﻿ 船载S波段雷达多普勒谱模型
 舰船科学技术  2018, Vol. 40 Issue (1): 120-124 PDF

1. 武汉大学 电子信息学院，湖北 武汉 430072;
2. 武汉大学 地球空间信息技术协同创新中心，湖北 武汉 430072

Doppler spectrum model based on ship-borne s-band radar
CHEN Ze-zong1,2, CHEN Pei-xian1, ZHAO Chen1, XIE Fei1
1. Electronic and Information School, Wuhan University, Wuhan 430072, China;
2. Collaborative Innovation Center for Geospatial Technology, Wuhan University, Wuhan 430072, China
Abstract: According to the scattering mechanism of sea surface and ship movement, three harmonic motion model of the ship is established. Based on ship-borne S-band radar, a theoretical model is proposed for the center frequency and bandwidth of Doppler spectrum. Next, using the method of simulation of Doppler spectrum, the relationship between the center frequency and bandwidth of spectrum and speed of the ship is analyzed. Meanwhile, the variation of Doppler spectrum caused by various ship motion is discussed. At last, by measuring the speed of ship and simulation of Doppler spectrum, the results show that the center frequency and bandwidth vary obviously. The research result of this paper can offer prior information and theoretical model for the extraction of wave parameters based on ship-borne S-band radar, which has important values.
Key words: ship-borne S-band radar     motion model     Doppler spectrum     center frequency     bandwidth
0 引　言

1 海表面散射机理

2 船载S波段雷达多普勒谱 2.1 船载雷达运动模型

2.2 多普勒谱模型

 $S(f) = \frac{{{\sigma _{vv}}(\theta )}}{{\sqrt {2\pi \delta _f^2} }}\exp \left( { - \frac{{{{(f \pm {f_d})}^2}}}{{2\delta _f^2}}} \right),$ (1)

 ${f_d} = {f_c} + {f_o}_r + = \frac{{2{\upsilon _c}}}{{{\lambda _0}}} + \frac{{2{\upsilon _{or}}}}{{{\lambda _0}}},$ (2)

 $\Delta {f_d} = \frac{{2\Delta {\upsilon _{or}}}}{{{\lambda _0}}} + 2{f_b}\text{。}$ (3)

 $\begin{split}&{f_d} = {f_c} + {f_o}_r + {f_{ship\_c}}(\theta ) + {f_{ship\_y}}(\theta ) = \frac{{2{\upsilon _c}}}{{{\lambda _0}}} + \frac{{2{\upsilon _{or}}}}{{{\lambda _0}}} +\\&\;\;\;\;\;\;\;\;\;\;\;\;\frac{{2{\upsilon _{ship\_c}}(\theta )}}{{{\lambda _0}}} + \frac{{2{\upsilon _{ship\_y}}(\theta )}}{{{\lambda _0}}}{\text{。}}\end{split}$ (4)

 图 2 单天线照射海面俯视图 Fig. 2 The overlook view of the sea surface by a single antenna

 $\Delta {f_d} = \frac{{2\Delta \nu }}{{{\lambda _0}}} + 2{f_b} = \frac{{2({\nu _{\max }} - {\nu _{\min }})}}{{{\lambda _0}}} + 2{f_b}\text{。}$ (5)

3 仿真结果分析

3.1 前向速度导致的多普勒谱

 图 3 六根天线的多普勒谱 Fig. 3 Doppler spectrums of six antennas

1）每根天线的多普勒谱特征不一样，随着船速的增大，多普勒谱中心频率偏移增大。

2）微波岸基雷达双峰比较明显，但在船载情况下展宽变得不可分辨，由于船速的存在，多普勒谱呈现出向一侧展宽的特点，使得求中心频率产生误差，船速越大，展宽宽度越大。

3）6根天线呈现相互对应的关系，1号和6号天线对应，2号和5号对应，3号和4号对应，中心频率向不同方向变化。

4）1号、6号天线与船速方向相近，得到的速度分量较大，导致中心频率的变化明显，但谱展宽宽度较小，3号和4号天线与船速方向几乎垂直，得到的速度分量较小，导致中心频率的变化较小，但谱展宽宽度较大。

 图 4 多普勒谱中心频率和带宽变化图 Fig. 4 Changes in the center frequency and bandwidth of the Doppler spectrum

3.2 横滚和纵摇速度导致的多普勒谱

 图 5 六根天线的多普勒谱 Fig. 5 Doppler spectrums of six antennas

 图 6 时间多普勒谱仿真结果 Fig. 6 Simulation results of time Doppler spectrums

3.3 实际海况中的多普勒谱

 图 7 实测速度和时间多普勒谱仿真结果 Fig. 7 The measured velocity and the simulation result of the time Doppler spectrum

 图 8 多普勒谱中心频率和带宽变化图 Fig. 8 Changes in the center frequency and bandwidth of the Doppler spectrum

4 结　语

本文推导得到了船载S波段微波多普勒雷达回波的多普勒谱中心频率和谱宽的理论模型，并使用仿真多普勒谱的方法分析了船载雷达多普勒谱，发现船前向运动和横纵摇运动6根天线多普勒谱变化的不同点和规律，并指出了6根天线多普勒谱中心频率误差和谱宽变化与船速的关系，船速愈大，中心频率误差愈大，谱宽愈大；最后给出一段实测船速，并仿真出雷达时间多普勒谱，发现中心频率的变化明显，且谱展宽程度较大。

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