动态环境下X波段航海雷达海浪参数反演研究

发布时间：2018-04-22 19:15

本文选题：X波段雷达 + 色散关系　；参考：《哈尔滨工程大学》2014年硕士论文

【摘要】：海浪是一种十分复杂的自然现象,研究海浪的物理信息对海洋工程建设与发展、海洋能源探索与挖掘、交通运输、海洋捕捞等都具有重大的意义。对于海浪的监测起源于20世纪50年代初,而近20年里基于X波段雷达图像的海洋参数反演研究备受瞩目。在平台处于静态环境下监测海浪已经取得显著成效的同时,如何处理动态环境带来的新问题,成为本文的重要研究方向。本文以在研项目为依托,对由于船速过大导致多普勒频移、色散关系滤波器带通不合适、频率混叠等问题展开进一步分析,并提出解决方案。首先,雷达平台运动时,增强了多普勒效应,多普勒效应令海浪功率谱发生频移。此时现有的基于色散关系的带通滤波器会保留几乎全部的图像谱能量,无法起到滤波效果。本文针对这一问题,构造一种新的带通滤波器,该滤波器与传统滤波器具有相同的时间复杂度;通过实验证明该滤波器不仅在动态环境下可以保留海浪的主要能量,在岸基实验下同样可以滤除更多的非海浪噪声。反演结果满足精度要求,且与WAMOS、WAVEX测量结果相近。其次,本文实验中所用雷达转速不能满足动态环境下的反演要求,导致信号在时间域欠采样的产生,从而发生频谱混叠现象。本文利用雷达海上试验参数分析混叠的产生机理,并计算出发生混叠的海浪参数与采样频率之间的关系和导致混叠现象发生的雷达平台相对于海浪的最小速度。随后,找到海浪频率谱的混叠方式,并借助傅里叶变换性质重构原始色散关系曲面。导航雷达反演的海面信噪比与有效波高真值的数据量分布不均匀会导致波高的拟合系数不准确,这是一直难以解决的问题。本文最后针对这一问题设计了一个新的渐近线回归方法,利用该方法可模拟大海浪下信噪比的开方与有效波高的比值并生成新的拟合系数,通过仿真实验证明该方法生成的波高在理论范围内。且利用已有数据对该方法进行验证,证明该方法对原数据点的模拟度高,仿真结果符合波高数据的分布和变化规律。
[Abstract]:Ocean wave is a very complicated natural phenomenon. It is of great significance to study the physical information of ocean wave for the construction and development of ocean engineering, exploration and excavation of ocean energy, transportation, marine fishing and so on. The ocean wave monitoring originated in the early 1950s, but in the last 20 years, the ocean parameter inversion based on X-band radar image has attracted much attention. While the platform has achieved remarkable results in monitoring waves under static environment, how to deal with the new problems brought by dynamic environment has become an important research direction in this paper. In this paper, based on the research project, the problems of Doppler frequency shift, inappropriate bandpass of dispersive filter and frequency aliasing due to excessive ship speed are analyzed, and solutions are put forward. Firstly, the Doppler effect is enhanced when the radar platform is moving, and the wave power spectrum is shifted frequently by the Doppler effect. In this case, the existing bandpass filter based on dispersion relation will retain almost all of the spectral energy of the image, and can not play a filtering effect. In this paper, a new bandpass filter is constructed, which has the same time complexity as the traditional filter, and it is proved by experiments that the filter can not only retain the main wave energy in the dynamic environment. More non-wave noise can also be removed in shore-based experiments. The inversion results meet the requirements of accuracy and are close to the WAVEX measurements. Secondly, the radar speed used in the experiments in this paper can not meet the inversion requirements in the dynamic environment, which leads to the generation of under-sampling signals in time domain, thus the phenomenon of spectrum aliasing occurs. In this paper, the mechanism of aliasing is analyzed by using radar sea test parameters, and the relationship between ocean wave parameters and sampling frequency is calculated, and the minimum velocity of radar platform relative to ocean waves which leads to the occurrence of aliasing is calculated. Then, the aliasing mode of wave frequency spectrum is found, and the original dispersion relation surface is reconstructed by Fourier transform. The inhomogeneous distribution of sea surface signal to noise ratio (SNR) and the true value of effective wave height in navigation radar will result in the inaccuracy of the fitting coefficient of wave height, which is always difficult to solve. At last, a new asymptote regression method is designed to solve this problem, which can be used to simulate the ratio of signal-to-noise ratio (SNR) to effective wave height and to generate a new fitting coefficient. The simulation results show that the wave height generated by this method is within the theoretical range. The method is verified by the existing data, and it is proved that the method has a high degree of simulation to the original data points, and the simulation results accord with the distribution and variation law of the wave height data.
【学位授予单位】：哈尔滨工程大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：P714.1

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