUENGO H, PARK H, CAMPS A, et al. Submeter ocean altimetry with GPS L1 C/A signal[C]//2012 IEEE International Geoscience and Remote Sensing Symposium(IGARSS). Piscataway, NJ: IEEE Press, 2012: 7071-7074. [8] GLEASON S, GEBRE-EGZIABHER D. GNSS applications and methods[M]. Norwood: Artech House, 2009: 399-433. [9] 杨东凯, 张其善. GNSS反射信号处理基础与实践[M]. 北京: 电子工业出版社, 2012: 165-174. YANG D K, ZHANG Q S. GNSS reflected signal processing:Fundamentals and applications[M]. Beijing: Publishing House of Electronics Industry, 2012: 165-174. (in Chinese) [10] 白永星. 利用GNSS-R信号反演土壤湿度的关键技术研究[D]. 北京: 北京航空航天大学, 2013. BAI Y X. Study on soil moisture remote sensing using GNSS-R signals[D]. Beijing: Beihang University, 2013. [11] 谢钢. 全球导航卫星系统原理——GPS、格洛纳斯和伽利略系统[M]. 北京: 电子工业出版社, 2013: 288-289. XIE G. Principles of GNSS:GPS, GLONASS, and Galileo[M]. Beijing: Publishing House of Electronics Industry, 2013: 288-289. (in Chinese) [12] 祁永强, 张波, 杨东凯, 等. 基于双基雷达原理的GNSS海面反射信号建模方法[J]. 北京航空航天大学学报, 2017, 43 (8): 1610–1615. QI Y Q, ZHANG B, YANG D K, et al. GNSS sea surface reflection signal modeling method based on the principle of bistatic radar[J]. Journal of Beijing University of Aeronautics and Astronautics, 2017, 43 (8): 1610–1615. (in Chinese) [13] MAURICE W L. Radar reflectivity of land and sea[M]. Boston: Artech House, 2001: 65-94. [14] ELFOUHAILY T, THOMPSON D R, LINDSTROM L. Delay-Doppler analysis of bistatical reflected signals from the ocean surface:Theory and application[J]. IEEE Transactions on Geoscience and Remote Sensing, 2002, 40 (3): 560–573. DOI:10.1109/TGRS.2002.1000316 [15] ELFOUHAILY T, CHAPRON B, KATSAROS K, et al. A unified directional spectrum for and short wind-driven waves[J]. Journal of Geophysical Research:Oceans, 1997, 104 (C7): 15781–15796. [16] 杨东凯, 丁文锐, 张其善. 软件定义的GNSS反射信号接收机设计[J]. 北京航空航天大学学报, 2009, 35 (9): 1048–1051. YANG D K, DING W R, ZHANG Q S. Software defined GNSS reflections receiver design[J]. Journal of Beijing University of Aeronautics and Astronautics, 2009, 35 (9): 1048–1051. (in Chinese) [17] ZAVOROTNY V, VORONOVICH A. Scattering of GPS signals from the ocean with wind remote sensing application[J]. IEEE Transactions on Geoscience and Remote Sensing, 2000, 38 (2): 951–964. DOI:10.1109/36.841977

#### 文章信息

QI Yongqiang, ZHANG Bo, YANG Dongkai, ZHANG Yanzhong, ZHANG Jianmin
GNSS海面反射信号的三维建模方法
Three-dimensional modeling method of GNSS sea surface reflection signal

Journal of Beijing University of Aeronautics and Astronsutics, 2018, 44(1): 125-131
http://dx.doi.org/10.13700/j.bh.1001-5965.2017.0023