本文關(guān)鍵詞： 鉆孔雷達(dá) Wu-King加載 偶極子天線 金屬背腔　出處：《長(zhǎng)江大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：近年來(lái),鉆孔探地雷達(dá)因其具有分辨率高、探測(cè)距離遠(yuǎn)以及結(jié)構(gòu)簡(jiǎn)單的特點(diǎn)而被廣泛研究,并且已經(jīng)廣泛的應(yīng)用于石油探測(cè)、地質(zhì)勘查、空洞探測(cè)等方面。鉆孔雷達(dá)系統(tǒng)在對(duì)外進(jìn)行電磁波的輻射和接收時(shí)是由鉆孔雷達(dá)系統(tǒng)的天線來(lái)完成的,因此,天線性能的好壞對(duì)一個(gè)鉆孔雷達(dá)系統(tǒng)性能的優(yōu)劣有著重大影響,這就使得鉆孔雷達(dá)天線的設(shè)計(jì)和相關(guān)的研究將是整個(gè)鉆孔雷達(dá)系統(tǒng)研究中的一個(gè)重要組成部分。鉆孔雷達(dá)天線的工作環(huán)境是在井下,并且天線需要套上抗壓的天線罩,因此天線的直徑受到孔眼大小的制約,致使天線的工作頻率、工作帶寬、增益、方向性以及輻射波形都將受到影響,很難達(dá)到全方面的優(yōu)良特性。本文結(jié)合鉆孔雷達(dá)天線的特點(diǎn),采用了新型的超寬帶天線加載技術(shù),即Wu-King加載方法,并在此基礎(chǔ)上,在天線外增加充填有吸波材料(鐵氧體)的金屬背腔來(lái)改善天線的定向性和寬頻性能。本文設(shè)計(jì)的鉆孔雷達(dá)天線為超寬帶電阻加載偶極子天線,采用分布式的Wu-King加載方法,將多個(gè)集總電阻元件按照等對(duì)數(shù)間隔對(duì)稱的加載到柱形的偶極子天線的兩臂上,使得電流在沿天線傳導(dǎo)的同時(shí)天線也在向周圍空間輻射電磁波,加載電阻在這個(gè)過(guò)程中吸收了部分電磁能量,使得從天線末端反射的能量明顯減小,從而使天線中的電流接近于行波,從而改善了天線的阻抗性能和寬頻帶性能并且減小了天線的長(zhǎng)度。另外,通過(guò)對(duì)加載電阻的偶極子天線增加填充有特殊材料的金屬背腔,可以進(jìn)一步優(yōu)化天線的性能,而且金屬背腔還能起到一定的天線罩的作用。填充材料的選用方面,考慮了鐵氧體材料的吸波特性及其與鉆孔周圍介質(zhì)如石灰?guī)r等的匹配關(guān)系,因此在本文的天線設(shè)計(jì)中選用鐵氧體吸波材料作為襯底材料。文中分別設(shè)計(jì)了兩種金屬背腔的加載電阻偶極子天線,一種是矩形背腔,在這種情況下,通過(guò)CST的優(yōu)化設(shè)計(jì),S參數(shù)在-10dB以下有兩段帶寬,分別是29MHz～ 38MHz和74MHz～600MHz,H面的半功率時(shí)域方向圖±50.4；另一種是柱形背腔,通過(guò)CST的優(yōu)化設(shè)計(jì),S參數(shù)10dB以下的帶寬為34MHz～156MHz,達(dá)到了5倍頻程的帶寬,并且H面的半功率時(shí)域方向圖±135。通過(guò)比較兩種不同背腔的加載天線,我們可以看出,柱形背腔加載偶極子天線較之矩形背腔加載偶極子天線的工作頻率要低,優(yōu)勢(shì)相對(duì)明顯。
[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 鹵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 鹵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.
【學(xué)位授予單位】：長(zhǎng)江大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：P631.3

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本文編號(hào)：1506255