JP2011038993A - Underwater object searching system, underwater object searching method and underwater object searching program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To alleviate a load of correlation signal processing by reducing a circuit size of an underwater object searching system. <P>SOLUTION: An excitation signal generating means 12 of a wave transmitting device 10 includes: a low Doppler sensitivity excitation signal generating means 12A for generating a first excitation signal whose frequency varies linearly; a high Doppler sensitivity excitation signal generating means 12B for generating a second excitation signal whose frequency varies nonlinearly; a Doppler modulation processing section 12C for generating a plurality of second excitation signals different in frequency ranges by sequentially modulating the second excitation signal; and a pulse train generating section 12E for generating an excitation-use composite signal by adding a plurality of excitation signals to the first excitation signal. A wave transmitting means 11 of the wave transmitting device 10 transmits a sound wave corresponding to the excitation-use composite signal toward an object 30. In regard to a reflected wave from the object 30, an echo signal contained in a reception signal is detected by conducting the correlation signal processing of a single-frequency replica signal and the reception signal received by a wave receiving device. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an underwater target search system and the like, and in particular, an underwater target search for detecting a target based on a Doppler effect obtained from echo waves from a target in water by transmitting and receiving sound waves. The present invention relates to an underwater target search method and an underwater target search program.

  An active sonar apparatus is widely known as an underwater target search system that detects a target based on a Doppler effect obtained from echo waves from a target in water by transmitting and receiving sound waves.

  The active sonar device in the related technology transmits a target search sound wave toward a target in the water, and includes an echo sound wave that is a reflected wave from the target object, a reverberant sound wave from the seabed, and other noise components. The sound wave is received by the wave receiving sensor and signal processing is performed to specify the direction of the target. Next, in this type of active sonar device, an echo signal included in the received reception signal is detected, and the distance to the target is specified. The specified direction of the target and the distance to the target are displayed by, for example, a two-dimensional image with the horizontal axis as the direction and the vertical axis as the distance.

  In an active sonar device, generally, correlation signal processing using a replica signal is performed as a method of detecting an echo signal from a received signal. The replica signal is a signal obtained by copying (replicating) the excitation signal, and in a narrow sense, is constituted by a conjugate signal obtained by inverting the phase of the imaginary part of the excitation signal. However, in a broad sense, even if the excitation signal is not duplicated, a correlated signal for performing correlation signal processing with the received signal is referred to as a replica signal.

  In this correlation signal processing, by repeating cross-correlation while shifting the time of the replica signal with respect to the received signal, the maximum value of the correlation degree appears at the time when the waveforms are most similar. As an excitation signal that is a source of a replica signal used for this correlation signal processing, a linear frequency modulation (LFM) signal whose frequency is linearly modulated, and a constant frequency continuous wave (PCW: Pulse) Two types of signals are mainly used.

  The active sonar device has a monostatic sonar system in which the transmitting side that transmits sound waves toward the target and the receiving side that receives the reflected wave from the target are integrated, and the transmitting side and the receiving side are separated. Thus, there is a multi-static sonar system that is arranged at different positions.

  As a related technique of the monostatic sonar method, for example, an adder that superimposes and adds an LFM pulse signal and a PCW pulse signal and superimposes the LMF pulse signal and the PCW pulse signal to generate an excitation signal is known. (See Patent Document 1).

  FIG. 11 is a block diagram showing the configuration of the active sonar device according to Patent Document 1. The active sonar device shown in FIG. 11 includes a transmission / reception unit 100 that transmits and receives a sound wave for searching for a target, a transmission unit 200 that supplies an excitation signal to the transmission / reception unit 100, and a transmission / reception unit 100. A receiving unit 300 that processes a received signal to be supplied and a display control unit 400 that displays a search result and performs other processing are provided. Hereinafter, a characteristic technique in Patent Document 1 will be described.

  In FIG. 11, the transmission unit 200 superimposes both the LFM pulse generated by the LFM pulse generation unit 201 and the PCW pulse generated by the PCW pulse generation unit 202 by an adder 203 to generate one excitation signal. Is generated.

  In addition, a reception signal including an echo signal obtained by reflection from the target is input to the reception unit 300. This received signal is frequency-separated and input to the LFM phase shifter 301 and the PCW phase shifter 302, and thereafter, correlation signal processing is performed based on a replica signal based on the excitation signal of the transmission unit 200.

  The LFM phase shifter 301 of the receiving unit 300 detects the position (distance) of the target by correlation signal processing according to the received signal of the LFM pulse component with high time resolution, and the detection result is sent to the video system processing unit 303. Output. On the other hand, the PCW phase adjuster 302 detects a Doppler shift amount representing a movement change of the target by correlation signal processing according to the received signal of the PCW pulse component having a high Doppler resolution (frequency resolution), and the detection result is Doppler. The data is output to the system processing unit 304.

  On the other hand, as a related technology of the multi-static sonar method, an excitation signal is generated in which an LFM signal whose frequency increases linearly and an LFM signal whose frequency decreases linearly is generated, and the Doppler is detected from the time difference of the echo signal at the time of detection. A technique for detecting the shift amount is known (see Patent Document 2).

  In addition, as another related technique of the multi-static sonar system, in order to perform correlation signal processing between the received signal and the replica signal, a technique for preparing a plurality of replica signals having different frequencies and detecting the presence or absence of Doppler shift of the echo signal Is known (see Patent Document 3).

  Furthermore, as another related technique of the monostatic sonar method, a wideband LFM signal is generated for environmental measurement, and based on the detection result, high time resolution and high tuning tuned to appropriate parameters for the environment In order to simultaneously realize Doppler resolution (frequency resolution), a frequency hopping PCW signal whose frequency changes irregularly is used, and the received signal is divided into a plurality of bands, and each divided received signal and the frequency hopping method are divided. A technique for performing matched filter processing with a replica signal is known (see Patent Document 4).

JP-A-9-281234 JP 59-225375 A JP-A-3-242586 JP 2000-304859 A

  As described in Patent Document 4, in order to improve the performance of the active sonar device, it is necessary to satisfy both time resolution and Doppler resolution (frequency resolution) at the same time.

  In particular, in order to improve the Doppler resolution, a plurality of excitation signals with different frequencies and different frequency ranges are generated on the transmission side, such as frequency hopping signals and HFM (Hyperbolic Frequency Modulation) signals. A replica signal of the plurality of excitation signals on the transmission side is prepared on the reception side, and correlation signal processing between the reception signal of the reflected wave received on the reception side and the replica signal is performed.

  For this reason, in Patent Document 1 to Patent Document 4, a signal generation circuit that generates a plurality of replica signals having different frequency ranges is provided on the receiving side to improve Doppler resolution.

  However, providing such a signal generation circuit that generates a plurality of replica signals increases the circuit scale and increases the load of correlation signal processing between the received signal and the plurality of replica signals.

  In particular, in the case of the multi-static sonar method in which the transmission side and the reception side are separated as in Patent Document 2 and Patent Document 3, an excitation signal on the transmission side cannot be used. Circuits and the like are also required, and there is a problem that the circuit scale further increases.

  Further, in Patent Document 2 and Patent Document 3 described above, the Doppler shift amount is detected using only two replica signals based on the LFM signal. However, the correlation signal processing between the received signal and the LFM signal has sufficient correlation. Since a signal output cannot be obtained, there is a problem that many false detections of the Doppler shift amount occur in an environment where there are many actual reverberations and noises.

(Object of invention)
The present invention has been made to solve the above-described problems of the related art. It is possible to reduce the load of correlation signal processing by reducing the circuit scale on the receiving side, and to realize actual reverberation. It is an object of the present invention to provide an underwater target search system, an underwater target search method, and an underwater target search processing program that can reliably detect a target even in an environment where there is a lot of noise and noise. And

  In order to achieve the above object, an underwater target search system according to the present invention includes a wave transmitting means for transmitting a target search sound wave toward an underwater target, and a received wave for receiving a reflected wave from the target. And an excitation signal generating means for generating an excitation signal for sound wave output, the excitation signal generating means is preset with a first excitation signal whose frequency changes linearly. An excitation signal generating function for generating a second excitation signal having a different frequency range for each of a plurality of fixed time intervals, and a combination for excitation by adding the second excitation signals of the plurality of intervals to the first excitation signal Correlation signal processing between the received signal and the replica signal based on the first excitation signal generated by the excitation signal generation means, comprising a composite signal generation function for generating a signal and generating an excitation signal for sound wave output; Receiving signal processing means for detecting an echo signal for target identification included in the received signal by performing correlation signal processing between the received signal and a single frequency replica signal having a preset single frequency. It is characterized by that.

  In order to achieve the above object, the underwater target searching method according to the present invention generates an excitation signal for sound wave output by an excitation signal generating means, and converts the generated excitation signal into a sound wave for target search. The wave transmitting means transmits toward the target in the water, the reflected wave from the target is received by the wave receiving means and converted into a received signal, and the converted received signal is processed by the received signal processing means. In the underwater target searching method for identifying the target by doing so, the frequency changes in a non-linear manner for each of a plurality of predetermined time intervals and a first excitation signal whose frequency changes linearly and Second excitation signals having different frequency ranges are individually generated by the excitation signal generating means, and then the second excitation signals for each of the plurality of sections are added to the first excitation signal to generate a combined signal for excitation. Is generated by the excitation signal generating means. , Using the synthesized signal for excitation as an excitation signal for sound wave output converted and output from the transmission means, and a correlation signal process between the received signal and the replica signal based on the generated first excitation signal; The received signal processing means detects an echo signal for specifying a target contained in the received signal by performing correlation signal processing between the received signal and a single frequency replica signal having a preset single frequency. It is characterized by that.

  In order to achieve the above object, an underwater target search program according to the present invention converts an excitation signal generated for sound wave output into a sound wave for target search and transmits it to an underwater target. An underwater target search system comprising: a wave means; a wave receiving means for receiving a reflected wave from the target and converting it into a received signal; and an excitation signal generating means for generating an excitation signal for outputting the sound wave. When generating the excitation signal, a first excitation signal generating function for generating a first excitation signal in which a frequency forming a part of the excitation signal for sound wave output changes linearly, and the excitation signal for sound wave output A second excitation signal generation function for generating a second excitation signal in which a frequency that is partly changed in a non-linear manner and a frequency range different for each of a plurality of constant time intervals, and the first excitation signal With the second excitation signal of the section Was synthesized signal generating function for generating an excitation for the synthesis signal, characterized in that so as to be executed by a computer in which said excitation signal generating means comprises.

  In order to achieve the above object, an underwater target search program according to the present invention converts an excitation signal generated for sound wave output into a sound wave for target search and transmits it to an underwater target. Wave means, wave receiving means for receiving a reflected wave from the target and converting it to a received signal, a first excitation signal whose frequency changes linearly, and a frequency connected to the first excitation signal are nonlinear An excitation signal generating means for generating a second excitation signal that varies in frequency intervals for each of a plurality of intervals of a certain time as an excitation synthetic signal for sound wave output, and the received signal processing means processes the received signal. In the underwater target searching system for identifying the target, the correlation signal processing between the captured received signal and the replica signal based on the first excitation signal generated by the excitation signal generating means is performed. And a received signal processing function for detecting an echo signal for specifying a target contained in the received signal by performing correlation signal processing between the received signal and a single frequency replica signal having a preset single frequency. A peak position detection processing function that analyzes the received signal and detects the signal peak position of the reflected peak signal, which is a reflected wave from the target, on the time coordinate. A time length signal extraction function for extracting a signal portion having a time length corresponding to the excitation composite signal starting from the signal peak position, and a correlation between the extracted signal portion having the time length and the single frequency replica signal An echo signal detection function for performing signal processing and detecting the echo signal included in the received signal, and these are included in the reception signal generating means. Characterized in that so as to execute Yuta.

  Since the present invention is configured as described above, according to this, on the transmitting side, the first excitation signal whose frequency changes linearly and the frequency connected to the first excitation signal change nonlinearly and A second excitation signal having a different frequency range for each interval of a certain time is generated as an excitation signal for sound wave output. On the reception side, correlation signal processing between the reception signal and the replica signal based on the first excitation signal, and the reception signal Since it is configured to detect the echo signal for target identification contained in the received signal by performing correlation signal processing with a single frequency replica signal consisting of a single frequency set in advance, the circuit scale on the receiving side Excellent underwater target that can reduce the load of correlation signal processing and reliably detect the target even in an environment where there is a lot of actual reverberation and noise Search system, it is possible to provide a water target searching method and underwater target search program.

It is a block diagram which shows the structure of the transmission device in the underwater target search system in 1st Embodiment of this invention. It is a block diagram which shows the structure of the receiving device in the underwater target search system in 1st Embodiment of this invention. It is explanatory drawing which shows the example of arrangement | positioning of each apparatus of transmission and reception of the underwater target search system in 1st Embodiment of this invention. It is a wave form diagram which shows the excitation signal produced | generated by the excitation signal production | generation means disclosed in FIG. It is a wave form diagram which shows the signal waveform processed by the received signal processing means disclosed in FIG. It is a conceptual diagram which shows the concept of the Doppler shift of the target in 1st Embodiment of this invention. It is a block diagram which shows the structure of the wave transmission apparatus of the underwater target search system in 2nd Embodiment of this invention. It is a flowchart which shows the procedure of the excitation signal generation process in the transmission apparatus disclosed in FIG. It is a block diagram which shows the structure of the receiving device of the underwater target search system in 2nd Embodiment of this invention. 10 is a flowchart illustrating a procedure of received signal processing in the wave receiving device disclosed in FIG. 9. It is a block diagram which shows an example of the active sonar apparatus in related technology.

A first embodiment of a multistatic sonar underwater target search system according to the present invention will be described below with reference to FIGS. 1 to 6.
[First embodiment]
First, in FIG. 3, the underwater target searching system 1 is a multistatic underwater system composed of one transmitting device 10 and three receiving devices 20A, 20B, and 20C installed in the search target sea. This is a target searching system, and each receiving device 20 receives a reflected wave from the target 30 that has received a sound wave transmitted from the wave transmitting device 10 to search for the target 30 moving in the sea or on the sea. .

  FIG. 1 is a block diagram showing an internal configuration of the transmission device 10 shown in FIG. In FIG. 1, a wave transmitting device 10 transmits a sound wave for target search toward a target 30 in water, and an excitation signal for sound wave output for input to the wave transmitting means 11. And an excitation signal generating means 12 for generating. In addition, the wave transmitting device 10 is connected to the radio communication unit 13 that performs radio communication with each of the wave receiving devices 20 (20A, 20B, and 20C) in FIG. And an antenna 14 extending upward from the sea surface for transmitting and receiving radio waves.

  FIG. 2 is a block diagram showing an internal configuration of the wave receiving device 20 shown in FIG. In FIG. 2, the wave receiving device 20 receives a reflected wave from the target 30 and captures the received signal, the received signal captured by the wave receiving unit 21 and the excitation of the wave transmitting device 10. A reception signal processing unit 22 that performs correlation signal processing with a replica signal based on the excitation signal generated by the signal generation unit 12 to detect an echo signal for target identification included in the reception signal; A wireless communication unit 23 that performs wireless communication between them, an antenna 24 that is connected to the wireless communication unit 23 and extends upward from the sea surface to transmit and receive radio waves in the air, and an echo signal detected by the received signal processing means 22 The display processing unit 25 that converts the image into a display signal, and the display unit 26 that displays an image based on the display signal processed by the display processing unit 25 are provided.

  For this reason, the echo signal is detected by correlation signal processing between the received signal and the replica signal based on the excitation signal, and the arrival time of the echo signal, the transmission time of the sound wave in the transmission device 10 obtained by wireless communication, and the speed of the sound wave The position of the target 30 can be specified.

  Here, although not shown in the figure, the receiving means 21 is provided with a receiving direction sensor, and the direction in which the target 30 is present is specified based on the direction of the reflected wave received by the receiving direction sensor. Can do. Since this reception direction sensor is already widely known in the related art, a detailed description thereof will be omitted.

(Configuration of excitation signal generating means)
Next, the excitation signal generation means 12 that is a main part of the transmission device 10 will be described. The excitation signal generating means 12 in FIG. 1 generates in advance an excitation signal used for target search. In this embodiment, the excitation signal generation means 12 has an excitation signal generation function and a combined signal generation function. Among these, the excitation signal generation function generates a first excitation signal (the LFM signal shown in FIG. 4 in this embodiment) whose frequency changes linearly when transmitting a sound wave to the target 30. The excitation signal generator 12A and a second excitation signal whose frequency changes nonlinearly (in this embodiment, as shown in FIG. 4, a high frequency that generates a hyperbolic frequency modulation (HFM) signal whose frequency changes hyperbolically in advance. This is realized by the Doppler sensitivity excitation signal generation unit 12B.

  Accordingly, the first excitation signal (LFM signal) whose frequency changes linearly and the second excitation signal (HFM signal) whose frequency changes nonlinearly can be easily obtained by a simple algorithm of a simple digital circuit or software. Can be generated.

  Further, the excitation signal generation means 12 sequentially modulates each second excitation signal generated by the high Doppler sensitivity excitation signal generation unit 12B, and sets three predetermined time intervals (in this embodiment, A Doppler modulation processing unit 12C that generates three second excitation signals (three HFM signals shown in FIG. 4) having different frequency ranges for each of the sections A, B, and C shown in FIG. 4, and a Doppler modulation process An excitation signal database 12D for storing three second excitation signals sequentially modulated by the unit 12C prior to the target searching operation. Here, the high Doppler sensitivity excitation signal generation unit 12B and the Doppler modulation processing unit 12C may be configured to generate more than three HFM signals.

  As a result, it is possible to generate a second excitation signal that covers a wide frequency range, and it is not necessary to generate a plurality of second excitation signals in real time at the start of the target search operation, thereby enabling a quick search operation. Become.

  Further, among the functions of the excitation signal generating means 12, the above-described combined signal generating function is a plurality of second excitation signals stored in the excitation signal database 12D when transmitting a sound wave toward the target 30. Is read out and coupled to the first excitation signal generated by the low Doppler sensitivity excitation signal generation unit 12A, thereby being executed by the pulse train generation unit 12E that generates the pulse train of the excitation composite signal.

  As a result, when the target search operation is started, a pulse train of the excitation composite signal can be quickly generated.

  Furthermore, the excitation signal generation means 12 includes an amplifier 12F that amplifies the excitation composite signal generated by the pulse train generation unit 12E to a sufficient level as power for sound wave output and outputs it to the wave transmission means 11.

  When the target searching operation is started, the sound wave transmitted from the wave transmitting means 11 upon receiving the excitation composite signal from the excitation signal generating means 12 propagates through the water and reaches the target 30 and each receiving device 20. Also reach. The sound wave that reaches the target object 30 is reflected by the target object 30, and the reflected wave of the sound wave propagates in the water. In this case, when the target 30 is moving, the reflected wave is affected by the movement change.

  This change in movement of the target 30 appears as a change in the Doppler shift amount of the reflected wave, and the change in the Doppler shift amount is performed by the correlation signal processing (which will be described later) in the wave receiving device 20 that receives the reflected wave. It is detected as a movement change of the object 30. That is, a plurality of movement change values of the target 30 are detected corresponding to a plurality of expected values of the Doppler shift amount.

  For this reason, when the Doppler modulation processing unit 12C shown in FIG. 1 sequentially modulates the plurality of second excitation signals, the Doppler modulation processing unit 12C converts the received signal captured by the receiving means 21 in the receiving device 20 shown in FIG. Modulation is performed according to an expected value of the included Doppler shift amount. That is, the Doppler modulation processing unit 12C modulates the second excitation signal at a frequency corresponding to a predicted Doppler shift amount of the received signal.

  In this case, the Doppler modulation processing unit 12C generates the reference excitation signal corresponding to the shift value 0 in the case where it is assumed that there is no Doppler shift amount, and the generated reference excitation signal is converted into a plurality of Doppler shift amounts. Each is modulated corresponding to (a plurality of expected values) and stored in the excitation signal database 12D. That is, the excitation signal generating means 12 is configured to include an excitation signal database 12D (storage means) that stores the generated second excitation signal for synthesis with the first excitation signal.

  Thereby, the excitation signal generating means 12 can detect an accurate movement change of the target 30 by predicting an appropriate amount of Doppler shift in advance, and can output a plurality of second excitation signals for synthesis. By reading out from the excitation signal database 12D, it is possible to generate the synthesized signal for excitation very quickly.

  Further, in this case, the Doppler modulation processing unit 12C increases or decreases the frequency in accordance with the increase or decrease of the Doppler shift amount with respect to the modulation according to the Doppler shift amount with respect to the reference excitation signal corresponding to the shift value 0. To modulate. Therefore, when the target 30 approaches the transmission device 10 or moves away from the transmission device 10, the position and speed change of the target 30 can be specified with high accuracy.

(Operation of excitation signal generating means)
Next, an operation of generating an excitation signal by the excitation signal generating unit 12 will be described with reference to FIG. In the pulse train generator 12E shown in FIG. 1, a plurality of (three in the first embodiment) high Doppler sensitivity excitation signals (second excitation signals) are connected to the low Doppler sensitivity excitation signals (first excitation signals). The composite signal for excitation is configured.

  As shown in FIG. 4, the low Doppler sensitivity excitation signal that is the first excitation signal is composed of an LFM signal. Moreover, the high Doppler sensitivity excitation signal which is each 2nd excitation signal of the three area A, the area B, and the area C added to the low Doppler sensitivity excitation signal is comprised by the HFM signal. An excitation composite signal in which three HFM signals are connected to an LFM signal has a certain time length T. The three HFM signals of section A, section B, and section C have excitation signals corresponding to the Doppler shift amount of 3 knots (kt), 2 knots, and 1 knot at the speed at which the target 30 moves away from the transmission device 10. It is generated by the generating means 12.

  For example, the center frequency of the HMF signal in section A corresponding to 3 knots is 806 Hz, the center frequency of the HMF signal in section B corresponding to 2 knots is 804 Hz, and the center frequency of the HMF signal in section C corresponding to 1 knot is 802 Hz. To do. In this case, the frequency drop due to the Doppler shift is 2 Hz with respect to the moving speed of 1 knot. Therefore, if the target 30 is moved away from the transmitter 10 by 3 knots, 2 knots, or 1 knot, the center frequency of the echo signal reflected by the target 30 and received by the receiver 20 is changed by the Doppler shift. The values decrease from 806 Hz, 804 Hz, and 802 Hz by 6 Hz, 4 Hz, and 2 Hz, respectively, and all decrease to 800 Hz.

  Here, in the first embodiment, the speed at which the target 30 approaches the transmission device 10 is a combination of three HFM signals created corresponding to a decrease in Doppler shift amount of 3 knots, 2 knots, and 1 knot. Although the case has been described, a total of six HFM signals added to the LFM signal may be used including the case where the Doppler shift amount increases. However, the number of HFM signals added to the LFM signal is not limited to six, but is appropriately created and added according to the target to be searched. As described above, since the plurality of second excitation signals are signals whose frequencies change in a hyperbola, the plurality of second excitation signals can be easily created by digital signal processing.

  Further, as the second excitation signal, a configuration using a frequency hopping signal whose frequency changes irregularly may be used instead of the hyperbolic frequency modulation. The frequency hopping method (FH-SS: Frequency Hopping Spread Spectrum) is one of the spread spectrum methods, and changes the frequency every very short time (for example, about 0.1 second). Even when the second excitation signal is configured by the frequency hopping method, a plurality of second excitation signals (FH-SS signals) in different frequency ranges are added to the first excitation signal (LFM signal). Therefore, for example, if the second excitation signal is generated by a frequency hopping method with an inexpensive configuration due to the mass production effect by being widely used for mobile phones and the like, the frequency can be changed every extremely short time. It is possible to cope with a case where the movement change range of the target 30 is large.

(Configuration of received signal processing means)
Next, the configuration of the received signal processing means 22 that is the main part of the wave receiving device 20 shown in FIG. 2 will be described. The received signal processing means 22 shown in FIG. 2 is a replica signal (first replica signal) of a conjugate signal based on the low Doppler sensitivity excitation signal (first excitation signal) generated by the excitation signal generation means 12 of the transmission device 10. A replica signal database 22A having an LFM replica signal memory 22A1 in which data is stored in advance and a memory 22A2 in which data of a single frequency replica signal having a preset single frequency of 800 Hz is stored in advance. I have.

  That is, the first replica signal based on the first excitation signal and the second replica signal having a single frequency are configured to use those stored in the replica signal database 22A (memory) provided in advance in the received signal processing means 22. ing. Accordingly, the correlation signal processing between the received signal and the replica signal can be performed quickly, and the replica signal read from the replica signal database 22A of the existing receiving device 20 can be used even when the receiving device 20 is newly added. It can be transferred to the new receiving device 20 and easily stored.

  The reception signal processing means 22 includes an amplifier 22B that amplifies the reception signal obtained from the wave reception means 21 to a level sufficient to perform signal processing.

  Further, the received signal processing means 22 includes a peak position detecting function for detecting the signal peak position of the reflected peak signal, which is a reflected wave from the target 30 obtained from the received signal, on the time coordinate, and the detected signal peak. A time length signal extraction function for extracting a signal portion having a time length (time length T shown in FIG. 4) corresponding to the excitation composite signal of the received signal starting from the position, and the extracted time length signal portion and An echo signal detection function for detecting an echo signal included in the received signal by performing correlation signal processing with the one-frequency replica signal.

  Therefore, in the correlation signal processing for detecting the echo signal from the signal portion of the time length corresponding to the excitation composite signal, a replica signal having a single frequency is used, so that compared to the case of generating a plurality of replica signals. Therefore, it is possible to reduce the circuit scale on the receiving side and reduce the load of correlation signal processing.

  The peak position detection function of the reception signal processing means 22 is a function for detecting the reflection peak signal by performing correlation signal processing between the reception signal and the replica signal based on the first excitation signal. The peak position detection function includes a low Doppler sensitivity replica signal correlator 22C that performs correlation signal processing between the received signal amplified by the amplifier 22B and the single frequency replica signal read from the replica signal database 22A, and a low Doppler sensitivity. By comparing the signal peak position of the reflection peak signal (referred to as the first reflection peak signal) included in the reception signal subjected to the correlation signal processing by the replica signal correlation unit 22C with a preset threshold value TH1, time This is realized by the low Doppler sensitivity replica signal detection unit 22D that detects on the coordinates.

  In addition, the time length signal extraction function of the received signal processing means 22 is an excitation synthesis of received signals starting from the signal peak positions detected by the low Doppler sensitivity replica signal correlator 22C and the low Doppler sensitivity replica signal detector 22D. This is realized by a detection signal cutout unit 22E that extracts a signal portion having a time length T corresponding to the signal.

  Then, the echo signal detection function of the reception signal processing means 22 is a high-level processing that performs correlation signal processing between the signal portion of time length T extracted by the detection signal cutout unit 22E and the single frequency replica signal read from the replica signal database 22A. A signal peak position of a reflection peak signal (this is referred to as a second reflection peak signal) included in the signal portion subjected to correlation signal processing by the Doppler sensitivity replica signal correlation unit 22F and the high Doppler sensitivity replica signal correlation unit 22F is set in advance. This is realized by the high Doppler sensitivity replica signal detection unit 22G that detects the echo signal by comparing with the threshold TH2.

  Further, the received signal processing means 22 includes a Doppler shift amount detection unit 22H that identifies the position and movement change of the target 30 based on the Doppler shift amount included in the echo signal detected by the high Doppler sensitivity replica signal detection unit 22G. (Target identification means).

(Operation of received signal processing means)
Next, in order to specify the position and movement change of the target 30, the signal processing operation by the reception signal processing means 22 will be described with reference to FIG.

  FIG. 5A is a waveform diagram showing a state in which the signal after correlation signal processing of the received signal and the first replica signal in the low Doppler sensitivity replica signal correlation unit 22C is compared with the threshold value TH1. In the case of correlation signal processing between the received signal and the first replica signal, since the level of correlation is high, it is possible to detect the signal peak position from the correlation signal output even if the threshold value TH1 is set to a high value. is there. In FIG. 5A, the signal peak position of the correlation output signal exceeding the threshold TH1 is detected by the correlation signal processing of the head portion of the excitation composite signal, that is, the first excitation signal (LFM signal) and the first replica signal. It represents the beginning of the sound wave.

  The sound wave transmitted from the wave transmitting device 10 is reflected by the target 30 and the seabed or rocks, but before the reflected wave reaches the wave receiving device 20, the direct wave transmitted from the wave transmitting device 10 is reflected. The sound wave reaches first. Therefore, the first signal peak position P1 is not caused by the reflected wave from the target 30 or the seabed or rocks, but is caused by the direct sound wave from the transmission device 10. That is, the second signal peak position P2, the third signal peak position P3, and the fourth and subsequent signal peak positions (not shown) are caused by reflected waves from the target 30, the seabed, rocks, or the like. For this reason, the low Doppler sensitivity replica signal detection unit 22D detects the second and subsequent signal peak positions as being caused by the reflected wave. The detection signal cutout unit 22E extracts the time length T (the time length T of the excitation composite signal shown in FIG. 4) starting from the second and subsequent signal peak positions.

  FIG. 5B is a waveform diagram showing a state in which a signal after correlation signal processing of a signal portion having a time length T starting from the signal peak position P2 and a single frequency replica signal of 800 Hz is compared with a threshold value TH2. It is. In the correlation signal processing of the received signal and the single frequency replica signal, the level of correlation is low, so the threshold value TH2 is set to a value lower than the threshold value TH1.

  As shown in FIG. 5B, the high Doppler sensitivity replica signal detection unit 26G detects a peak signal having a high degree of correlation in the center of the section B within the period of the time length T corresponding to the excitation composite signal. . That is, the high Doppler sensitivity replica signal detection unit 26G has a threshold value on the time coordinate corresponding to the section B of the second replica signal based on the HFM signal generated assuming that the target 30 moves away at a speed of 2 knots. The signal peak position of the peak signal exceeding TH2 is detected as the arrival time of the echo signal and input to the Doppler shift amount detection unit 22H.

  The frequencies of the three HFM signals constituting the excitation composite signal shown in FIG. 4, that is, the frequencies of the sound waves corresponding to the three HFM signals transmitted from the transmission device 10 are 806 Hz, 804 Hz, and 802 Hz, respectively. For this reason, when the target 30 is moving away from the transmission device 10 at a constant speed (for example, x knots), as described above, the three HFM signals among the reception signals received by the reception device 20 are converted into three HFM signals. Since the frequency of the corresponding reflected wave is reduced by 2 Hz with respect to 1 knot, when the target 30 is moving away by x knots, the frequency of the received signal is reduced by 2 x Hz.

The position of the echo signal detected by the high Doppler sensitivity replica signal detection unit 22G is the center of the section B of the 804 Hz HFM signal transmitted from the transmission device 10, as shown in FIG. Therefore, it can be seen from the following calculation formula that the target 30 is moving away by 2 knots.
804-2x = 800
x = 2

  Here, when the frequency range of the HFM signal corresponding to the section B transmitted from the transmission device 10 is 804 Hz ± 1 Hz, the target 30 is moving away by 2 knots ± y (0 <y <0.5) knots. In some cases, the position of the detected echo signal is shifted forward or backward from the center of the section B.

If the position of the echo signal detected by the high Doppler sensitivity replica signal detection unit 22G is the center of the section A or the section C, the target 30 is moved away by 3 knots or 1 knot according to the following equation. I understand that.
806-2x = 800
x = 3
802-2x = 800
x = 1

  The Doppler shift amount detection unit 22H moves away at a speed of 2 knots in the Doppler shift amount, that is, the movement of the target 30 according to the arrival time of the echo signal detected by the high Doppler sensitivity replica signal detection unit 22G. (State) is specified, and the distance to the target 30 is calculated based on the time from the transmission time of the sound wave to the arrival time of the echo signal and the sound speed in water.

  For example, when the transmission time of the transmission means 11 received from the wireless communication unit 13 of the transmission apparatus 10 shown in FIG. 1 via the wireless communication unit 23 is t0, the high Doppler sensitivity replica signal detection shown in FIG. It is assumed that the arrival time of the echo signal detected by the unit 22G is t1. In this case, the Doppler shift amount detection unit 22H determines the distance D1 from the transmission device 10 to the target 30 and the distance D2 from the target 30 to the reception device 20 according to the sound velocity v specified by the conditions of the marine environment. Is calculated by the following arithmetic expression.

D1 + D2 = (t1-t0) × v
The calculated distance (D1 + D2) indicates that the target 30 is present on the circumference of the ellipse when the transmitting device 10 and the receiving device 20 are two focal points of the ellipse. As described above, the receiving device 20 is provided with a receiving direction sensor (not shown) for detecting the direction of the received reflected wave, that is, the direction of the target 30. The position of the target 30 can be specified by the direction.

  FIG. 5C is a waveform diagram showing a state in which the signal after correlation signal processing of the signal portion having the time length T starting from the peak position P3 and the second replica signal is compared with the threshold value TH2. In this case, a peak signal exceeding the threshold value TH2 is not detected. This state represents a state in which the Doppler shift amount of the echo signal included in the received signal is 0 or a value close thereto. That is, the reflected wave corresponding to the signal portion having the time length T starting from the peak position P3 is a reflected wave including a noise component such as reverberation from a non-moving object such as the seabed or a rock. Therefore, the received signal processing means 22 does not erroneously detect a reflected wave including a noise component such as reverberation from the seabed or rock as a reflected wave from the target 30.

  FIG. 6 is a diagram illustrating a state in which a sound wave transmitted from the wave transmitting device 10 is reflected by the target 30 and the reflected waves are received by the three wave receiving devices 20A, 20B, and 20C. In this case, the target 30 moves so as to draw a circle centered on the wave receiving device 20A. That is, the distance between the wave receiving device 20A and the target 30 does not change. Therefore. In the wave receiving device 20A, the Doppler shift amount of the echo signal detected by the reflected wave from the target 30 is zero.

  In contrast, the target 30 moves so as to approach the wave receiving device 20B and also moves away from the wave receiving device 20C. Accordingly, in the wave receiving device 20B, the Doppler shift amount of the echo signal detected by the reflected wave from the target 30 increases with a positive value when the Doppler shift amount of the wave receiving device 20A is used as a reference. On the other hand, in the receiving device 20C, the Doppler shift amount of the echo signal detected by the reflected wave from the target 30 increases as a negative value when the Doppler shift amount of the receiving device 20A is used as a reference. Yes. Therefore, the wave transmitting device 10 that has received the Doppler shift amount data in the three wave receiving devices 20A, 20B, and 20C can accurately specify the moving direction and moving speed of the target 30.

  As described above, in the first embodiment, in the transmission device 10 shown in FIG. 1, the excitation signal generating means 12 generates the excitation signal for sound wave output, and the generated excitation signal is used as the sound wave for target search. The wave transmitting means 11 transmits to the target 30 underwater. In the wave receiving device 20 shown in FIG. 2, the wave receiving means 21 receives the reflected wave from the target 30 and converts it into a received signal, and the received signal processing means 22 performs signal processing on the converted received signal. It is configured to do.

  In this case, the excitation signal generation means 12 in the transmission device 10 individually generates a first excitation signal whose frequency changes linearly and a plurality of second excitation signals whose frequency changes nonlinearly and whose frequency ranges are different. To generate. Next, the excitation signal generation unit 12 generates a composite signal for excitation by adding a plurality of second excitation signals to the first excitation signal, and the sound wave converted and output from the composite signal for excitation by the transmission unit 11. Used as an excitation signal for output.

  On the other hand, the received signal processing means 22 in the wave receiving device 20 shown in FIG. 2 analyzes the received signal and determines the signal peak position of the reflected peak signal that is the reflected wave from the target 30 on the time coordinate. To detect. Next, the reception signal processing means 22 extracts a signal portion having a time length T of the reception signal starting from the detected signal peak position. Further, the received signal processing means 22 performs correlation signal processing of the extracted signal portion having a length of time and a replica signal based on the reference signal to detect an echo signal for specifying a target contained in the received signal.

  Here, the low Doppler sensitivity excitation signal generator 12A in the excitation signal generator 12 shown in FIG. 1 generates the first excitation signal when transmitting the sound wave to the target 30. Similarly to the second excitation signal, the excitation signal is generated in advance before transmitting a sound wave to the target 30 and stored in the excitation signal database 12D, and a pulse train is generated when the sound wave is transmitted to the target 30. The unit 12E may be configured to read both the first excitation signal and the plurality of second excitation signals from the excitation signal database 12D and generate a composite signal for excitation of a pulse train. In this way, there is an advantage that it is possible to shorten the time for generating the real-time first excitation signal by the low Doppler sensitivity excitation signal generating unit 12A when transmitting the sound wave to the target 30.

(Effect of 1st Embodiment)
As described above, according to the underwater target search system 1 of the first embodiment, on the transmission side, the first excitation signal whose frequency changes linearly and the frequency connected to the first excitation signal are nonlinear. And a second excitation signal having a different frequency range for each of a plurality of predetermined time intervals is generated as an excitation signal for sound wave output, and on the receiving side, a correlation signal between the received signal and a replica signal based on the first excitation signal Since the processing and correlation signal processing of the received signal and a single frequency replica signal consisting of a preset single frequency are performed, an echo signal for target identification included in the received signal is detected. Therefore, it is possible to reduce the circuit scale on the receiving side and reduce the load of correlation signal processing.

  Further, the received signal processing means 50 analyzes the received signal, detects the signal peak position of the reflected peak signal, which is a reflected wave from the target 30, on the time coordinate, and uses the detected signal peak position as a starting point. Since a signal portion having a time length T corresponding to the synthesized signal for excitation is extracted, and an echo signal included in the received signal is detected by performing correlation signal processing between the extracted signal portion having the time length T and the single frequency replica signal. After detecting the signal peak position that becomes the head of the reflected wave from the target 30 by correlation signal processing with a high degree of correlation, the degree of correlation is low with respect to a signal portion having a fixed time length starting from the signal peak position. With the two-stage correlation signal processing for performing the correlation signal processing, the target can be reliably detected even in an environment where there is a lot of actual reverberation and noise.

[Second Embodiment]
(Configuration of excitation signal generating means)
Next, a second embodiment of the present invention will be described with reference to FIGS. 7 to 10 and with reference to FIGS. 4 and 5 in the first embodiment. FIG. 7 is a block diagram showing the configuration of the excitation signal generating means 40 in the second embodiment. In FIG. 7, the transmission device 10 transmits a sound wave for target search toward a target 30 in the water, and an excitation signal for sound wave output for input to the wave transmission means 11. And an excitation signal generating means 40 for generating.

  Further, the excitation signal generating means 40 includes a CPU (Central Processing Unit) 41 that controls the excitation signal generating means 40 as a whole, and a system for exchanging data and commands between the CPU 41 and the following units. A bus 42 is provided.

  The system bus 42 includes a ROM (Read Only Memory) 43 in which a program executed by the CPU 41 is stored, a RAM (Random Access Memory) 44 for temporarily storing data processed by the CPU 41, and a target search. A display unit 47 for displaying messages and the like, and an I / F (Interface) 45 for exchanging data between the CPU 41 and an input unit 48 such as a keyboard or pointing device for inputting data and commands such as conditions for searching for a target. Is connected.

  Further, the system bus 42 includes a D / A converter (Digital to Analog Converter) 46 that converts the excitation signal for sound wave output generated by the CPU 41 from a digital signal to an analog signal and inputs the analog signal to the wave transmission means 11. ing. Although omitted in FIG. 7, an amplifier having the same configuration as that of the amplifier 12F in the first embodiment shown in FIG. 1 is provided between the D / A converter 46 and the transmission means 11. .

  The excitation signal generation means 40 in the second embodiment corresponds to a part of the excitation signal generation means 12 in the first embodiment shown in FIG. The CPU 41 in the excitation signal generating means 40 executes a program stored in the ROM 43 to generate a first excitation signal (LFM signal shown in FIG. 4) whose frequency changes linearly as shown in FIG. A function to be generated (a function corresponding to the low Doppler sensitivity excitation signal generation unit 12A shown in FIG. 1) and a second excitation signal (three HFM signals shown in FIG. 4) whose frequency changes nonlinearly are generated in advance. Function (function corresponding to the high Doppler sensitivity excitation signal generation unit 12B shown in FIG. 1), and a function of sequentially generating a plurality of second excitation signals to generate a plurality of second excitation signals having different frequency ranges. (A function corresponding to the Doppler modulation processing unit 12C shown in FIG. 1) and a function for generating a composite signal for excitation by adding a plurality of second excitation signals to the first excitation signal (the pulse train generation shown in FIG. 1) Function corresponding to parts 12E) to realize.

  For other information processing, for example, input processing of command information from the input unit 49 via the I / F 45 and output processing of image information to the display unit 48, the CPU 41 executes a program stored in the ROM 43. Executed.

  Further, the RAM 44 in the second embodiment corresponds to the excitation signal database 12D in the first embodiment shown in FIG. 1, and is an excitation composite signal generated by the CPU 41, that is, the LFM signal ( An excitation composite signal obtained by concatenating and adding three HFM signals (second excitation signals) in different frequency ranges every three fixed time intervals to the first excitation signal) is stored.

  Also in the second embodiment, actually, the speed at which the target 30 approaches the transmission device 10 includes three HFM signals created corresponding to the increase in the Doppler shift amount of 1 knot, 2 knots, and 3 knots. Thus, a total of six HFM signals are added to the LFM signal. Further, the number of HFM signals added to the LFM signal is not limited to six, but is appropriately created and added according to the target to be searched. As described above, since the plurality of second excitation signals are signals whose frequencies change in a hyperbola, the plurality of second excitation signals can be easily created by a digital signal processing algorithm executed by the CPU 41.

  Here, the second excitation signal may be composed of a frequency hopping FH-SS signal whose frequency changes irregularly, instead of hyperbolic frequency modulation. Even when the second excitation signal is composed of a frequency hopping signal, a second excitation signal (FH-SS signal) having a different frequency range is added to the first excitation signal (LFM signal) for each of a plurality of predetermined time intervals. . Therefore, if the second excitation signal is generated by the frequency hopping method, the frequency can be changed every extremely short time, so that it is possible to cope with a case where the movement change range of the target 30 is large.

  In the case of the first embodiment described above, as shown in FIG. 1, a plurality of second excitation signals generated by the high Doppler sensitivity excitation signal generator 12B and the Doppler modulation processor 12C are stored in the excitation signal database 12D. Then, the pulse train generation unit 12E reads the plurality of second excitation signals stored in the excitation signal database 12D and adds them to the first excitation signal generated in real time by the low Doppler sensitivity excitation signal generation unit 12A. .

However, in the second embodiment, the first excitation signal is generated by software executed by the CPU 41 in place of the hardware low Doppler sensitivity excitation signal generation unit 12A capable of high-speed processing. In some cases, the generation of the first excitation signal in real time may not be in time. For this reason, the first excitation signal is also created in advance and stored in the RAM 44.
(Operation of excitation signal generating means)

  Next, the operation of the excitation signal generation process executed by the CPU 41 of the excitation signal generation means 40 shown in FIG. 7 will be described based on the flowchart of FIG. The CPU 41 generates a first excitation signal (step S101) and stores the generated excitation signal in the RAM 44 (step S102), so that the frequency forming a part of the sound wave output excitation signal is linear. A first excitation signal generation step of generating a first excitation signal that changes to

  Next, the CPU 41 generates a reference second excitation signal corresponding to the shift amount 0 (step S103), and modulates the reference second excitation signal into a second excitation signal corresponding to the predicted Doppler shift amount. The process (step S104), the process for determining whether or not the modulation process corresponding to all predicted shift amounts has been completed (step S105), and the case where the modulation process corresponding to all predicted shift amounts has not been completed (step S105). In step S105; NO), by repeating the process in step S104 until the modulation process corresponding to all the predicted shift amounts is completed (step S105; YES), the frequency forming a part of the excitation signal for sound wave output is changed. A second excitation signal generating step for generating a plurality of second excitation signals that change nonlinearly and have different frequency ranges is executed.

  Next, the CPU 41 executes a composite signal generation step of generating an excitation composite signal by a process of adding a plurality of second excitation signals to the first excitation signal stored in the RAM 44 (step S106). As a result, the excitation composite signal of time length T connected by adding a plurality of HFM signals (second excitation signals) to the LFM signal (first excitation signal) shown in FIG.

  In this way, the excitation signal generating means 40 modulates the second excitation signal at a frequency corresponding to a presumed Doppler shift amount of the received signal. In this case, the CPU 41 generates a reference excitation signal corresponding to a shift value 0 when it is assumed that there is no Doppler shift amount, and generates the reference excitation signal for a plurality of Doppler shift amounts (a plurality of expected Doppler shift amounts). Each of the signals is modulated in accordance with each value and stored in the RAM 44. That is, the excitation signal generating means 40 is configured to include a RAM 44 (storage means) that stores the generated second excitation signal for synthesis with the first excitation signal.

  Therefore, the excitation signal generation means 40 can detect an accurate movement change of the target 30 by predicting an appropriate Doppler shift amount in advance, and can read a plurality of second excitation signals for synthesis from the RAM 44 and A composite signal for excitation can be generated quickly.

  Further, in this case, the CPU 41 modulates the modulation according to the Doppler shift amount with respect to the reference excitation signal corresponding to the shift value 0 so as to increase or decrease the frequency corresponding to the increase or decrease of the Doppler shift amount. . Therefore, when the target 30 approaches the transmission device 10 or moves away from the transmission device 10, the position and speed change of the target 30 can be specified with high accuracy.

After that, when a sound wave transmission command, that is, a command to start searching for the target 30 is input from the input unit 49, the CPU 41 reads the excitation composite signal from the RAM 44, and the D / A converter 46 and an amplifier (not shown) Is input to the wave transmission means 11.
(Configuration of received signal processing means)

  FIG. 9 shows the configuration of the received signal processing means 50 in the second embodiment. In FIG. 9, a received signal processing means 50 is a CPU (Central Processing Unit) 51 that controls the received signal processing means 50 as a whole, and for exchanging data and commands between the CPU 51 and the following units. A system bus 52 is provided.

  The system bus 52 includes a ROM (Read Only Memory) 53 in which a program executed by the CPU 51 is stored, a RAM (Random Access Memory) 54 that temporarily stores data processed by the CPU 51, and the searched target 30. The display unit 57 for displaying the data and the selection of the data to be displayed and the input unit 58 for inputting other conditions and an I / F (Interface) 55 for transferring data between the CPU 51 and the CPU 51 are connected. Has been.

  Further, the system bus 52 includes an A / D converter (Analog to Digital Converter) 56 that converts the received signal captured by the wave receiving means 21 from an analog signal to a digital signal and inputs the signal to the CPU 51. Although not shown in FIG. 9, an amplifier similar to the amplifier 22 </ b> B shown in FIG. 2 is provided between the wave receiving means 21 and the A / D converter 56.

  The RAM 54 in the second embodiment has a storage area corresponding to the replica signal database 22A shown in FIG. 2, is generated by the excitation signal generation means 40 shown in FIG. 7, and is stored in the RAM 44. A replica signal (first replica signal) and a single frequency replica signal (second replica signal) are stored in advance.

  That is, the first replica signal and the second replica signal (single frequency replica signal) based on the first excitation signal are stored in the RAM 54 (memory) provided in advance in the received signal processing means 50. ing. Therefore, correlation signal processing between the received signal and the replica signal can be performed quickly, and even when a new wave receiving device 20 is newly added, the replica signal read from the RAM 54 of the existing wave receiving device 20 is added to the new signal. It can be transferred to the receiving device 20 and stored easily.

  The received signal processing means 50 in the second embodiment corresponds to a part of the received signal processing means 22 in the first embodiment shown in FIG. That is, the received signal processing means 50 performs correlation signal processing between the received signal captured by the wave receiving means 21 and the replica signal stored in the RAM 54 to detect an echo signal included in the received signal.

  The reception signal processing means 50 detects the signal peak position of the reflected peak signal, which is a reflected wave from the target 30, from the received signal on the time coordinate by causing the CPU 51 to execute the program stored in the ROM 53. A peak position detection function, a time length signal extraction function for extracting a signal portion having a time length corresponding to the synthesized signal for excitation of the received signal starting from the detected signal peak position, and a signal of the extracted time length An echo signal detection function for detecting an echo signal included in the received signal by performing correlation signal processing between the portion and the single frequency replica signal.

  In this case, the peak position detection function of the reception signal processing means 50 is a function for detecting the reflection peak signal by performing correlation signal processing between the reception signal and the replica signal based on the first excitation signal. The peak detection function includes a function for performing correlation signal processing between the received signal and the first replica signal read from the RAM 54 (a function corresponding to the low Doppler sensitivity replica signal correlator 22C shown in FIG. 2), and a correlation signal. A function of detecting on the time coordinate by comparing the signal peak position of the reflection peak signal (first reflection peak signal) included in the processed reception signal with a preset threshold TH1 (low level shown in FIG. 2). And the Doppler sensitivity replica signal detection unit 22D).

  Further, the time length signal extraction function of the received signal processing means 50 is a time length corresponding to the synthesized signal for excitation of the received signal starting from the signal peak position detected by the peak position detecting function (the time shown in FIG. 4). This is realized by a function (a function corresponding to the detection signal cutout unit 22E shown in FIG. 2) for extracting a signal portion having a length T).

  The echo signal detection function of the received signal processing means 50 is a correlation signal between the signal portion of the time length T extracted by the time length signal extraction function and the single frequency replica signal (second replica signal) read from the RAM 54. A function of performing processing (function corresponding to the high Doppler sensitivity replica signal correlator 22F shown in FIG. 2) and a signal of a reflection peak signal (second reflection peak signal) included in a signal portion subjected to correlation signal processing by this function By comparing the peak position with a preset threshold value TH2, it is realized by the function of detecting as an echo signal (a function corresponding to the high Doppler sensitivity replica signal detection unit 22G shown in FIG. 2).

  Further, the received signal processing means 50 has a function of specifying the position and movement change of the target 30 based on the Doppler shift amount included in the echo signal detected by the function corresponding to the high Doppler sensitivity replica signal detection unit 22G ( The function corresponding to the Doppler shift amount detection unit 22H shown in FIG. 2 is realized.

(Operation of received signal processing means)
Next, the operation of the received signal processing executed by the CPU 51 of the received signal processing means 50 in FIG. 9 will be described.

  The sound wave transmitted from the wave transmitting means 11 in FIG. 7 is reflected by the target 30 and the reflected wave is captured by the wave receiving means 21 in FIG. The received signal processing means 50 inputs the received signal captured by the wave receiving means 21 to the CPU 51 via an amplifier and A / D converter 56 (not shown).

  In the flowchart of FIG. 10, the CPU 51 detects the received signal and the first replica signal received signal (step S111), compares the first threshold value with the received signal (step S112), and detects the signal peak position. A peak position detection process step of analyzing the received signal and detecting the signal peak position of the reflected peak signal, which is a reflected wave from the target 30, on the time coordinate by the process of determining whether or not (step S113). Execute.

  Next, the CPU 51 determines whether or not the peak signal detected in step S113 is a direct wave from the wave transmitting means 11 of FIG. 7 (step S114), and if it is a direct wave (step S114; YES). Then, the subsequent processing is not performed, the process proceeds to step S112, and the peak position detection processing step is executed again.

  When the peak signal detected in step S113 is not a direct wave from the wave transmission means 11 of FIG. 7 (step S114; NO), the CPU 51 extracts a signal portion starting from the signal peak position of the peak signal (step S114: NO). In step S115), a time length signal extraction step of extracting a signal portion having a time length corresponding to the excitation signal starting from the detected signal peak position is executed. Further, correlation signal processing between the extracted signal portion and the single frequency replica signal (step S116), processing for comparing the second threshold value with the extracted signal portion (step S117), and determination of whether a peak signal has been detected. By performing the processing (step S118), an echo signal detection step is performed in which the correlation signal processing of the extracted signal portion having the length of time and the replica signal based on the excitation signal is performed to detect an echo signal included in the received signal.

  As described above, in the second embodiment, in the transmission device 10 shown in FIG. 7, the excitation signal generating means 40 generates the excitation signal for sound wave output, and the generated excitation signal is used as the sound wave for target search. The wave transmitting means 11 transmits to the target 30 underwater. Then, in the wave receiving device 20 shown in FIG. 9, the wave receiving means 21 receives the reflected wave from the target 30 and converts it into a received signal, and the received signal processing means 22 performs signal processing on the converted received signal. It is configured to do.

  In this case, the excitation signal generation means 40 in the transmission device 10 individually generates a first excitation signal whose frequency changes linearly and a plurality of second excitation signals whose frequency changes nonlinearly and whose frequency ranges are different. To generate. Next, the excitation signal generating unit 40 generates a composite signal for excitation by adding a plurality of second excitation signals to the first excitation signal, and the sound wave converted and output from the composite signal for excitation by the transmission unit 11. Used as an excitation signal for output.

  On the other hand, the received signal processing means 50 in the wave receiving device 20 shown in FIG. 9 analyzes the received signal and determines the signal peak position of the reflected peak signal that is the reflected wave from the target 30 on the time coordinate. To detect. Next, the reception signal processing means 50 extracts a signal portion having a time length T of the reception signal starting from the detected signal peak position. Further, the received signal processing means 50 performs correlation signal processing of the extracted signal portion having a length of time and the single frequency replica signal to detect an echo signal for specifying a target contained in the received signal.

(Effect of 2nd Embodiment)
According to the underwater target search system 1 of the second embodiment, on the transmission side shown in FIG. 7, the first excitation signal whose frequency changes linearly and the frequency connected to the first excitation signal are nonlinear. And generating a second excitation signal having a different frequency range for each of a plurality of intervals of a certain time as an excitation signal for sound wave output. On the receiving side shown in FIG. 9, a replica based on the received signal and the first excitation signal is generated. Performs correlation signal processing with the signal and correlation signal processing between the received signal and a single frequency replica signal consisting of a preset single frequency to detect an echo signal for target identification contained in the received signal With this configuration, it is possible to reduce the circuit scale on the receiving side and reduce the load of correlation signal processing.

  Further, the received signal processing means 50 analyzes the received signal, detects the signal peak position of the reflected peak signal, which is a reflected wave from the target 30, on the time coordinate, and uses the detected signal peak position as a starting point. Since a signal portion having a time length T corresponding to the synthesized signal for excitation is extracted, and an echo signal included in the received signal is detected by performing correlation signal processing between the extracted signal portion having the time length T and the single frequency replica signal. After detecting the signal peak position that becomes the head of the reflected wave from the target 30 by correlation signal processing with a high degree of correlation, the degree of correlation is low with respect to the signal portion of the time length corresponding to the excitation signal from the signal peak position. By the two-stage correlation signal processing for performing the correlation signal processing, the target can be reliably detected even in an environment where there is a lot of actual reverberation and noise.

  Here, in the said 1st and 2nd embodiment, although it was set as the structure which performs radio | wireless communication between the transmission apparatus 10 and each receiving apparatus 20, the underwater target search which installed the transmission apparatus 10 in the seabed. A system is also conceivable. In this case, since wireless communication cannot be performed with each of the wave receiving devices 20, both are connected by a cable and wired communication is performed. Alternatively, in the case of a configuration in which the position and movement change of the target 30 specified by each wave receiving device 20 are wirelessly transmitted to an information management system other than the wave transmitting device 10, the wave transmitting device 10 required by each wave receiving device 20. This information is only the transmission time of transmission.

  Therefore, when the distance between the wave transmitting device 10 installed on the seabed and each wave receiving device 20 installed in the water near the sea surface is determined in advance, the certain wave receiving device 20 determines the distance. When the distance is D and the arrival time of the direct wave signal peak position P1 shown in FIG. 5B is t0 ′, the transmission time t0 of the transmission of the transmission device 10 is measured by a temperature sensor (not shown). The sound velocity v in the sea specified by the current temperature is expressed by the following equation.

t0 = t0′−D / v
Thus, even in the underwater target searching system in which the wave transmitting device 10 is installed on the seabed, the position and moving speed of the target 30 can be specified by each wave receiving device 20.

  In each of the above embodiments, the present invention has been described with respect to an underwater target search system that searches for an underwater target. However, the present invention relates to an air target search system that searches for an air target such as a flying object. Can also be applied. For example, on the sea or on land, a sound wave is transmitted from a wave transmitting device arranged at a certain position toward a search target space, and a reflected wave from the search space is received by a wave receiving device arranged at another position, An aerial target search system that detects changes in the position and movement of a target passing through the search space can be considered.

  The present invention relates to an underwater target search system in which a transmission device and a reception device are separated, or a manufacturing industry that manufactures an underwater target search system in which a transmission device and a reception device are integrated, and others. Applicable to industries related to.

DESCRIPTION OF SYMBOLS 1 Underwater target search system 10 Transmission apparatus 11 Transmission means 12 Excitation signal generation means 12A Low Doppler sensitivity excitation signal generation part 12B High Doppler sensitivity excitation signal generation part 12C Doppler modulation processing part 12D Excitation signal database 12E Pulse train generation part 20 Reception Wave device 21 receiving means 22 received signal processing means 22A replica signal database 22C low Doppler sensitivity replica correlation unit 22D low Doppler sensitivity replica detection unit 22E detection signal cutout unit 22F high Doppler sensitivity replica correlation unit 22G high Doppler sensitivity replica detection unit 22H Doppler Shift amount detection unit 30 Target 40 Excitation signal generation means 41 CPU
44 RAM
50 Received signal processing means 51 CPU
54 RAM

Claims (19)

A wave transmitting means for transmitting a target search sound wave toward an underwater target; a wave receiving means for receiving a reflected wave from the target; and an excitation signal generating means for generating an excitation signal for the sound wave output. Underwater target search system with
The excitation signal generating means is
An excitation signal generating function for generating a first excitation signal whose frequency changes linearly and a second excitation signal having a different frequency range for each of a plurality of preset time intervals; and A composite signal generation function for generating a composite signal for excitation by adding a second excitation signal of a plurality of sections and making the excitation signal for sound wave output,
Correlation signal processing of the received signal and a replica signal based on the first excitation signal generated by the excitation signal generating means, and the reception signal and a single frequency replica signal composed of a preset single frequency An underwater target searching system comprising: a received signal processing means for performing correlation signal processing to detect an echo signal for specifying a target contained in the received signal. The underwater target search system according to claim 1,
Each of the second excitation signals for each of the plurality of sections is a signal whose frequency changes in a hyperbolic manner. The underwater target search system according to claim 1,
Each underwater target search system characterized in that each second excitation signal for each of the plurality of sections is a signal whose frequency changes irregularly. The underwater target search system according to claim 1,
The received signal processing means detects a signal peak position of a reflected peak signal, which is a reflected wave from the target, on a time coordinate by correlation signal processing of the received signal and a replica signal based on the first excitation signal. A peak position detecting function, a time length signal extracting function for extracting a signal portion having a time length corresponding to the excitation composite signal of the received signal starting from the detected signal peak position, and a time length of the extracted time length An underwater target search system comprising: an echo signal detection function for performing correlation signal processing between a signal portion and the single frequency replica signal to detect the echo signal included in the received signal. In the underwater target search system according to claim 4,
The peak position detection function of the reception signal processing means is a function of detecting the reflection peak signal by performing correlation signal processing of the reception signal and a replica signal based on the first excitation signal, and the reception signal processing The echo signal detection function of the means is characterized in that the signal peak position in one section is shifted by Doppler shift of the echo signal by the correlation signal processing of the signal portion corresponding to the second excitation signal in the plurality of sections and the single frequency replica signal. An underwater target search system comprising a Doppler shift amount detection function for detecting a quantity. In the underwater target search system according to claim 5,
The underwater target search system characterized in that the replica signal based on the first excitation signal and the single frequency replica signal are stored in a memory provided in advance in the reception signal processing means. In the underwater target search system according to claim 5,
The excitation signal generation function of the excitation signal generation means includes a low Doppler sensitivity excitation signal generation unit that generates a first excitation signal whose frequency changes linearly, and the frequency that changes nonlinearly for each of the plurality of intervals. An underwater target search system characterized by having a function realized by a high Doppler sensitivity excitation signal generation unit and a Doppler modulation generation unit that generate a second excitation signal. In the underwater target search system according to claim 7,
The composite signal generation function of the excitation signal generation means is a function realized by a pulse train generation unit that connects the generated second excitation signals of the plurality of sections to the first excitation signal. Search system. In the underwater target search system according to any one of claims 1 to 8,
An underwater target searching system, wherein the received signal processing means is further provided with target specifying means for specifying the position and movement change of the target based on an echo signal detected by the received signal processing means. The underwater target search system according to claim 1,
The excitation signal generating means includes
A function of generating the second excitation signal by modulating at a frequency corresponding to a Doppler shift amount of a reception signal assumed in advance;
When generating the second excitation signal by this modulation, a reference excitation signal is generated corresponding to a shift value of 0 when it is assumed that there is no Doppler shift amount, and the generated reference excitation signal is converted to the Doppler shift. It is configured to modulate each according to the amount,
An underwater target search system, wherein the excitation signal generating means is further provided with storage means for storing the second excitation signal generated by the excitation signal generating means for synthesis with the first excitation signal. In the underwater target search system according to claim 10,
The underwater target search system according to claim 1, wherein the modulation according to the Doppler shift amount with respect to the reference excitation signal is a modulation in which the frequency is increased or decreased in response to the increase or decrease of the Doppler shift amount. An excitation signal generating means generates an excitation signal for sound wave output, converts the generated excitation signal into a sound wave for target search, and transmits the sound wave toward a target in water. In the underwater target searching method for specifying the target by receiving the reflected wave and converting the received signal into a received signal, and the received signal processing means performs signal processing on the converted received signal.
A first excitation signal whose frequency changes linearly and a second excitation signal whose frequency changes nonlinearly and has a different frequency range for each of a plurality of preset time intervals, the excitation signal generating means Generated separately,
Next, the excitation signal generating means generates the excitation composite signal by adding the second excitation signal for each of the plurality of sections to the first excitation signal,
This excitation composite signal is used as an excitation signal for sound wave output converted and output from the transmission means,
Correlation signal processing between the received signal and a replica signal based on the generated first excitation signal and correlation signal processing between the received signal and a single frequency replica signal having a preset single frequency are performed. An underwater target searching method, wherein the received signal processing means detects an echo signal for specifying a target contained in the received signal. The underwater target searching method according to claim 12,
The received signal processing means detects the signal peak position of the reflected peak signal which is a reflected wave from the target by analyzing the received signal on the time coordinate,
The received signal processing means extracts a signal portion having a time length corresponding to the synthesized signal for excitation of the received signal starting from the detected signal peak position,
The received signal processing means detects the echo signal for specifying the target contained in the received signal by performing correlation signal processing between the extracted signal portion of the time length and the single frequency replica signal. An underwater target search method characterized by The underwater target searching method according to claim 13,
The step of detecting the peak position by the received signal processing means is performed by performing correlation signal processing of the reflected peak signal between the received signal and a replica signal based on the first excitation signal, and the received signal processing means The step of detecting the echo signal according to the method includes the step of correlating the signal portion corresponding to the second excitation signal in the plurality of sections and the single frequency replica signal to determine the signal peak position in one section as a Doppler of the echo signal. An underwater target search method, which is executed by detecting as a shift amount. The underwater target searching method according to claim 13,
When generating the excitation signal by the excitation signal generating means, a low Doppler sensitivity excitation signal generating unit generates a first excitation signal whose frequency changes linearly, and the frequency changes nonlinearly for each of the plurality of sections. And a second Doppler sensitivity excitation signal generator and a Doppler modulation processor that generate second excitation signals having different frequency ranges. The underwater target searching method according to claim 15,
When generating the excitation composite signal by the excitation signal generating means, a pulse train generation unit connects the generated second excitation signals of the plurality of sections to the first excitation signal. Target search method. The underwater target searching method according to claim 16,
An underwater target searching method characterized in that, based on an echo signal detected by the received signal processing means, a pre-equipped target specifying means specifies the position and movement change of the target. A wave transmitting means for converting an excitation signal generated for sound wave output into a sound wave for target search and transmitting it to an underwater target, and a received wave for receiving a reflected wave from the target and converting it into a received signal An underwater target search system comprising: means; and an excitation signal generating means for generating an excitation signal for sound wave output,
In generating the excitation signal,
A first excitation signal generating function for generating a first excitation signal in which a frequency forming a part of the excitation signal for sound wave output changes linearly;
Corresponding to a single frequency replica signal consisting of a single frequency used for correlation signal processing in the receiving means, a frequency forming a part of the excitation signal for sound wave output varies in a non-linear manner and a plurality of A second excitation signal generation function for generating a second excitation signal having a different frequency range for each interval of a fixed time;
And a composite signal generation function for generating a composite signal for excitation by adding the second excitation signal of the plurality of sections to the first excitation signal,
Is executed by a computer provided in the excitation signal generating means. A wave transmitting means for converting an excitation signal generated for sound wave output into a sound wave for target search and transmitting it to an underwater target, and a received wave for receiving a reflected wave from the target and converting it into a received signal And a first excitation signal whose frequency changes linearly and a second excitation signal whose frequency connected to the first excitation signal changes nonlinearly and whose frequency range is different for each of a plurality of fixed time intervals. In an underwater target searching system for specifying the target by performing signal processing on the received signal by the received signal processing means, and an excitation signal generating means for generating as a synthetic signal for excitation for sound wave output,
Correlation signal processing between the captured received signal and a replica signal based on the first excitation signal generated by the excitation signal generating means, and a single frequency replica signal composed of the reception signal and a preset single frequency And a reception signal processing function for detecting an echo signal for target identification contained in the reception signal by performing correlation signal processing with
The execution contents of this received signal processing function are
A peak position detection processing function for analyzing the received signal and detecting a signal peak position of a reflected peak signal, which is a reflected wave from the target, on a time coordinate;
A time length signal extraction function for extracting a signal portion of a time length corresponding to the synthesized signal for excitation starting from the detected signal peak position;
And an echo signal detection function for detecting the echo signal included in the received signal by performing correlation signal processing between the extracted time-length signal portion and the single frequency replica signal,
An underwater target searching program characterized in that the program is executed by a computer provided in the reception signal generating means.

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