| 发射电流波形对瞬变电磁响应的影响 |
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| 引用本文： | 陈曙东,林君,张爽.发射电流波形对瞬变电磁响应的影响[J].地球物理学报,2012,55(2):709-716. |
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| 作者姓名： | 陈曙东 林君 张爽 |
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| 作者单位： | 1. 吉林大学仪器科学与电气工程学院, 长春 130026;
2. 吉林大学电子科学与工程学院, 长春 130012 |
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| 摘 要： | 本文研究了不同发射电流波形对瞬变电磁(TEM)响应的影响,利用自由空间中回线作为目标体,推导出方波、梯形波、半正弦波、三角波激励的响应.研究表明:对于低电导率目标体,同种波形激励的响应在有发射电流期间(on-time)与无发射电流期间(off-time)的幅度相近,四种波形中方波激励响应最强.由于off-time采集可以获得更高的信噪比,因而探测低电导率目标体时一般采用方波激励,采集off-time信号.对于高电导率目标体,off-time响应幅度随电导率增加而迅速下降,而半正弦与三角波激励的on-time响应幅度基本不随电导率变化,因而航空TEM可以采用半正弦与三角波进行on-time采集,并通过适当地提高激励电流的基频,以提高信噪比与空间分辨率.
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| 关 键 词： | 瞬变电磁 发射电流波形 有发射电流期间 无发射电流期间 航空电磁 |
| 收稿时间： | 2010-12-09 |
Effect of transmitter current waveform on TEM response |
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| CHEN Shu-Dong
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LIN Jun
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ZHANG Shuang.Effect of transmitter current waveform on TEM response[J].Chinese Journal of Geophysics,2012,55(2):709-716. |
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| Authors: | CHEN Shu-Dong LIN Jun ZHANG Shuang |
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| Institution: | 1. College of Instrumentation and Electrical Engineering, Jilin University, Changchun 130026, China;
2. College of Electronic Science and Engineering, Jilin University, Changchun 130012, China |
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| Abstract: | This paper investigates the effect of different transmitter waveforms on the transient electromagnetic(TEM) system response.For a loop target in free space,the voltage response is derived for waveforms of square,trapezoidal,half-sine and triangular shape.It is found that,for lower conductivity object,every waveform excites almost the same response during on-time and off-time,respectively.Among all waveforms,the maximum response is generated by a square pulse.For low signal to noise ratio(SNR) during off-time,square pulse is usually used for lower conductivity object detection.For higher conductivity object,response sharply decreased with the increase of the conductivity during off-time.While the responses of half-sine and triangular shapes are constant with the increase of conductivity.So we concluded that half-sine and triangular shapes are suitable for on-time detection.By properly increasing the base frequency,high SNR and high space resolution can be obtained. |
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| Keywords: | Transient electromagnetic(TEM) Transmitter current waveform On-time Off-time Airborne electromagnetic(AEM) |
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