一种新型钻孔雷达天线仿真设计

发布时间：2018-02-12 18:18

本文关键词： 钻孔雷达 Wu-King加载偶极子天线金属背腔　出处：《长江大学》2015年硕士论文　论文类型：学位论文

【摘要】：近年来,钻孔探地雷达因其具有分辨率高、探测距离远以及结构简单的特点而被广泛研究,并且已经广泛的应用于石油探测、地质勘查、空洞探测等方面。钻孔雷达系统在对外进行电磁波的辐射和接收时是由钻孔雷达系统的天线来完成的,因此,天线性能的好坏对一个钻孔雷达系统性能的优劣有着重大影响,这就使得钻孔雷达天线的设计和相关的研究将是整个钻孔雷达系统研究中的一个重要组成部分。钻孔雷达天线的工作环境是在井下,并且天线需要套上抗压的天线罩,因此天线的直径受到孔眼大小的制约,致使天线的工作频率、工作带宽、增益、方向性以及辐射波形都将受到影响,很难达到全方面的优良特性。本文结合钻孔雷达天线的特点,采用了新型的超宽带天线加载技术,即Wu-King加载方法,并在此基础上,在天线外增加充填有吸波材料(铁氧体)的金属背腔来改善天线的定向性和宽频性能。本文设计的钻孔雷达天线为超宽带电阻加载偶极子天线,采用分布式的Wu-King加载方法,将多个集总电阻元件按照等对数间隔对称的加载到柱形的偶极子天线的两臂上,使得电流在沿天线传导的同时天线也在向周围空间辐射电磁波,加载电阻在这个过程中吸收了部分电磁能量,使得从天线末端反射的能量明显减小,从而使天线中的电流接近于行波,从而改善了天线的阻抗性能和宽频带性能并且减小了天线的长度。另外,通过对加载电阻的偶极子天线增加填充有特殊材料的金属背腔,可以进一步优化天线的性能,而且金属背腔还能起到一定的天线罩的作用。填充材料的选用方面,考虑了铁氧体材料的吸波特性及其与钻孔周围介质如石灰岩等的匹配关系,因此在本文的天线设计中选用铁氧体吸波材料作为衬底材料。文中分别设计了两种金属背腔的加载电阻偶极子天线,一种是矩形背腔,在这种情况下,通过CST的优化设计,S参数在-10dB以下有两段带宽,分别是29MHz～ 38MHz和74MHz～600MHz,H面的半功率时域方向图±50.4；另一种是柱形背腔,通过CST的优化设计,S参数10dB以下的带宽为34MHz～156MHz,达到了5倍频程的带宽,并且H面的半功率时域方向图±135。通过比较两种不同背腔的加载天线,我们可以看出,柱形背腔加载偶极子天线较之矩形背腔加载偶极子天线的工作频率要低,优势相对明显。
[Abstract]:In recent years, drilling GPR has been widely studied because of its high resolution, long detection range and simple structure, and has been widely used in oil exploration and geological exploration. Hole detection and other aspects. The borehole radar system is completed by the antenna of the borehole radar system when it radiates and receives electromagnetic waves outside, so the performance of the antenna has a significant impact on the performance of a borehole radar system. As a result, the design of borehole radar antenna and related research will be an important part of the whole drilling radar system. The working environment of borehole radar antenna is downhole, and the antenna needs to be fitted with anti-pressure radome. Therefore, the diameter of the antenna is restricted by the size of the hole, which will affect the frequency, bandwidth, gain, directivity and radiation waveform of the antenna. It is very difficult to achieve the excellent characteristics in all aspects. In this paper, a new UWB antenna loading technique, Wu-King loading method, is adopted based on the characteristics of borehole radar antenna. A metal back cavity filled with absorbing material (ferrite) is added to the antenna to improve the directionality and broadband performance of the antenna. The borehole radar antenna designed in this paper is an ultra-wideband resistor loaded dipole antenna with distributed Wu-King loading method. A plurality of lumped resistor elements are symmetrically loaded into the two arms of a cylindrical dipole antenna at equal logarithmic intervals, so that the current is transmitted along the antenna and the antenna radiates electromagnetic waves into the surrounding space. The loading resistor absorbs part of the electromagnetic energy in this process, so that the energy reflected from the end of the antenna is obviously reduced, so that the current in the antenna is close to the traveling wave. Thus, the impedance performance and broadband performance of the antenna are improved and the length of the antenna is reduced.; in addition, the performance of the antenna can be further optimized by adding a metal back cavity filled with special materials to the dipole antenna loaded with resistor. In addition, the metal back cavity can also play a role as a radome. In the selection of filling materials, the wave absorption characteristics of ferrite materials and their matching relationship with the surrounding media such as limestone are considered. Therefore, ferrite absorbing material is selected as substrate material in the antenna design of this paper. Two kinds of loaded resistor dipole antennas of metal back cavity are designed in this paper, one is rectangular back cavity, in this case, Through the optimization design of CST, there are two bands of bandwidth below -10dB, which are 29MHz ~ 38MHz and 74MHz ~ 600MHz / H plane half-power pattern 卤50.4.The other is cylindrical back cavity. By optimizing the design of CST, the bandwidth below 10dB is 34 MHz ~ 156MHz, which reaches the bandwidth of 5 times frequency path, and the half power half power pattern of H plane is 卤135. By comparing two kinds of loaded antennas with different back cavities, we can see that, The working frequency of cylindrical back cavity loaded dipole antenna is lower than that of rectangular back cavity loaded dipole antenna, and the advantage is relatively obvious.
【学位授予单位】：长江大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P631.3

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