JPH07151859A - Sonar equipment - Google Patents
Sonar equipmentInfo
- Publication number
- JPH07151859A JPH07151859A JP32325193A JP32325193A JPH07151859A JP H07151859 A JPH07151859 A JP H07151859A JP 32325193 A JP32325193 A JP 32325193A JP 32325193 A JP32325193 A JP 32325193A JP H07151859 A JPH07151859 A JP H07151859A
- Authority
- JP
- Japan
- Prior art keywords
- signal
- frequency
- modulation
- target
- transmission
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Landscapes
- Measurement Of Velocity Or Position Using Acoustic Or Ultrasonic Waves (AREA)
Abstract
Description
【0001】[0001]
【産業上の利用分野】本発明は、直線状周波数変調され
たパルス状音波を送受信するソーナー装置に係り、特に
目標と当該ソーナー装置を搭載する船舶との相対速度の
検出方式に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sonar device for transmitting and receiving pulsed sound waves linearly frequency-modulated, and more particularly to a method for detecting a relative velocity between a target and a ship equipped with the sonar device.
【0002】[0002]
【従来の技術】周知のように、ソーナー装置は、目標の
方位と距離を検出する機能と、目標と船舶との相対速度
を検出する機能とを有するが、直線状周波数変調された
パルス状音波を用いれば、目標からの反射波が微弱であ
っても時間圧縮などの信号処理により信号対雑音比の向
上が図れることから、直線状周波数変調されたパルス状
音波は目標の方位と距離の検出に好適である。As is well known, a sonar device has a function of detecting a heading and a distance of a target and a function of detecting a relative speed between the target and a ship. , The signal-to-noise ratio can be improved by signal processing such as time compression even if the reflected wave from the target is weak, so the linear frequency-modulated pulsed sound wave can detect the target direction and distance. Suitable for
【0003】一方、目標と船舶との相対速度の検出で
は、発生するドップラ周波数を検出するのであるから、
周波数領域で幅を持つ直線状周波数変調波よりも単一の
周波数成分しか持たないパルス状音波を用いた方が検出
容易である。On the other hand, in detecting the relative speed between the target and the ship, the generated Doppler frequency is detected.
It is easier to detect a pulsed sound wave having only a single frequency component than a linear frequency modulation wave having a width in the frequency domain.
【0004】このようなことから従来のソーナー装置で
は、目標の方位と距離の検出には直線状周波数変調され
たパルス状音波を用い、相対速度の検出には単一周波数
からなるパルス状音波を用いるようにしている。For this reason, in the conventional sonar apparatus, linear frequency-modulated pulsed sound waves are used to detect the target azimuth and distance, and single frequency pulsed sound waves are used to detect the relative velocity. I am trying to use it.
【0005】[0005]
【発明が解決しようとする課題】しかし、2種のパルス
状音波を用いる方式では送受信系を2系統設け、切り替
え制御が必要であり、装置構成が複雑化するという問題
がある。また、直線状周波数変調されたパルス状音波と
単一周波数からなるパルス状音波は、信号長は同程度で
あるから、目標の方位と距離を検出する機能と相対速度
を検出する機能との双方を実施する場合には一方の機能
実施時間の約2倍の送信時間を要し、その分消費電力が
増加するという問題もある。However, the method using two types of pulsed sound waves has a problem in that two transmission / reception systems are provided and switching control is required, which complicates the device configuration. Further, since the signal lengths of the linear frequency-modulated pulsed sound wave and the pulsed sound wave of a single frequency are about the same, both the function of detecting the target azimuth and distance, and the function of detecting the relative speed are performed. However, there is also a problem that the transmission time is about twice as long as the execution time of one function, and the power consumption increases by that amount.
【0006】本発明の目的は、直線状周波数変調された
パルス状音波のみの送受信によって目標の方位と距離の
検出だけでなく相対速度の検出も可能にするソーナー装
置を提供することにある。It is an object of the present invention to provide a sonar device which can detect not only the azimuth and distance of a target but also the relative velocity by transmitting and receiving only the pulsed sound waves linearly frequency-modulated.
【0007】[0007]
【課題を解決するための手段】前記目的を達成するた
め、本発明のソーナー装置は次の如き構成を有する。即
ち、本発明のソーナー装置は、直線状周波数変調された
パルス状送信信号を出力する送信手段と; 前記送信信
号を音波に変換して水中へ送波し、目標で反射して戻っ
て来た音波を電気変換して受信信号を出力する送受波手
段と; 前記受信信号を増幅ろ波した後ディジタル化す
る受信手段と; 前記ディジタル受信信号を前記送信信
号の中心周波数を単一周波数として持つ連続波で直交変
調を行う変調手段Aと; 前記変調手段Aの出力から送
信時の時間長と同じ時間分の信号を切り出す反射波切り
出し手段と; 前記切り出した信号を前記送信信号とは
逆の周波数特性(中心周波数は0Hzである)を持つパ
ルス状変調信号で直交変調する変調手段Bと; 前記変
調手段Bの出力をフーリェ変換して周波数領域の情報へ
変換する変換手段と; を備えたことを特徴とするもの
である。In order to achieve the above object, the sonar device of the present invention has the following constitution. That is, the sonar apparatus of the present invention includes a transmitting unit that outputs a linear frequency-modulated pulse-shaped transmission signal; the transmission signal is converted into a sound wave, and the sound wave is transmitted to the water. Transmitting and receiving means for electrically converting a sound wave to output a reception signal; receiving means for amplifying and filtering the reception signal and then digitizing the reception signal; A modulation means A for performing quadrature modulation with a wave; a reflection wave cutting-out means for cutting out a signal for the same time as the time length at the time of transmission from the output of the modulation means A; and a frequency of the cut-out signal opposite to that of the transmission signal. A modulation means B for performing quadrature modulation with a pulsed modulation signal having a characteristic (a center frequency is 0 Hz); It is characterized by having.
【0008】[0008]
【作用】次に、前記の如く構成される本発明のソーナー
装置の作用を説明する。本発明のソーナー装置では、次
のようにして直線状周波数変調されたパルス状音波の反
射波から相対速度、即ち、ドップラ周波数を検出する。
方位・距離の測定系に存する変調手段Aにおいてディジ
タル受信信号を送信信号の中心周波数を単一周波数とし
て持つ連続波で直交変調を行い、送信信号の中心周波数
を差し引いたベースバンド信号を形成し、反射波切り出
し手段においてそのベースバンド信号から送信時の時間
長と同じ時間分の信号を切り出し、変調手段Bにおいて
その切り出した信号を送信信号とは逆の周波数特性で0
Hzを中心周波数とするパルス状変調信号で直交変調
し、目標のドップラ周波数成分のみの信号を形成し、変
換手段においてフーリェ変換して周波数領域情報、つま
りドップラ周波数へ変換する。Next, the operation of the sonar device of the present invention configured as described above will be described. In the sonar apparatus of the present invention, the relative velocity, that is, the Doppler frequency is detected from the reflected wave of the pulsed sound wave linearly frequency-modulated as follows.
In the modulation means A existing in the azimuth / distance measuring system, the digital reception signal is quadrature-modulated with a continuous wave having the center frequency of the transmission signal as a single frequency to form a baseband signal from which the center frequency of the transmission signal is subtracted, The reflected wave cutting-out means cuts out a signal for the same time as the transmission time length from the baseband signal, and the cut-out signal in the modulating means B has a frequency characteristic opposite to that of the transmission signal.
Quadrature modulation is performed with a pulse-shaped modulation signal having a center frequency of Hz to form a signal having only a target Doppler frequency component, and Fourier transform is performed by the conversion means to convert to frequency domain information, that is, Doppler frequency.
【0009】斯くして、本発明のソーナー装置では、目
標の方位、距離、相対速度が直線状周波数変調波だけで
検出できるので、装置構成の簡素化が図れ、送信時間の
短縮による消費電力の低減が可能となる。Thus, in the sonar apparatus of the present invention, the target azimuth, distance, and relative velocity can be detected only by the linear frequency modulation wave, so that the apparatus configuration can be simplified and the transmission time can be shortened to reduce power consumption. It is possible to reduce.
【0010】[0010]
【実施例】以下、本発明の実施例を図面を参照して説明
する。図1は、本発明の一実施例に係るソーナー装置を
示す。本発明は、ドップラ周波数の検出を目的とする
が、目標の方位と距離の検出系と一部重複した形で構成
される。Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a sonar device according to an embodiment of the present invention. The present invention aims to detect the Doppler frequency, but is configured so as to partially overlap with the detection system for the target azimuth and distance.
【0011】即ち、送信手段1と送受波手段2と受信手
段3と変調手段A4とが共用できる部分であり、反射波
切り出し手段5と変調手段B6と変換手段7とが本発明
に係る部分である。That is, the transmitting means 1, the transmitting / receiving means 2, the receiving means 3 and the modulating means A4 can be shared, and the reflected wave cutting means 5, the modulating means B6 and the converting means 7 are the portions according to the present invention. is there.
【0012】図1において、送信手段1では、直線状周
波数変調されたパルス状送信信号を発振し(送信発振部
11)、その送信信号を電力増幅し(送信増幅部1
2)、送受波手段2に与える。直線状周波数変調された
パルス状送信信号は、例えば図2に示すように、周波数
変調幅をFW、中心周波数をf0 とすると、送信信号長
(pw)の時間内において、周波数がf0 −FW/2か
らf0 +FW/2まで直線状に増加する信号である。In FIG. 1, the transmitting means 1 oscillates a linear frequency-modulated pulse-shaped transmission signal (transmission oscillating section 11) and amplifies the power of the transmission signal (transmission amplifying section 1).
2) Apply to the transmitting / receiving means 2. For example, as shown in FIG. 2, when the frequency modulation width is FW and the center frequency is f 0 , the linear frequency-modulated pulsed transmission signal has a frequency f 0 − within the time of the transmission signal length (pw). It is a signal that increases linearly from FW / 2 to f 0 + FW / 2.
【0013】送受波手段2では、パルス状送信信号をパ
ルス状音波に変換して水中へ送波し(送波器21)、目
標8で反射して戻って来た音波を受波して電気変換し
(受波器22)、受信信号を受信手段3に与える。この
受信信号は、例えば図3に示すように、送信信号に対し
目標のドップラ周波数Δfを付加した信号である。In the wave transmitting / receiving means 2, the pulsed transmission signal is converted into pulsed sound waves and transmitted into water (transmitter 21), and the sound waves reflected by the target 8 and returned are received and converted into electricity. The signal is converted (receiver 22) and the received signal is given to the receiving means 3. This received signal is, for example, as shown in FIG. 3, a signal obtained by adding a target Doppler frequency Δf to the transmitted signal.
【0014】受信手段3では、受信信号を増幅し(受信
増幅部31)、必要な周波数帯域のみをろ波し(帯域ろ
波器32)、その後ディジタル化し(A/D変換器3
3)、変調手段A4に与える。The receiving means 3 amplifies the received signal (reception amplifier 31), filters only a necessary frequency band (band filter 32), and digitizes it (A / D converter 3).
3), giving to the modulation means A4.
【0015】変調手段A4では、送信信号の中心周波数
f0 を単一周波数として持つ連続波信号を発生し(変調
信号発生器41)、それとディジタル受信信号とを乗算
し、つまり直交変調を行い(直交変調器42)、受信周
波数(図3)から送信信号の中心周波数f0 を差し引い
たベースバンド信号を形成する。このベースバンド信号
は方位と距離の検出に使用されるが、本発明では反射波
切り出し手段5に与える。The modulation means A4 generates a continuous wave signal having the center frequency f 0 of the transmission signal as a single frequency (modulation signal generator 41) and multiplies it by the digital reception signal, that is, performs quadrature modulation ( The quadrature modulator 42) forms a baseband signal by subtracting the center frequency f 0 of the transmission signal from the reception frequency (FIG. 3). This baseband signal is used for detecting the azimuth and the distance, and is given to the reflected wave cutting means 5 in the present invention.
【0016】反射波切り出し手段5では、ベースバンド
信号から送信時の時間長と同じ時間分の信号を切り出し
(反射波切り出し器51)、変調手段B6に与える。The reflected wave cut-out means 5 cuts out a signal for the same length of time as the transmission time from the baseband signal (reflected wave cut-out device 51) and supplies it to the modulation means B6.
【0017】変調手段B6では、0Hzを中心周波数と
し送信信号とは逆の周波数特性(図4)を持つパルス状
変調信号を発生し(変調パルス発生器61)、それと切
り出した信号とを乗算し、つまり直交変調を行い(直交
変調器62)、目標のドップラ周波数成分(図5)のみ
の信号を形成し、変換手段7に与える。なお、念のため
付記すれば0Hzを中心周波数とするのは、ドップラシ
フトがない状態ではドップラ周波数は0Hzであり、こ
れを基準に±方向へシフトした形でドップラ周波数が検
出されるからである。The modulating means B6 generates a pulse-shaped modulated signal having a frequency characteristic (FIG. 4) opposite to that of the transmission signal with a center frequency of 0 Hz (modulation pulse generator 61), and multiplies it by the cut-out signal. That is, quadrature modulation is performed (quadrature modulator 62), a signal having only the target Doppler frequency component (FIG. 5) is formed, and the signal is supplied to the conversion means 7. It should be noted that the center frequency is 0 Hz, as a precaution, because the Doppler frequency is 0 Hz when there is no Doppler shift, and the Doppler frequency is detected in a form shifted in the ± direction with reference to this. .
【0018】変調手段Bの動作を具体的に説明する。切
り出した反射波を切り出し幅(パルス長)に相当する時
間t=0〜pwにおいて複素数で表現すれば式1とな
る。The operation of the modulation means B will be specifically described. If the cut-out reflected wave is expressed as a complex number at a time t = 0 to pw corresponding to the cut-out width (pulse length), Formula 1 is obtained.
【0019】[0019]
【数1】 [Equation 1]
【0020】これに対し、パルス状変調信号を同じ時間
幅で表現すると、式2となる。On the other hand, when the pulse-shaped modulated signal is represented by the same time width, the equation 2 is obtained.
【0021】[0021]
【数2】 [Equation 2]
【0022】そして、式1と同2を乗算すると式3が得
られ、変調手段B6の出力信号は、目標のドップラ周波
数成分Δfのみの信号となることが理解できる。Then, when the equations 1 and 2 are multiplied, the equation 3 is obtained, and it can be understood that the output signal of the modulating means B6 is a signal of only the target Doppler frequency component Δf.
【0023】[0023]
【数3】 [Equation 3]
【0024】従って、変換手段7において、変調手段B
6の出力信号をフーリェ変換(高速フーリェ変換器7
1)して時間領域信号から周波数領域信号へ変換すれ
ば、周波数領域においてドップラ周波数Δfを認識で
き、目標と船舶の相対速度を求めることができる。Therefore, in the conversion means 7, the modulation means B
Fourier transform of the output signal of 6 (high speed Fourier transformer 7
If 1) is performed and the time domain signal is converted to the frequency domain signal, the Doppler frequency Δf can be recognized in the frequency domain and the relative speed between the target and the ship can be obtained.
【0025】[0025]
【発明の効果】以上説明したように、本発明のソーナー
装置では、方位と距離の測定系で形成するベースバンド
信号から送信信号長と同じ時間長の信号を切り出し、そ
れを送信信号とは逆の周波数特性で0Hzを中心周波数
とするパルス状変調信号で直交変調し、ドップラ周波数
成分を検出できるようにしてあるので、目標の方位、距
離、相対速度が直線状周波数変調波だけで検出でき、装
置構成の簡素化が図れ、送信時間の短縮による消費電力
の低減が可能となる効果がある。As described above, in the sonar device of the present invention, a signal having the same time length as the transmission signal length is cut out from the baseband signal formed by the azimuth and distance measurement system, and the signal is inverted from the transmission signal. With the frequency characteristic of, since it is possible to detect the Doppler frequency component by performing quadrature modulation with a pulse-shaped modulation signal having a center frequency of 0 Hz, the target azimuth, distance, and relative velocity can be detected only by the linear frequency modulation wave. The device configuration can be simplified, and the transmission time can be shortened to reduce power consumption.
【図1】本発明の一実施例に係るソーナー装置の構成ブ
ロック図である。FIG. 1 is a configuration block diagram of a sonar device according to an embodiment of the present invention.
【図2】送信信号(直線状周波数変調波)の特性図であ
る。FIG. 2 is a characteristic diagram of a transmission signal (linear frequency modulation wave).
【図3】受信信号(反射波)の周波数特性図である。FIG. 3 is a frequency characteristic diagram of a received signal (reflected wave).
【図4】切り出し信号を直交変調するパルス状変調信号
の周波数特性図である。FIG. 4 is a frequency characteristic diagram of a pulse-shaped modulated signal that quadrature-modulates a cutout signal.
【図5】変調手段Bの出力信号の周波数特性図である。5 is a frequency characteristic diagram of the output signal of the modulation means B. FIG.
1 送信手段 2 送受波手段 3 受信手段 4 変調手段A 5 反射波切り出し手段 6 変調手段B 7 変換手段 8 目標 DESCRIPTION OF SYMBOLS 1 transmitting means 2 transmitting / receiving means 3 receiving means 4 modulating means A 5 reflected wave cutting-out means 6 modulating means B 7 converting means 8 target
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【手続補正書】[Procedure amendment]
【提出日】平成6年7月7日[Submission date] July 7, 1994
【手続補正1】[Procedure Amendment 1]
【補正対象書類名】明細書[Document name to be amended] Statement
【補正対象項目名】特許請求の範囲[Name of item to be amended] Claims
【補正方法】変更[Correction method] Change
【補正内容】[Correction content]
【特許請求の範囲】[Claims]
【手続補正2】[Procedure Amendment 2]
【補正対象書類名】明細書[Document name to be amended] Statement
【補正対象項目名】0007[Correction target item name] 0007
【補正方法】変更[Correction method] Change
【補正内容】[Correction content]
【0007】[0007]
【課題を解決するための手段】前記目的を達成するた
め、本発明のソーナー装置は次の如き構成を有する。即
ち、本発明のソーナー装置は、直線状周波数変調された
パルス状音波を送受波し、ディジタル受信信号を送信信
号の中心周波数を単一周波数として持つ連続波で直交変
調を行って送信信号の中心周波数を差し引いたベースバ
ンド信号を形成し、そのベースバンド信号に基づき方位
と距離を測定するソーナー装置において; 前記ベース
バンド信号から送信時の時間長と同じ時間分の信号を切
り出す手段と; 前記切り出した信号を前記送信信号と
は逆の周波数特性(中心周波数は0Hzである)を持つ
パルス状変調信号で直交変調する手段と; を備えたこ
とを特徴とするものである。さらに本発明のソーナー装
置は、パルス状変調信号で直交変調する手段の出力をフ
ーリェ変換して周波数領域の情報へ変換する変換手段
と; を備えたことを特徴とするものである。 In order to achieve the above object, the sonar device of the present invention has the following constitution. That is, the sonar device of the present invention transmits and receives a pulsed sound wave that is linearly frequency-modulated and transmits a digital reception signal.
A continuous wave with the center frequency of the signal as a single frequency
Adjustment and subtract the center frequency of the transmitted signal.
The baseband signal, and the azimuth based on the baseband signal.
And a sonar device for measuring distance; the base
From the band signal, cut off the signal for the same length of time as the transmission.
Means for outputting; the cut-out signal as the transmission signal
Has the opposite frequency characteristic (center frequency is 0 Hz)
Means for performing quadrature modulation with a pulsed modulation signal ; Furthermore, the sonar device of the present invention
The output of the means for quadrature modulation with a pulse-shaped modulation signal.
Conversion means for converting the Fourier transform to information in the frequency domain
And; are provided.
【手続補正3】[Procedure 3]
【補正対象書類名】明細書[Document name to be amended] Statement
【補正対象項目名】0008[Correction target item name] 0008
【補正方法】変更[Correction method] Change
【補正内容】[Correction content]
【0008】[0008]
【作用】次に、前記の如く構成される本発明のソーナー
装置の作用を説明する。本発明のソーナー装置では、次
のようにして直線状周波数変調されたパルス状音波の反
射波から相対速度、即ち、ドップラ周波数を検出する。
方位・距離の測定系では、ディジタル受信信号を送信信
号の中心周波数を単一周波数として持つ連続波で直交変
調を行い、送信信号の中心周波数を差し引いたベースバ
ンド信号を形成するが、本発明では、そのベースバンド
信号から送信時の時間長と同じ時間分の信号を切り出
し、その切り出した信号を送信信号とは逆の周波数特性
で0Hzを中心周波数とするパルス状変調信号で直交変
調し、目標のドップラ周波数成分のみの信号を形成し、
さらに必要に応じてフーリェ変換して周波数領域情報、
つまりドップラ周波数へ変換する。Next, the operation of the sonar device of the present invention configured as described above will be described. In the sonar apparatus of the present invention, the relative velocity, that is, the Doppler frequency is detected from the reflected wave of the pulsed sound wave linearly frequency-modulated as follows.
In the azimuth / distance measurement system , a digital received signal is quadrature-modulated with a continuous wave having a center frequency of a transmission signal as a single frequency to form a baseband signal from which the center frequency of the transmission signal is subtracted. , A signal for the same time as the time length at the time of transmission is cut out from the baseband signal , and the cut out signal is subjected to quadrature modulation with a pulsed modulation signal having a center frequency of 0 Hz with a frequency characteristic opposite to that of the transmission signal, and the target Form a signal with only Doppler frequency components of
Further, if necessary, Fourier transform is performed to perform frequency domain information,
That is, it is converted to the Doppler frequency.
Claims (1)
号を出力する送信手段と; 前記送信信号を音波に変換
して水中へ送波し、目標で反射して戻って来た音波を電
気変換して受信信号を出力する送受波手段と; 前記受
信信号を増幅ろ波した後ディジタル化する受信手段と;
前記ディジタル受信信号を前記送信信号の中心周波数
を単一周波数として持つ連続波で直交変調を行う変調手
段Aと; 前記変調手段Aの出力から送信時の時間長と
同じ時間分の信号を切り出す反射波切り出し手段と;
前記切り出した信号を前記送信信号とは逆の周波数特性
(中心周波数は0Hzである)を持つパルス状変調信号
で直交変調する変調手段Bと; 前記変調手段Bの出力
をフーリェ変換して周波数領域の情報へ変換する変換手
段と; を備えたことを特徴とするソーナー装置。1. Transmitting means for outputting a pulse-like transmission signal linearly frequency-modulated; converting the transmission signal into a sound wave for transmission into water, and electrically converting a sound wave reflected by a target and returning. Transmitting and receiving means for outputting a received signal by means of the above; receiving means for amplifying and filtering the received signal and then digitizing the received signal;
Modulation means A for performing quadrature modulation of the digital reception signal with a continuous wave having a center frequency of the transmission signal as a single frequency; reflection for cutting out from the output of the modulation means A a signal for the same time length as the transmission time Wave cutting means;
Modulation means B for quadrature modulating the cut-out signal with a pulse-like modulation signal having a frequency characteristic (center frequency is 0 Hz) opposite to that of the transmission signal; A sonar device comprising:
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP5323251A JP2596360B2 (en) | 1993-11-29 | 1993-11-29 | Sonar device |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP5323251A JP2596360B2 (en) | 1993-11-29 | 1993-11-29 | Sonar device |
Publications (2)
Publication Number | Publication Date |
---|---|
JPH07151859A true JPH07151859A (en) | 1995-06-16 |
JP2596360B2 JP2596360B2 (en) | 1997-04-02 |
Family
ID=18152703
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP5323251A Expired - Fee Related JP2596360B2 (en) | 1993-11-29 | 1993-11-29 | Sonar device |
Country Status (1)
Country | Link |
---|---|
JP (1) | JP2596360B2 (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2001296360A (en) * | 2000-04-11 | 2001-10-26 | Nec Corp | Active signal detecting apparatus |
US8726733B2 (en) | 2010-02-18 | 2014-05-20 | Panasonic Corporation | Ultrasonic measuring method and ultrasonic measuring apparatus |
-
1993
- 1993-11-29 JP JP5323251A patent/JP2596360B2/en not_active Expired - Fee Related
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2001296360A (en) * | 2000-04-11 | 2001-10-26 | Nec Corp | Active signal detecting apparatus |
US8726733B2 (en) | 2010-02-18 | 2014-05-20 | Panasonic Corporation | Ultrasonic measuring method and ultrasonic measuring apparatus |
Also Published As
Publication number | Publication date |
---|---|
JP2596360B2 (en) | 1997-04-02 |
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