钻孔雷达发射前端及天馈系统研制

发布时间：2018-03-29 20:47

本文选题：钻孔雷达　切入点：发射前端　出处：《电子科技大学》2014年硕士论文

【摘要】：钻孔雷达是探地雷达的一种,其工作于钻孔之中,利用发射天线向介质中发射高频电磁波,然后接收返回的电磁波,通过分析接收到的电磁波,来确定钻井周边的地下情况。钻孔雷达被广泛应用于环境保护、资源勘测和考古挖掘等诸多领域。钻孔雷达发射机和天线作为钻孔雷达电磁波的产生和发射单元,其性能的优劣直接决定了钻孔雷达的整体性能。因此,设计出高性能的钻孔雷达发射机及天线对弥补我国研发钻孔雷达系统,并应用于商业领域有着重要的意义。本文结合钻孔雷达工作环境的特殊性,研究并设计了钻孔雷达发射前端和天线系统,其中发射前端包括了触发信号产生电路和脉冲形成及增压电路。对于钻孔雷达的天线,分别设计了应用于井下的阻容混合加载偶极子宽带天线和工作于地面的非频变平面蝶形天线。钻孔雷达的发射前端主要是利用晶体管的雪崩原理来设计的,采用了MARX电路形式,将多个雪崩管级联以获得高幅度、窄脉宽的脉冲信号,同时利用短路传输线将单极性脉冲转换成双极性脉冲,方便发射天线将信号辐射出去。在实施案例中,仿真设计并加工了一个峰峰值幅度为300V,峰峰脉宽4.5ns的双极性脉冲信号源,其所产生信号的3dB频带为25MHz-117MHz,信号的拖尾小,适用于钻孔雷达系统。阻容混合加载的偶极子天线是在分析了钻孔雷达井下天线的特点后设计的。其加载方式为Wu-King加载方式,在75MHz-500MHz的频带内,驻波系数小于1.8。该天线比起采用纯电阻加载方式的天线,在效率方面有所提高。同时,该天线的横向尺寸小,结构简单,适于时域脉冲钻孔雷达系统使用。另外,针对钻孔雷达的孔地测量方法中地面天线的要求,还设计了一种指数形电阻加载的蝶形天线。该天线背面采用了填充吸波材料的屏蔽腔来屏蔽来自外界的干扰。采用微带巴伦对天线进行馈电,巴伦同时起到了阻抗变换和不平衡-平衡转换的作用。通过仿真分析表明,所设计的天线在0.49-1.65GHz的工作频带内,驻波系数小于1.9,辐射波形拖尾相对幅值小于10%,最小探测深度为20cm,能够满足超宽带工作的钻孔雷达的需要。
[Abstract]:Borehole radar is a kind of ground penetrating radar, which works in borehole, emits high frequency electromagnetic wave into medium by transmitting antenna, then receives the return electromagnetic wave, and analyzes the received electromagnetic wave. Borehole radar is widely used in many fields, such as environmental protection, resource survey and archaeological excavation, etc. Borehole radar transmitters and antennas are used as generating and transmitting units of borehole radar electromagnetic waves. Its performance directly determines the overall performance of borehole radar. Therefore, a high performance drill hole radar transmitter and antenna are designed to make up for the development of drilling radar system in China. It is of great significance to apply it to the commercial field. This paper studies and designs the head-end and antenna system of borehole radar, which is based on the particularity of the working environment of borehole radar. The transmitting front end includes trigger signal generation circuit and pulse forming and booster circuit. The wideband antenna with resistive and capacitive mixed loading and the non-frequency-variant planar butterfly antenna used in the ground are designed respectively. The transmitting front end of borehole radar is designed mainly by using the avalanche principle of transistors, and the MARX circuit is adopted. Several avalanche tubes are cascaded to obtain high amplitude and narrow pulse width pulse signals, while unipolar pulses are converted into bipolar pulses by using short circuit transmission lines, which makes it convenient for transmitting antennas to radiate the signals out. A bipolar pulse signal source with a peak amplitude of 300V and peak pulse width 4.5ns is designed and fabricated. The 3dB frequency band of the generated signal is 25MHz-117MHz, and the tail of the signal is small. The dipole antenna, which is suitable for drilling radar system, is designed after analyzing the characteristics of borehole radar antenna. Its loading mode is Wu-King loading mode, which is in the frequency band of 75MHz-500MHz. The standing wave coefficient is less than 1.8. The antenna is more efficient than the antenna with pure resistance loading mode. At the same time, the antenna is small in transverse size, simple in structure and suitable for use in time domain pulse drilling radar system. According to the requirements of ground antenna in borehole ground measurement method of drilling radar, A butterfly antenna with exponential resistor loading is also designed. The shielding cavity filled with absorbing material is used to shield the interference from the outside world. Microstrip Barron is used to feed the antenna. Barron also acts as an impedance transform and an unbalanced balance conversion. The simulation results show that the designed antenna is in the operating band of 0.49-1.65GHz. The standing wave coefficient is less than 1.9, the relative amplitude of radiation waveform tail is less than 10 and the minimum detection depth is 20 cm, which can meet the needs of ultra-wideband drilling radar.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN957.3

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