基于
  <strong>SNR</strong>的
  <strong>GPS-IR</strong>技术机理分析

doi:10.11867/j.issn.1001-8166.2019.02.0156

地球科学进展 ›› 2019, Vol. 34 ›› Issue (2): 156 -163. doi: 10.11867/j.issn.1001-8166.2019.02.0156

基于 SNR的 GPS-IR技术机理分析

孙小荣 ^1, ²,张书毕 ¹,吴继忠 ³,郑南山 ¹

1. 中国矿业大学国土环境与灾害监测国家测绘地理信息局重点实验室，江苏徐州 221116
2. 宿迁学院建筑工程学院，江苏宿迁 223800
3. 南京工业大学测绘科学与技术学院，江苏南京 211800

收稿日期:2018-09-04 修回日期:2018-12-21 出版日期:2019-02-10
基金资助:
国家自然科学基金项目“GPS-IR监测土壤水分含量的反演模型研究”（编号：41504024）和“基于自适应节点与降相关技术的GNSS实时水汽层析理论与方法”（编号：41774026）资助.

Mechanism Analysis of GPS-IR Technology Based on SNR

Xiaorong Sun ^1, ²,Shubi Zhang ¹,Jizhong Wu ³,Nanshan Zheng ¹

1. NASG Key Laboratory of Land Environment and Disaster Monitoring, China University of Mining and Technology, Jiangsu Xuzhou 221116, China
2. School of Civil Engineering and Architecture, Suqian College, Jiangsu Suqian 223800, China
3. School of Geomatics Science and Technology, Nanjing Tech University, Nanjing 211800, China

Received:2018-09-04 Revised:2018-12-21 Online:2019-02-10 Published:2019-03-26
About author:Sun Xiaorong（1980-）, male, Yangzhou City, Jiangsu Province, Associate professor. Research areas include GNSS remote sensing. E-mail:19044@sqc.edu.cn
Supported by:
Project supported by the National Natural Science Foundation of China “Retrieval model of monitoring soil moisture using GPS-Interferometric reflectometry” （No.41504024） and “GNSS real-time water vapor tomography theory and method based on adaptive node and correlation reduction technique”(No.41774026);Project supported by the National Natural Science Foundation of China “Retrieval model of monitoring soil moisture using GPS-Interferometric reflectometry” （No.41504024） and “GNSS real-time water vapor tomography theory and method based on adaptive node and correlation reduction technique” （No.41774026）.

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鉴于现有研究对GPS-IR技术的反射波接收、低高度角信噪比观测值的使用、信噪比残差的形态等机理还未阐释清楚，且几乎是通过实验进行解释，因此，从理论和实验2个方面对GPS-IR技术机理进行分析。理论和实验证明：GPS卫星发射的右旋圆极化波经一次反射后部分转换为左旋圆极化波，转换比例随着高度角和介电常数增大而变大，当右旋圆极化波垂直入射到理想导体表面时，经一次反射才能全部转换为左旋圆极化波；同时在测量型GPS接收机安装有抑径板的情况下，因衍射现象的存在，测量型GPS接收机天线仍能接收反射波中的右旋圆极化波。当高度角越小或介电常数越大时，GPS入射波中的垂直极化波和平行极化波的能量透射到反射物中就越少，其反射波的强度就越大，信噪比受反射波影响就越严重，且能够接收的右旋圆极化波较多，因此GPS-IR使用的是低高度角（如30°以下）的信噪比观测值。当高度角变化范围较小时，信噪比残差序列呈近似“余弦曲线”形态，从而建立了基于信噪比残差的反演模型。

关键词: SNR, GPS-IR技术, 机理分析, 极化特性, 反演模型

The available research on technology mechanism of reflected wave reception, the use of the SNR observations of low elevating angle and the form of SNR residuals for GPS-IR is not clear enough, and they are almost interpreted by experiments. This paper analyzed the GPS-IR technology mechanism from the aspects of theories and experiments. The right hand circular polarized wave transmitted by GPS satellite is partly converted into left hand circular polarized wave after one reflection, and the conversion ratio increases with the increase of satellite elevating angle and dielectric constant. When the right hand circular polarized wave is perpendicular to the surface of the perfect conductor, it can be all converted into left hand circular polarized wave after a reflection; At the same time, in the case of the measuring GPS receiver equipped with the baffle plate, because of the diffraction phenomenon, the antenna of the measuring GPS receiver can still receive the right hand circular polarized wave in the reflected signal. When the elevating angle is smaller or the dielectric constant of the reflector is larger, the less GPS incident wave energy of vertically polarized wave and parallel polarized wave is transmitted to the reflector. The more intense the reflected wave is, the worse the SNR is affected by the reflected wave, and there are more right hand circular polarized waves that can be received. Therefore, the GPS-IR uses the SNR observations of low elevating angle (such as under 30°). When the elevating angle changes and the range is smaller, the SNR residuals sequence is approximately "cosine curve", and thus, an inversion model based on SNR residuals is established.

Key words: SNR, GPS-IR technology, Mechanism analysis, Polarization characteristic, Inversion model.

中图分类号:

P228.4

表1 反射物的近似物理参数 ^{[

21
]}

Table 1 Approximate physical parameters of the reflectors ^{[

21
]}

	$ε r$	$σ × 10 - 3$ /(S/m)	$t a n δ 1$	$t a n δ 2$
海水	81.0	3000.00	0.42000	0.54000
淡水	81.0	0.50	0.00007	0.00009
雪	1.4~3.0	0.01	0.00008~0.00004	0.00010~0.00005
土壤	3.0~40.0	0.10~50.00	0.00003~0.19000	0.00004~0.24000

表1 反射物的近似物理参数 ^{[

21
]}

Table 1 Approximate physical parameters of the reflectors ^{[

21
]}

	$ε r$	$σ × 10 - 3$ /(S/m)	$t a n δ 1$	$t a n δ 2$
海水	81.0	3000.00	0.42000	0.54000
淡水	81.0	0.50	0.00007	0.00009
雪	1.4~3.0	0.01	0.00008~0.00004	0.00010~0.00005
土壤	3.0~40.0	0.10~50.00	0.00003~0.19000	0.00004~0.24000

图1 线极化波反射系数的模

Fig.1 The modulus of the reflection coefficients of linear polarized waves

图2 线极化波透射系数的模

Fig.2 The modulus of the transmission coefficients of linear polarized waves

图3 圆极化波反射系数的模

Fig.3 The modulus of the reflection coefficients of circular polarized waves

图4 直射波和反射波的天线增益

Fig.4 Antenna gain of direct waves and reflected waves

图5 PRN26卫星SNR变化曲线

Fig.5 SNR variation curves of PRN26 satellite

图6 实验观测环境

Fig.6 Experimental observation environment

图7 PRN5卫星SNR变化曲线

Fig.7 SNR variation curves of PRN5 satellite

图8 PRN5卫星的L2载波dSNR观测值与拟合值

Fig.8 Observations and estimates of L2 carrier dSNR of PRN5 satellite

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