JP2000088942A - Method for discriminating left/right of bistatic sonar - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method for discriminating the left/right of a bistatic sonar where a wave transmission level and directional characteristics can be matched left and right easily by using an identical frequency band for two acoustic waves to be transmitted left and right from an sound source array. SOLUTION: For output where either one and the other of two pulsive signals with the same frequency band and different waveforms are transmitted to the left half space and the right half space of its platform, respectively, from a sound source array and are received by a receiver array being located away from the sound source array for performing phase-adjusting processing 5, the replica signal of above waveforms 1 and 2 are used and correlation processing 52 and 53 of two systems and signal detection processing 54 and 55 of the correlation output are performed in parallel, and it is judged whether the arrival azimuth of an echo sound is located at the left or right side of the above platform by comparing the level of the correlation output values of the above two systems at the signal detection positions 56, thus estimating the position of a target 57.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for receiving, at a position apart from a sound source array and a receiver array, a reverberation sound of a target object of an acoustic pulse wave radiated from the sound source by the receiver array. The present invention relates to a method for determining the right and left of a target in a bistatic sonar that detects the presence of the target and estimates its position.

[0002]

2. Description of the Related Art At a position distant from a sound source array and a receiver array, a receiver array receives an echo (echo) of an acoustic pulse wave radiated from a sound source from the target, thereby receiving the target array. Bistatic sonars that detect presence and estimate position have been used in the past. This bistatic sonar allows the depth of the sound source and receiver to be set according to environmental conditions, and allows the dimensions of the receiver array to be designed without restrictions on the platform dimensions. Bistatic sonar using an array is an effective technique for improving target detection capability. The beam formed by the towed receiver array has a directional pattern that is rotationally symmetric with respect to the axis of the receiver array (hereinafter, this axis is called the array axis), and the maximum sensitivity plane of the beam is about the array axis. It becomes a conical surface.

FIG. 4 is an explanatory view of a conical beam shape of a linear array, in which a linear array of receivers, an array axis, a beam forming horizontal direction, and a cone surface of maximum sensitivity are shown. Therefore, the echo from the target
When a certain receiving beam arrives, it is impossible to distinguish in which direction the target object is located on the maximum sensitivity conical surface of the receiving beam. Conventionally, the following method has been used to solve this problem. In the conventional method, the sound source arrays are provided separately on the left and right, and different frequencies are transmitted on the left and right, respectively, and the frequency of the received echo is measured to determine whether the target exists on the left or right.

FIG. 5 is an explanatory view of a conventional bistatic sonar left / right discriminating method. In FIG. 5, the pulse frequency F _L from the left sound source array attached to the left side of the sound source, also emits pulses of frequency F _R from the right sound source array attached to the right side. Then, to come back echoes of the frequency F _R is an echo of the frequency F _L is also the goal of being in the right of the half-space of the towing line from the target existing in the half-space on the left side of the towing line, the wave receiver array By measuring the frequency of the echo, the left and right discrimination of the position where the target exists can be performed.

[0005]

However, the above-mentioned conventional method for determining the left and right sides of a bistatic sonar has the following problems. (1) When a pulse wave is transmitted from the sound source at left and right separate frequencies, the frequency band of the left and right sound sources is adjusted to a very wide band. Especially in environmental conditions where reverberation is a problem, the transmitted signal is moving toward a wider band. To achieve this, a transmitter with a very wide band characteristic or a transmitter with different frequency characteristics on the left and right Vessel is required. (2) Further, when performing transmission with different frequencies, additional considerations are necessary in adjusting the transmission level and the directional characteristics on the left and right, and it is necessary to design different arrangement dimensions and electric systems. Become. SUMMARY OF THE INVENTION An object of the present invention is to provide a method for performing left / right discrimination with a simple configuration by overcoming the above-described problems of the conventional method when transmitting from a sound source separately for left and right.

[0006]

According to the present invention, there is provided a bistatic sonar left / right discriminating method in which a sound pulse wave radiated from a sound source is reflected from a target at a position separated from a sound source array and a receiver array. In a bistatic sonar for detecting a target by receiving sound with a receiver array and estimating its position, one of two pulse signals having the same frequency band and different waveforms is obtained from the sound source array. A replica signal of the two pulse signals is transmitted to the left half space of the platform and the other is transmitted to the right half space of the platform and received by the receiver array and subjected to phasing processing. Is used to perform two systems of correlation processing and signal detection processing of the correlation output in parallel, and the correlation of the two systems at these signal detection positions is performed. Arrival direction of reverberation by the size comparison of force values to determine whether a right or a left of said platform. As a result, while solving the conventional problem of determining the direction of arrival of the reverberant sound, the two acoustic waves transmitted from the sound source use the same frequency band, so the band becomes narrower than before, and the transmission level and directivity of the sound source are further reduced. It is also easy to match the characteristics on the left and right.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing the embodiments of the present invention, the outline of the present invention will be described. The present invention provides a receiver array that uses left and right different pulse signals in order to distinguish between two pulse signals transmitted in the same frequency band when transmitting from a sound source separately in the left and right directions. The two phase correlation processing using the respective replica signals of the pulse signals having different waveforms is performed on the phasing beam output of It is determined whether the signal has arrived. Therefore, it is possible to stably determine left and right of the direction of arrival of the reverberation sound using a receiver array composed of a linear array of sound sources and single receivers having the same left and right, relatively narrow band characteristics. Having.

FIG. 1 is a schematic explanatory view of a method for judging left and right of a bistatic sonar according to the present invention. In FIG. 1, reference numerals 51 to 57 indicate signal processing steps, respectively. In FIG. 1, two sound sources separately arranged on the left and right respectively emit pulse waves into a left half space and a right half space of the platform. As transmission waveforms, waveforms 1 and 2 having different waveforms but the same band are prepared, and waveform 1 is transmitted from the left sound source, and waveform 2 is transmitted from the right sound source. Then, the transmission signal of the waveform 1 is incident on the target 1 located on the left side of the sound source platform, and the echo returns to the receiver array. For target 2 on the right side of the platform, waveform 2
Is transmitted, and the echo returns to the receiver array.

Therefore, two correlation processes (52, 53) using waveforms 1 and 2 as replica signals are respectively applied to the received beam output obtained by phasing (51) the received signal of the receiver array. And the signal detection processing (54, 55) is performed on each of the two correlation processing outputs. If the echo of the target 1 on the left side is a signal obtained by detecting the correlation output using the waveform 1 as a replica signal, a high level value is given to the echo. The echo of the target 2 on the right side produces a high level value in a signal obtained by detecting a correlation output using the waveform 2 as a replica signal. For this reason, the two signal detection values are compared, and if the signal detection value of the correlation output with the replica of the waveform 1 is larger, it is determined that the target exists on the left side, and the signal of the correlation output with the replica of the waveform 2 is determined. When it is determined that the target exists on the right side when the detected value is larger (56), the position of the target can be estimated (57) without causing left-right ambiguity.

Embodiment 1 In Embodiment 1 of the present invention, a linear frequency modulation signal (Linear FM signal is abbreviated and hereinafter referred to as LFM signal) is used as a transmission waveform. As the waveform 1, an LFM waveform whose frequency linearly increases with time from a frequency fl to a frequency f2 within a pulse length of a certain time width is used, and as a waveform 2, the frequency f2 is increased within a pulse length of the same time width. An LFM waveform linearly falling from time to time f1 is used.

FIG. 2 is an explanatory diagram of a left / right discriminating method of the bistatic sonar according to the first embodiment of the present invention. FIG.
, 1 and 2 are LFM signal generators, 3 and 4 are amplifiers, 5 and 6 are transmitters (arrays), 7 is receiver arrays, 8
Is a plurality of phase adjusters for forming beams in a plurality of directions, respectively, and 9 and 10 are for the respective phasing outputs of the plurality of phase adjusters 8 together with the time generated by the LFM generators 1 and 2, respectively. LFM signal rising, LF falling with time
This is a two-system LFM correlator that performs a correlation process using each replica signal with the M signal, and the same number of LFM correlators as the number of the phase adjusters 8 are provided for each system. 11 and 12
Is a signal detector, 13 is a corresponding point extractor for extracting corresponding points of two signal detection outputs, 14 is a comparator for comparing correlation output signals of corresponding points, and 15 is an output on the side selected by the comparator. This is a target position measuring instrument that performs precise measurement of the target position by using the target position measuring device.

The operation of the first embodiment will be described with reference to FIG.
The LFM signal generator 1 generates an LFM pulse signal (hereinafter, referred to as a signal 1) whose instantaneous frequency increases linearly with time from the frequency f1 to f2, is amplified by the amplifier 3, and is transmitted from the transmitter 5. Radiated into the sea on the port side of the platform. On the other hand, the LFM signal generator 2 generates an LFM pulse signal (hereinafter, referred to as signal 2) whose instantaneous frequency decreases linearly with time from the frequency f2 to f1 and is amplified by the amplifier 4 to transmit the signal to the transmitter Radiated from 6 into the sea on the starboard side of the platform. If the target is underwater, signal 1 will be incident on the target on the port side of the platform and signal 2 will be incident on the target on the starboard side, and its echo will return to the receiver array 7. .

The signal received by the receiver array 7 is sent to a plurality of phase adjusters 8. The plurality of phase shifters 8 form a plurality of beams having the maximum sensitivity in a plurality of directions from the front direction to the rear direction of the receiver array 7, and divide the plurality of beam outputs into a plurality of corresponding beams. It is sent to LFM correlators 9 and 10. At this point, the bearing is indistinguishable between port and starboard, and represents the angle θ from the array axis of the receiver array. The direction cosine value cos θ may be used instead of this angle value. In each of the plurality of LFM correlators 9, the plurality of beam outputs sent from each of the phase adjusters 8 perform correlation processing and integration processing with the replica signal of the signal 1, respectively.
The output is sent to the signal detector 11. At the output of the LFM correlator 9, a large correlation output is obtained for echoes from a target on the port side of the platform from which the signal 1 was transmitted,
In addition, a small correlation output is obtained for an echo from a target located on the starboard side of the platform from which the signal 2 is transmitted. Since the LFM pulse signal is used as the transmission signal, the correlation output is slightly deteriorated due to the Doppler effect caused by the target motion.

The signal detector 11 outputs correlation processing of a plurality of beams sent from the plurality of LFM correlators 9 (hereinafter, referred to as "correlation processing output").
This is called a left correlation output), a portion that can be determined as an echo from the target is detected, and the beam and time information are sent to the corresponding point extractor 13 together with the left correlation output. As a method of detecting an echo from a target, for example, there is the following method. That is, the correlation processing output of each time and beam is normalized with reference to the average value of the beam × time around the two-dimensional space, and a signal whose normalized value is higher than a preset threshold value is detected. . If the level of the signal detected in the two-dimensional space is higher than the level of the adjacent beam at the same time, it is determined that the beam is an echo.

On the other hand, each of the plurality of LFM correlators 10 performs a correlation process and an integration process with the replica signal of the signal 2 on each of the plurality of beam outputs sent from each of the phase adjusters 8, and outputs the outputs. The signal is sent to the signal detector 12. At the output of the LFM correlator 10, there is a large correlation output for echoes from targets on the starboard side of the platform from which signal 2 was transmitted, and from targets on the port side of the platform from which signal 1 was transmitted. , A small correlation output is obtained. The signal detector 12 detects a portion that can be determined as an echo from a target from a correlation processing output of a plurality of beams (hereinafter referred to as a right correlation output) sent from the plurality of LFM correlators 10, and detects the beam. , And sends the time information to the corresponding point extractor 13 together with the right correlation output. The method of detecting the echo from the target is the same as that described for the signal detector 11.

Upon receiving the beam and time information of the detected echo from the signal detectors 11 and 12, the corresponding point extractor 13 outputs a left correlation output of a corresponding position with respect to the detected echo beam and time. And the right correlation output are extracted and sent to the comparator 14. The comparator 14 compares the received left correlation output with the right correlation output, and determines that there is a target that produces the echo on the port side when the left correlation output is large, and on the starboard when the right correlation output is large. Then, the judgment result is sent to the target position measuring instrument 15. The target position precise measuring device 15 precisely measures the direction and the distance by interpolation from the correlation output data in the vicinity of the echo detection direction.

As described above in detail, according to the first embodiment of the present invention, the LFM pulse signal (signal 1) whose frequency increases with time from the port transmitter to the port side of the platform, LFM whose frequency decreases with time from the starboard transmitter to the starboard side of the platform
A pulse signal (signal 2) is transmitted, and two systems of correlators are provided for the phasing output of the receiver array, and the signals 1 and 2 are used as replicas, respectively. Because the size is compared, it is possible to determine whether the target that caused the echo is on the port side or starboard side of the platform, which is a problem with the conventional method, whether the target is left or right The problem of being unable to do so can be solved. Further, as a transmission signal, L
Since the FM pulse signal is used, the deterioration of the correlation output due to the Doppler effect caused by the movement of the target is slightly suppressed, and detection can be performed with a small processing amount even for the target where Doppler occurs.

Second Embodiment Next, a second embodiment of the present invention will be described. In the second embodiment, a signal waveform in which the correlation between the echo and the transmission signal is greatly reduced due to the Doppler effect caused by the movement of the target is used as the transmission waveform. By preparing a replica signal corresponding to echo compression or decompression by Doppler in the replica correlation process in reception, not only detection of a target, but also information on movement (for example, proximity and separation speed of the target) can be extracted. . In the second embodiment, for example, a pseudo random signal (Pseudo Rando
If a signal in which the mNoise signal is omitted and the PRN signal is hereinafter limited by the transmission band or a signal obtained by modulating a pulsed CW (continuous wave) signal with a code signal (hereinafter referred to as a pulse code modulation signal) is used, this purpose is achieved. Can be achieved. As the code signal, for example, two types of combinations having low mutual correlation such as a Walsh function and a Gold code are used.

FIG. 3 is an explanatory diagram of a left / right discriminating method of the bistatic sonar according to the second embodiment of the present invention. FIG.
, 3 and 4 are amplifiers, 5 and 6 are transmitters (arrays), 7 is a receiver array, 8 is a plurality of phase adjusters for forming beams in a plurality of directions, and each of devices 3 to 8 Is the same as FIG. In FIG. 3, reference numeral 21 denotes a transmission signal generator that generates a signal waveform to be transmitted to the port side, 22 denotes a transmission signal generator that generates a signal waveform to be transmitted to the starboard side, and 29 denotes each of the plurality of phase adjusters 8. Corresponding to the phase output, the same waveform as the transmission signal generated by the transmission signal generator 21 and a plurality of waveforms obtained by compressing and expanding the same in several stages in time are individually subjected to correlation processing as replica signals. The plurality of replica correlators 30 compress and compress the same waveform of the transmission signal generated by the transmission signal generator 22 and several stages thereof with respect to each of the phasing outputs of the plurality of phasing devices 8. A plurality of replica correlators that individually perform correlation processing using the plurality of expanded waveforms as replica signals, 31 and 32 are signal detectors, 33 is a corresponding point extractor that extracts corresponding points of two signal detection outputs, and 34 is a corresponding point extractor. Corresponding point phase Comparator for comparing the output signal, 35 is a target position precision measuring instruments for performing measurement accuracy of the target position using the output of the side selected by the comparator.

The operation of the second embodiment will be described with reference to FIG.
The transmission signal generator 21 generates a signal transmitted from the port-side transmitter 5 (this signal is also referred to as signal 1 in the second embodiment), is amplified by the amplifier 3, and is output from the transmitter 5. Radiated into the sea on the port side of the platform. on the other hand,
The transmission signal generator 22 generates a signal transmitted from the starboard-side transmitter 6 (this signal is also referred to as a signal 2 in the second embodiment), is amplified by the amplifier 4, and is amplified. Radiated from the platform into the starboard case into the sea. Based on the signal 1 transmitted from the transmitter 5 to the port side and the signal 2 transmitted from the transmitter 6 to the starboard side, when a target exists in the sea, the target is located on the port side of the platform. The signal 1 is input to the target on the starboard side, and the echo returns to the receiver array 7. The operations of the receiver array 7 and the phase adjuster 8 are the same as those in the first embodiment.

The plurality of replica correlators 29 perform temporal compression and expansion of echoes due to the Doppler effect generated by relative movement with respect to the plurality of beam outputs sent from the plurality of phase adjusters 8. Correspondingly, replica correlation processing and integration processing of signal 1 and each replica signal waveform of a plurality of signals obtained by compressing or expanding this signal 1 are performed in parallel. The output is sent to the signal detector 31 as two-dimensional information of beam × Doppler. The signal detector 31 normalizes the time series of the correlation processing output (hereinafter, referred to as a left correlation output) sent from the replica correlator 29 to extract a portion that can be determined as an echo signal from the target. , Its beam, Doppler, and time information are sent to the corresponding point extractor 33 together with the left correlation output. This normalization processing can be realized by, for example, using a beam × time characteristic of an output corresponding to the same Doppler to convert the value into a relative value to an average value around a point of interest. If the normalized value is a local maximum that exceeds the threshold value and the value before the normalization is a local maximum with respect to the value corresponding to the adjacent Doppler value at the same point, it is determined to be an echo.

On the other hand, in the plurality of replica correlators 30, the temporal compression of echoes due to the Doppler effect generated by the relative motion with respect to the target with respect to the plurality of beam outputs sent from the plurality of phase adjusters 8, In response to expansion, signal 2
The replica correlation process and the integration process of each replica signal waveform of a plurality of signals obtained by compressing or expanding the signal 2 are performed in parallel. The output is sent to the signal detector 32 as beam × Doppler two-dimensional information. The signal detector 32 extracts a portion that can be determined as an echo signal in the same manner as the signal processor 31 from the time series of the correlation processing output (hereinafter, referred to as right correlation output) sent from the replica correlator 30. Then, the beam, Doppler and time information are sent to the corresponding point extractor 33 together with the right correlation output.

The corresponding point extractor 33 receives the beam, Doppler, and time information of the echoes detected from the signal detectors 31 and 32, and receives a corresponding position with respect to the beam, Doppler, and time of the detected echo. The left correlation output and the right correlation output are extracted and sent to the comparator 34. The comparator 34 compares the received left correlation output with the right correlation output,
When the left correlation output is large, it is determined that there is a target that produces the echo on the port side, and when the right correlation output is large, it is on the starboard. The determination result is sent to the target position measuring instrument 35. The target position precise measuring device 35 accurately measures the azimuth, the distance, and the Doppler by interpolation from the echo detection azimuth on the relevant side and the correlation output data near Doppler.

As described above in detail, according to the second embodiment of the present invention, one of two types of pulse signals (signal 1 and signal 2) having a small mutual relation is transmitted from the port transmitter. Transmit each to the port side of the platform and the other side from the starboard transmitter to the starboard side of the platform, based on the signal 1 and signal 2 for the phasing output of the receiver array, respectively. Since the correlation processing of the two systems is performed by the replica signal and the magnitude of the correlation processing output of the two systems is compared, it is possible to determine whether the target generating the echo is on the port side or the starboard side of the platform. It is possible to solve the problem that the conventional method cannot determine whether the target is left or right. Further, in response to the temporal compression and expansion of the echo due to the Doppler effect caused by the movement of the target, the correlation processing is performed in parallel with a plurality of replica signals obtained by time-compressing and expanding the signal 1 and the signal 2 to obtain a maximum output. Since the Doppler amount corresponding to the replica is measured, the approach and separation speeds of the target can be determined simultaneously with signal detection.

[0025]

As described above, according to the present invention, at a position apart from the sound source array and the receiver array, the echo sound from the target of the acoustic pulse wave radiated from the sound source is received by the receiver array. In a bistatic sonar for detecting a target target by receiving and estimating its position, from the sound source array, one of two pulse signals having the same frequency band and different waveforms is placed in the left half space of the platform. The other is transmitted to the right half space of the platform, received by the receiver array, and subjected to phasing processing. Processing and signal detection processing of the correlation output are performed in parallel, and the arrival of the reverberation sound is determined by comparing the magnitude of the correlation output values of the two systems at these signal detection positions. Is determined to be the left side or the right side of the platform. As a result, the conventional problem of determining the direction of arrival of the reverberation sound is solved, and the two acoustic waves transmitted from the sound source are the same. Since the frequency band is used, the band becomes narrower than before, and it becomes easy to match the transmission level and the directional characteristics of the sound source on the left and right.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory diagram of a left / right discriminating method of a bistatic sonar according to the present invention.

FIG. 2 is an explanatory diagram of a left / right determination method for a bistatic sonar according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of a left / right determination method for a bistatic sonar according to a second embodiment of the present invention.

FIG. 4 is an explanatory view of a conical beam shape of a linear array.

FIG. 5 is an explanatory diagram of a conventional left / right determination method for a bistatic sonar.

[Explanation of symbols]

 1, 2 LFM signal generator 3, 4 amplifier 5, 6 transmitter 7 receiver array 8 phase adjuster 9, 10 LFM correlator 11, 12, 31, 32 signal detector 13, 33 corresponding point extractor 14 , 34 Comparator 15, 35 Target position precise measuring instrument 29, 30 Replica correlator 51 Phasing processing 52 Replica correlation processing by waveform 1 53 Replica correlation processing by waveform 2 54, 55 Signal detection processing 56 Left / right determination processing by output comparison 57 Target position measurement processing

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Minami-kuni 1-7-12 Toranomon, Minato-ku, Tokyo Inside Oki Electric Industry Co., Ltd. (72) Inventor Yoshio Okita 1-7-112 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd. F term (reference) 5J083 AA02 AB12 AC32 AD01 AF15 AF17 BA03 BA07 BA09 BA10 BB03 BE10 CA12 DA00

Claims (5)

[Claims] 1. A target object is detected by receiving a reverberation sound from a target object of an acoustic pulse wave radiated from a sound source at a position apart from the sound source array and the receiver array, In the bistatic sonar for estimating the position, from the sound source array, one of two pulse signals having the same frequency band and different waveforms is placed in the left half space of the platform, and the other is placed in the right half space of the platform. Respectively, and two-phase correlation processing and signal detection processing of the correlation output are performed using the replica signal of the two pulse signals with respect to the phasing output received by the receiver array and subjected to the phasing processing. It is performed in parallel, and by comparing the magnitudes of the correlation output values of the two systems at these signal detection positions, the direction of arrival of the reverberation sound is Right and left discriminating method bistatic sonar, characterized in that to determine whether a right or is. 2. The two frequency bands having the same frequency band but different waveforms.
2. A pulse signal comprising: a first linear frequency-modulated pulse signal whose instantaneous frequency increases linearly with time; and a second linear frequency-modulated pulse signal whose instantaneous frequency decreases linearly with time. The left / right discrimination method of the bistatic sonar described in the section. 3. A target object is detected by receiving, at a position apart from the sound source array and the receiver array, a reverberation sound of the acoustic pulse wave emitted from the sound source from the target object by the receiver array, In the bistatter sonar for estimating the position, from the sound source array, one of two pulse signals having the same frequency band and different waveforms is placed in the left half space of the platform and the other is placed in the right half of the platform. Each of the two pulse signals and a plurality of time-compressed or decompressed replica signals of the two pulse signals are used for the phasing output that has been transmitted to the space, received by the receiver array, and subjected to the phasing processing, and In the system, a plurality of correlation processes and a signal detection process of the correlation output are performed in parallel for each system, and the correlations at a plurality of signal detection positions are performed for each system in the two systems. Right and left discriminating method bistatic sonar, characterized in that the arrival direction of the reflected sound by the size comparison of force values to determine whether a right or a left of said platform. 4. The two frequency bands having the same frequency band but different waveforms.
4. The method according to claim 3, wherein two pulse-limited pseudo-random pulse signals are used as one pulse signal. 5. The two frequency bands having the same frequency and different waveforms.
4. The bistatic sonar left / right discrimination according to claim 3, wherein two pulse code modulation signals obtained by modulating a pulsed continuous wave signal with two types of code signals having low mutual correlation are used as one pulse signal. Method.