钻孔雷达系统天线的设计与研究

发布时间：2018-01-19 04:25

本文关键词： 钻孔雷达半波对称低频带宽铁氧体　出处：《华中师范大学》2015年硕士论文　论文类型：学位论文

【摘要】：钻孔雷达天线作为一类新型的井中探测的方法,在探地雷达研究领域掀起了-股新热潮。主要是因为钻孔雷达天线相比于其他探地雷达天线具有能够深入地层的优点,又有较高分辨率。在钻孔雷达系统中,我们通常以全向天线发射脉冲信号,定向天线接收被测的反射信号。本文主要研究基于工作频率较低的钻孔雷达天线的模型设计,通过理论分析、数值仿真和实验测试来分析钻孔雷达天线模型的性能,寻找适合频率带宽模型结构进行模拟测试。本文设计了三种结构的钻孔雷达天线模型：第一种是由于钻孔雷达系统中受井口的限制,采用了简单半波对称振子结构的钻孔雷达天线。简单的半波振子天线的设计是由于工作频带的确定,从而得到天线工作的中心频率,然后通过计算得出波长。仿真结果表明,当振子长度一定时,半径的变化对于在某一个固定频点上的阻抗值变化还是挺大的,天线的频率带宽主要取决于振子的长度。第二种模型是一种电阻分布加载的半波对称振子天线,是将电阻加载于每两节之间缝隙中。本文采用了等距和不等距两种加载电阻的方式。仿真结果表明,当天线采用等距加载电阻时,天线的带宽过.；当天线采用离散不均匀分布加载电阻后,对比于第一种模型,在保证天线具备良好的脉冲信号保真性的基础上,雷达天线的带宽增加。第三种模型是在第二种模型的基础上加载一种新颖的铁氧体吸波材料的背腔,该材料是用来吸收或衰减自由空间入射来的电磁能量,使反射电波大大降低或完全消除。仿真结果表明,相比第二种模型,天线工作的频带由原来的160MHz-180MHz降低到100MHz以下,并且工作频带为40～60MHz。此外进一步通过实验测试后得出工作频带为40-80MHz,实验测试结果与仿真结果基本一致吻合。通过方向图的仿真我们可以知道,加载铁氧体吸波材料后,天线由原来的全向天线变为定向天线,天线的辐射效益增强。通过对于新型半波振子天线的研究和分析,着重研究设计电小天线。仿真和实验结果表明,本文设计的钻孔雷达天线具重要的研究价值,且将在探地雷达系统中有非常广阔的应用前景。
[Abstract]:Borehole radar antenna is a new method of borehole detection. There has been a new upsurge in the field of ground penetrating radar, mainly because the borehole radar antenna has the advantages of being able to penetrate into the ground and has high resolution compared with other ground penetrating radar antennas. We usually transmit pulse signal with omnidirectional antenna and receive measured reflection signal by directional antenna. This paper mainly studies the model design of borehole radar antenna based on low working frequency, through theoretical analysis. The performance of borehole radar antenna model is analyzed by numerical simulation and experimental test. In this paper, three kinds of borehole radar antenna models are designed. Firstly, the borehole radar system is restricted by the wellhead. A drilling radar antenna with simple half-wave symmetrical dipole structure is adopted. The design of simple half-wave dipole antenna is based on the determination of the working frequency band, thus the central frequency of the antenna is obtained. Then the wavelength is calculated. The simulation results show that when the oscillator length is fixed, the variation of radius is quite large for the impedance value at a fixed frequency point. The frequency bandwidth of the antenna mainly depends on the length of the dipole. The second model is a half-wave symmetrical dipole antenna loaded with resistive distribution. The resistor is loaded into the gap between two sections. In this paper, the isometric and non-equidistant methods are used to load the resistor. The simulation results show that the bandwidth of the antenna is too high when the antenna is loaded with the isometric resistor. Compared with the first model, the antenna has good fidelity of pulse signal when the resistor is loaded with discrete and uneven distribution. The third model is to load the back cavity of a novel ferrite absorbing material which is used to absorb or attenuate the electromagnetic energy from the free space. The simulation results show that, compared with the second model, the frequency band of antenna is reduced from 160MHz to 180MHz to less than 100MHz. The operating frequency band is 40,60MHz. In addition, the operating frequency band is 40-80MHz after further experimental test. The experimental results are consistent with the simulation results. Through the simulation of the pattern, we can know that the antenna changed from the original omnidirectional antenna to the directional antenna after the ferrite absorbing material was loaded. Through the research and analysis of the new half-wave dipole antenna, we focus on the design of the small electric antenna. The simulation and experimental results show that the borehole radar antenna designed in this paper has important research value. And will have a very broad application prospect in the ground penetrating radar system.
【学位授予单位】：华中师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN957.2

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