JP2001074836A - Display device for bistatic active sonar - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display device by which a distance can be recognized directly by a method wherein a reflected signal generated at a time when a signal is reflected by an object is extracted and the distance up to the object from a receiver is displayed so as to be superposed on coordinates which are formed of the receiving direction and the receiving time of the reflected signal. SOLUTION: By a transmitting-signal generator 1, a linear FM(LFM) signal and a pulse continuous wave(PCW) signal whose frequency bands are different are generated as transmitting signals in an omnidirectional transmission(ODT) shape, and the transmission signals which are amplified by an amplifier 22 are transmitted from a transmitting array 3. On the basis of a received signal which is received by a receiver 4, a beam which is directional is formed by a phasing device 5. The beam is filtered by a PCW band-pass filter 9 so as to be input to a signal detector 11 from a frequency analyzer 10. The signal detector 11 compares an output from a normalization processor 8 with a preset threshold value. When the output from the normalization processor 8 exceeds the threshold value, it is detected as an echo from a target.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflection signal (hereinafter referred to as an echo) of an acoustic signal transmitted from a transmission array.
And a display device in a bistatic active sonar for estimating a reflection point of a detected reflection signal as a target position by receiving the signal at a receiving array at a different position.

[0002]

2. Description of the Related Art In the case of a monostatic active sonar, a transmitting array and a receiving array are at the same position or at positions that can be regarded as the same position. Therefore, the time required for the transmission signal from the transmission array to be received as an echo from the target is the time required for the round-trip propagation of the same path between the transmission array (or the reception array) and the target. it is conceivable that. Therefore, the distance between the transmission array (or reception array) and the target can be simply obtained by halving the time and multiplying by the sound speed. The display processor converts the azimuth versus time data into azimuth versus distance data and displays the data, so that the operator recognizes the azimuth and distance from the transmission array (or reception array). That is, the position of the target can be visually recognized.

[0003]

However, in the bistatic active sonar, since the transmitting array and the receiving array are located at different positions, the signal transmitted from the transmitting array is reflected by the target and the receiving array Is the time required for propagation on two separate paths between the transmitting array and the target and between the target and the receiving array. Therefore, unlike the case of the monostatic active sonar, it is impossible to uniquely determine the distance from the transmission array (or the reception array) to the target from the time required for receiving the echo. For this reason, the display processor used in the conventional monostatic active sonar cannot be used as it is.

[0004]

SUMMARY OF THE INVENTION A bistatic active sonar display device of the present invention includes a transmitter for transmitting an acoustic signal, and a transmitter located at a different position from the transmitter and receiving the acoustic signal transmitted from the transmitter. A receiver, a reflected signal extracting unit for extracting a reflected signal generated by reflecting a signal transmitted from the transmitter from an object from an acoustic signal received by the receiver, and a reflected signal extracted by the reflected signal extracting unit The distance from the receiver (or transmitter) to the object is superimposed and displayed on the coordinate axis formed by the reception direction and the reception time of
Display means for displaying the reflection signal extracted by the reflection signal extraction means.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION << Specific Example 1 >><Configuration> An embodiment of the present invention will be described. FIG. 1 is a block diagram illustrating the flow of a transmission / reception process according to an embodiment of the present invention.

[0006] The transmission signal generator 1 is connected to an amplifier 2, which is connected to a transmission array 3. The receiving array 4 is connected to a phase adjuster 5, which is connected to an LFM band pass filter 6 and a PCW band pass filter 9. The LFM band pass filter 6 is connected to the LFM correlator 7 and the LFM
The correlator 7 is connected to a normalization processor 8, and the normalization processor 8 is connected to a signal detector 11 and a display processor 12. PC
The W bandpass filter 9 is connected to a frequency analyzer 10, which is connected to a signal detector 11. The signal detector 11 is connected to a display processor 12, and the display processor 12 is connected to a bistatic distance calculator 13.

<Operation> Next, the operation of the first embodiment of the present invention will be described. ODT (Omni Directional)
LFM (Linear FM) and PCW (Pulse Continu
ous Wave), and the transmission signal amplified by the amplifier 2 is transmitted from the transmission array 3. A beam having directivity in each direction is formed by the phase adjuster 5 from the reception signal received by the reception array 4.

The LFM band pass filter 6 filters out the LFM transmission band component from the beam having directivity in each direction,
The FM correlator 7 performs a correlation process with the LFM transmission signal waveform. The normalization processor 8 performs normalization on the beam and the time space, and the output of the normalization processor 8 is input to the display processor 12 and the signal detector 11.

The transmission band component of the PCW is filtered from the beam having directivity in each direction by the PCW band-pass filter 9, the frequency is analyzed by the frequency analyzer 10, and is input to the signal detector 11. The signal detector 11 compares the output from the normalization processor 8 with a preset threshold value, and detects an echo from the target if the output from the normalization processor 8 exceeds the threshold value. If detected as an echo, use the correlation output data near the azimuth where the echo was detected,
By interpolating, the receiving direction and the receiving time of the echo are precisely measured. Further, the Doppler shift is detected from the frequency analysis result in the vicinity of the echo output from the frequency analyzer 10 and converted into a relative velocity, and information on the echo such as the reception direction, the reception time, and the relative velocity is output to the display processor 12. .

Here, the relationship between the receiving direction and the receiving time is
This will be described with reference to FIG. FIG. 2 is a diagram illustrating an arrangement of a transmission array, a reception array, and a target. The distance between the transmitting array 3 and the receiving array 4 is Rsr, the target is T, the distance between the receiving array 4 and the target T is R1, and the distance between the transmitting array 3 and the target T is R2. , The receiving direction in which the wave receiving array 4 receives the echo from the target T is θr.

The time Ttotal at which the acoustic signal transmitted from the transmission array 3 at time t = 0 is reflected at the target T and arrives at the reception array 4 is represented by the following equation (1). At this time, the time Rtotal required for the signal transmitted from the transmission array 3 to be reflected by the target T and received by the reception array 4 is expressed by the following equation (2). Further, the distance R2 between the transmission array 3 and the target T is represented by equation (3).

[0012]

(Equation 1)

Here, c is the speed of sound. Therefore, the reception time Ttota when the reception direction of the echo is given θr
l, the relationship between the distance R1 between the receiving array 4 and the target T and the distance R2 between the transmitting array 3 and the target T can be obtained.

The bistatic distance calculator 13 calculates the distance R1 between the receiving array 4 and the target T to, for example, 100 m.
The echo receiving direction is changed to 0, for example.
From 180 degrees to (3)
The calculated value is calculated using the equation and sent to the display processor 12.

The display processor 12 converts the output of the normalization processor 8 into data of the reception direction versus the reception time, and adjusts the output level of the reception signal in shades and simultaneously receives the echo input from the bistatic distance calculator 13. Indicate by symbols. FIG. 3 shows a display example of the reception direction versus the reception time. The numbers in the figure indicate the distance from the receiving array.

In the first embodiment, the distance R1 between the receiving array 4 and the target T is obtained and displayed.
May be obtained and displayed. 1 <Effect> As described in detail above, by superimposing and displaying the distance from the receiving array to the target on the display of the receiving direction versus the receiving time, the azimuth and distance of the target from the receiving array can be visually determined. Can be easily recognized. Therefore, even in a bistatic active sonar in which the transmitting array and the receiving array are at different positions, the distance from the receiving array to the target can be directly recognized.

<< Embodiment 2 >><Structure> FIG. 4 is a block diagram illustrating the flow of transmission and reception processing in Embodiment 2 of the present invention. Example 2
Is a cursor distance calculator 1 in addition to the same configuration as in the first embodiment.
4 is provided.

<Operation> The operation of the embodiment 2 will be described with reference to FIG. The operation up to the bistatic distance calculator 13 is the same as that of the first embodiment, and a description thereof will be omitted.

The display processor 12 is a cursor distance calculator 14
The operation other than the interface with is the same as in the first embodiment. Further, the display processor 13 sends the cursor position (reception direction, reception time) on the direction versus reception time screen to the cursor distance calculator 14.

Next, the operation of the cursor distance calculator 14 will be described. When the transmission time is set to 0, the propagation time from transmission to reception is defined as the cursor reception time. This is represented by Ttotal in the equation (1), and the direction of the cursor is represented by θr.
And the wave receiving array 4 using the equations (1) to (3).
The distance R1 between the target and the target T is calculated. Rtotal = Ttotal × c (4) R2 = Rtotal−R1 (5) By substituting equation (5) into equation (3), squaring both sides and solving for R1, the following equation is obtained. become. R1 = (Rsr ² + Rtotal ² ) / (2Rsr · cos θ−2Rtotal) (6) The cursor distance calculator 14 inputs the direction and time of the cursor from the display processor 12 and uses the formula (6). The distance R1 between the receiving array 4 and the target T is calculated, and the display processor 12
Output to The display processor 12 displays the distance R1 between the input receiving array 4 and the target T.

<Effect> As described in detail above, the echo is displayed on the display of the reception direction versus the reception time, the distance from the reception array to the target is calculated and displayed, and the echo on the screen is displayed. By positioning the cursor on, it is possible to recognize a more accurate target position.

Therefore, even in a bistatic active sonar in which the transmitting array and the receiving array are at different positions, the distance from the receiving array to the target can be directly recognized.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a flow of a transmission / reception process according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating an arrangement of a transmission array, a reception array, and a target.

FIG. 3 is a diagram illustrating a display example of reception direction versus reception time.

FIG. 4 is a block diagram illustrating a flow of transmission / reception processing according to a second embodiment of the present invention.

[Description of Signs] 1: Transmitter signal generator 2: Amplifier 3: Transmitter array 4: Receiver array 5: Phase adjuster 6: LFM bandpass filter 7: LFM correlator 8: Normalization processor 9: PCW band Pass filter 10: Frequency analyzer 11: Signal detector 12: Display processor 13: Bistatic distance calculator

Claims (3)

[Claims] A transmitter for transmitting an acoustic signal; a receiver located at a different position from the transmitter, for receiving an acoustic signal transmitted from the transmitter; and a receiver for receiving an acoustic signal received by the receiver. A reflection signal extraction unit for extracting a reflection signal generated by reflecting a signal transmitted from the transmitter from the object to the object, and a reception direction and a reception time of the reflection signal extracted by the reflection signal extraction unit. Display means for displaying the distance from the receiver (or transmitter) to the object on a coordinate axis in a superimposed manner, and displaying the reflection signal extracted by the reflection signal extraction means. Static active sonar display. 2. The bistatic active according to claim 1, wherein said display means displays information related to the reflection signal extracted by said reflection signal extraction means corresponding to a cursor position on a display screen. Sonar display. 3. The information relating to the reflected signal extracted by the reflected signal extracting means, which is displayed by the display means, includes: the transmitter position, the receiver position, and the reflected signal extracted by the reflected signal extracting means. The bistatic active sonar display device according to claim 2, wherein the distance is a distance from the receiver (or the transmitter) to the object, which is calculated based on a sound speed.