本文選題：鉆孔雷達　切入點：發(fā)射前端　出處：《電子科技大學(xué)》2014年碩士論文

【摘要】：鉆孔雷達是探地雷達的一種,其工作于鉆孔之中,利用發(fā)射天線向介質(zhì)中發(fā)射高頻電磁波,然后接收返回的電磁波,通過分析接收到的電磁波,來確定鉆井周邊的地下情況。鉆孔雷達被廣泛應(yīng)用于環(huán)境保護、資源勘測和考古挖掘等諸多領(lǐng)域。鉆孔雷達發(fā)射機和天線作為鉆孔雷達電磁波的產(chǎn)生和發(fā)射單元,其性能的優(yōu)劣直接決定了鉆孔雷達的整體性能。因此,設(shè)計出高性能的鉆孔雷達發(fā)射機及天線對彌補我國研發(fā)鉆孔雷達系統(tǒng),并應(yīng)用于商業(yè)領(lǐng)域有著重要的意義。本文結(jié)合鉆孔雷達工作環(huán)境的特殊性,研究并設(shè)計了鉆孔雷達發(fā)射前端和天線系統(tǒng),其中發(fā)射前端包括了觸發(fā)信號產(chǎn)生電路和脈沖形成及增壓電路。對于鉆孔雷達的天線,分別設(shè)計了應(yīng)用于井下的阻容混合加載偶極子寬帶天線和工作于地面的非頻變平面蝶形天線。鉆孔雷達的發(fā)射前端主要是利用晶體管的雪崩原理來設(shè)計的,采用了MARX電路形式,將多個雪崩管級聯(lián)以獲得高幅度、窄脈寬的脈沖信號,同時利用短路傳輸線將單極性脈沖轉(zhuǎn)換成雙極性脈沖,方便發(fā)射天線將信號輻射出去。在實施案例中,仿真設(shè)計并加工了一個峰峰值幅度為300V,峰峰脈寬4.5ns的雙極性脈沖信號源,其所產(chǎn)生信號的3dB頻帶為25MHz-117MHz,信號的拖尾小,適用于鉆孔雷達系統(tǒng)。阻容混合加載的偶極子天線是在分析了鉆孔雷達井下天線的特點后設(shè)計的。其加載方式為Wu-King加載方式,在75MHz-500MHz的頻帶內(nèi),駐波系數(shù)小于1.8。該天線比起采用純電阻加載方式的天線,在效率方面有所提高。同時,該天線的橫向尺寸小,結(jié)構(gòu)簡單,適于時域脈沖鉆孔雷達系統(tǒng)使用。另外,針對鉆孔雷達的孔地測量方法中地面天線的要求,還設(shè)計了一種指數(shù)形電阻加載的蝶形天線。該天線背面采用了填充吸波材料的屏蔽腔來屏蔽來自外界的干擾。采用微帶巴倫對天線進行饋電,巴倫同時起到了阻抗變換和不平衡-平衡轉(zhuǎn)換的作用。通過仿真分析表明,所設(shè)計的天線在0.49-1.65GHz的工作頻帶內(nèi),駐波系數(shù)小于1.9,輻射波形拖尾相對幅值小于10%,最小探測深度為20cm,能夠滿足超寬帶工作的鉆孔雷達的需要。
[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.
【學(xué)位授予單位】：電子科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TN957.3

【參考文獻】

相關(guān)博士學(xué)位論文 前1條

1 張春青;小型化脈沖及超寬帶天線的研究[D];北京交通大學(xué);2008年

相關(guān)碩士學(xué)位論文 前1條

1 張海平;超寬帶（UWB）窄脈沖發(fā)生器的研究[D];西南交通大學(xué);2007年

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本文編號：1682780