本文關鍵詞： 鉆孔雷達 半波對稱 低頻帶寬 鐵氧體　出處：《華中師范大學》2015年碩士論文　論文類型：學位論文

【摘要】：鉆孔雷達天線作為一類新型的井中探測的方法,在探地雷達研究領域掀起了-股新熱潮。主要是因為鉆孔雷達天線相比于其他探地雷達天線具有能夠深入地層的優(yōu)點,又有較高分辨率。在鉆孔雷達系統(tǒng)中,我們通常以全向天線發(fā)射脈沖信號,定向天線接收被測的反射信號。本文主要研究基于工作頻率較低的鉆孔雷達天線的模型設計,通過理論分析、數值仿真和實驗測試來分析鉆孔雷達天線模型的性能,尋找適合頻率帶寬模型結構進行模擬測試。本文設計了三種結構的鉆孔雷達天線模型：第一種是由于鉆孔雷達系統(tǒng)中受井口的限制,采用了簡單半波對稱振子結構的鉆孔雷達天線。簡單的半波振子天線的設計是由于工作頻帶的確定,從而得到天線工作的中心頻率,然后通過計算得出波長。仿真結果表明,當振子長度一定時,半徑的變化對于在某一個固定頻點上的阻抗值變化還是挺大的,天線的頻率帶寬主要取決于振子的長度。第二種模型是一種電阻分布加載的半波對稱振子天線,是將電阻加載于每兩節(jié)之間縫隙中。本文采用了等距和不等距兩種加載電阻的方式。仿真結果表明,當天線采用等距加載電阻時,天線的帶寬過.；當天線采用離散不均勻分布加載電阻后,對比于第一種模型,在保證天線具備良好的脈沖信號保真性的基礎上,雷達天線的帶寬增加。第三種模型是在第二種模型的基礎上加載一種新穎的鐵氧體吸波材料的背腔,該材料是用來吸收或衰減自由空間入射來的電磁能量,使反射電波大大降低或完全消除。仿真結果表明,相比第二種模型,天線工作的頻帶由原來的160MHz-180MHz降低到100MHz以下,并且工作頻帶為40～60MHz。此外進一步通過實驗測試后得出工作頻帶為40-80MHz,實驗測試結果與仿真結果基本一致吻合。通過方向圖的仿真我們可以知道,加載鐵氧體吸波材料后,天線由原來的全向天線變?yōu)槎ㄏ蛱炀�,天線的輻射效益增強。通過對于新型半波振子天線的研究和分析,著重研究設計電小天線。仿真和實驗結果表明,本文設計的鉆孔雷達天線具重要的研究價值,且將在探地雷達系統(tǒng)中有非常廣闊的應用前景。
[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.
【學位授予單位】：華中師范大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TN957.2

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本文編號：1442631