探地雷达超宽带天线设计与仿真

发布时间：2018-01-21 23:08

本文关键词： 探地雷达天线低频段超宽带加载方法　出处：《中国科学院大学(中国科学院国家空间科学中心)》2017年硕士论文　论文类型：学位论文

【摘要】：探地雷达是一种用于探测及识别地下目标物体的无损探测工具,具有探测速度快、数据连续、操作方便灵活、分辨率高等特点,近年来广泛应用于民用和军用领域。天线是探地雷达系统的关键部分,其性能的好坏直接影响探测结果。探地雷达系统的天线应该具备超宽带、辐射能量集中、波形保真度高、收发天线耦合小、小型化等特点。与其它超宽带雷达不同,探地雷达系统要求天线的大部分能量对地辐射,但地下环境多为有耗媒质,对信号有衰减作用,且信号中心工作频率越高,衰减越大。因此,若想增大探测深度,需要降低发射信号的中心工作频率,即天线应该在低频段具有超宽带特性。基于车载移动平台的探地雷达系统的要求,为了实现对地下深层埋藏物的探测,本文以传统蝶形天线为基础,设计出两款工作在低频段的超宽带天线:(1)提出了一种三面屏蔽型球根状天线。以传统蝶形天线为基础,采用结构加载的方法改善天线表面的电流分布,得到比蝶形天线更加平坦的输入阻抗特性曲线和更优异的辐射特性。改进后的天线可工作在131MHz~422MHz频率范围内,其端口输入阻抗在100 ohms左右,利于实现阻抗匹配,符合探地雷达系统要求。(2)提出一种五面屏蔽型截臂开槽式末端加载天线。采用末端加载和开槽的方法以增加电流在天线臂末端的聚拢作用,降低天线的最低工作频点,进而增大天线的阻抗带宽;使用截臂、圆化等形状加载的方法可以减小天线的尺寸;五面屏蔽结构则可以减弱收发天线之间的互耦作用。设计的天线可工作在10MHz~470MHz,端口输入阻抗约为150 ohms,可应用于基于车载移动平台的探地雷达系统,并适用于干燥土壤、沥青、混凝土、干雪等多种常见探测环境。论文中设计的两款天线在低频段都具有超宽带的特性,也容易实现与同轴馈线的阻抗匹配,适合应用于探测深埋物的探地雷达系统;文中提出的结构加载与集总加载方法相结合的设计也可用于改进多种天线。
[Abstract]:Ground penetrating radar (GPR) is a nondestructive detection tool used to detect and identify underground objects. It has the characteristics of high detection speed, continuous data, convenient and flexible operation, high resolution and so on. In recent years, it has been widely used in civil and military fields. Antenna is a key part of GPR system, and its performance directly affects the detection results. The antenna of GPR system should have ultra-wideband (UWB) and concentrated radiation energy. Unlike other UWB radars, the GPR system requires most of the antenna energy to radiate to the ground, but the underground environment is mostly a lossy medium. It can attenuate the signal, and the higher the operating frequency of the signal center, the greater the attenuation. Therefore, if we want to increase the detection depth, we need to reduce the central operating frequency of the transmitted signal. That is, the antenna should have ultra-wideband characteristics in low frequency band. In order to realize the detection of underground buried objects, this paper is based on the traditional butterfly antenna, which is based on the requirements of ground penetrating radar system based on vehicle-mounted mobile platform. Two ultra-wideband antennas working in low frequency band: 1) A three-side shielded spherical antenna is proposed. Based on the traditional butterfly antenna, the structure loading method is used to improve the current distribution on the antenna surface. The input impedance curves and radiation characteristics of the improved antenna are flatter than those of the butterfly antenna. The improved antenna can work in the frequency range of 131 MHz / 422MHz. The input impedance of the port is about 100 ohms, which is propitious to realize impedance matching. In accordance with the requirements of ground penetrating radar (GPR), a five-side shielded grooved end loading antenna is proposed. The method of end loading and grooving is used to increase the convergence of current at the end of the antenna arm. Reducing the minimum operating frequency of the antenna and increasing the impedance bandwidth of the antenna; The size of antenna can be reduced by using the shape loading method such as truncated arm and circle. The five-side shielding structure can reduce the mutual coupling between the transceiver antennas. The designed antenna can work at 470MHz at 10 MHz, and the port input impedance is about 150 ohms. It can be used in ground penetrating radar system based on vehicle-mounted mobile platform, and can be used in dry soil, asphalt and concrete. The two antennas designed in this paper have the characteristics of ultra-wideband in low frequency band, and can easily match the impedance of coaxial feeder, so they are suitable for the ground penetrating radar system to detect deep buried objects. The structure loading method combined with lumped loading method proposed in this paper can also be used to improve multiple antennas.
【学位授予单位】：中国科学院大学(中国科学院国家空间科学中心)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN957.2

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