JP5203829B2 - Synthetic aperture sonar - Google Patents

Description

  The present invention relates to a synthetic aperture sonar including a single transmitter and a plurality of receivers arranged in a moving direction, and more particularly to a synthetic aperture sonar that corrects fluctuation of a traveling body.

  Synthetic aperture sonar is a sonar that applies the technology developed in synthetic aperture radar. In order to improve the resolution of the radar, it is necessary to increase the aperture length of the receiver. In other words, a synthetic aperture radar is mounted on an aircraft, an artificial satellite, or the like, and continuously receives received radar waves while moving in orbit. Is synthesized. As a result, the resolution is improved by increasing the aperture length equivalently. The synthetic aperture sonar is mounted on a water or underwater vehicle based on the same principle to improve the resolution of the sonar.

  As shown in Non-Patent Document 1 and Non-Patent Document 2, synthetic aperture processing is known as a CS (Chirp Scaling) algorithm using fast Fourier transform and complex multiplication. In particular, Non-Patent Document 2 shows a method of performing shake correction by multiplying a time axis signal by a shake correction function.

  In the synthetic aperture sonar, the acoustic wave underwater propagation speed of 1,500 m / s is very slow compared to the radar wave air propagation speed of 300,000 km / s. It is necessary to take a long pulse repetition period until the start of transmission. On the other hand, in this case, the moving distance between the samples of the traveling body becomes extremely short, and the synthetic aperture length cannot be obtained. Furthermore, since the speed of the traveling body is too slow, there arises a disadvantage that the speed cannot be kept constant.

  That is, the reciprocal of this pulse repetition period is the pulse repetition frequency PRF, and it is necessary to satisfy the following (Equation 1) between the vehicle speed ν and the receiving aperture width D.

この問題は、１回の送信に対して１台の受波器で受信する単一受波器の場合、非特許文献３に示すように１回の送信に対して移動方向に配列した複数台の受波器で同時に受信するＤＰＣＡ（Displaced Phase-Center Antenna）方式により解決することができる。

In the case of a single receiver that receives a single transmission with respect to a single transmission, the problem is that, as shown in Non-Patent Document 3, a plurality of units arranged in the moving direction with respect to a single transmission. This can be solved by the DPCA (Displaced Phase-Center Antenna) method in which the receiver is simultaneously received.

  DPCA is the sum of the propagation distance from the transmitter to the target and from the target to the receiver is the round-trip propagation distance from the virtual transmitter to the target located between the transmitter and receiver. Based on the principle of being almost equal. This virtual transducer is called DPCA, and is a method of performing synthetic aperture processing on the assumption that a signal is transmitted / received from DPCA.

  When receiving with a single receiver, the azimuth sampling frequency in the moving direction (hereinafter referred to as azimuth sampling frequency fas) is the pulse repetition frequency PRF. In the case of the DPCA method, the azimuth sampling frequency fas can be made higher than the pulse repetition frequency PRF by arranging the intervals of the plurality of receivers in accordance with the azimuth sampling interval. At this time, there is a relationship of (Equation 2) with the number E of receivers.

ここで、ｄは受波開口長ではなく受波器間隔である。パルス繰り返し周波数ＰＲＦは、（式２）に基づき航走体速度νの実測値により時々刻々補正される。以降ＤＰＣＡ方式の合成開口ソーナーをＤＰＣＡ合成開口ソーナーと称することにする。

Here, d is not the receiving aperture length but the receiver interval. The pulse repetition frequency PRF is corrected from time to time based on the measured value of the vehicle speed ν based on (Equation 2). Hereinafter, the DPCA type synthetic aperture sonar is referred to as a DPCA synthetic aperture sonar.

With reference to FIG. 1, a conventional shake correction process will be described. Here, FIG. 1 is a block diagram of a synthetic aperture sonar. In FIG. 1, the synthetic aperture sonar 600 includes a transmission / reception processing unit 100, a shake correction processing unit 200, a synthetic aperture processing unit 300, a display control processing unit 400, and a shake detection processing unit 500. The transmission / reception unit 100 includes a receiver 110, a transmitter 120, a receiver 130, a transmitter 140, and a PRF controller 150.

  The transmitter 140 generates a transmission signal based on the external setting, outputs the transmission signal with the transmission trigger signal from the PRF controller 150 as a period, and sends it to the transmitter 120. The transmitter 120 performs electroacoustic conversion on the transmission signal and transmits the signal into water. The PRF controller 150 performs control based on the actual speed ν based on the speed signal 10 (Equation 3),

を計算し、送信器１４０に送信トリガー信号として出力する。受波器１１０は、受波エコーを音響電気変換する。受信器１３０は、受波器１１０からの受信信号を、増幅、濾波、アナログ／ディジタル変換の後、ベースバンドに周波数変換する。

Is output to the transmitter 140 as a transmission trigger signal. The receiver 110 performs acoustoelectric conversion on the received echo. The receiver 130 frequency-converts the received signal from the receiver 110 to baseband after amplification, filtering, and analog / digital conversion.

  The shake correction processing unit 200 includes a shake corrector 210 and a correction amount calculator 220. The correction amount calculator 220 calculates a phase correction amount Δφ based on the correction amount τ based on the shake information coming from the shake detection unit 500 according to (Equation 4) and outputs it to the shake corrector 210 as a correction signal.

動揺補正器２１０は、補正量計算器２２０からの補正量に基づき受信信号に（式５）を複素乗算して、位相回転により動揺量を補正する。

The fluctuation corrector 210 performs complex multiplication of (Equation 5) on the received signal based on the correction amount from the correction amount calculator 220 and corrects the fluctuation amount by phase rotation.

合成開口処理部３００は、合成開口処理を行う部分である。合成開口処理部３００は、レンジ方向とアジマス方向の２次元時間信号を入力し、レンジ方向とアジマス方向の２次元座標信号を表示制御処理部４００に出力する。ここで、アジマス方向は航走体の航走方向、レンジ方向は水平面内でアジマス方向に垂直方向である。なお、合成開口処理部３００は、ＣＳアルゴリズム等が非特許文献１および非特許文献２に記載がある。

The synthetic aperture processing unit 300 is a portion that performs synthetic aperture processing. The synthetic aperture processing unit 300 inputs a two-dimensional time signal in the range direction and the azimuth direction, and outputs a two-dimensional coordinate signal in the range direction and the azimuth direction to the display control processing unit 400. Here, the azimuth direction is the traveling direction of the traveling body, and the range direction is a direction perpendicular to the azimuth direction in the horizontal plane. The synthetic aperture processing unit 300 has a CS algorithm described in Non-Patent Document 1 and Non-Patent Document 2.

The display control processing unit 400 is formatting, level adjustment, and a man-machine interface for displaying processing results. The display control processing unit 400 is known to those skilled in the art. The motion detection processing unit 500 is, for example, a high-precision inertial guidance device and is commercially available from France IXSEA. Further, for example, Non-Patent Document 5 discloses a method for acoustically detecting fluctuation from a received signal, both of which are publicly known.

The background art described above has the following problems. The first problem is that the fluctuation correction is not compatible with the DPCA arrangement consisting of one transmitter and a plurality of receivers. The second problem is that the distance traveled by the receiver varies with the propagation time in addition to the speed of the vehicle. However, the error due to the propagation time cannot be corrected. The third problem is that the synthetic aperture processing is based on a single array consisting of one transmitter and one receiver, so that the error in the DPCA array as seen in Patent Document 2 cannot be corrected. That is.
It is an object of the present invention to provide a synthetic aperture sonar that simultaneously corrects the above-mentioned errors together with fluctuation correction.

Japanese Patent Laid-Open No. 10-142333 US Pat. No. 4,244,036 R. K. Raney, H. Runge, I. G. Cumming, R. Bamler, and F. H. Wong, “Precision of SAR processing using chirp scaling”, IEEE Trans. Geosci. Remote Sensing, vol. 32, pp. 786-799, July 1994. A. Moreira, J. Mittermayer, and R. Scheiber “Extended chirp Scaling Algorithm for Air- and Spaceborne SAR Data Processing in Stripmap and ScanSAR Imaging Modes”, IEEE Trans. Geosci. Remote Sensing, vol. 34. pp. 1123-1136 , Sept. 1996. E. J. Kelly and G. N. Tsandouls, “A Displaced Phase Center Antenna Concept for Space Based Radar Applications”, IEEE Eascon, pp. 225-230, Sept. 1983. A. Bellettini, and M. A. Pinto, “Theoretical Accuracy of Synthetic Aperture Sonar Micronavigation Using a Displaced Phase- Center Antenna”, IEEE J. Oceanic Eng., Vol. 27, pp. 780-789, Oct. 2002. R. Heremans, M. Acheroy, Y. Dupont, “Motion Compensation on Synthetic Aperture Sonar Images”, IEEE Ultrasonics Symposium, pp. 152-155, Oct. 2006

  The synthetic aperture sonar is mounted on the traveling body and is subjected to fluctuations due to rotation and movement in three axial directions during traveling. The fluctuation causes a phase rotation because it slightly changes the propagation distance, and has a significant effect on the synthetic aperture processing. The problem to be solved by the present invention is to perform the shake correction of the synthetic aperture sonar based on the shake data detected by the external sensor.

  In addition to the DPCA array, which is a DPCA transducer array, as a reference for oscillation correction, an ideal single array consisting of a set of transducers that are not subject to oscillation and a transducer array identical to the DPCA array By combining the DPCA array with the DPCA array and simulating the fluctuation based on the fluctuation data detected by the external sensor to the DPCA array, the difference between the propagation distance from the reference point of the ideal single array and the DPCA array is used as the fluctuation correction amount. to correct.

That is,
Propagation distance between DPCA array after shake correction and arbitrary target point = Propagation distance between DPCA array before shake correction and arbitrary target point-(Propagation distance between virtual DPCA array with shake and reference point) (correction formula)
-Propagation distance between ideal single array and reference point without shaking)
As shown in (), it is corrected by the fluctuation correction amount in parentheses.

  The above-described problem is that a transmission / reception processing unit including a single transmitter and a plurality of receivers arranged in the moving direction, a shake detection processing unit, and a transmission / reception processing unit using the output of the shake detection processing unit. The shake correction processing unit for adding the shake correction to the received signal, the synthetic aperture processing unit, and the display control processing unit. The shake correction processing unit includes one transmitter and one unit based on the reference position information. A first propagation distance calculator for calculating an ideal propagation distance between an ideal single array of receivers and a reference position, and one virtual transmitter and a moving direction based on the reference position information. A second propagation distance calculator for calculating a virtual propagation distance between an array of a plurality of arrayed virtual receivers and a reference position, and a correction amount based on a propagation distance difference between the virtual propagation distance and the ideal propagation distance. A correction amount calculator to calculate, and a shake that corrects the received signal based on this correction amount A synthetic aperture sonar comprising a righteous be achieved.

  Since the received signal is corrected based on the propagation distance difference between the DPCA array that receives the fluctuation and the ideal single array that does not receive the fluctuation, the fluctuation correction of the synthetic aperture sonar can be performed with high accuracy without increasing the side lobe. it can.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings and mathematical formulas using examples. The same reference numerals are assigned to substantially the same parts, and the description will not be repeated.

First, the configuration of the synthetic aperture sonar will be described with reference to FIG. Here, FIG. 2 is a block diagram of the synthetic aperture sonar. In FIG. 2, the synthetic aperture sonar 700 includes a transmission / reception processing unit 100, a shaking correction processing unit 200 </ b> A, a synthetic aperture processing unit 300, a display control processing unit 400, and a shaking detection processing unit 500. The transmission / reception processing unit 100 includes a receiver 110, a transmitter 120, a receiver 130, a transmitter 140, and a PRF controller 150. Furthermore, the shake correction processing unit 200A includes a shake corrector 210, a correction amount calculator 220A, an ideal single array propagation distance calculator 230, and a virtual DPCA array propagation distance calculator 240.

  The transmitter 140 generates a transmission signal based on the external setting, outputs the transmission signal with the transmission trigger signal from the PRF controller 150 as a period, and sends it to the transmitter 120. The transmitter 120 performs electroacoustic conversion on the transmission signal and transmits the signal into water. The PRF controller 150 calculates the PRF value of (Equation 3) controlled based on the actual speed ν based on the speed signal 10 and outputs it to the transmitter 140 as a transmission trigger signal. The receiver 110 performs acoustoelectric conversion on the received echo. The receiver 130 frequency-converts the received signal from the receiver 110 to baseband after amplification, filtering, and analog / digital conversion.

The reference position information 20 is reference position information for the synthetic aperture process, and is usually provided with reference position information on the assumption that the reference position is at the center of the synthetic aperture process.
The ideal single array propagation distance calculator 230 calculates the propagation distance of the ideal single array from the reference position information 20. Here, the ideal single array is an array composed of one transmitter and one receiver. The virtual DPCA array propagation distance calculator 240 calculates the DPCA array propagation distance from the reference position information 20. Here, the DPCA arrangement is an arrangement of the transmitter and the receiver shown in FIG. 3 or FIG. The ideal single array distance and the DPCA array propagation distance are functions of only the azimuth sampling time.

The correction amount calculation unit 220A takes the propagation distance difference, which is an output of the ideal single array propagation distance calculator 230 and the virtual DPCA array propagation distance calculator 240, converts this into a phase difference as a correction amount, and a shake corrector Send to 210. The shake corrector 210 performs complex correction on the received signal coming from the receiver 130 by a correction amount, and performs shake correction by phase rotation. The synthetic aperture processing unit 300 is a portion that performs synthetic aperture processing. The synthetic aperture processing unit 300 inputs a two-dimensional time signal in the range direction and the azimuth direction, and outputs a two-dimensional coordinate signal in the range direction and the azimuth direction to the display control processing unit 400. The display control processing unit 400 is formatting, level adjustment, and a man-machine interface for displaying processing results. The fluctuation detection processing unit 500 is a highly accurate inertial guidance device. The output of the motion detection processing unit 500 is a rolling angle that is a rotation angle of three axes, a pitching angle, a yawing angle, a surging amount that is a displacement amount of three axes, a swaging amount, and a heaving amount, and is output as a time function in real time. Is done. When the traveling direction of the vehicle is defined as the x-axis, the vertical direction is defined as the z-axis, and the y-axis is defined as the right-handed system, the rolling angle is the amount of rotation about the x-axis, the pitching angle is the amount of rotation about the y-axis, and the yawing angle Is the amount of rotation about the z-axis. Similarly, the surging amount is the amount of movement in the x-axis direction, the swaging amount is the amount of movement in the y-axis direction, and the heaving amount is the amount of movement in the z-axis direction.

  The arrangement of the transmitter, receiver and DPCA will be described with reference to FIGS. Here, FIG. 3 is a block diagram for explaining an arrangement of a transmitter, a receiver and a DPCA having an odd number of receivers. FIG. 4 is a block diagram for explaining the arrangement of transmitters, receivers and DPCAs having an even number of receivers. 3 and 4, the position of the transmitter 120 is indicated by ◯, the position of the receiver 110 is indicated by ●, and the position of the DPCA is indicated by ◎. A box surrounding the transmitter 120 and the receiver 110 is a transmitter / receiver array 160. 3 and 4, the horizontal axis (x-axis) is the traveling direction of the traveling body, and the vertical direction (t-axis) is the time.

  In FIG. 3, consider a case where the transducer array 160 has one transmitter 120 and seven receivers 110 (E = 7). The coordinate of the x-axis of the transmitter 120 at the top of FIG. When the receiver interval is d, the position of the receiver 120 is −3d, −2d, −d, 0, d, 2d, and 3d. Further, the positions of DPCA are -1.5d, -d, -0.5d, 0, 0.5d, d, and 1.5d. Further, in order to make DPCA continuous, the transmission timing of the transmitter 120 is every E · d / 2 (3.5d) movement.

  In FIG. 4, consider a case where the transducer array 160 has one transmitter 120 and six receivers 110 (E = 6). The x-axis coordinate of the transmitter 120 at the top of FIG. If the receiver interval is d, the positions of the receiver 120 are -2.5d, -1.5d, -0.5d, 0.5d, 1.5d, and 2.5d. The positions of DPCA are −1.25d, −0.75d, −0.25d, 0.25d, 0.75d, and 1.25d. Further, in order to make DPCA continuous, the transmission timing of the transmitter 120 is every E · d / 2 (3d) movement.

Oscillation correction describes swaying and yawing that have a large effect on the characteristics of the synthetic aperture sonar among the triaxial oscillation parameters. Other shaking parameters can be corrected by the same principle. That is, the following four shaking parameters are set.
(1) Swaying maximum amplitude Esway
(2) Swaging cycle Tsway
(3) Yawing maximum angle fyau
(4) Yawing cycle Tyau
The azimuth direction, which is the moving direction of the traveling body, is the x-axis, the range direction that is orthogonal to the moving direction is the y-axis, and the altitude direction is the z-axis. First, the coordinates of the swaying vehicle at time ta are given by (Equation 6), (Equation 7), and (Equation 8), where v is the ground speed of the vehicle and h is the altitude from the seabed.

また、動揺する送波器の座標は、航走体の座標と同じであるので、（式９）（式１０）（式１１）で与えられる。

Moreover, since the coordinates of the waved transmitter are the same as the coordinates of the traveling body, they are given by (Equation 9), (Equation 10), and (Equation 11).

一方、受波器はＥ台で構成されており、ｉ番目受波器の航走体中心からの相対距離をＬix, Ｌiy, Ｌiz（但しｉは０以上（Ｅ−１）以下の整数）として、エコー受信時のＤＰＣＡ配列のｉ番目受波器の座標は、伝搬時間Δｔaの間に航走体が移動している分を考慮し、（式１２）（式１３）（式１４）で与えられる。

On the other hand, the receiver is composed of E units, and the relative distance from the center of the traveling body of the i-th receiver is Lix, Liy, Liz (where i is an integer of 0 or more and (E-1) or less). The coordinates of the i-th receiver of the DPCA array at the time of echo reception are given by (Equation 12), (Equation 13), and (Equation 14) in consideration of the movement of the traveling body during the propagation time Δta. It is done.

基準点の座標は、例えば合成開口処理の中心に選ぶと、航走体と基準点間の直距離Ｒ０、海底からの高度ｈのとき、（式１５）（式１６）（式１７）で与えられる。

If the coordinates of the reference point are selected, for example, as the center of the synthetic aperture processing, when the straight distance R0 between the vehicle and the reference point and the altitude h from the seabed, (Equation 15) (Equation 16) (Equation 17) It is done.

これから、ＤＰＣＡ配列の送波器と基準点間の伝搬距離は、（式１８）で与えられる。また基準点とＤＰＣＡ配列のｉ番目受波器間の伝搬距離は、（式１９）で与えられる。従って、基準点とＤＰＣＡ配列のｉ番目受波器間のＤＰＣＡ伝搬距離は、（式２０）で与えられる。ここで、伝播時間は、（式２１）で与えられる。または、伝播時間は、（式２２）から、近似的に計算する。すなわち、ＰＤＣＡ配列伝搬距離計算器２４０は、（式２０を計算して、補正量計算器２２０Ａに出力する。

From this, the propagation distance between the transmitters of the DPCA array and the reference point is given by (Equation 18). The propagation distance between the reference point and the i-th receiver in the DPCA array is given by (Equation 19). Accordingly, the DPCA propagation distance between the reference point and the i-th receiver in the DPCA array is given by (Equation 20). Here, the propagation time is given by (Equation 21). Alternatively, the propagation time is approximately calculated from (Equation 22). That is, the PDCA array propagation distance calculator 240 calculates (Expression 20 and outputs it to the correction amount calculator 220A.

次に、基準点と理想単一配列の伝搬距離を求める。基準点と理想単一配列の伝搬距離は、理想単一配列の送受波器の座標をＰsinglex(ｔa), Ｐsingley(ｔa), Ｐsinglez(ｔa)として、（式２３）で与えられる。すなわち、理想単一配列伝搬距離計算器２３０は、（式２３）を計算して、補正量計算器２２０Ａに出力する。

Next, the propagation distance between the reference point and the ideal single array is obtained. The propagation distance between the reference point and the ideal single array is given by (Equation 23), where the coordinates of the transducer of the ideal single array are Psinglex (ta), Psingley (ta), and Psinglez (ta). That is, the ideal single array propagation distance calculator 230 calculates (Equation 23) and outputs it to the correction amount calculator 220A.

ここで、伝播時間による誤差も同時に補正するため、理想単一配列には伝播時間Δｔaを含めない。これより動揺補正時の伝搬距離補正量は、（式２４）により、与えられる。

Here, since the error due to the propagation time is also corrected simultaneously, the propagation time Δta is not included in the ideal single array. Thus, the propagation distance correction amount at the time of fluctuation correction is given by (Equation 24).

以上に基づき、動揺補正のための補正を、時刻ｔaにおけるｉ番目受波器出力の各々について（式２５）の位相回転を施すことにより行う。ここでは、距離の次元である（式２４）に２π／λを乗算し、２往復なのでさらに２倍している。

Based on the above, correction for fluctuation correction is performed by performing phase rotation of (Equation 25) for each i-th receiver output at time ta. Here, the distance dimension (Equation 24) is multiplied by 2π / λ, and since it is 2 round trips, it is further doubled.

ここで、航走体の時刻ｔaは、航走体のアジマスサンプリングｆasの逆数を周期とする離散値（式２６）に置き換える。

Here, the time ta of the traveling body is replaced with a discrete value (formula 26) having a cycle of the reciprocal of the azimuth sampling fas of the traveling body.

すなわち、（式２４）の伝搬距離補正量は、（式２７）で表わされる。さらに、（式２５）の位相回転は、（式２８）で与えられる。補正量計算器２２０Ａは、（式２８）を計算して、動揺補正器２１０に出力する。動揺補正器２１０は、受信器１３０からくる受信信号に補正量を複素乗算し、位相回転により動揺補正を行う。

That is, the propagation distance correction amount of (Expression 24) is expressed by (Expression 27). Further, the phase rotation of (Equation 25) is given by (Equation 28). The correction amount calculator 220 </ b> A calculates (Equation 28) and outputs it to the fluctuation corrector 210. The shake corrector 210 performs complex correction on the received signal coming from the receiver 130 by a correction amount, and performs shake correction by phase rotation.

（式２８）は、受波器の位置を示す番号ｉと航走体の位置を示す番号ｋに依存する。

(Equation 28) depends on the number i indicating the position of the receiver and the number k indicating the position of the traveling body.

  Next, the DPCA arrangement of the DPCA synthetic aperture sonar will be described with reference to FIGS. Here, in FIG. 3, the transmitter is located at the center of a plurality of receivers, and the positions of the receivers are different depending on whether the number of receivers is odd or even.

  In the DPCA array, as shown in FIGS. 3 and 4, the receiver interval is ½ of the actual receiver interval, and the azimuth sampling interval based on the azimuth sampling frequency fas is ½ of the receiver interval d. Must match.

  In consideration of the case where the number of receivers E is an odd number and an even number, the transmitter position is generally as shown in (Equation 29). The receiver position is (Expression 30).

航走体速度がｖ＝ｄ・ｆas／２に一致する場合は、送波器と受波器の位置は（式２９）（式３０）の通りになる。しかし、航走体速度がこれから外れる場合は、送波器の位置は受波器間隔ｄ＝２ｖ／ｆasに置き換え、受波器の位置は送波器からの相対位置から計算する。すなわち、送波器位置は、（式３１）、受波器位置は、（式３２）で与えられる。

When the vehicle speed matches v = d · fas / 2, the positions of the transmitter and the receiver are as shown in (Expression 29) and (Expression 30). However, if the vehicle speed deviates from this, the position of the transmitter is replaced with the receiver interval d = 2 v / fas, and the position of the receiver is calculated from the relative position from the transmitter. That is, the transmitter position is given by (Equation 31) and the receiver position is given by (Equation 32).

本実施例は、以上述べてきたとおり、理想単一配列およびＤＰＣＡ配列とを組み合わせ、ＤＰＣＡ配列に外部動揺データに基づく動揺を加えて、理想単一配列と基準点およびＤＰＣＡ配列と基準点との伝搬距離差により、受信信号に補正を施すことにより、合成開口ソーナーの動揺補正を行うものである。

As described above, the present embodiment combines an ideal single array and a DPCA array, adds a shake based on external shake data to the DPCA array, and creates an ideal single array and a reference point, and a DPCA array and a reference point. The fluctuation of the synthetic aperture sonar is corrected by correcting the received signal based on the propagation distance difference.

  With reference to FIG. 5, the beam patterns before and after the shake correction according to this embodiment will be described. Here, FIG. 5 is a diagram for explaining the reception level with respect to the azimuth distance. In FIG. 5, the horizontal axis represents the azimuth distance (m), and the vertical axis represents the reception level (dB). 5 (a) shows a case in which there is no swaying in the traveling body, FIG. 5 (b) shows a case in which yawing and swaying sway are equivalent to 1 / 8λ, and FIG. 5 (c) corresponds to 1 / 8λ. After yawing and swaying motion, and after motion compensation. From the comparison between FIG. 5B and FIG. 5C, the effect of the shake correction is clear.

  According to the above-described embodiment, since the received signal is corrected based on the propagation distance difference between the DPCA array that receives the fluctuation and the ideal single array that does not receive the fluctuation, the fluctuation of the synthetic aperture sonar is corrected. Even for a swing larger than the 1 / 8λ swing amount, which is said to be the limit, a highly accurate swing correction can be performed without increasing the side lobe.

  In addition, an error in which the receiver position slightly deviates from the moving distance that can be achieved by the speed of the traveling body due to the propagation distance includes this propagation distance in the DPCA array position and does not include this propagation distance in the ideal single array position. Even when there is no fluctuation, the synthetic aperture processing with higher accuracy can be performed.

  Further, since the DPCA array is corrected so as to become a single array, even in the synthetic aperture processing based on the single array, an ideal synthetic aperture processing state is obtained, the DPCA-specific error is corrected, and Even in the absence, a synthetic aperture process with higher accuracy can be performed.

  The arrangement of the transmitter, receiver and DPCA will be described with reference to FIGS. Here, FIG. 6 is a block diagram for explaining the arrangement of an odd-numbered transmission / reception array and DPCA. FIG. 7 is a block diagram for explaining an arrangement of an even-numbered transmission / reception array and DPCA. 6 and 7, the position of the transmitter 120 is indicated by ◯, the position of the receiver 110 is indicated by ●, and the position of the DPCA is indicated by ◎. A box surrounding the transmitter 120 and the receiver 110 is a transmitter / receiver array 160. 6 and 7, the horizontal axis (x-axis) is the traveling direction of the traveling body, and the vertical direction (t-axis) is the time.

  In FIG. 6, a case is considered where the transducer array 160 is one transmitter 120, the receiver 110 is seven (E = 7), and the DPCA overlap number (L) is three. The x-axis coordinate of the transmitter 120 at the top of FIG. Assuming that the receiver interval is d, the position of the receiver 120 is −3d, −2d, −d, 0, d, 2d, and 3d as in FIG. Further, the position of DPCA is also -1.5d, -d, -0.5d, 0, 0.5d, d, and 1.5d, as in FIG. On the other hand, in order to overlap the DPCA, the transmission timing of the transmitter 120 is every (E−L) · d / 2 (2d) movement.

  In FIG. 7, a case is considered where the transducer array 160 is one transmitter 120, the receiver 110 is six (E = 6), and the DPCA overlap number (L) is three. The coordinate of the x-axis of the transmitter 120 at the top of FIG. When the receiver interval is d, the position of the receiver 120 is −2.5d, −1.5d, −0.5d, 0.5d, 1.5d, and 2.5d, as in FIG. In addition, the position of DPCA is also −1.25d, −0.75d, −0.25d, 0.25d, 0.75d, and 1.25d, as in FIG. On the other hand, in order to overlap the DPCA, the transmission timing of the transmitter 120 is every (E−L) · d / 2 (1.5d) movement.

As for fluctuation correction using DPCA, Patent Document 2 and Non-Patent Document 4 disclose a method of overlapping DPCA and correcting the position by superimposing statistical processing of information at the same reception position. The overlap can be achieved by reducing the transmitter interval by 0.5 d × the overlap number L. It can be calculated by replacing .

すなわち、オーバラップ数Ｌの送波器位置は、（式３４）、受波器位置は、（式３５）で与えられる。

That is, the transmitter position of the overlap number L is given by (Equation 34), and the receiver position is given by (Equation 35).

オーバラップ構成においても、動揺補正が適用できることは以上の議論から自明である。また、オーバラップ部は、雑音と動揺が無ければ同じ値を取るはずであるので、逆に動揺量を計測することができる。

It is obvious from the above discussion that the shake correction can be applied even in the overlap configuration. Further, since the overlap portion should have the same value if there is no noise and fluctuation, the amount of fluctuation can be measured conversely.

It is a block diagram of the synthetic aperture sonar of background art. It is a block diagram of a synthetic aperture sonar. It is a block diagram explaining the arrangement | sequence of DPCA and an odd-numbered transmission / reception array and DPCA. It is a block diagram explaining the arrangement | sequence of DPCA and DPCA with an even receiver. It is a figure explaining the reception level with respect to azimuth distance. DPCA array example with 7 receivers and 3 DPCA overlaps DPCA array example with 6 receivers and 3 DPCA overlaps

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Speed signal, 20 ... Reference position information, 100 ... Transmission / reception processor, 110 ... Receiver, 120 ... Transmitter, 130 ... Receiver, 140 ... Transmitter, 150 ... PRF controller, 160 ... Transmitter / receiver Array: 200 ... Shaking correction processing unit, 210 ... Shaking correction unit, 220 ... Correction amount calculator, 230 ... Ideal single array propagation distance calculator, 240 ... Virtual DPCA array propagation distance calculator, 300 ... Synthetic aperture processing unit, 400: Display control processing unit, 500: Motion detection processing unit, 600: Synthetic aperture sonar, 700: Synthetic aperture sonar.

Claims (2)

A reception processing unit comprising a plurality of receivers which are arranged in the movement direction with one wave transmitter, and upset detection processing unit, and the upset correction processing unit adding upset correction to the received signal from the pre-Symbol transceiver unit In the synthetic aperture sonar composed of the synthetic aperture processing unit and the display control processing unit,
The fluctuation correction processing unit calculates the ideal propagation distance between an ideal single array composed of one transmitter and one receiver and a reference position based on the reference position information. A distance calculator;
Based on the reference position information, the reference is obtained by adding a shake based on the shake data detected by the shake detection processing unit to an array composed of one virtual transmitter and a plurality of virtual receivers arranged in the moving direction. A second propagation distance calculator for calculating a virtual propagation distance to and from the position;
A correction amount calculator that calculates a correction amount from a propagation distance difference between the virtual propagation distance and the ideal propagation distance;
A synthetic aperture sonar comprising a motion compensator for correcting a received signal based on the correction amount. The synthetic aperture sonar of claim 1,
The first propagation distance calculator calculates the ideal propagation distance without including the travel distance during propagation of the ideal receiver,
The synthetic propagation sonar wherein the second propagation distance calculator calculates the virtual propagation distance including a moving distance during propagation of the virtual receiver.

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