地中レーダ用ファントム内装型キャビティ付ボウタイアンテナ

摘要

Ground penetrating radars are mainly using the electromagnetic waves between sevral MHz through lGHz frequency band. Since the attenuatin of those nadiowaves in the ground, has realized buried investigation by using the electromagnetic waves of a lGHz frequency band from several MHz. In this frequency band, a wavelength is long and it has the property of being hard to receive underground attenuation. However, since several centimeters resolution is required for mine investigation or underground-pipe investigation, they need to emit the pulse which has a band of lGHz or more. For this reason, the technique of the ability to oppress the problem of the ringing accompanying broadband-izing generated with the antenna with a mold cavity generally used especially by an underground radar by carrying out the interior of the phantom is proposed. It is investigation about a burial thing with a size of several centimeters to the soil of especially low moisture content, Electromagnetic-field analysis by the FDTD method was conducted for the purpose of detecting.%地中レーダでは数MHzから1GHzの周波数帯における電磁波を用いることで地中レーダを実現している．この周波数帯域では，地中の減衰を受けにくい特性を有する反面，地雷探査や埋設管探査には数cmの分解能が必要となるため，1GHz以上の帯域を有するパルスを放射する必要がある．このため，地中レーダで使われているキャビティ付アンテナで発生する広帯域化に伴うリンギングの問題を，ファントムを内装することで低減できる手法を提案する．特に，低含水率の土壌に対して数cmの大きさの埋設物を探査し，検知することを目的に，ファントムを内装した広帯域な特性を持つ抵抗装荷キャビティ付ボウタイアンテナをFDTD法でアンテナ特性や過渡特性分析し，低リンギング特性を示すアンテナ構造を評価する．