JP5568237B2 - 3D position estimation system and dipole array antenna - Google Patents
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本発明は、地中に埋め込まれた坑井内にアンテナを配置し、地中に放射された電磁波の地中内の亀裂、断層、地下水などによる散乱波又は反射波を当該アンテナが受信し、受信した散乱波又は反射波を解析することで地中内の亀裂、断層、地下水などの位置及び形状を計測する三次元位置推定システム、及びこれに用いるアンテナ素子に関する。 In the present invention, an antenna is disposed in a well buried in the ground, and the antenna receives a scattered wave or a reflected wave of an electromagnetic wave radiated into the ground due to a crack, fault, groundwater, etc. The present invention relates to a three-dimensional position estimation system that measures the position and shape of cracks, faults, groundwater, etc. in the ground by analyzing scattered waves or reflected waves, and an antenna element used therefor.
直径１０ｃｍほどの坑井内に電磁波を受信・送信するためのアンテナを配置し、地中内の亀裂、断層、地下水などの位置及び形状を計測可能なボアホールレーダが１９７０年代以降、国際的に研究開発されている。送受信に使用する電磁波の周波数は１０〜５００ＭＨｚ程度で、地中での波長は２０ｃｍ〜数ｍ程度である。水を含まない岩石、砂や土は電磁気学的には空気に近く、亀裂や断層中へ水が流入すると含水率が高くなり、電磁気学的なコントラストが生じる。即ち、ボアホールレーダでは地中の含水率の空間分布を推定することで、亀裂や断層の位置を推定できることになる。ボアホールレーダでは坑井の形状による制約から、通常、ダイポールアンテナを用いるが、この場合、坑井の周方向で無指向性となる。このため、一本の坑井に送信アンテナ及び受信アンテナを挿入した場合、物体が存在する深度や距離に対する推定に限定されていた。複数の坑井を掘削することは困難な場合も多いため、坑井の周方向で指向性をもつアンテナ、及び、一本の坑井だけで三次元推定が可能な指向性ボアホールレーダの開発が急務となっていた。 An international borehole radar that can measure the position and shape of cracks, faults, groundwater, etc. in the ground by placing an antenna for receiving and transmitting electromagnetic waves in a well with a diameter of about 10 cm has been internationally researched and developed since the 1970s. Has been. The frequency of the electromagnetic wave used for transmission and reception is about 10 to 500 MHz, and the wavelength in the ground is about 20 cm to several m. Rocks, sand, and soil that do not contain water are electromagnetically close to air, and when water flows into cracks and faults, the water content increases and electromagnetic contrast occurs. That is, the borehole radar can estimate the positions of cracks and faults by estimating the spatial distribution of moisture content in the ground. In borehole radar, a dipole antenna is usually used due to restrictions due to the shape of the well, but in this case, it becomes omnidirectional in the circumferential direction of the well. For this reason, when a transmitting antenna and a receiving antenna are inserted into one well, the estimation is limited to the depth and distance at which the object exists. Since it is often difficult to drill multiple wells, the development of an antenna that has directivity in the circumferential direction of the well and a directional borehole radar that can perform three-dimensional estimation using only one well It was an urgent need.
ボアホールレーダに用いる指向性アンテナの例として、直交クロスループアンテナを用いる構成（非特許文献１）、キャビティバックドダイポールアンテナを用いる構成（特許文献１）、ダイポールアレイアンテナを用いる構成（非特許文献２及び３）が、夫々、開発されている。 As an example of a directional antenna used for borehole radar, a configuration using an orthogonal cross-loop antenna (Non-Patent Document 1), a configuration using a cavity-backed dipole antenna (Patent Document 1), and a configuration using a dipole array antenna (Non-Patent Document 2) And 3) have been developed respectively.
非特許文献１に示されている構成は、ループアンテナを直交配置し、ループアンテナの八の字の指向性パターンを利用して振幅情報のみで受信波の到来方向を推定するものであるが、位相情報は用いられず高分解能計測には向かない。 In the configuration shown in Non-Patent Document 1, the loop antennas are orthogonally arranged, and the arrival direction of the received wave is estimated only by the amplitude information using the eight-directional pattern of the loop antenna. Phase information is not used and is not suitable for high resolution measurements.
特許文献１に開示されている構成は、ダイポールアンテナの一側面に反射板をつけたキャビティバックドダイポールアンテナを坑井内で回転させることによって生じる受信信号の振幅変化により受信波の到来方向を推定するものであり、送信用としても受信用としても使用可能であるが、アンテナを回転させるための機械的動作が必要になる。 In the configuration disclosed in Patent Document 1, the arrival direction of a received wave is estimated based on a change in amplitude of a received signal generated by rotating a cavity-backed dipole antenna having a reflector on one side of a dipole antenna in a well. Although it can be used for both transmission and reception, a mechanical operation for rotating the antenna is required.
そこで、複数のダイポールアンテナを、各ダイポールアンテナの軸が互いに平行になるように、かつダイポールアンテナの軸に直交する平面上で円形に配列させたダイポールアレイアンテナが非特許文献２及び３において提案されている。これは、受信波の到達時刻をダイポールアンテナ毎に計測し、各ダイポールアンテナ間の受信波の到達時刻の差から受信波の到来方向を推定するもので、送信用としても受信用としても使用可能であり、アンテナを回転させる機械的動作が必要ない、という利点があり、各ダイポールアンテナからの受信信号の位相情報を用いて到来方向推定を行うことにより高分解能な指向性レーダシステムが構築可能となる。 Accordingly, Non-Patent Documents 2 and 3 propose dipole array antennas in which a plurality of dipole antennas are arranged in a circle on a plane orthogonal to the dipole antenna axes so that the axes of the dipole antennas are parallel to each other. ing. It measures the arrival time of the received wave for each dipole antenna and estimates the arrival direction of the received wave from the difference in arrival time of the received wave between each dipole antenna. It can be used for both transmission and reception There is an advantage that the mechanical operation to rotate the antenna is not required, and it is possible to construct a high-resolution directional radar system by estimating the direction of arrival using the phase information of the received signal from each dipole antenna Become.
実際に坑井内で使用されるダイポールアレイアンテナ８００の構成例を図８に示す。ダイポールアレイアンテナ８００は、中心の給電線の外周上に複数（例えば、４個）のダイポールアンテナ８０１ａ〜８０１ｄを配列して構成されている。図８（Ａ）に側面図を、図８（Ｂ）に給電線に対して垂直方向から見た図を示す。尚、図８（Ａ）では、簡単のため、中心の給電線８０４を挟んで向かい合う二本のダイポールアンテナ８０１ａ，８０１ｃのみ図示し、他のダイポールアンテナ８０１ｂ，８０１ｄの図示は割愛している。当該ダイポールアレイアンテナ８００はＦＲＰ（Ｆｉｂｅｒ Ｒｅｉｎｆｏｒｃｅｄ Ｐｌａｓｔｉｃｓ）製ベッセルで覆われた状態で坑井内に挿入される。各ダイポールアンテナ８０１ａ〜８０１ｄが受信した受信信号は、給電点の変圧比が１：１のＲＦトランス８０２ａ〜８０２ｄ、及び、ダイポールアンテナ毎に一対の同軸ケーブル８０３ａ〜８０３ｄを介して給電線８０４へと伝送される。各同軸ケーブル８０３ａ〜８０３ｄは、夫々、中心を通る給電線８０４に束ねられた後、当該給電線８０４を介して受信信号が地上へと伝送される。 A configuration example of a dipole array antenna 800 actually used in a well is shown in FIG. The dipole array antenna 800 is configured by arranging a plurality of (for example, four) dipole antennas 801a to 801d on the outer periphery of a central feeder line. FIG. 8A shows a side view, and FIG. 8B shows a view as viewed from the direction perpendicular to the feeder line. In FIG. 8A, for the sake of simplicity, only two dipole antennas 801a and 801c facing each other with the central feeder line 804 interposed therebetween are shown, and the other dipole antennas 801b and 801d are not shown. The dipole array antenna 800 is inserted into a well in a state of being covered with a vessel made of FRP (Fiber Reinforced Plastics). The received signals received by the dipole antennas 801a to 801d are fed to the feed line 804 via the RF transformers 802a to 802d having a transformation ratio of 1: 1 at the feed point and a pair of coaxial cables 803a to 803d for each dipole antenna. Is transmitted. Each of the coaxial cables 803a to 803d is bundled with a feed line 804 passing through the center, and then a reception signal is transmitted to the ground via the feed line 804.
ダイポールアレイアンテナを用いて受信波の到来方向を推定する場合、実際には、中心導体柱である給電線の共振により受信波が給電線から等方的に散乱され、当該散乱波が受信波と干渉することにより、受信波の到来方向の推定が困難となる周波数帯（以下、第１周波数帯域と称す）が存在し、精確に受信波の到来方向の推定を行うことができない。 When estimating the direction of arrival of a received wave using a dipole array antenna, the received wave is actually scattered isotropically from the feed line due to resonance of the feed line, which is the central conductor column, and the scattered wave becomes the received wave. There is a frequency band (hereinafter referred to as a first frequency band) that makes it difficult to estimate the arrival direction of the received wave due to interference, and the arrival direction of the received wave cannot be accurately estimated.
更に、ダイポールアンテナ間の共振（Ｐｈａｓｅ Ｓｅｑｕｅｎｃｅ Ｒｅｓｏｎａｎｃｅ）により受信波が散乱されることにより、受信波の到来方向の推定が困難となる周波数帯（以下、第２周波数帯域と称す）が存在し、精確に受信波の到来方向の推定を行うことができない。 Furthermore, there is a frequency band (hereinafter referred to as the second frequency band) that makes it difficult to estimate the direction of arrival of the received wave due to scattering of the received wave due to resonance (phase sequence resonance) between dipole antennas. In addition, the direction of arrival of the received wave cannot be estimated.
このうち、前者の第１周波数帯域については、中心導体柱である給電線部分を極力短くすることにより排除可能である。具体的には、給電点で光変調器によって受信電圧信号を光信号に変換し、受信信号を光ファイバで地上へ伝送することにより給電線部分を排除した構成が非特許文献２及び３に開示されている。しかしながら、光変調器とダイポールアンテナ間のインピーダンス整合が極めて悪く、レーダシステム全体の感度が低下する。また、光変調器を用いるため、受信用としてのみ使用可能であり、送信用アンテナとして使用することはできない。更に言えば、光変調器は高価である。 Of these, the former first frequency band can be eliminated by shortening the feeder line portion, which is the central conductor column, as much as possible. Specifically, Non-Patent Documents 2 and 3 disclose a configuration in which a feeding voltage portion is eliminated by converting a received voltage signal into an optical signal by an optical modulator at a feeding point and transmitting the received signal to the ground via an optical fiber. Has been. However, impedance matching between the optical modulator and the dipole antenna is extremely poor, and the sensitivity of the entire radar system is lowered. Moreover, since an optical modulator is used, it can be used only for reception and cannot be used as a transmission antenna. Furthermore, the optical modulator is expensive.
尚、後者の第２周波数帯域については、光変調器を用いて当該第１周波数帯域を排除した構成において、計算機シミュレーションによる解析が本願発明者によりなされており、解析の結果が非特許文献４により示されている。 The latter second frequency band is analyzed by a computer simulation in the configuration in which the first frequency band is excluded using an optical modulator, and the result of the analysis is shown in Non-Patent Document 4. It is shown.
本発明は、第１周波数帯域と第２周波数帯域が同時に存在する場合に係る上記の問題を解決するものであり、精確に受信波の到来方向の推定を行うことが可能なダイポールアレイアンテナ、及び、当該ダイポールアレイアンテナから受信した受信波を解析することにより地中の詳細な三次元位置情報を得ることのできるボアホールレーダシステムを提供することを目的とする。 The present invention solves the above-described problem when the first frequency band and the second frequency band are present simultaneously, and a dipole array antenna capable of accurately estimating the arrival direction of the received wave, and Another object of the present invention is to provide a borehole radar system capable of obtaining detailed three-dimensional position information in the ground by analyzing a received wave received from the dipole array antenna.
本発明に係る三次元位置推定システムは、地中に掘削された坑井内に、中心導体柱の外周に前記中心導体柱と平行な方向に伸びる複数のアンテナ素子が配置された、前記中心導体柱の長さよりも前記アンテナ素子の長さが短いダイポールアレイアンテナを、ベッセル内に収納して設置し、前記ダイポールアレイアンテナが受信した地中から到来する電磁波を前記アンテナ素子毎に解析し、前記電磁波の前記アンテナ素子間の遅延時間を求めることにより前記電磁波の到来方向の推定を行い、地中の三次元位置情報を得る三次元位置推定システムであって、
前記ダイポールアレイアンテナは、前記坑井内に設置したときに、前記中心導体柱と前記アンテナ素子間の干渉の影響により受信波の到来方向の推定が困難な第１周波数帯域の上限周波数が、前記アンテナ素子間の共振の影響により受信波の到来方向の推定が困難な第２周波数帯域の下限周波数よりも小さくなるように設定されており、
前記ダイポールアレイアンテナが受信した前記電磁波のうち、前記第１周波数帯域と前記第２周波数帯域を帯域通過フィルタにより通過させず、前記第１周波数帯域と前記第２周波数帯域の間の帯域である受信波の到来方向の推定が可能な第３周波数帯域のみ通過させる処理を行った後、当該フィルタ処理後の時間領域の前記電磁波を前記アンテナ素子毎に解析することを第１の特徴とする。
更に、本発明に係る三次元位置推定システムは、上記第１の特徴に加えて、前記第１周波数帯域の上限周波数が、前記中心導体柱に散乱され前記アンテナ素子に受信される散乱波の受信電圧と直接前記アンテナ素子に受信される受信電圧との比により表される干渉度Ｉ（ｆ）が、周波数の増加に伴い一旦極大値を取った後減少して−１０ｄＢ以下となる最小の周波数で定義され、
前記第２周波数帯域の下限周波数が、ＰＳＲ（Ｐｈａｓｅ Ｓｅｑｕｅｎｃｅ Ｒｅｓｏｎａｎｃｅ）における０次の振動に対応する電界強度が１次の振動に対応する電界強度と一致する周波数で定義されることを第２の特徴とする。
In the three-dimensional position estimation system according to the present invention, the central conductor column includes a plurality of antenna elements extending in a direction parallel to the central conductor column on an outer periphery of the central conductor column in a well drilled in the ground. A dipole array antenna having a length of the antenna element shorter than the length of the antenna element is housed and installed in a vessel, and an electromagnetic wave arriving from the ground received by the dipole array antenna is analyzed for each antenna element. A three-dimensional position estimation system for estimating the arrival direction of the electromagnetic wave by obtaining a delay time between the antenna elements, and obtaining three-dimensional position information in the ground,
When the dipole array antenna is installed in the well, the upper limit frequency of a first frequency band in which it is difficult to estimate the arrival direction of a received wave due to the influence of interference between the central conductor column and the antenna element, It is set to be smaller than the lower limit frequency of the second frequency band where it is difficult to estimate the arrival direction of the received wave due to the influence of resonance between elements,
Among the dipole said electromagnetic wave array antenna has received, wherein the first frequency band without passing through the second frequency band bandpass filter, a band between the second frequency band and said first frequency band receiver The first feature is that after performing the process of passing only the third frequency band in which the arrival direction of the wave can be estimated, the electromagnetic wave in the time domain after the filter process is analyzed for each antenna element.
Furthermore, in the three-dimensional position estimation system according to the present invention, in addition to the first feature, the upper limit frequency of the first frequency band is received by a scattered wave that is scattered by the central conductor column and received by the antenna element. The minimum frequency at which the degree of interference I (f) represented by the ratio between the voltage and the received voltage directly received by the antenna element takes a maximum value once as the frequency increases and then decreases to -10 dB or less. Defined in
The second feature is that the lower limit frequency of the second frequency band is defined by a frequency at which the electric field intensity corresponding to the zeroth order vibration in PSR (Phase Sequence Resonance) matches the electric field intensity corresponding to the first order vibration. And
本発明に係る三次元位置推定システムは、地中に掘削された坑井内に、中心導体柱の外周に前記中心導体柱と平行な方向に伸びる複数のアンテナ素子が配置された、前記中心導体柱の長さよりも前記アンテナ素子の長さが短いダイポールアレイアンテナを、ベッセル内に収納して設置し、前記ダイポールアレイアンテナが受信した地中から到来する電磁波を前記アンテナ素子毎に解析し、前記電磁波の前記アンテナ素子間の遅延時間を求めることにより前記電磁波の到来方向の推定を行い、地中の三次元位置情報を得る三次元位置推定システムであって、In the three-dimensional position estimation system according to the present invention, the central conductor column includes a plurality of antenna elements extending in a direction parallel to the central conductor column on an outer periphery of the central conductor column in a well drilled in the ground. A dipole array antenna having a length of the antenna element shorter than the length of the antenna element is housed and installed in a vessel, and an electromagnetic wave arriving from the ground received by the dipole array antenna is analyzed for each antenna element. A three-dimensional position estimation system for estimating the arrival direction of the electromagnetic wave by obtaining a delay time between the antenna elements, and obtaining three-dimensional position information in the ground,
前記ダイポールアレイアンテナは、前記坑井内に設置したときに、前記アンテナ素子間の共振の影響により受信波の到来方向の推定が困難な第２周波数帯域を有する一方、前記中心導体柱に散乱され前記アンテナ素子に受信される散乱波の受信電圧と直接前記アンテナ素子に受信される受信電圧との比により表される干渉度Ｉ（ｆ）の極大値が−１０ｄＢ以下となって、前記中心導体柱と前記アンテナ素子間の干渉の影響を無視できるように設定されており、When the dipole array antenna is installed in the well, the dipole array antenna has a second frequency band in which it is difficult to estimate the arrival direction of the received wave due to the resonance between the antenna elements, and is scattered by the central conductor column. The maximum value of the interference degree I (f) represented by the ratio of the received voltage of the scattered wave received by the antenna element and the received voltage directly received by the antenna element is −10 dB or less, and the central conductor column And the influence of interference between the antenna elements is set to be negligible,
前記ダイポールアレイアンテナが受信した前記電磁波のうち、前記第２周波数帯域を帯域通過フィルタにより通過させず、前記第２周波数帯域の下限周波数よりも低周波数帯域である受信波の到来方向の推定が可能な第３周波数帯域のみ通過させる処理を行った後、当該フィルタ処理後の時間領域の前記電磁波を前記アンテナ素子毎に解析することを第３の特徴とする。Among the electromagnetic waves received by the dipole array antenna, it is possible to estimate the direction of arrival of a received wave that is lower than the lower limit frequency of the second frequency band without passing the second frequency band by a band pass filter. The third feature is that after the process of passing only the third frequency band is performed, the electromagnetic wave in the time domain after the filter process is analyzed for each antenna element.
更に、本発明に係る三次元位置推定システムは、上記第３の特徴に加えて、前記第２周波数帯域の下限周波数が、ＰＳＲ（Ｐｈａｓｅ Ｓｅｑｕｅｎｃｅ Ｒｅｓｏｎａｎｃｅ）における０次の振動に対応する電界強度が１次の振動に対応する電界強度と一致する周波数で定義されることを第４の特徴とする。Furthermore, in the three-dimensional position estimation system according to the present invention, in addition to the third feature, the lower limit frequency of the second frequency band is an electric field strength corresponding to zero-order vibration in PSR (Phase Sequence Resonance). A fourth feature is that the frequency is defined by a frequency that matches the electric field intensity corresponding to the next vibration.
本発明に係るダイポールアレイアンテナは、地中に掘削された坑井内に設置される、中心導体柱の外周に、前記中心導体柱と平行な方向に伸びる複数のアンテナ素子が配置された、ベッセル内に収納されたダイポールアレイアンテナであって、前記ダイポールアレイアンテナは、前記中心導体柱の長さよりも前記アンテナ素子の長さが短く、前記坑井内に設置したときに、前記中心導体柱と前記アンテナ素子間の干渉の影響により受信波の到来方向の推定が困難な第１周波数帯域の上限周波数が、前記アンテナ素子間の共振の影響により受信波の到来方向の推定が困難な第２周波数帯域の下限周波数よりも小さくなるように設定されており、
前記第１周波数帯域と前記第２周波数帯域の間の帯域である受信波の到来方向の推定が可能な第３周波数帯域を有することを第１の特徴とする。
更に、本発明に係るダイポールアレイアンテナは、上記第１の特徴に加えて、前記第１周波数帯域の上限周波数が、 前記中心導体柱に散乱され前記アンテナ素子に受信される散乱波の受信電圧と直接前記アンテナ素子に受信される受信電圧との比により表される干渉度Ｉ（ｆ）が、周波数の増加に伴い一旦極大値を取った後減少して−１０ｄＢ以下となる最小の周波数で定義され、
前記第２周波数帯域の下限周波数が、ＰＳＲ（Ｐｈａｓｅ Ｓｅｑｕｅｎｃｅ Ｒｅｓｏｎａｎｃｅ）における０次の振動に対応する電界強度が１次の振動に対応する電界強度と一致する周波数で定義されることを第２の特徴とする。
The dipole array antenna according to the present invention is installed in a well bored in the ground, and a plurality of antenna elements extending in a direction parallel to the central conductor column are arranged on the outer periphery of the central conductor column . The dipole array antenna is housed in the dipole array antenna, and the dipole array antenna has a length of the antenna element shorter than that of the central conductor column, and when installed in the well, the central conductor column and the antenna The upper limit frequency of the first frequency band in which it is difficult to estimate the direction of arrival of the received wave due to the influence of interference between elements is the second frequency band in which the direction of arrival of the received wave is difficult to estimate due to the influence of resonance between the antenna elements. It is set to be smaller than the lower limit frequency,
A first characteristic is that it has a third frequency band capable of estimating the direction of arrival of a received wave, which is a band between the first frequency band and the second frequency band .
Furthermore, in the dipole array antenna according to the present invention, in addition to the first feature, an upper limit frequency of the first frequency band is a scattered voltage received by the antenna element and scattered by the central conductor column. The degree of interference I (f), which is expressed by the ratio with the received voltage directly received by the antenna element, is defined as the minimum frequency at which it takes a maximum value once as the frequency increases and then decreases to -10 dB or less. And
The second feature is that the lower limit frequency of the second frequency band is defined by a frequency at which the electric field intensity corresponding to the zeroth order vibration in PSR (Phase Sequence Resonance) matches the electric field intensity corresponding to the first order vibration. And
本発明に係るダイポールアレイアンテナは、地中に掘削された坑井内に設置される、中心導体柱の外周に、前記中心導体柱と平行な方向に伸びる複数のアンテナ素子が配置された、ベッセル内に収納されたダイポールアレイアンテナであって、前記ダイポールアレイアンテナは、前記中心導体柱の長さよりも前記アンテナ素子の長さが短く、前記坑井内に設置したときに、前記アンテナ素子間の共振の影響により受信波の到来方向の推定が困難な第２周波数帯域を有する一方、前記中心導体柱に散乱され前記アンテナ素子に受信される散乱波の受信電圧と直接前記アンテナ素子に受信される受信電圧との比により表される干渉度Ｉ（ｆ）の極大値が−１０ｄＢ以下となって、前記中心導体柱と前記アンテナ素子間の干渉の影響を無視できるように設定されており、The dipole array antenna according to the present invention is installed in a well bored in the ground, and a plurality of antenna elements extending in a direction parallel to the central conductor column are arranged on the outer periphery of the central conductor column. The dipole array antenna is housed in the dipole array antenna, and the dipole array antenna has a length of the antenna element shorter than the length of the central conductor column, and when installed in the well, resonance between the antenna elements is achieved. While having a second frequency band in which it is difficult to estimate the direction of arrival of the received wave due to influence, the received voltage of the scattered wave scattered by the central conductor column and received by the antenna element and the received voltage received directly by the antenna element The maximum value of the degree of interference I (f) represented by the ratio of ≦ 10 dB is −10 dB or less, and the influence of interference between the central conductor column and the antenna element can be ignored. Is set to,
前記第２周波数帯域より低周波数側に、受信波の到来方向の推定が可能な第３周波数帯域を有することを第３の特徴とする。A third feature is that a third frequency band is provided on the lower frequency side than the second frequency band so that the arrival direction of the received wave can be estimated.
更に、本発明に係るダイポールアレイアンテナは、上記第３の特徴に加えて、前記第２周波数帯域の下限周波数が、ＰＳＲ（Ｐｈａｓｅ Ｓｅｑｕｅｎｃｅ Ｒｅｓｏｎａｎｃｅ）における０次の振動に対応する電界強度が１次の振動に対応する電界強度と一致する周波数で定義されることを第４の特徴とする。Furthermore, in the dipole array antenna according to the present invention, in addition to the third feature described above, the lower limit frequency of the second frequency band is such that the electric field strength corresponding to the zeroth order vibration in PSR (Phase Sequence Resonance) is the first order. A fourth feature is that the frequency is defined by a frequency that matches the electric field intensity corresponding to the vibration.
また、本発明に係る受信波の到来方向の推定方法は、本発明の第１乃至第４の何れかの特徴のダイポールアンテナが受信した地中から到来する電磁波のうち、前記第３周波数帯域のみを帯域通過フィルタにより通過させた後、当該フィルタ処理後の時間領域の受信波形を解析することを第１の特徴とする。
The method of estimating the arrival direction of the received waves according to the present invention, first, among the electromagnetic waves fourth one of the features of the dipole antenna comes from the ground received, before Symbol third frequency band of the present invention The first feature is to analyze the received waveform in the time domain after the filter processing after passing only the signal through the band pass filter .
本発明の三次元位置推定システムは、ダイポールアレイアンテナにより受信した受信波信号のうち、上述の第１周波数帯域、及び、第２周波数帯域に係る周波数帯を予め帯域通過フィルタにより減衰させ、ダイポールアレイアンテナにより受信した受信波のうち、ダイポールアンテナと給電線間の干渉及びダイポールアンテナ相互間の干渉の影響を受けず、到来方向の推定が可能な周波数帯域（第３周波数帯域）のみを用いて受信波の解析をすることにより、受信波の到来方向の推定を精確に行うことができ、結果、地中の詳細な三次元位置情報を得ることができる。 The three-dimensional position estimation system of the present invention attenuates the frequency bands related to the first frequency band and the second frequency band in the received wave signal received by the dipole array antenna in advance with a band pass filter, Of the received wave received by the antenna, it is received using only the frequency band (third frequency band) in which the direction of arrival can be estimated without being affected by interference between the dipole antenna and the feeder line and between the dipole antennas. By analyzing the wave, the direction of arrival of the received wave can be accurately estimated, and as a result, detailed three-dimensional position information in the ground can be obtained.
特に、第１周波数帯域が低周波数側、第２周波数帯域が高周波側にあり、第１周波数帯域と第２周波数帯域とが互いに重なり合わない場合には、第１周波数帯の上限周波数ｆ０と第２周波数帯の下限周波数ｆ１の間の帯域を第３周波数帯域とし、受信波の到来方向の推定が可能な第３周波数帯域のみを帯域通過フィルタにより通過させることにより、受信波の到来方向の推定を精確に行うことができる。 In particular, when the first frequency band is on the low frequency side, the second frequency band is on the high frequency side, and the first frequency band and the second frequency band do not overlap each other, the upper limit frequency f0 of the first frequency band and the second frequency band The band between the lower limit frequencies f1 of the two frequency bands is set as the third frequency band, and only the third frequency band in which the direction of arrival of the received wave can be estimated is passed through the band-pass filter, so that the direction of arrival of the received wave is estimated. Can be performed accurately.
ここで、受信波の到来方向の推定が困難な第１周波数帯域および第２周波数帯域が生じる原因について、詳しく説明する。 Here, the reason why the first frequency band and the second frequency band in which it is difficult to estimate the arrival direction of the received wave will be described in detail.
第１周波数帯域は、中心導体柱である給電線での半波長共振によって給電線に過大な電流が流れることにより、給電線から等方的に散乱波が放射され、全てのダイポールアンテナで同じ信号が受信されることに起因して生じる。これにより、給電線に散乱された後ダイポールアンテナに受信される散乱波の受信電圧と、直接ダイポールアンテナに受信される受信電圧との比により表される、給電線とダイポールアンテナ間の干渉の大きさを表す指標（以下、干渉度と称す）Ｉ（ｆ）が極大値をとる。 In the first frequency band, an excessive current flows through the feed line due to half-wave resonance at the feed line that is the central conductor column, so that isotropically scattered waves are radiated from the feed line, and all dipole antennas have the same signal. Is caused by being received. As a result, the magnitude of interference between the feed line and the dipole antenna expressed by the ratio of the received voltage of the scattered wave received by the dipole antenna after being scattered by the feed line and the received voltage directly received by the dipole antenna. An index (hereinafter referred to as interference degree) I (f) representing the maximum value takes a maximum value.
以下、具体的に説明する。図９に示されるように、坑井内にある二つのダイポールアンテナＡ１とＡ２に角周波数ωの正弦波が入射し、ダイポールアンテナＡ１の受信電圧をＹ１（ｔ）、Ａ２の受信電圧をＹ２（ｔ）とすると、時刻ｔにおける受信電圧は複素数表記で数１のように表される。このとき二つのアンテナ間に生じる受信波の位相遅延時間τはｔ２−ｔ１である。 This will be specifically described below. As shown in FIG. 9, a sine wave having an angular frequency ω is incident on two dipole antennas A 1 and A 2 in the well , and the received voltage of the dipole antenna A 1 is received by Y 1 (t) and A 2 . Assuming that the voltage is Y 2 (t), the received voltage at time t is expressed as the following equation 1 in complex number notation. At this time, the phase delay time τ of the received wave generated between the two antennas is t 2 −t 1 .
ここで、給電線を導体棒で近似し、この導体棒で散乱波が発生し、当該散乱波が夫々のアンテナの受信電圧に同様に付加され、各受信電圧が複素数表記で数２のように表されるとする。このとき、干渉度Ｉ（ｆ）を数３で定義する。 Here, the feeder line is approximated by a conductor rod, and a scattered wave is generated by this conductor rod. The scattered wave is added to the reception voltage of each antenna in the same manner, and each reception voltage is expressed by a complex number notation as shown in Equation 2. Let it be represented. At this time, the degree of interference I (f) is defined by Equation 3.
このとき、位相遅延τは数４で表される。ただし、θ１及びθ２は夫々、θ１＝ａｒｇＹ１（０）＝∠Ｙ１（０）及びθ２＝ａｒｇＹ２（０）＝∠Ｙ２（０）で表される初期位相である。 At this time, the phase delay τ is expressed by Equation 4. However, θ 1 and θ 2 are initial phases represented by θ 1 = argY 1 (0) = ∠Y 1 (0) and θ 2 = argY 2 (0) = ∠Y 2 (0), respectively.
ダイポールアンテナ間の間隔を７ｃｍとし、均質媒質中に各ダイポールアンテナが存在すると仮定して位相遅延時間を計算した結果を図１０に示す。給電線との干渉が全く無い場合、遅延時間は０．７ｎｓであるが、干渉度が高くなるにつれ遅延時間が低下する。一般のレーダシステムでは０．３ｎｓ以下の遅延時間差を検出することは難しく、受信波の到来方向を推定することは困難であるが、０．５ｎｓ程度の遅延時間差であれば現在のレーダシステムで容易に推定することができる。そこで、干渉度が−１０ｄＢ以下となる周波数帯域を用いることにより、好適に受信波の到来方向の推定を行うことができる。 FIG. 10 shows the result of calculating the phase delay time assuming that the distance between the dipole antennas is 7 cm and each dipole antenna is present in a homogeneous medium. When there is no interference with the feeder line, the delay time is 0.7 ns, but the delay time decreases as the degree of interference increases. In general radar systems, it is difficult to detect a delay time difference of 0.3 ns or less, and it is difficult to estimate the direction of arrival of the received wave. Can be estimated. Therefore, by using a frequency band in which the degree of interference is −10 dB or less, the arrival direction of the received wave can be estimated appropriately.
このため、第１周波数帯域の上限周波数は、前述の干渉度Ｉ（ｆ）が周波数の増加に伴い一旦極大値を取った後減少して−１０ｄＢ以下となる最小の周波数ｆ０として定義することができる。 For this reason, the upper limit frequency of the first frequency band may be defined as the minimum frequency f0 at which the above-described interference degree I (f) takes a local maximum once as the frequency increases and then decreases to −10 dB or less. it can.
上記の理由により、第１周波数帯域は給電線である中心導体柱の半波長共振周波数ｆｒ付近に存在する。当該共振周波数ｆｒは、主として給電線の長さ２ｈ’、給電線の周囲の誘電率に依存し、給電線が比誘電率εｒの均質媒質中にあると仮定すると、下記の数５で近似される。ここでνは真空中の電磁波の速度である。 For the above reason, the first frequency band exists in the vicinity of the half-wave resonance frequency fr of the central conductor column that is the feeder line. The resonance frequency fr mainly depends on the length 2h ′ of the feed line and the dielectric constant around the feed line. If it is assumed that the feed line is in a homogeneous medium having a relative dielectric constant ε r , the resonance frequency fr is approximated by the following formula 5. Is done. Here, ν is the speed of the electromagnetic wave in vacuum.
より精確には、干渉度Ｉ（ｆ）は、アンテナを覆うＦＲＰ製ベッセルの周囲に円筒状に存在する坑井内の媒質（主として水）の影響を考慮した上で、アンテナ周囲に存在する円筒状境界面からの散乱波を考慮したモーメント法によるアンテナ特性の解析を行い、入射電磁波を介して中心導体及び各ダイポールアンテナに誘起される受信電圧を夫々求め、ダイポールアンテナの給電点に誘起される受信電圧のうち、中心導体柱による寄与分を算出することにより求めることができる。 More precisely, the interference degree I (f) is determined by taking into consideration the influence of the medium (mainly water) in the well existing in a cylindrical shape around the FRP vessel covering the antenna, and the cylindrical shape existing around the antenna. Analysis of antenna characteristics by the moment method taking into account scattered waves from the boundary surface, obtaining the reception voltage induced in the central conductor and each dipole antenna via the incident electromagnetic wave, respectively, and reception induced at the feed point of the dipole antenna Of the voltage, it can be obtained by calculating the contribution of the central conductor column.
次に、第２周波数帯域は、ダイポールアンテナ間の共振現象（Ｐｈａｓｅ Ｓｅｑｕｅｎｃｅ Ｒｅｓｏｎａｎｃｅ、以下ＰＳＲと称す）により受信波の到来方向に無関係な電磁界がダイポールアンテナ周辺で発生することに起因して生じる。非特許文献４によれば、ダイポールアンテナの数をＭとすると、この共振は１次からＭ／２次（Ｍが奇数の場合は（Ｍ−１）／２次）まで存在し、これらの共振周波数は主としてダイポールアンテナが単体で存在したときの半波長共振周波数付近に存在する。 Next, the second frequency band is generated due to an electromagnetic field that is irrelevant to the arrival direction of the received wave being generated around the dipole antenna due to a resonance phenomenon (hereinafter referred to as PSR) between the dipole antennas. According to Non-Patent Document 4, when the number of dipole antennas is M, this resonance exists from the first order to the M / 2 order (when M is an odd number, (M-1) / 2 order). The frequency mainly exists near the half-wave resonance frequency when the dipole antenna is present alone.
このため、第２周波数帯域の下限周波数を、当該ＰＳＲ現象において１次の振動に対応する電界強度が周波数の上昇に伴って増加し、０次の振動に対応する電界強度（即ち、全アンテナにおいて同位相で観測される成分であり、十分に低い周波数でアンテナ間の相互作用が小さい場合は入射波の電界強度とみなせる）が１次のそれと一致する周波数ｆ１として定義することができる。 For this reason, the lower limit frequency of the second frequency band is set such that the electric field strength corresponding to the first-order vibration in the PSR phenomenon increases as the frequency increases, and the electric field strength corresponding to the zero-order vibration (that is, in all antennas). It can be defined as a frequency f1 that is a component observed in the same phase and can be regarded as the electric field strength of an incident wave when the interaction between antennas is small at a sufficiently low frequency.
上記の理由により、第２周波数帯域は当該ダイポールアンテナの半波長共振周波数ｆＲ付近に存在し、Ｍ個のダイポールアンテナが比誘電率εｒ’の均質媒質中にあると仮定すると、ｆＲは下記の数６で近似される。ここでｈは当該ダイポールアンテナの長さである。 For the above reason, assuming that the second frequency band exists in the vicinity of the half-wave resonance frequency fR of the dipole antenna, and M dipole antennas are in a homogeneous medium having a relative permittivity ε r ′, fR is It is approximated by Equation 6. Here, h is the length of the dipole antenna.
ここで、上記数５及び数６において、比誘電率εｒ、εｒ’は共にアンテナ周囲に存在する水或いは岩石の影響を受けるが、本発明のアンテナは線状であり、ＦＲＰ製のベッセルに収納されているため、アンテナ近傍の媒質は空気が多く、εｒ＝εｒ’と近似できる。このとき、ｈ＜ｈ’、即ち、アンテナの長さよりも給電線の長さの方が長ければ、ｆｒ＜ｆＲとなり、第１周波数帯域が第２周波数帯域よりも低周波数側に位置するので、第１周波数帯域の上限周波数ｆ０が第２周波数帯域の下限周波数ｆ１よりも小さければ、周波数がｆ０からｆ１の間の帯域を第３周波数帯域として帯域通過フィルタにより通過させることにより、受信波の到来方向の推定を精確に行うことが可能になる。 Here, in the above formulas 5 and 6, the relative dielectric constants ε r and ε r ′ are both affected by water or rocks existing around the antenna, but the antenna of the present invention is linear and is a FRP vessel. Therefore, the medium near the antenna has a lot of air and can be approximated to ε r = ε r ′. At this time, if h <h ′, that is, if the length of the feeder line is longer than the length of the antenna, fr <fR, and the first frequency band is located on the lower frequency side than the second frequency band. If the upper limit frequency f0 of the first frequency band is smaller than the lower limit frequency f1 of the second frequency band, the band between f0 and f1 is passed through the bandpass filter as the third frequency band, and the received wave arrives. The direction can be accurately estimated.
図１１は、ダイポールアレイアンテナを用いて受信波形の解析を行う場合に、受信波の到来方向の推定が困難な第１及び第２周波数帯域と受信波の到来方向の推定が可能な第３周波数帯域との位置関係を、具体的に、ダイポールアレイアンテナの主要な設計パラメータ毎に場合分けし、干渉度Ｉ（ｆ）のグラフと共に示す図である。 FIG. 11 shows the first and second frequency bands in which it is difficult to estimate the direction of arrival of the received wave and the third frequency capable of estimating the direction of arrival of the received wave when analyzing the received waveform using a dipole array antenna. It is a figure which classifies the positional relationship with a zone | band specifically for every main design parameter of a dipole array antenna, and shows with the graph of interference degree I (f).
給電線（中心導体柱）の端部にダイポールアンテナが配置された、給電線の長さがダイポールアンテナの長さよりも十分長いダイポールアレイアンテナを坑井内に設置する場合、図１１（Ａ）に示されるように、ｆ０＜ｆ１であり、第１周波数帯域が低周波数側に、第２周波数域が高周波数側に位置し、第１周波数帯域と第２周波数帯域は互いに重なり合わないので、第１周波数帯域と第２周波数帯域の間、ｆ０とｆ１の間の帯域を第３周波数帯域とし、当該第３周波数帯域のみを帯域通過フィルタにより通過させることにより、受信波の到来方向の推定を精確に行うことが可能になる。 When a dipole array antenna in which a dipole antenna is disposed at the end of a feed line (central conductor column) and the length of the feed line is sufficiently longer than the length of the dipole antenna is shown in FIG. Since f0 <f1, the first frequency band is located on the low frequency side, the second frequency band is located on the high frequency side, and the first frequency band and the second frequency band do not overlap each other. The band between f0 and f1 is set as the third frequency band between the frequency band and the second frequency band, and only the third frequency band is passed through the band-pass filter, thereby accurately estimating the arrival direction of the received wave. It becomes possible to do.
給電線（中心導体柱）の端部にダイポールアンテナが配置された、給電線の長さがダイポールアンテナの長さよりも長いが、絶対的には十分短いダイポールアレイアンテナを坑井内に設置する場合には、図１１（Ｂ）に示されるように、ｆｒ及びｆ０が高周波側にシフトするが、同時にｆｒ及びｆ０が高周波側にシフトするに従い坑井の影響により給電線の共振が抑制されるため、干渉度の極大値が低下する。この場合、給電線による干渉の影響は無視することができ、ＰＳＲのみが問題になる。第２周波数帯域の下限ｆ１以下の周波数帯域を帯域通過フィルタにより通過させることにより、受信波の到来方向の推定を精確に行うことが可能になる。 When a dipole antenna is placed at the end of the feed line (central conductor column), and the feed line is longer than the dipole antenna, but is absolutely short enough to be installed in the well As shown in FIG. 11 (B), fr and f0 shift to the high frequency side. At the same time, as fr and f0 shift to the high frequency side, the resonance of the feeder line is suppressed due to the influence of the well, The maximum value of the interference level decreases. In this case, the influence of interference caused by the feeder line can be ignored, and only PSR becomes a problem. By passing a frequency band equal to or lower than the lower limit f1 of the second frequency band by the band pass filter, it is possible to accurately estimate the arrival direction of the received wave.
給電線（中心導体柱）の端部にダイポールアンテナが配置され、給電線の長さがダイポールアンテナの長さよりも短いダイポールアレイアンテナを坑井内に設置する場合、図１１（Ｃ）及び図１１（Ｄ）に示されるように、ｆ１＜ｆ０であり、第２周波数帯域が低周波数側に位置する。この場合、第２周波数帯域より高周波側の周波数帯域を帯域通過フィルタにより通過させることにより、受信波の到来方向の推定を行うことが可能になると考えられる。 When a dipole antenna is disposed at the end of the feed line (center conductor column) and a dipole array antenna whose feed line is shorter than the length of the dipole antenna is installed in the well, FIG. 11 (C) and FIG. As shown in D), f1 <f0 and the second frequency band is located on the low frequency side. In this case, it is considered that the arrival direction of the received wave can be estimated by passing the frequency band higher than the second frequency band through the band pass filter.
一方、給電線（中心導体柱）の中央部にダイポールアンテナが配置された、給電線の長さがダイポールアンテナの長さよりも十分長いダイポールアレイアンテナを坑井内に設置する場合、図１１（Ｅ）に示されるように、共振周波数ｆｒよりも低い周波数で干渉度が低くなる傾向があり、第１周波数帯域よりも低周波数側の周波数帯域を帯域通過フィルタにより通過させることにより、受信波の到来方向の推定を精確に行うことが可能になる。 On the other hand, when a dipole array antenna in which a dipole antenna is arranged at the center of a feed line (central conductor column) and the length of the feed line is sufficiently longer than the length of the dipole antenna is installed in the well, FIG. As shown in FIG. 4, the interference degree tends to be low at a frequency lower than the resonance frequency fr, and by passing the frequency band lower than the first frequency band by the band pass filter, the arrival direction of the received wave Can be accurately estimated.
尚、ダイポールアンテナを空気中に設置した場合には、中心導体柱である給電線の半波長共振だけでなく、より高次の共振も干渉度に影響を与えるため、使用可能な周波数帯域が制限される。給電線の端部にダイポールアンテナが配置された、給電線の長さがダイポールアンテナの長さよりも十分長いダイポールアレイアンテナの場合には、図１１（Ｆ）に示されるように、第２周波数帯域の下限周波数ｆ１以下で、かつ給電線とダイポールアンテナとの干渉の影響を受けない周波数帯域のみ帯域通過フィルタにより通過させ、第２周波数帯域と複数の第１周波数帯域を帯域通過フィルタにより通過させないことにより、受信波の到来方向の推定を精確に行うことが可能になる。 When the dipole antenna is installed in the air, not only the half-wave resonance of the feed line that is the central conductor column but also the higher-order resonance affects the interference, so the usable frequency band is limited. Is done. In the case of a dipole array antenna in which a dipole antenna is arranged at the end of the feed line and the length of the feed line is sufficiently longer than the length of the dipole antenna, as shown in FIG. Only the frequency band that is lower than the lower limit frequency f1 and that is not affected by the interference between the feed line and the dipole antenna is allowed to pass through the band pass filter, and the second frequency band and the plurality of first frequency bands are not allowed to pass through the band pass filter. This makes it possible to accurately estimate the direction of arrival of the received wave.
尚、上記第１〜第３周波数帯域の位置関係については、一般的な傾向を述べたに過ぎず、給電線及びダイポールアンテナの長さ等、ダイポールアレイアンテナの形状のほか、アンテナを収納するベッセルの形状や、坑井内外の媒質にも依存するため、所望の第３周波数帯域を有するアンテナの作製に当たっては、当該アンテナの実際の使用環境における干渉度Ｉ（ｆ）、及びＰＳＲの電界強度を予めアンテナ特性の解析シミュレーションにより求めながら、アンテナの設計を行うことが重要である。 Note that the positional relationship between the first to third frequency bands described above is merely a general trend. In addition to the shape of the dipole array antenna, such as the length of the feed line and the dipole antenna, the vessel that houses the antenna is used. Therefore, when manufacturing an antenna having a desired third frequency band, the interference degree I (f) in the actual use environment of the antenna and the electric field strength of the PSR are determined. It is important to design the antenna while obtaining it beforehand by analysis simulation of the antenna characteristics.
また、本発明のダイポールアレイアンテナは、上述の第１及び第２周波数帯域が互いに重なり合わず、受信波の到来方向の推定が可能な第３周波数帯域を有するように設計され、当該ダイポールアレイアンテナが受信した受信波のうち、受信波の到来方向の推定が困難な第１周波数帯域及び第２周波数帯域を帯域通過フィルタにより通過させず、受信波の到来方向の推定が可能な第３周波数帯域のみを用いて受信波の解析を行うことにより、受信波の到来方向の推定を精確に行うことができる。 Further, the dipole array antenna of the present invention is designed so that the first and second frequency bands described above do not overlap each other and has a third frequency band capable of estimating the arrival direction of the received wave. The third frequency band in which the arrival direction of the received wave can be estimated without passing through the first frequency band and the second frequency band, which are difficult to estimate the arrival direction of the received wave, by the band pass filter. The direction of arrival of the received wave can be accurately estimated by analyzing the received wave using only the signal.
特に、第１周波数帯域が低周波数側、第２周波数帯域が高周波側にあり、第１周波数帯域の上限周波数ｆ０が第２周波数帯域の下限周波数ｆ１よりも低周波数側にあるようにアンテナを設計することにより、周波数がｆ０からｆ１の間の周波数帯域を第３周波数帯域として、受信波の到来方向の推定が可能な第３周波数帯域のみを用いて受信波の解析を行うことができるので、受信波の到来方向の推定を精確に行うことができる。 In particular, the antenna is designed so that the first frequency band is on the low frequency side, the second frequency band is on the high frequency side, and the upper limit frequency f0 of the first frequency band is on the lower frequency side than the lower limit frequency f1 of the second frequency band. As a result, the received wave can be analyzed using only the third frequency band in which the direction of arrival of the received wave can be estimated, with the frequency band between f0 and f1 being the third frequency band. The arrival direction of the received wave can be accurately estimated.
ここで、ｆ０及びｆ１は、給電線の長さ及び太さ（直径）、ダイポールアンテナの長さ、直径、数、及び給電線との位置関係等、ダイポールアレイアンテナの形状に依存し、また、ダイポールアレイアンテナを収納するベッセルの形状に依存するが、一般的な傾向については既に図１１を用いて説明した通りであり、給電線の長さがダイポールアンテナの長さよりも十分長ければｆ０＜ｆ１を満足する。更に、坑井外の媒質（水、岩石など）の影響により、数５及び数６における媒質の比誘電率εｒ、εｒ’が変調され、ｆ０及びｆ１が増減する。本発明のダイポールアレイアンテナはＦＲＰ製のベッセルに収納されているため、アンテナ近傍の媒質は空気が多く、εｒ≒εｒ’であり、ｆ０とｆ１の増減は同様に起こるため、ｆ０＜ｆ１の関係は坑井外の媒質に拘わらず成立する。 Here, f0 and f1 depend on the shape of the dipole array antenna such as the length and thickness (diameter) of the feed line, the length, diameter, number, and positional relationship with the feed line of the dipole antenna, Although depending on the shape of the vessel housing the dipole array antenna, the general tendency is as already described with reference to FIG. 11. If the length of the feed line is sufficiently longer than the length of the dipole antenna, f0 <f1 Satisfied. Further, the relative dielectric constants ε r and ε r ′ of the medium in Equations 5 and 6 are modulated by the influence of the medium (water, rock, etc.) outside the well, and f0 and f1 increase or decrease. Since the dipole array antenna of the present invention is housed in a FRP vessel, the medium in the vicinity of the antenna has a lot of air and ε r ≈ε r ′, and f0 and f1 increase and decrease similarly, so that f0 <f1 This relationship holds regardless of the medium outside the well.
従って、坑井の外の媒質や坑井の直径などは、予め代表的なパラメータを用いてｆ０及びｆ１を設定した上で、当該設定条件を満足するアンテナを設計し、その後、測定する実験場の状態を反映したアンテナ特性の解析シミュレーションを行うことによりｆ０及びｆ１を再設定することができる。これにより、フィルタ処理により通過させる第３周波数帯域を微調整することができ、受信波の到来方向の推定が可能な第３周波数帯域を用いて、受信波の到来方向の推定を精確に行うことができる。 Therefore, the medium outside the well and the diameter of the well are set in advance using f0 and f1 using typical parameters, and an antenna that satisfies the setting conditions is designed and then measured. It is possible to reset f0 and f1 by performing an analysis simulation of the antenna characteristics reflecting the state. Thereby, it is possible to finely adjust the third frequency band to be passed by the filter processing, and to accurately estimate the arrival direction of the received wave using the third frequency band capable of estimating the arrival direction of the received wave. Can do.
以下において、本発明に係る三次元位置推定システムの一実施形態（以下、適宜「本システム１００」と称する）につき、図面を参照して説明する。図１は、本システム１００の構成図である。本システム１００は一周波数ｆで利得（振幅）と位相を測定し、この周波数ｆを掃引することで周波数領域のデータを直接取得するステップ周波数連続波（ＳＦＣＷ）レーダシステムであり、電磁波を送信する為の坑井１０１と、坑井１０１から送信され、地中で反射・散乱された電磁波を受信する為の坑井１０２が地中に設けられている。坑井１０１内にはＦＲＰ製ベッセル１０３が、フォトダイオード（図示せず）、アンプ（図示せず）、及び、送信アンテナ１０６を収納して構成され、坑井内１０１に挿入されている。坑井１０２内にはＦＲＰ製ベッセル１０７が、ダイポールアレイアンテナ１０８、電気／光変換ユニット１０９、及び、ダイポールアレイアンテナ１０８の坑井内の向きを知る為の方位計１１０を収納して構成され、坑井１０２内に挿入されている。尚、坑井内の、ＦＲＰ製ベッセル１０３、１０７の周囲は通常水（地下水）或いは空気で覆われている。 Hereinafter, an embodiment of a three-dimensional position estimation system according to the present invention (hereinafter, referred to as “the system 100” as appropriate) will be described with reference to the drawings. FIG. 1 is a configuration diagram of the system 100. The system 100 is a step frequency continuous wave (SFCW) radar system that measures gain (amplitude) and phase at one frequency f and directly acquires frequency domain data by sweeping the frequency f, and transmits electromagnetic waves. A well 101 and a well 102 for receiving electromagnetic waves transmitted from the well 101 and reflected / scattered in the ground are provided in the ground. In the well 101, an FRP vessel 103 is configured to house a photodiode (not shown), an amplifier (not shown), and a transmission antenna 106, and is inserted into the well 101. In the well 102, an FRP vessel 107 is configured to house a dipole array antenna 108, an electrical / optical conversion unit 109, and a compass 110 for knowing the orientation of the dipole array antenna 108 in the well. It is inserted in the well 102. In addition, the surroundings of the FRP vessels 103 and 107 in the well are usually covered with water (ground water) or air.
ベクトルネットワークアナライザ１１１は、地上に設けられ、ステップ周波数連続波（ＳＦＣＷ）を出力する。当該連続波は電気／光変換部１１２内のアンプ１１３により増幅され、レーザダイオード１１４により光信号に変換されて、光ファイバを介して坑井１０１内の送信アンテナ部１０３に送信される。 The vector network analyzer 111 is provided on the ground and outputs a step frequency continuous wave (SFCW). The continuous wave is amplified by the amplifier 113 in the electrical / optical conversion unit 112, converted into an optical signal by the laser diode 114, and transmitted to the transmission antenna unit 103 in the well 101 through the optical fiber.
坑井１０１内に挿入されたＦＲＰ製ベッセル１０３は、地上から送信された光信号をフォトダイオード（図示せず）により電気信号に変換し、アンプ（図示せず）により増幅した後、送信アンテナ１０６を介して地中から電磁波を放射する。 The FRP vessel 103 inserted into the well 101 converts an optical signal transmitted from the ground into an electrical signal by a photodiode (not shown), amplifies it by an amplifier (not shown), and then transmits to the transmitting antenna 106. Radiates electromagnetic waves from the ground via
坑井１０２内に挿入されたＦＲＰ製ベッセル１０７は、送信アンテナ１０６から送信され、地中から反射、或いは散乱された電磁波をダイポールアレイアンテナ１０８を介して受信する。尚、ダイポールアレイアンテナ１０８は、特性インピーダンス５０Ωの同軸ケーブルで各ダイポールアンテナへ接続されており、これによりインピーダンス整合が改善されている。当該同軸ケーブルは、夫々、中心に集められ、円柱状に束ねられて給電線を構成し、当該給電線を介して受信信号が電気／光変換ユニット１０９に伝送される。電気／光変換ユニット１０９は、当該受信信号をアンプにより増幅し、レーザダイオードにより光信号に変換して、これによりＳ／Ｎ比が向上された受信信号を光ファイバを介して地上に送信する。 The FRP vessel 107 inserted into the well 102 receives an electromagnetic wave transmitted from the transmitting antenna 106 and reflected or scattered from the ground via the dipole array antenna 108. The dipole array antenna 108 is connected to each dipole antenna by a coaxial cable having a characteristic impedance of 50Ω, thereby improving impedance matching. The coaxial cables are each collected at the center and bundled in a columnar shape to form a power supply line, and a reception signal is transmitted to the electrical / optical conversion unit 109 via the power supply line. The electrical / optical conversion unit 109 amplifies the received signal with an amplifier, converts the received signal into an optical signal with a laser diode, and transmits the received signal with an improved S / N ratio to the ground via an optical fiber.
地上に送信された受信信号は、光／電気変換部１１７のフォトダイオード１１８により電気信号に変換され、アンプ１１９により増幅された後、当該受信信号がベクトルネットワークアナライザ１１１に入力される。これにより、周波数領域の受信波データを得る。当該受信波データはＧＰＩＢインタフェースを介してパソコン１２０に送られる。パソコン１２０は、当該周波数領域の受信波データを取り込み、ケーブル及び電子回路で生じる減衰や遅延時間の補正を行った後、フィルタ処理を行う。このとき、ダイポールアンテナと給電線間の干渉、或いは各ダイポールアンテナ間の共振の影響により受信波の到来方向の推定が困難な周波数帯域を通過させず、受信波の到来方向の推定が可能な周波数帯域のみ通過させるフィルタ処理を行い、当該フィルタ処理後のデータを逆フーリエ変換することで時間領域の受信波形を得る。当該受信波形をダイポールアンテナ毎に解析し、受信波の到達時刻を求めることによりダイポールアンテナ毎の遅延時間を求め、受信波の到来方向の推定を精確に行うことが可能になる。送信アンテナ１０６から放射され、地中内の亀裂、断層、地下水などにより反射或いは散乱された電磁波を受信用ダイポールアレイアンテナ１０８が受信する。受信用ダイポールアレイアンテナ１０８と送信アンテナ１０６の双方を深度方向に走査し、地中物体から反射或いは散乱された受信波の到来方向の推定を精確に行い、推定された受信波の到来方向と受信波の到来時刻との関係を解析することにより、地中の詳細な三次元位置情報を得ることができる。 The reception signal transmitted to the ground is converted into an electric signal by the photodiode 118 of the optical / electrical conversion unit 117, amplified by the amplifier 119, and then input to the vector network analyzer 111. As a result, received wave data in the frequency domain is obtained. The received wave data is sent to the personal computer 120 via the GPIB interface. The personal computer 120 takes in the received wave data in the frequency domain, corrects attenuation and delay time generated in the cable and the electronic circuit, and then performs filter processing. At this time, the frequency at which the direction of arrival of the received wave can be estimated without passing through a frequency band in which it is difficult to estimate the direction of arrival of the received wave due to the interference between the dipole antenna and the feeder line or the resonance between each dipole antenna. A filtering process that allows only the band to pass is performed, and the received data in the time domain is obtained by performing an inverse Fourier transform on the data after the filtering process. By analyzing the received waveform for each dipole antenna and obtaining the arrival time of the received wave, the delay time for each dipole antenna is obtained, and the arrival direction of the received wave can be accurately estimated. The reception dipole array antenna 108 receives electromagnetic waves radiated from the transmission antenna 106 and reflected or scattered by cracks, faults, groundwater, etc. in the ground. Both the receiving dipole array antenna 108 and the transmitting antenna 106 are scanned in the depth direction, and the direction of arrival of the received wave reflected or scattered from the underground object is accurately estimated. By analyzing the relationship with the arrival time of the waves, detailed three-dimensional position information in the ground can be obtained.
以下に、本発明に係る受信波の到来方向の推定方法について、具体的に説明する。 The method for estimating the arrival direction of the received wave according to the present invention will be specifically described below.
まず、ｆ０（第１周波数帯域の上限）＜ｆ１（第２周波数帯域の下限）となるようにダイポールアレイアンテナを設計する。坑井の外の媒質については代表的パラメータを代入し、アンテナ特性の解析シミュレーションを行い、干渉度、及びＰＳＲにおける各振動の電界強度を求める。ここでは、当該計算結果に基づき、直径１０ｃｍの坑井内で使用するための、長さ１．３４ｍ、直径５ｍｍの給電線の端部に長さ０．２ｍ、直径２ｍｍのダイポールアンテナが４個、給電線に対して半径３．５ｃｍの円周上に等間隔に配置されたダイポールアレイアンテナを直径９ｃｍのＦＲＰ製ベッセル内に収納して作製した。 First, the dipole array antenna is designed so that f0 (upper limit of the first frequency band) <f1 (lower limit of the second frequency band). For the medium outside the well, representative parameters are substituted, and an antenna characteristic analysis simulation is performed to obtain the interference degree and the electric field strength of each vibration in the PSR. Here, based on the calculation result, four dipole antennas having a length of 1.34 m, a diameter of 5 mm and a diameter of 2 mm at the end of a feeder line having a length of 1.34 m and a diameter of 5 mm for use in a well having a diameter of 10 cm, Dipole array antennas arranged at equal intervals on a circumference of a radius of 3.5 cm with respect to the feeder line were housed in a FRP vessel having a diameter of 9 cm.
次に、坑井の外の岩石を採出して、坑井の外の媒質の比誘電率（＝９．７）を求める。坑井の壁とベッセルの間は水（比誘電率８０）で満たされ、ベッセルの周囲には水の円筒状の層が形成されているとして、干渉度及びＰＳＲにおけるｍ次（ｍ＝０、１、２）の振動に対応する電界強度を、再度計算しなおすことができる。当該計算結果を図２及び図３に示す。図２は干渉度Ｉ（ｆ）の周波数依存性を示すグラフ、図３はＰＳＲにおける各振動の電界強度の周波数依存性を示すグラフである。尚、図３中、０次、１次、２次の振動に対応する電界強度を夫々、破線、点線、一点鎖線で示し、全ての振動成分の和で表される、実際の受信電圧を実線で示している。図２及び図３において、干渉度Ｉ（ｆ）が−１０ｄＢ以下となる上限周波数ｆ０、及び、ＰＳＲにおける１次の振動に対応する電界強度が０次のそれと等しくなる下限周波数ｆ１は、ｆ０＝１３８ＭＨｚ、ｆ１＝２７７ＭＨｚであり、ｆ０＜ｆ１である。 Next, the rock outside the well is extracted, and the relative dielectric constant (= 9.7) of the medium outside the well is obtained. The space between the well wall and the vessel is filled with water (relative dielectric constant 80), and a cylindrical layer of water is formed around the vessel, and the m-th order (m = 0, The electric field strength corresponding to the vibrations 1 and 2) can be recalculated. The calculation results are shown in FIGS. FIG. 2 is a graph showing the frequency dependence of the interference degree I (f), and FIG. 3 is a graph showing the frequency dependence of the electric field strength of each vibration in the PSR. In FIG. 3, the electric field strengths corresponding to the 0th, 1st, and 2nd vibrations are indicated by broken lines, dotted lines, and alternate long and short dash lines, respectively. Is shown. 2 and 3, the upper limit frequency f0 at which the degree of interference I (f) is −10 dB or less and the lower limit frequency f1 at which the electric field intensity corresponding to the first order vibration in the PSR is equal to that of the zeroth order are f0 = 138 MHz, f1 = 277 MHz, and f0 <f1.
坑井１０２の送信アンテナ部を介してステップ周波数連続波（ＳＦＣＷ）が放射され、ダイポールアレイアンテナに受信された電磁波の受信電圧のパワースペクトルを、送信アンテナ給電点での送信電圧の大きさに対するダイポールアレイアンテナで受信された受信電圧の大きさの比として、四つのダイポールアンテナ毎に図４（ａ）に示す。当該受信電磁波に対し、異なる帯域通過フィルタＡとＢを用いてフィルタ処理を行い、受信波の到来方向の推定を行った。当該帯域通過フィルタＡとＢの周波数特性を図４（ｂ）及び図４（ｃ）に示す。図４（ｂ）に示されるフィルタＡは広帯域で通過するハニングウィンドウ型のフィルタであり、図４（ｃ）に示されるフィルタＢは本発明の、ダイポールアンテナと給電線間の、及び、ダイポールアンテナ間の干渉を考慮した、ｆ０とｆ１の間の第３周波数帯域のみを通過させるハニングウィンドウ型のフィルタである。 Step frequency continuous wave (SFCW) is radiated through the transmission antenna part of the well 102, and the power spectrum of the reception voltage of the electromagnetic wave received by the dipole array antenna is expressed as a dipole with respect to the magnitude of the transmission voltage at the transmission antenna feeding point. FIG. 4A shows the ratio of the magnitudes of the received voltages received by the array antenna for each of the four dipole antennas. The received electromagnetic wave was subjected to filter processing using different bandpass filters A and B, and the arrival direction of the received wave was estimated. The frequency characteristics of the bandpass filters A and B are shown in FIGS. 4 (b) and 4 (c). The filter A shown in FIG. 4B is a Hanning window type filter that passes in a wide band, and the filter B shown in FIG. 4C is a dipole antenna and a dipole antenna according to the present invention. This is a Hanning window type filter that allows only the third frequency band between f0 and f1 to pass through in consideration of the interference between them.
図５（ａ）に図４（ｂ）のフィルタＡの周波数特性を逆フーリエ変換することに得られる、フィルタＡの周波数特性を持つ入射パルスの時間領域波形を示す。図５（ａ）に示される入射パルスが送信されたとき、当該入射パルス波が各ダイポールアンテナにて受信される受信波の時間領域波形は、図４（ａ）のパワースペクトルを用いて、図４（ａ）のパワースペクトルに図４（ｂ）で示されるフィルタを乗じて逆フーリエ変換することにより得られる。図５（ｂ）に当該受信波のダイポールアンテナ毎の時間領域波形を示す。図５（ｃ）に、図５（ｂ）の時間領域波形を用いて受信波の到来方向の推定を行った結果を示す。到来方向の推定が精確に行えているのは直接波の初動部分である５５ｎｓ〜６０ｎｓ付近に限られていることが分かる。 FIG. 5A shows a time domain waveform of an incident pulse having the frequency characteristic of the filter A, which is obtained by performing inverse Fourier transform on the frequency characteristic of the filter A of FIG. 4B. When the incident pulse shown in FIG. 5 (a) is transmitted, the time domain waveform of the received wave in which the incident pulse wave is received by each dipole antenna is shown in the figure using the power spectrum of FIG. 4 (a). It is obtained by multiplying the power spectrum of 4 (a) by the filter shown in FIG. 4 (b) and performing inverse Fourier transform. FIG. 5B shows a time domain waveform of each received wave for each dipole antenna. FIG. 5C shows the result of estimation of the arrival direction of the received wave using the time domain waveform of FIG. It can be seen that the direction of arrival can be estimated accurately only in the vicinity of 55 ns to 60 ns, which is the initial motion part of the direct wave.
図６（ａ）に図４（ｃ）のフィルタＢの周波数特性を逆フーリエ変換することに得られる、フィルタＢの周波数特性を持つ入射パルスの時間領域波形を示す。図６（ａ）に示される入射パルスが送信されたとき、当該入射パルス波が各ダイポールアンテナにて受信される受信波の時間領域波形は、図４（ａ）のパワースペクトルを用いて、図４（ａ）のパワースペクトルに図４（ｃ）で示されるフィルタを乗じて逆フーリエ変換することにより得られる。図６（ｂ）に当該受信波のダイポールアンテナ毎の時間領域波形を示す。図６（ｃ）に、図６（ｂ）の時間領域波形を用いて受信波の到来方向の推定を行った結果を示す。直接波のエネルギーが高い、５０ｎｓから７０ｎｓの全領域において到来方向の推定が精確に行えていることがわかる。 FIG. 6A shows a time domain waveform of an incident pulse having the frequency characteristic of the filter B, which is obtained by performing inverse Fourier transform on the frequency characteristic of the filter B of FIG. 4C. When the incident pulse shown in FIG. 6 (a) is transmitted, the time domain waveform of the received wave in which the incident pulse wave is received by each dipole antenna is shown in the figure using the power spectrum of FIG. 4 (a). It is obtained by multiplying the power spectrum of 4 (a) by the filter shown in FIG. 4 (c) and performing inverse Fourier transform. FIG. 6B shows a time domain waveform of each received wave for each dipole antenna. FIG. 6C shows the result of estimating the arrival direction of the received wave using the time domain waveform of FIG. 6B. It can be seen that the direction of arrival is accurately estimated in the entire region from 50 ns to 70 ns where the energy of the direct wave is high.
図５（ｃ）及び図６（ｃ）の点Ｘに相当する、受信波の６３ｎｓ付近の時間領域波形を用いて、受信波の到来方向の推定を行った場合の結果を図７に示す。図７中の丸印は、各ダイポールアンテナが受信した受信波の到来時刻と当該アンテナの存在する方向を示す。図７では、ダイポールアンテナ毎の受信波形間の位相遅延（波形の位相が同じところの時間差）、即ち到来波の受信波形が極大・極小になる時間のダイポールアンテナ毎の差を解析することにより受信波の到来方向の推定を行っている。当該ダイポールアンテナ毎の到来時間差は、円周上に配列しているダイポールアンテナの方位角に対し正弦関数で表されるので、実際に測定された当該ダイポールアンテナ毎の到来時間を正弦関数で近似し、最小自乗法を用いてフィッティングし、正弦関数の極小点を求めることにより、受信波の到来方向及び到来時間の推定を行うことができる。 FIG. 7 shows the result when the arrival direction of the received wave is estimated using the time-domain waveform around 63 ns of the received wave, which corresponds to the point X in FIGS. 5C and 6C. The circles in FIG. 7 indicate the arrival time of the received wave received by each dipole antenna and the direction in which the antenna exists. In FIG. 7, the phase delay between the received waveforms for each dipole antenna (the time difference where the phase of the waveform is the same), that is, the time difference between the dipole antennas for the time when the received waveform of the incoming wave is maximized or minimized is The direction of arrival of waves is estimated. Since the arrival time difference for each dipole antenna is expressed by a sine function with respect to the azimuth angle of the dipole antennas arranged on the circumference, the arrival time for each dipole antenna actually measured is approximated by a sine function. The arrival direction and the arrival time of the received wave can be estimated by fitting using the least square method and obtaining the minimum point of the sine function.
図７（ａ）は図４（ｂ）に示される広帯域フィルタＡを用いてフィッティングを行った場合の結果であり、正弦関数によるフィッティングがうまくいっていないことが分かる。これはダイポールアンテナと給電線間の干渉、及びダイポールアンテナ間の干渉により、受信波の到来方向の推定が困難な周波数帯域が広帯域フィルタＡに含まれているためである。このため、推定された受信波の到来方向と真の方向とのずれが非常に大きく、受信波の到来方向の推定を行うことができていない。 FIG. 7A shows the result when fitting is performed using the broadband filter A shown in FIG. 4B, and it can be seen that fitting by a sine function is not successful. This is because the broadband filter A includes a frequency band in which it is difficult to estimate the arrival direction of the received wave due to interference between the dipole antenna and the feeder line and interference between the dipole antennas. For this reason, the difference between the estimated arrival direction of the received wave and the true direction is very large, and the arrival direction of the received wave cannot be estimated.
図７（ｂ）は図４（ｃ）に示される、ダイポールアンテナと給電線間の、及び、ダイポールアンテナ間の干渉を考慮した、ｆ０とｆ１の間の第３周波数帯域のみを通過させるフィルタＢを用いてフィッティングを行った場合の結果であり、各到来時間は正弦関数で非常に良くフィッティングできている。このため、推定された受信波の到来方向は真の方向とほぼ一致し、受信波の到来方向の推定を精確に行うことができている。 FIG. 7B shows the filter B shown in FIG. 4C that passes only the third frequency band between f0 and f1 in consideration of interference between the dipole antenna and the feed line and between the dipole antennas. This is a result of fitting using, and each arrival time can be fitted very well with a sine function. For this reason, the estimated arrival direction of the received wave substantially coincides with the true direction, and the arrival direction of the received wave can be estimated accurately.
従って、本発明の受信波の到来方向の推定が可能な第３周波数帯域を有するダイポールアンテナを用いて電磁波を受信し、当該受信波のうち到来方向の推定が困難な第１及び第２周波数帯域の周波数成分を帯域通過フィルタにより通過させない処理を行うことにより、受信波の到来方向の推定を精確に行うことができる。 Accordingly, the first and second frequency bands in which the electromagnetic wave is received using the dipole antenna having the third frequency band capable of estimating the arrival direction of the received wave of the present invention, and the arrival direction of the received wave is difficult to estimate. By performing a process that does not pass the frequency component of the received signal by the band pass filter, the arrival direction of the received wave can be accurately estimated.
以上、上述の実施形態は本発明の好適な実施形態の一例である。本発明の実施形態はこれに限定されるものではなく、本発明の要旨を逸脱しない範囲内において種々の変形実施が可能である。 The above-described embodiment is an example of a preferred embodiment of the present invention. The embodiment of the present invention is not limited to this, and various modifications can be made without departing from the gist of the present invention.
〈別実施形態〉
以下、本発明の別実施形態について説明する。
<Another embodiment>
Hereinafter, another embodiment of the present invention will be described.
〈１〉上述の本システム１００は、送信アンテナ１０６を送信用の坑井１０１内に、受信アンテナ１０８を受信用の坑井１０２内に、夫々別々の坑井に挿入する構成であるが、送信アンテナ１０６と受信アンテナ１０８の双方とも同一の坑井内に挿入して使用することもでき、これにより不要な坑井を掘削する必要が無くなる。送信アンテナ１０６から放射され、地中内の亀裂、断層、地下水などにより反射された電磁波を受信用ダイポールアレイアンテナ１０８が受信する。受信用ダイポールアレイアンテナ１０８と送信アンテナ１０６の両方を同一坑井で深度方向に走査し、地中物体からの反射受信波の到来方向の推定を精確に行い、推定された受信波の到来方向と受信波の到来時刻との関係を解析することにより、地中の詳細な三次元位置情報を得ることができる。 <1> The system 100 described above has a configuration in which the transmitting antenna 106 is inserted into the transmitting well 101 and the receiving antenna 108 is inserted into the receiving well 102, respectively. Both the antenna 106 and the receiving antenna 108 can be used by being inserted into the same well, thereby eliminating the need for excavating unnecessary wells. The reception dipole array antenna 108 receives electromagnetic waves radiated from the transmission antenna 106 and reflected by cracks, faults, groundwater, etc. in the ground. Both the reception dipole array antenna 108 and the transmission antenna 106 are scanned in the depth direction in the same well, and the arrival direction of the reflected reception wave from the underground object is accurately estimated. By analyzing the relationship with the arrival time of the received wave, detailed three-dimensional position information in the ground can be obtained.
〈２〉また、上述の本システム１００は、ベクトルネットワークアナライザ１１１が発生したステップ周波数連続波をダイポールアレイアンテナが受信し、ベクトルネットワークアナライザ１１１により得られる周波数領域のデータを直接解析し、受信波の到来方向の推定を行う構成であるが、所定の周波数特性を持つ送信パルスをダイポールアンテナが受信し、受信した時間領域の波形を解析することにより受信波の到来方向の推定を行うシステム構成としても良い。この場合、上記第３周波数帯域のみに周波数成分を持つ送信パルスを坑井１０１の送信アンテナ１０６から送信し、坑井１０２のダイポールアンテナ１０８が受信した時間領域の受信波形を解析することにより本発明の効果が得られる。 <2> Further, in the system 100 described above, the dipole array antenna receives the step frequency continuous wave generated by the vector network analyzer 111, directly analyzes the frequency domain data obtained by the vector network analyzer 111, and the received wave Although it is a configuration that estimates the direction of arrival, a system configuration that estimates the direction of arrival of the received wave by receiving a transmission pulse with a predetermined frequency characteristic by the dipole antenna and analyzing the received time domain waveform good. In this case, the transmission pulse having the frequency component only in the third frequency band is transmitted from the transmission antenna 106 of the well 101, and the received waveform in the time domain received by the dipole antenna 108 of the well 102 is analyzed. The effect is obtained.
〈３〉上述の本システム１００では、ダイポールアンテナ毎の受信波形間の位相遅延を用いて受信波の到来方向の推定を行っているが、上記第３周波数帯域が高周波数帯域にあり、ダイポールアンテナ毎の受信波形間の位相差がπ以上ずれる場合には、この推定方法は適用できない。しかしながら、この場合であっても、当該第３周波数帯域のみを通過させるフィルタを用いて受信波形をフィルタ処理し、処理後の受信波形間の群遅延（時間領域で受信波形の包絡線を取り、当該包絡線が極大値を取る時刻の時間差）を求めることにより受信波の到来方向の推定を精確に行うことができる。 <3> In the system 100 described above, the arrival direction of the received wave is estimated using the phase delay between the received waveforms for each dipole antenna, but the third frequency band is in the high frequency band, and the dipole antenna This estimation method cannot be applied when the phase difference between the received waveforms is shifted by π or more. However, even in this case, the received waveform is filtered using a filter that passes only the third frequency band, and the group delay between the received waveforms after processing (takes the envelope of the received waveform in the time domain, The arrival direction of the received wave can be accurately estimated by obtaining the time difference between the times when the envelope takes a maximum value.
〈４〉上述の実施形態において、給電線（中心導体柱）の端部にダイポールアンテナを配置したアレイアンテナを設計し、受信波の到来方向の推定を精確に行う方法を開示したが、図１の受信アンテナ１０８の構成に見られるような、給電線の端部と中央部に、上下二つのダイポールアレイアンテナを配置した場合についても、同様に受信波の到来方向の推定を精確に行うことができる。この場合、上下のアンテナ間の干渉が問題になるが、ダイポールアンテナ間の干渉は軸に垂直な方向で強く、軸方向では弱いため、上下のアンテナ間の間隔が開いているならば、上下のアレーアンテナ間の干渉は殆ど起こらず、上下のアレーアンテナ夫々について、独立にアンテナの設計を行うことができる。即ち、上側に設置されたアレーアンテナの干渉度Ｉ（ｆ）及びＰＳＲが生じる周波数帯域については図１１（Ｅ）で、下側に設置されたアレーアンテナのそれは図１１（Ａ）で、夫々近似される。上下に二つのダイポールアレイアンテナを配置し、上下方向のダイポールアンテナ間の受信波の到来時間差を解析することにより、受信アンテナを坑井の深さ方向に移動させることなく、受信波の到来方向の方位角のみならず、受信波の到来方向の仰角についても精確に推定することができる。 <4> In the above-described embodiment, an array antenna in which a dipole antenna is arranged at the end of a feeder line (central conductor column) is designed, and a method for accurately estimating the arrival direction of a received wave has been disclosed. Even when two upper and lower dipole array antennas are arranged at the end and center of the feeder line as seen in the configuration of the receiving antenna 108, the arrival direction of the received wave can be accurately estimated in the same manner. it can. In this case, interference between the upper and lower antennas becomes a problem, but the interference between the dipole antennas is strong in the direction perpendicular to the axis and weak in the axial direction. Interference between array antennas hardly occurs, and antenna design can be performed independently for the upper and lower array antennas. That is, the frequency band where the interference degree I (f) of the array antenna installed on the upper side and the PSR are generated is shown in FIG. 11E, and that of the array antenna installed on the lower side is approximated in FIG. Is done. By arranging two dipole array antennas at the top and bottom and analyzing the arrival time difference of the received waves between the dipole antennas in the vertical direction, the direction of the received waves can be measured without moving the receiving antenna in the depth direction of the well. It is possible to accurately estimate not only the azimuth angle but also the elevation angle of the incoming direction of the received wave.
本発明は、入射電磁波の地中からの反射波を受信することにより、地中内の亀裂、断層、地下水などの位置及び形状を計測する三次元位置推定システム、及びこれに用いるアンテナ素子に利用可能である。 INDUSTRIAL APPLICABILITY The present invention is used for a three-dimensional position estimation system that measures the position and shape of cracks, faults, groundwater, etc. in the ground by receiving a reflected wave of the incident electromagnetic wave from the ground, and an antenna element used therefor Is possible.
１００： 本発明に係る三次元位置推定システム
１０１，１０２： 坑井
１０３，１０７： ＦＲＰ製ベッセル
１０６： 送信アンテナ
１０８： 受信アンテナ（ダイポールアレイアンテナ）
１０９： 電気／光変換ユニット
１１０： 方位計
１１１： ベクトルネットワークアナライザ
１１２： 電気／光変換部
１１３，１１９： アンプ
１１４： レーザダイオード
１１７： 光／電気変換部
１１８： フォトダイオード
１２０： パソコン
８００： ダイポールアレイアンテナ
８０１ａ〜８０１ｄ： アンテナ素子（ダイポールアンテナ）
８０２ａ〜８０２ｄ： ＲＦトランス
８０３ａ〜８０３ｄ： 同軸ケーブル
８０４： 中心導体柱（給電線）
100: Three-dimensional position estimation system 101, 102 according to the present invention: Well 103, 107: FRP vessel 106: Transmitting antenna 108: Receiving antenna (dipole array antenna)
109: Electrical / optical conversion unit 110: Direction meter 111: Vector network analyzer 112: Electrical / optical conversion unit 113, 119: Amplifier 114: Laser diode 117: Optical / electrical conversion unit 118: Photo diode 120: Personal computer 800: Dipole array Antennas 801a to 801d: Antenna element (dipole antenna)
802a to 802d: RF transformers 803a to 803d: coaxial cable 804: central conductor column (feed line)
Claims (4)
中心導体柱の外周に前記中心導体柱と平行な方向に伸びる複数のアンテナ素子が配置された、前記中心導体柱の長さよりも前記アンテナ素子の長さが短いダイポールアレイアンテナを、ベッセル内に収納して設置し、
前記ダイポールアレイアンテナが受信した地中から到来する電磁波を前記アンテナ素子毎に解析し、前記電磁波の前記アンテナ素子間の遅延時間を求めることにより前記電磁波の到来方向の推定を行い、地中の三次元位置情報を得る三次元位置推定システムであって、
前記ダイポールアレイアンテナは、前記坑井内に設置したときに、前記中心導体柱と前記アンテナ素子間の干渉の影響により受信波の到来方向の推定が困難な第１周波数帯域の上限周波数が、前記アンテナ素子間の共振の影響により受信波の到来方向の推定が困難な第２周波数帯域の下限周波数よりも小さくなるように設定されており、
前記ダイポールアレイアンテナが受信した前記電磁波のうち、前記第１周波数帯域と前記第２周波数帯域を帯域通過フィルタにより通過させず、前記第１周波数帯域と前記第２周波数帯域の間の帯域である受信波の到来方向の推定が可能な第３周波数帯域のみ通過させる処理を行った後、当該フィルタ処理後の時間領域の前記電磁波を前記アンテナ素子毎に解析することを特徴とする三次元位置推定システム。 In the well drilled underground,
A dipole array antenna in which a plurality of antenna elements extending in a direction parallel to the central conductor column are arranged on the outer periphery of the central conductor column and the antenna element is shorter than the length of the central conductor column is stored in a vessel Installed,
Analyzing the electromagnetic wave coming from the ground received by the dipole array antenna for each antenna element, estimating the arrival direction of the electromagnetic wave by obtaining the delay time between the antenna elements of the electromagnetic wave, A three-dimensional position estimation system for obtaining original position information,
When the dipole array antenna is installed in the well, the upper limit frequency of a first frequency band in which it is difficult to estimate the arrival direction of a received wave due to the influence of interference between the central conductor column and the antenna element, It is set to be smaller than the lower limit frequency of the second frequency band where it is difficult to estimate the arrival direction of the received wave due to the influence of resonance between elements,
Among the electromagnetic waves received by the dipole array antenna, reception is a band between the first frequency band and the second frequency band without passing the first frequency band and the second frequency band by a band pass filter. A three-dimensional position estimation system characterized by analyzing the electromagnetic wave in the time domain after the filter processing for each antenna element after performing processing to pass only a third frequency band in which the direction of arrival of waves can be estimated .
前記中心導体柱に散乱され前記アンテナ素子に受信される散乱波の受信電圧と直接前記アンテナ素子に受信される受信電圧との比により表される干渉度Ｉ（ｆ）が、周波数の増加に伴い一旦極大値を取った後減少して−１０ｄＢ以下となる最小の周波数で定義され、
前記第２周波数帯域の下限周波数が、
ＰＳＲ（Ｐｈａｓｅ Ｓｅｑｕｅｎｃｅ Ｒｅｓｏｎａｎｃｅ）における０次の振動に対応する電界強度が１次の振動に対応する電界強度と一致する周波数で定義されることを特徴とする請求項１に記載の三次元位置推定システム。 The upper limit frequency of the first frequency band is
The degree of interference I (f) represented by the ratio between the received voltage of the scattered wave scattered by the central conductor column and received by the antenna element and the received voltage directly received by the antenna element increases with an increase in frequency. It is defined as the minimum frequency that takes a maximum once and then decreases to -10 dB or less.
The lower limit frequency of the second frequency band is
2. The three-dimensional position estimation system according to claim 1, wherein an electric field intensity corresponding to a zeroth order vibration in a PSR (Phase Sequence Resonance) is defined by a frequency that matches an electric field intensity corresponding to the first order vibration. .
中心導体柱の外周に前記中心導体柱と平行な方向に伸びる複数のアンテナ素子が配置された、前記中心導体柱の長さよりも前記アンテナ素子の長さが短いダイポールアレイアンテナを、ベッセル内に収納して設置し、
前記ダイポールアレイアンテナが受信した地中から到来する電磁波を前記アンテナ素子毎に解析し、前記電磁波の前記アンテナ素子間の遅延時間を求めることにより前記電磁波の到来方向の推定を行い、地中の三次元位置情報を得る三次元位置推定システムであって、
前記ダイポールアレイアンテナは、前記坑井内に設置したときに、前記アンテナ素子間の共振の影響により受信波の到来方向の推定が困難な第２周波数帯域を有する一方、前記中心導体柱に散乱され前記アンテナ素子に受信される散乱波の受信電圧と直接前記アンテナ素子に受信される受信電圧との比により表される干渉度Ｉ（ｆ）の極大値が−１０ｄＢ以下となって、前記中心導体柱と前記アンテナ素子間の干渉の影響を無視できるように設定されており、
前記ダイポールアレイアンテナが受信した前記電磁波のうち、前記第２周波数帯域を帯域通過フィルタにより通過させず、前記第２周波数帯域の下限周波数よりも低周波数帯域である受信波の到来方向の推定が可能な第３周波数帯域のみ通過させる処理を行った後、当該フィルタ処理後の時間領域の前記電磁波を前記アンテナ素子毎に解析することを特徴とする三次元位置推定システム。 In the well drilled underground,
A dipole array antenna in which a plurality of antenna elements extending in a direction parallel to the central conductor column are arranged on the outer periphery of the central conductor column and the antenna element is shorter than the length of the central conductor column is stored in a vessel Installed,
Analyzing the electromagnetic wave coming from the ground received by the dipole array antenna for each antenna element, estimating the arrival direction of the electromagnetic wave by obtaining the delay time between the antenna elements of the electromagnetic wave, A three-dimensional position estimation system for obtaining original position information,
When the dipole array antenna is installed in the well, the dipole array antenna has a second frequency band in which it is difficult to estimate the arrival direction of the received wave due to the resonance between the antenna elements, and is scattered by the central conductor column. The maximum value of the interference degree I (f) represented by the ratio of the received voltage of the scattered wave received by the antenna element and the received voltage directly received by the antenna element is −10 dB or less, and the central conductor column And the influence of interference between the antenna elements is set to be negligible,
Among the electromagnetic waves received by the dipole array antenna, it is possible to estimate the direction of arrival of a received wave that is lower than the lower limit frequency of the second frequency band without passing the second frequency band by a band pass filter. A three-dimensional position estimation system characterized by analyzing the electromagnetic wave in the time domain after the filtering process for each antenna element after performing a process of passing only the third frequency band.
ＰＳＲ（Ｐｈａｓｅ Ｓｅｑｕｅｎｃｅ Ｒｅｓｏｎａｎｃｅ）における０次の振動に対応する電界強度が１次の振動に対応する電界強度と一致する周波数で定義されることを特徴とする請求項３に記載の三次元位置推定システム。
The lower limit frequency of the second frequency band is
The three-dimensional position estimation system according to claim 3, wherein an electric field strength corresponding to a zeroth order vibration in a PSR (Phase Sequence Resonance) is defined by a frequency that matches an electric field strength corresponding to the first order vibration. .
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