探地雷达的脉冲发生器设计与相位成像研究

发布时间：2018-05-13 21:02

本文选题：探地雷达 + 脉冲合成　；参考：《浙江大学》2017年硕士论文

【摘要】：在地质研究领域,探地雷达的应用价值越来越高,例如在地质科研领域;在工程应用中,建筑工程人员利用探地雷达进行地下介质分布情况的探测等。正因为探地雷达应用场景之多,所以对于探地雷达的性能指标的要求也就更加多而复杂。探地雷达发射高压脉冲信号,通过接收目标所反射的信号,再进一步对接收信号做分析处理进行二维成像。雷达脉冲能够探测到的深度与脉冲频率有关,不同频段的雷达适应于不同深度的应用场景。而传统的探地雷达发射信号频段单一,无法适应多个应用场景,大大限制了探地雷达的应用价值。所以在考虑如何提高单一探地雷达设备的适应性时,提高探地雷达脉冲发生器的发射频段可调节性是一个可行的方案;另一方面,传统的探地雷达基于若干个反射信号的瞬时振幅生成雷达二维图像,基于瞬时振幅的二维图像分辨率低,不利于观测,而由于电磁波信号在穿越电磁特性差异较大的两种介质时相位发生突变,所以我们考虑通过提取雷达反射信号的瞬时相位信息,生成基于瞬时相位雷达二维图像来解决或改善这一问题;本文首先介绍了探地雷达的发展历史和现状,传统探地雷达设备应用场景及其优缺点,讨论了传统雷达脉冲发生方法的原理及优缺点。由于单个探地雷达装置通常只能提供一个频段的雷达脉冲信号,探地雷达可探测的深度与雷达脉冲频段有关,这使得探地雷达的适应性受到限制,所以本文提出一种基于光诱导开关的通过脉冲合成生产高压雷达脉冲的方法来设计雷达脉冲发生器。该方法通过将两个方向相反的窄脉冲在时域上相加,通过控制两个脉冲之间的相对时延来改变合成信号的中心频段。文中详细介绍了该方法的理论推导和硬件实现方案,并在之后的章节中进行了仿真进行验证;探地雷达系统还包括二维图像生成模块,用于数据可视化以及探测结果显示。本文介绍了基于瞬时振幅的传统成像方法,由于该方法成像很多情况下并不能足够清晰地观察被探测物,因此本文引入了基于瞬时相位的成像方法。为了提取雷达信号中瞬时相位信息,本文介绍了经验模态分解及希尔伯特频谱,介绍了算法原理并分析了其优缺点,并提出EMD边缘效应的优化方案。最后进行了相关的仿真实验验证,并对实验结果进行了详细的分析,最后得出结论。
[Abstract]:In the field of geological research, the application value of ground penetrating radar (GPR) is more and more high, for example, in the field of geological scientific research, in engineering application, GPR is used by construction engineers to detect the distribution of underground media. Because there are many applications of GPR, the requirements of GPR performance are more and more complicated. Ground penetrating radar transmits high voltage pulse signal, and by receiving the signal reflected from target, the received signal is further analyzed and processed for two-dimensional imaging. The depth of radar pulse detection is related to the pulse frequency. However, the traditional ground penetrating radar (GPR) has a single frequency band and can not adapt to multiple application scenarios, which greatly limits the application value of GPR. Therefore, when considering how to improve the adaptability of single ground penetrating radar equipment, it is feasible to improve the tunability of transmitting frequency band of ground penetrating radar pulse generator; on the other hand, Traditional ground penetrating radar generates two-dimensional radar image based on the instantaneous amplitude of several reflected signals, and the resolution of two-dimensional image based on instantaneous amplitude is low, which is not conducive to observation. Because the phase of electromagnetic wave signal is abrupt when it passes through two kinds of medium with great difference in electromagnetic characteristics, we consider extracting the instantaneous phase information of radar reflection signal. This paper first introduces the development history and present situation of GPR, the application scene of traditional GPR equipment and its advantages and disadvantages. The principle, advantages and disadvantages of the traditional radar pulse generation method are discussed. Since a single GPR device usually provides only one band of radar pulse signal, the detectable depth of GPR is related to the radar pulse band, which limits the adaptability of GPR. So this paper presents a method of producing high voltage radar pulse by pulse synthesis based on light induced switch to design radar pulse generator. By adding two narrow pulses in the time domain and controlling the relative delay between the two pulses, the central frequency band of the synthesized signal is changed. In this paper, the theoretical derivation and hardware implementation of the method are introduced in detail, and the simulation results are verified in the following chapters. The GPR system also includes a two-dimensional image generation module for data visualization and the display of detection results. In this paper, the traditional imaging method based on instantaneous amplitude is introduced. Because the imaging method can not clearly observe the detected object in many cases, an imaging method based on instantaneous phase is introduced in this paper. In order to extract instantaneous phase information from radar signal, this paper introduces empirical mode decomposition and Hilbert spectrum, introduces the principle of the algorithm, analyzes its advantages and disadvantages, and puts forward an optimized scheme of EMD edge effect. Finally, the relevant simulation experiments are carried out, and the experimental results are analyzed in detail. Finally, the conclusion is drawn.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P631.3

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