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Propagation Experiment of VLF Electromagnetic Pulses in the Uuderground for Development of Deep Earth Radar

深地雷达研制中甚低频电磁脉冲地下传播实验

基本信息

批准号：
05650350
负责人：
NAGANO Isamu
金额：
$ 1.41万
依托单位：
Kanazawa University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-05650350/
关键词：
Underground Exploration High-power Electromagnetic Pulse Radiation Loop Antenna Search Coil VLF Underground Propagation Hertz Vector Computer Simulation Physical Optics Approximation VLF大電流パルス波形解析

项目摘要

This research has been carried out over two years on the basis of following two categories :(1) Improvement of a high-power VLF electromagnetic pulse generator and a signal reception system(2) Theoretical analysis of VLF propagation in the undergroundAs for the item (1) , we have developed a wave form capture receiver which can memorize two channels of received waveforms over 500 msec at the 12-bit accuracy and at the sampling frequency of 60kHz, to reduce the effect of commercial power line noise. A waterproof search coil has been developed which will be used for signal detection even in the water in the underground. We have replaced a transistor circuit driving SIT for high-power radiation, with a diode circuit to improve high-frequency (up to 100kHz) response of pulse transmission.As for the item (2) , a Sommerfeld integration method has been developed to calculate spherical electromagnetic fields in the underground which is radiated by a horizontal loop antenna placed on the ground surface. Using this, we have evaluated attenuation of a radiated VLF wave in a horizontally stratified underground and also intensity of reflected waves from an object in the underground on the basis of the physical optics approximation. On the other hand, one-and two-dimensional computer simulation codes have been developed to analyze wave propagation in a more complicated underground medium, which conventional theoretical calculations fail to deal with.

本课题的研究是在以下两个方面进行的：（1）大功率甚低频电磁脉冲发生器和信号接收系统的改进;（2）甚低频在地下传播的理论分析。针对第（1）项，我们研制了一种波形捕获接收机，它能以12位的精度和60 kHz的采样频率存储500毫秒以上的两路接收波形，以减少商用电力线噪声的影响。一种防水探测线圈已经开发出来，即使在地下的水中也将用于信号探测。为了提高脉冲传输的高频（100 kHz以下）响应性，我们将驱动SIT的晶体管电路替换为二极管电路。对于第（2）项，我们开发了Sommerfeld积分法，用于计算由放置在地面上的水平环形天线辐射的地下球形电磁场。利用这一点，我们已经评估了衰减的辐射VLF波在一个水平分层的地下，也从一个对象在地下的物理光学近似的基础上的反射波的强度。另一方面，一维和二维的计算机模拟程序已经开发出来，以分析波在更复杂的地下介质中的传播，这是传统的理论计算无法处理的。