JP6610224B2 - Bistatic active sonar device and its receiver - Google Patents

Description

  The present invention relates to an active sonar device, and more particularly, by reflecting a reflected signal of an acoustic signal transmitted from a transmitting array by receiving arrays at different positions, thereby reflecting the detected reflected signal. The present invention relates to a bistatic active sonar apparatus that estimates a point as a target position and a receiver thereof.

  Conventionally, a transmitter that transmits an acoustic signal, a receiver that is located at a different position from the transmitter, receives an acoustic signal transmitted from the transmitter, and transmits from the transmitter among the acoustic signals received by the receiver. The reflection signal extraction means for extracting the reflection signal generated by reflecting the reflected signal on the object, and the coordinate axis formed by the reception direction and reception time of the reflection signal extracted by the reflection signal extraction means, or the reception direction and reception There is known a bistatic active sonar device including display means for displaying a reflected signal extracted by the reflected signal extracting means on a coordinate axis formed by a distance from a device (or transmitter) to an object (for example, Patent Document 1).

JP 2001-74836 A

  In the bistatic active sonar device described in Patent Document 1, in order to detect a target reflected signal (hereinafter referred to as “echo”) in the reflected signal extraction means, a signal received by the receiving array and a transmission signal waveform Correlate with. However, since the ship equipped with the bistatic active sonar device and the target to be detected are usually moving, the echoes of the target received by the receiving array are different from the transmission signal waveform due to Doppler shift. . As a result, the correlation result between the waveform of the signal received by the receiving array and the transmission signal waveform deteriorates, and the target detection performance deteriorates.

  An object of the present invention is to provide a bistatic active sonar device and a receiver thereof that can prevent the deterioration of the correlation result due to the Doppler shift and improve the target detection performance.

The bistatic active sonar device according to the present invention includes a transmitter that transmits an acoustic signal, and a reflected signal that is generated when the acoustic signal transmitted from the received signal is reflected by the transmitter from the received signal. A receiver that extracts the replica waveform of the acoustic signal after the Doppler shift that occurs from transmission to reception, and that generates a plurality of replica waveforms corresponding to a plurality of assumed speeds of the object. A correlator for correlating the received signal with the replica waveform, and a signal detector for extracting a reflected signal based on the correlation result of the correlator, and the acoustic signal is an LFM (Linear Frequency Modulation) signal And a PCW (Pulse Continuous Wave) signal, the replica creator generates a plurality of LFM replica waveforms and a plurality of PCW replica waveforms as a plurality of replica waveforms. The correlator includes an LFM correlator that correlates the received signal and the LFM replica waveform, and a PCW correlator that correlates the received signal and the PCW replica waveform. extracts reflection signals based on the correlation results LFM correlator, detect the absolute speed of the object based on the correlation results PCW correlator.

  According to the bistatic active sonar device of the present invention, by extracting the reflected signal by correlating the replica waveform of the acoustic signal after the Doppler shift generated from transmission to reception and the received signal, the ship and the detection target The target detection performance can be improved even when the transmission signal waveform has been Doppler shifted due to the movement of the target.

It is a schematic block diagram of the bistatic active sonar apparatus in embodiment of this invention. It is a figure which shows the arrangement | positioning of the transmission array, receiving array, and target in embodiment of this invention. It is a schematic block diagram of the bistatic active sonar apparatus in the modification of this invention.

  Embodiments of the bistatic active sonar device of the present invention will be described below in detail with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of an active sonar device 1 according to an embodiment of the present invention. As shown in FIG. 1, the active sonar apparatus 1 of the present embodiment includes a transmitter 10 and a receiver 20. The active sonar device 1 of the present embodiment is a bistatic active sonar device in which the transmitter 10 and the receiver 20 are located at different positions on the same ship. The transmitter 10 and the receiver 20 can communicate with each other by a communication unit (not shown), and exchange various types of information described later.

  The transmitter 10 includes a transmission signal generator 101, an amplifier 102, and a transmission array 103. The transmission signal generator 101 generates an acoustic signal including an LFM (Linear Frequency Modulation) signal and a PCW (Pulse Continuous Wave) signal each having a different frequency band as a transmission signal. The amplifier 102 is connected to the transmission signal generator 101 and amplifies the transmission signal generated by the transmission signal generator 101. The transmission array 103 is connected to the amplifier 102 and transmits the transmission signal amplified by the amplifier 102 into water.

  The receiver 20 includes a receiving array 201, a phasing device 202, an LFM bandpass filter 203, an LFM correlator 204, a normalization processor 205, a correlation result synthesis processor 206, and a Doppler shift replica creator. 207, a PCW band pass filter 208, a PCW correlator 209, a signal detector 210, and a display processor 211.

  The receiving array 201 receives a signal propagating in water. The phase adjuster 202 is connected to the wave receiving array 201 and forms a beam having directivity in each direction from the signal received by the wave receiving array 201. The LFM band pass filter 203 is connected to the phase adjuster 202, and filters a signal in the LFM band from a beam having directivity in each direction output from the phase adjuster 202. The LFM correlator 204 is connected to the LFM band pass filter 203, and performs an LFM band signal correlation process in order to extract an echo from the LFM band signal filtered by the LFM band pass filter 203.

  The normalization processor 205 is connected to the LFM correlator 204 and normalizes the correlation result of the LFM correlator 204 in the beam and time space. The correlation result synthesis processor 206 is connected to the normalization processor 205, compares the output from the normalization processor 205 with a preset threshold value, removes correlation errors, and performs correlation result synthesis processing. I do.

  The Doppler shift replica creator 207 calculates the Doppler shift amount from the initial frequency, bandwidth, pulse length, own ship speed, target target speed, and the like of the transmission signal, and the LFM signal and PCW signal transmitted from the transmitter 10 are Doppler. A shifted LFM replica waveform and PCW replica waveform are created. The Doppler shift replica creator 207 is connected to the LFM correlator 204 and the PCW correlator 209, and outputs the created LFM replica waveform and PCW replica waveform, respectively.

  The PCW band pass filter 208 is connected to the phase adjuster 202 and filters a signal in the PCW band from a beam having directivity in each direction output from the phase adjuster 202. The PCW correlator 209 is connected to the PCW band pass filter 208 and performs correlation processing of signals in the PCW band in order to measure the target absolute speed.

  The signal detector 210 is connected to the correlation result synthesis processor 206, compares the output from the correlation result synthesis processor 206 with a preset threshold value, and outputs the threshold from the correlation result synthesis processor 206. If it exceeds the value, it is detected as an echo from the target, and the reception azimuth and reception time are obtained. The signal detector 210 is connected to the PCW correlator 209, and detects the target absolute speed according to the correlation result of the PCW correlator 209.

  The display processor 211 is connected to the signal detector 210 and the correlation result synthesis processor 206, and receives reception direction, reception time, absolute speed information inputted from the signal detector 210, and distance information using underwater sound speed from the reception time. Is calculated and displayed, and the output from the correlation result synthesis processor 206 is converted into data having the vertical axis distance or time, the horizontal axis reception azimuth, and the correlation value as luminance and color and displayed (this is generally B scope) Called display).

  Next, the operation of the active sonar device 1 will be described. First, the transmitter 10 generates an LFM signal and a PCW signal having different frequency bands by the transmission signal generator 101, amplifies them by the amplifier 102, and transmits them from the transmission array 103 to the water. The transmission signal transmitted from the transmission array 103 propagates in the water, reaches the target object, and is reflected. A reflected signal reflected by the target, that is, an echo propagates in the water.

  The receiver 20 forms a beam having directivity in each direction by the phase adjuster 202 from the received signal received by the receiving array 201. Then, the LFM band pass filter 203 filters the LFM band signal from the beam having directivity in each direction. The LFM correlator 204 performs correlation processing in order to extract an echo from the LFM band signal filtered by the LFM band pass filter 203. Here, in the prior art, the correlation processing between the LFM band signal and the LFM signal generated by the transmission signal generator 101 is performed. The LFM correlator 204 of the present embodiment has the received LFM band. Correlation between the signal and the LFM replica waveform created by the Doppler shift replica creator 207 is performed.

A specific method for creating an LFM replica waveform in the Doppler shift replica creator 207 will be described. The LFM replica waveform is sequentially generated in units of processing time for performing correlation processing in the LFM correlator 204 and in beam azimuth units of the phasing output in the phasing unit 202. Doppler shift replica generator 207, the initial frequency of the transmitted signal _{f p} [Hz], FM bandwidth of the transmission signal B, pulse length of the transmitted signal _{T 0} [sec], the reception beam of the theta _r phasing Output Azimuth [degree], θ _s in the direction of the target as viewed from the transmission array 103, V is the ship's speed (here, the speed of the ship on which the transmitter 10 and the receiver 20 are mounted) [m / sec] , M is the target assumed speed [m / sec], C is the underwater sound speed [m / sec], F _s is the sampling frequency [Hz], repd is the replica waveform size, and t ′ is the time series sample number, t The replica waveform value y (t ') at' is obtained from the following equation (1).

Here, f _p2 and T ₁ are the frequency and pulse length after Doppler shift, respectively, and are obtained by the following equations (2) and (3). Moreover, k is the number of samples and is calculated | required by following formula (4). Further, dopRatio is a frequency change rate due to Doppler shift, and is obtained by the following equation (5). As shown in the following equation (5), in the present embodiment, both transmission and reception Doppler shifts, that is, Doppler shifts that occur from transmission of a signal from the transmitter 10 to reception of a signal at the receiver 20 are performed. Based on the above, a replica waveform is created.

Here, f _p , B, T ₀ , θ _r , C, F _s and repd are known values. Specifically, f _p , B, and T ₀ are obtained from the transmission signal generator 101, and θ _r is obtained from the phase adjuster 202. Further, C is obtained from such a separately provided water sound velocity meter, F _s and repd is a value determined when designing the device. For example, F _s is set to twice the initial frequency f _p , and repd is determined in consideration of hardware capability and capability to obtain a necessary gain (search range, etc.). On the other hand, θ _s and m are unknown information determined by the target motion.

  However, a certain range can be predicted for the target assumed speed m. Therefore, a plurality of replica waveforms are created by assuming a plurality of target assumed speeds m (for example, in increments of 1 kt from 0 to 10 kt), and the LFM correlator 204 performs correlation processing on the plurality of replica waveforms. And It is also possible to assume that the target assumed speed m as a vector approaches the ship when the sign is positive, for example, and leaves the ship when the sign is negative.

Next, how to obtain the direction θ _{s in} the target direction viewed from the transmission array 103 will be described with reference to FIG. FIG. 2 is a diagram showing the arrangement of the transmission array 103, the reception array 201, and the target. As shown in FIG. 2, the relationship between the transmitting array 103 (transmitting point), the receiving array 201 (receiving point), and the target position (reflecting point) is a triangle with each apex. Here, the distance between the transmission array 103 (transmission point) and the reception array 201 (reception point) is R [m], and the distance between the transmission array 103 (transmission point) and the target position (reflection point). Is a [m], and the distance between the target position (reflection point) and the receiving array 201 (receiving point) is b [m], θ _s can be obtained by the following equation (6) from the cosine theorem.

  Here, the underwater sound velocity is C, and the propagation time until the signal transmitted from the transmission array 103 (transmission point) is received by the reception array 201 via the target position (reflection point) is T [seconds]. Then, the distance (a + b) from the transmission point to the reception point via the reflection point is obtained by T × C. Moreover, a and b are calculated | required by the following formula | equation (7) and (8), respectively.

  The distance R between the transmission array 103 (transmission point) and the reception array 201 (reception point) is a known value as a precondition for obtaining a bistatic target distance. For the propagation time T, the same clock (time-synchronized clock) that notifies the LFM correlator 204 of the transmission start time and measures the transmission start time in units of processing time for the reception data to be correlated. ), The propagation time T can be calculated by obtaining the difference from the start time of transmission.

Therefore, from these, it is possible to obtain a replica waveform for each target assumed speed m in the processing time unit for performing the correlation processing and in the beam azimuth unit of the phasing output. Also, if actually present the target to the beam orientation theta _r of the propagation time T a and phasing output, a correlation value when correlated with the replica waveform is increased, the correlation value unless the target is present Therefore, it is sufficient to always perform the correlation processing sequentially after the transmission is started.

  Further, the Doppler shift replica creator 207 creates a plurality of PCW replica waveforms for each target assumed speed m in the same manner as the LFM replica waveform creation method. However, when creating the PCW replica waveform, the FM bandwidth B of the transmission signal is set to 0 [Hz], and the PCW replica waveform for each target assumed speed m in the processing time unit and the beam direction unit of the phasing output is generated. create.

  The correlation result in the LFM correlator 204 is output to the normalization processor 205. The normalization processor 205 normalizes the correlation result on the beam and time space. The output from the normalization processor 205 is input to the correlation result synthesis processor 206. The correlation result synthesis processor 206 compares a preset threshold value with the output of the normalization processor 205 to remove the correlation error. Specifically, the correlation result synthesis processor 206 replaces the correlation value smaller than a preset threshold value among the outputs of the normalization processor 205 with 0. Then, all correlation values at the assumed speed m of each target are added for each beam direction of the phasing output. As another method, the maximum correlation value at the assumed speed m of each target may be extracted without adding the correlation value. These results are input to the signal detector 210 and the display processor 211 as outputs of the correlation result synthesis processor 206.

  The PCW band pass filter 208 filters a PCW band signal from a beam having directivity in each direction. The PCW correlator 209 performs correlation processing between a plurality of PCW replica waveforms created by the Doppler shift replica creator 207 and signals in the PCW band.

  The outputs of the correlation result synthesis processor 206 and the PCW correlator 209 are input to the signal detector 210. The signal detector 210 compares the output from the correlation result synthesis processor 206 with a preset threshold, and if the output from the correlation result synthesis processor 206 exceeds the threshold, the signal detector 210 Detect as an echo. Further, when detecting the echo from the target, the signal detector 210 uses the correlation output data in the vicinity of the direction in which the echo is detected and interpolates to precisely measure the reception direction and the reception time of the echo. Further, the assumed speed m corresponding to the maximum value (maximum correlation value) of the correlation results for each target assumed speed m near the echo output from the PCW correlator 209 is set as the target absolute speed. Here, in the calculation formula (5) in the Doppler shift replica creator 207 described above, the speed component of the ship is taken into consideration, so that the absolute speed of the target can be obtained. Then, the reception direction, the reception time, and the target absolute velocity are output to the display processor 211 as echo information.

  The display processor 211 calculates and displays distance information using the underwater sound speed from the input echo information, and outputs the output from the correlation result synthesis processor 206 as the vertical axis distance or time, the horizontal axis reception azimuth, and the correlation. The value is converted into data with brightness and color and displayed.

  As described above, according to the active sonar device 1 of the present embodiment, the target detection performance when the transmission signal is Doppler shifted due to the movement of the ship and the target to be detected is improved as compared with the prior art. . Moreover, the target absolute velocity of the detection target can be measured by performing correlation in consideration of the moving velocity of the ship with respect to the PCW transmission signal waveform.

  The above is the description of the embodiment of the present invention, but the present invention is not limited to the configuration of the above embodiment, and various modifications and combinations are possible within the scope of the technical idea. . For example, in the embodiment described above, both the LFM replica waveform and the PCW replica waveform are generated by the Doppler shift replica generator 207, and the correlation processing is performed. However, the present invention is not limited to this.

  FIG. 3 is a schematic configuration diagram of an active sonar device 1A according to a modification of the present invention. The active sonar device 1A in the present modification is different from the embodiment in that the receiver 20A includes a frequency analyzer 220 instead of the PCW correlator 209. Further, the Doppler shift replica creator 207 of this modification creates only the LFM replica waveform. Other configurations and operations of this modification are the same as those of the embodiment.

  In this modification, a PCW band signal is filtered from a beam having directivity in each direction by the PCW band pass filter 208, and frequency analysis is performed by the frequency analyzer 220. Then, the signal detector 210 detects the Doppler shift from the frequency analysis result in the vicinity of the echo output from the frequency analyzer 220, converts it to a relative speed, and displays echo information such as the reception direction, reception time, and relative speed. Output to the processor 211. Also in such a modification, the target detection performance when the transmission signal has been Doppler shifted can be improved as in the embodiment.

  1, 1A active sonar device, 10 transmitter, 20, 20A receiver, 101 transmit signal generator, 102 amplifier, 103 transmit array, 201 receive array, 202 phase adjuster, 203 LFM bandpass filter, 204 LFM correlation 205, normalization processor, 206 correlation result synthesis processor, 207 Doppler shift replica generator, 208 PCW bandpass filter, 209 PCW correlator, 210 signal detector, 211 display processor, 220 frequency analyzer.

Claims (7)

A transmitter for transmitting acoustic signals;
A receiver for receiving a signal, and extracting a reflected signal generated by reflecting the acoustic signal transmitted by the transmitter to an object from the received signal;
The receiver is
A replica generator for generating a plurality of replica waveforms corresponding to a plurality of assumed speeds of the object, and a replica waveform of the acoustic signal after Doppler shift generated from transmission to reception;
A correlator that correlates the received signal with the replica waveform;
A signal detector for extracting the reflected signal based on a correlation result of the correlator;
Equipped with a,
The acoustic signal includes an LFM (Linear Frequency Modulation) signal and a PCW (Pulse Continuous Wave) signal,
The replica creator creates a plurality of LFM replica waveforms and a plurality of PCW replica waveforms as the plurality of replica waveforms,
The correlator is
An LFM correlator for correlating the received signal with the LFM replica waveform;
A PCW correlator for correlating the received signal with the PCW replica waveform,
Wherein the signal detector, the LFM based on the correlation result of the correlator extracts the reflected signal, detect the absolute speed of the object based on the correlation results of the PCW correlator, bistatic active sonar device. The replica generator, the initial frequency of the LFM signal and the PCW signal, bandwidth and pulse length, the movement speed of the transmitter, the orientation of the object as seen from the transmitter, assuming the speed and the reception of the object based on the orientation of the object as viewed from the vessel, creating the LFM replica waveform and the PCW replica waveform, bistatic active sonar system according to claim 1. A normalization processor for normalizing a correlation result by the LFM correlator;
A correlation result synthesis processor that compares the output of the normalization processor with a preset threshold value and removes a correlation error;
Further comprising, bistatic active sonar system according to claim 1 or 2. The correlation result synthesis processor
Add the correlation value for each estimated speed of the object after removing the correlation error, or output, or
The bistatic active sonar device according to claim 3 , wherein a maximum correlation value among correlation values for each assumed speed of the object after the correlation error is removed is output. The signal detector compares the output of the correlation result synthesis processor with a preset threshold value, and when the output of the correlation result synthesis processor is greater than or equal to a preset threshold value, The bistatic active sonar device according to claim 4 which extracts. Wherein the signal detector, the PCW result of the correlation processing in the correlator, the assumed speed of the object reaches the maximum correlation value is detected as the absolute speed of the object, according to any one of claims 1 to 5 Bistatic active sonar device. A receiver of a bistatic active sonar device that receives a signal and extracts a reflected signal generated by reflecting an acoustic signal transmitted by a transmitter to an object from the received signal,
The receiver is
A replica generator for generating a plurality of replica waveforms corresponding to a plurality of assumed speeds of the object, and a replica waveform of the acoustic signal after Doppler shift generated from transmission to reception;
A correlator that correlates the received signal with the replica waveform;
A signal detector for extracting the reflected signal based on a correlation result of the correlator;
Equipped with a,
The acoustic signal includes an LFM (Linear Frequency Modulation) signal and a PCW (Pulse Continuous Wave) signal,
The replica creator creates a plurality of LFM replica waveforms and a plurality of PCW replica waveforms as the plurality of replica waveforms,
The correlator is
An LFM correlator for correlating the received signal with the LFM replica waveform;
A PCW correlator for correlating the received signal with the PCW replica waveform,
Wherein the signal detector, the LFM based on the correlation result of the correlator extracts the reflected signal, detect the absolute speed of the object based on the correlation results of the PCW correlators, receiving the bistatic active sonar device vessel.

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