Stochastic voltage model and experimental measurement of ocean-scattered GPS signal statistics
Stochastic voltage model and experimental measurement of ocean-scattered GPS signal statistics
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DOI：
10.1109/tgrs.2004.834628
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发表时间：
2004-10
影响因子：
8.2
通讯作者：
Huaizu You;J. Garrison;G. Heckler;V. Zavorotny
中科院分区：
文献类型：
--
作者：
Huaizu You;J. Garrison;G. Heckler;V. Zavorotny
关于海洋表面粗糙度和有关的地球物理参数（如风速）的信息以前向散射全球定位系统（GPS）信号的码相关波形的形式呈现。开发了一个模型，用于设计检索算法和预测地球物理参数估计的准确性，这个波形的统计。该模型的一个潜在应用是评估从卫星轨道进行双基地GPS测量的可行性。复杂的“电压”相关波形的时域和频域模型的开发和实验结果进行比较。电压模型可用于确定检测前积分时间的上限。所得到的时间和空间相关函数具有类似于货车Cittert-Zernike定理的形式，因为它可以用二维傅里叶变换来表示。因此，快速傅立叶变换用于有效的计算。波形是由1999年在波多黎各附近飞行期间从3200米高度的机载接收器记录的反射GPS信号的测量值产生的。复杂的电压相关性产生使用粗采集代码与1毫秒的集成时间在一个范围内的代码延迟“箱”。多普勒补偿频率被设置为等于通过跟踪直接视线GPS信号获得的多普勒频率。在每个延迟箱中的电压信号时间序列的所得频谱和导出的相关时间与模型的预测进行了比较。该模型与实验数据吻合良好，在镜面反射点附近，相关时间在4-6 ms之间。
Information about the roughness of the ocean surface and related geophysical parameters, such as wind speed, is present in the shape of the code-correlation waveform of forward-scattered Global Positioning System (GPS) signals. A model is developed for the statistics of this waveform to be used in designing retrieval algorithms and predicting their accuracy in the estimation of geophysical parameters. One potential application of this model is to assess the feasibility of bistatic GPS measurements from satellite orbits. Time and frequency domain models for the complex "voltage" correlation waveform are developed and compared against experimental results. The voltage model can be applied to determine the upper limit for predetection integration time. The resulting temporal and spatial correlation function has a form similar to the van Cittert-Zernike theorem in that it can be expressed in terms of two-dimensional Fourier transform. The fast Fourier transform is, thus, used for efficient computation. Waveforms were generated from measurements of reflected GPS signals recorded in 1999 from an airborne receiver at an altitude of 3200 m during a flight near Puerto Rico. Complex voltage correlations were produced using the coarse-acquisition code with a 1-ms integration time over a range of code delay "bins". The Doppler compensation frequency was set equal to the Doppler frequency obtained by tracking the direct line-of-sight GPS signal. The resulting spectra and derived correlation times of the voltage signal time series in each delay bin were compared with the predictions of the model. The model agreed well with the experimental data, near the specular point, showing correlation times between 4-6 ms.