| Project/Area Number |
05650350
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
情報通信工学
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| Research Institution | Kanazawa University |
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Principal Investigator |
NAGANO Isamu Kanazawa University, Faculty of Engineering, Professor, 工学部, 教授 (50019775)
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| Co-Investigator(Kenkyū-buntansha) |
YAGITANI Satoshi Kanazawa University, Faculty of Engineering, Research Associate, 工学部, 助手 (30251937)
CHETTRI Samir r. Kanazawa University, Faculty of Engineering, Lecturer, 工学部, 講師 (00251942)
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| Project Period (FY) |
1993 – 1994
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| Project Status |
Completed (Fiscal Year 1994)
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| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1994: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1993: ¥1,500,000 (Direct Cost: ¥1,500,000)
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| Keywords | 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 |
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| Research Abstract |
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 underground
As 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.
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