JPH09243733A - Active sonar - Google Patents

Abstract

PROBLEM TO BE SOLVED: To change a transmit-receive frequency according to the applied hydraulic pressure to a transducer to provide a stable receiving performance. SOLUTION: An acoustic signal is transmitted from a transmitter 1 at a wide angle by a transmit signal generated by a transmit signal generating circuit 3. This echo sound is received by a receiver 6, and a plurality of receive beams of narrow angle are generated by a phasing circuit 7 to provide a plurality of receive signals. The depth information from a depth sensor 4 is supplied to a frequency setting circuit 5, the transmit-receive frequency is determined on the basis of the depth information, and the selected frequency information is imparted to the transmit signal generating circuit 3, the phasing circuit 7, and a band pass filter 8. In the phasing circuit 7, the phasing is controlled so that the beam width is constant even when the received frequency is changed, and in the band pass filter 8, the central frequency of the received frequency band is controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active sonar, and more particularly, it relates to an active sonar intended to improve the deterioration of the target search function due to the water pressure applied to the transducer.

[0002]

2. Description of the Related Art Conventionally, this type of active sonar is
It is mounted on a submersible research vessel, etc., and is used to search and track a target in the sea by emitting sound waves into the water and extracting reflected sound from the target. When the transducer used in this type of active sonar is operated from shallow depth to deep depth, the transducer has a depth pressure dependent characteristic, and its resonance frequency changes according to the depth pressure, and the transmitted sound The pressure and the reception sensitivity may be lowered. For this reason, the wave transmitter / receiver generally has a structure that is oil-immersed and stabilized.

Further, in Japanese Patent Laid-Open No. 62-103589, an active sonar (hereinafter referred to as a first sonar) equipped with a transmission frequency changing means for changing the transmission frequency in response to a change in the resonance frequency of the transducer based on the applied water pressure. (Referred to as an example).

FIG. 5 is a block diagram showing an example of the first example. The wave transmitter / receiver 11 includes an electrostrictive vibrator 11-1, a matching transformer 11-2, a shading transformer 11-3, and the like, and performs desired wave transmission / reception and wave transmission / reception with a received beam pattern. The transmission / reception switch 22 has a control unit 55.
Under the control of the transmitter 33, the receiver 44 and the transmitter / receiver 11
Switch the connection with. Further, the transmission unit 33 and the reception unit 44 also perform the operation setting of the transmission and the reception state at the transmission timing and the reception timing determined under the control of the control unit 55, respectively.

The depth detector 77 detects the magnitude of the applied water pressure corresponding to the depth of the moving platform and provides it to the transmission frequency control circuit 66. Transmission frequency control circuit 6
6 generates a frequency equal to the resonance frequency of the wave transmitter / receiver 11 that changes corresponding to the depth information received from the depth detector 77. This frequency is set by using the data which is obtained by previously investigating and determining the relationship between the resonance frequency of the transducer 11 to be used and the applied water pressure. This frequency is provided to the transmission unit 33 as frequency information in a predetermined format and causes the transmission frequency to be generated. The transmission frequency control circuit 66 also provides the frequency information to the receiving unit 44, and the center value of the reception frequency is always matched with the transmission frequency including the change of the transmission frequency. The reception unit 44 receives and processes a reception signal input via the transmission / reception switch 22.

In this way, the transmission frequency is changed in response to the change in the resonance frequency of the wave transmitter / receiver due to the application of water pressure, and it is possible to always use the transmission frequency that matches the resonance frequency of the wave transmitter / receiver regardless of the depth. ing.

On the other hand, Japanese Patent Laid-Open No. 61-44382 proposes an active sonar (hereinafter, referred to as a second example) which utilizes the dependency of the applied water pressure on the transducer. This second example collects water depth and pitch angle data from a depth sensor and a pitch angle sensor, and controls the frequency of a transmission signal supplied to a transducer from the data to determine the directivity of a sound wave beam. It changes.

In this second example, generally, the directivity pattern of the transmitter / receiver uses the principle that it can be changed only by the frequency if the number of elements of the transmitter / receiver and the arrangement interval are fixed. According to this principle, the acoustic wave beam having the optimum directivity according to the water depth and the pitch angle is automatically formed only by changing the frequency, so that only the signal from the target can be taken out while avoiding the reverberation of the sea surface or the reverberation of the sea floor.

[0009]

However, in the first example, when the transmission frequency is changed, the acoustic wave beam pattern of the transducer is changed, and it is impossible to always form a constant beam pattern regardless of the depth. Then, when the beam width becomes narrow, there arises a problem that a target between adjacent beams cannot be detected.

The reason is that the acoustic wave beam pattern of the transducer is determined by the number of elements of the transducer, the arrangement interval, and the frequency. The beam width changes when the frequency changes, and the arrangement gain increases when the beam width increases. Go down.

Further, when the beam width becomes narrow, the array gain is high at the peak position, but as the beam deviates from the peak,
This is because the array gain is reduced, and as a result, there is a hindrance when searching for a target at an arbitrary position.

On the other hand, in the second example, if the target of an arbitrary direction and distance can be searched for, the hardware scale of the receiving section becomes large. The reason is that the beam width becomes narrower as the frequency becomes higher, and the number of received beams must be determined by the beam width at this time, and the number of channels in the phasing circuit increases.

An object of the present invention is to provide an active sonar which equalizes the target search performance from a shallow depth to a deep depth without increasing the hardware of the receiving section.

[0014]

An active sonar according to the present invention comprises a transmission signal generating means for generating a transmission signal, a transmission means for converting the transmission signal into a sound wave and transmitting the sound wave in water.
Receiving means for generating a reception signal by receiving the sound waves reflected by an underwater object, detection means for detecting water depth, and frequency setting means for setting transmission frequency and reception frequency based on depth information from the detection means. And a phasing means for phasing the received signal from the wave receiving means based on the frequency information from the frequency setting means while controlling the received beam width to a constant value. The transmission signal generation means changes the frequency of the transmission signal according to the water depth, and the phasing means keeps the reception beam width constant.

The frequency setting means stores the transmission frequency and the reception frequency corresponding to the depth information individually in a table format.

The receiving means has a plurality of receiving elements,
The phasing means is provided corresponding to a plurality of sets of shading module groups for receiving the output of each receiver element and adjusting the amplitude thereof, and a plurality of shading module groups for performing delay phasing processing. A plurality of sets of phasing modules, and an addition module provided corresponding to the plurality of sets for adding signals of the phasing modules of each set,
And a shading controller for changing a weighting coefficient of each of the shading module groups based on the frequency information.

The wave transmitting means and the wave receiving means are integrally provided as wave transmitting / receiving means, and the transmission signal is transmitted only during a period in which the transmission signal should be transmitted by the signal from the transmission signal generating means. Switching means may be provided for outputting to the means and for outputting the reception signal from the wave receiving means to the phasing means during a period in which the sound wave should be received.

[0018]

Function: The transmission / reception frequency is set so as to match the resonance frequency in response to the change in the resonance frequency of the active sonar and the receiver due to the change of water pressure, and the beam of the acoustic beam The width is controlled to be constant regardless of the frequency. For this reason, the array gain of the received beam is always constant, and the beam pattern itself does not change.Therefore, by adopting an oil-immersed structure for the transmitter / receiver, the adverse effect of suppressing the resonance frequency can be avoided, and the relationship with depth pressure can be avoided. Without being able to maintain a certain level of target searching ability.

That is, even if the depth of the submersible research vessel changes from shallow depth to deep depth, the transmission / reception frequency of the active sonar is made to follow in accordance with the change of the resonance frequency of the transducer based on the applied water pressure, and the frequency is changed. By controlling the weighting coefficient of the shading module of the phasing means of the receiving section, the receiving beam width is kept constant, and the decrease of the receiving sensitivity in a given direction from a predetermined value is basically excluded.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1, in the first embodiment of the present invention, a transmission signal generated by a transmission signal generation circuit 3 is amplified by a power amplification circuit 2, an electric signal is converted into an acoustic signal by a wave transmitter 1, and a desired signal is obtained. An acoustic signal is transmitted in the sea with the transmission beam pattern of. The echo sound from the target is received by the wave receiver 6 in which a plurality of wave receiver elements are arranged, and the acoustic signal is converted into an electric signal. The phasing circuit 7 receives the received signals from the respective wave receiver elements in the wave receiver 6 so that a plurality of narrow-angle reception beam patterns can be obtained.
Phase the received signal of. The plurality of phasing signals are band-limited by the band pie filter 8 and then input to the display processing circuit 9. The phasing signals are subjected to display processing and are sent to the display device 10 to be targeted. The image is displayed.

In the active sonar for searching and displaying such a target, the depth sensor 4 supplies depth information corresponding to the depth of the submersible research ship to the frequency setting circuit 5. In the frequency setting circuit 5, the depth-resonance in which one of the resonance frequencies of the wave transmitter 1 and the wave receiver 6 that varies depending on pressure is stored in advance based on the depth information of the depth sensor 4 is stored. The frequency information is extracted from the frequency table and this frequency information is sent to the transmission signal generation circuit 3 to generate a transmission signal.

The frequency setting circuit 5 also sends the frequency information to the phasing circuit 7 and the bandpass filter 8 at the same time.
The phasing circuit 7 controls the phasing shading coefficient so that the reception beam width is constant even if the frequency of the reception signal changes, and the bandpass filter 8 sets the center frequency of the pass bandwidth of the phasing signal to the transmission frequency. To match.

FIG. 2 is a block diagram showing a configuration example of the wave transmitter 1, the wave receiver 6, and the phasing circuit 7 in the present invention.
In FIG. 2 (a), a plurality of wave transmitter elements 1 a are built in the inside of the wave transmitter 1, which receives a transmission signal from the power amplification circuit 2 and transmits an acoustic signal with a wide-angle sound wave beam into the sea. To wave.

In FIG. 2B, the reverberant sound of the transmitted signal is received by the group of receiver elements 6a inside the receiver 6, and the respective received signals are input to the phasing circuit 7. The amplitude of each received signal is adjusted by the shading module 7a group for each output of each receiver element, and processing such as delay phasing is performed by the phasing module 7b group. The phased signal is added by the addition module 7c
By adding the received signals together, a received beam with a narrow angle is formed, and the phased output of one received beam is obtained.

By preparing a plurality of sets of the above circuit blocks, a plurality of regularly-received beams are formed,
Phased outputs are obtained, and these signals are sent to the band pass filter 8 in the next stage. Here, when the shading controller 7d in the phasing circuit 7 receives the frequency information from the frequency setting circuit 5, the shading controller 7d changes the weighting coefficient (shading coefficient) of each shading module 7a by a built-in program. Even if the frequency is changed, it is possible to control the reception beam width to be constant at all times. The number of sets of the above circuit blocks is determined according to the angle of the reception beam.

Next, the operation of the present invention will be described in detail with reference to FIG. FIG. 3 (a) is a general wave transmission sensitivity and wave reception sensitivity characteristic diagram when the oil immersion structure of the wave transmitter 1 and the wave receiver 6 is not adopted, and FIG. 3 (b) is a wave transmitter. 1 is a depth vs. resonance frequency table of the wave transmitter 1 and the wave receiver 6 built in the frequency setting circuit 5 based on the measurement data of the wave receiver 6 as shown in FIG. Based on the depth information of the depth sensor 4, the frequency setting circuit 5 selects from the above table and sends the set frequency to the transmission signal generation circuit 3, the phasing circuit 7 and the bandpass filter 8 at the same time.

Thus, even if the depth of the submersible research ship changes, the transmitter / receiver frequency of the active sonar is made to follow the fluctuations of the resonant frequencies of the transmitter / receiver used, depending on the depth of the receiver. It is possible to keep the receiving beam width constant without making the wave receiver have an oil-immersed structure.

Next, a second embodiment of the present invention will be described in detail with reference to FIG. In this active sonar, the wave transmitter / receiver 11 having both functions of the wave transmitter 1 and the wave receiver 6 of FIG. 1 and the transmission signal of the output of the power amplifier circuit 2 are output to the wave transmitter / receiver 11 only during the transmission period. A switching circuit 12 is provided for connecting the wave transmitter / receiver 11 to the phasing circuit 7 during the reception period. When it is necessary to search a target to a long distance, the switching circuit 12 inevitably increases in size of the transmitter and the receiver, and there is no space to be equipped outside the ship. Has been added to change the transceiver with and separate the transmitted and received signals. The operation after the phasing circuit 7 is the same as that of the first embodiment, and it is possible to keep the receiving beam width constant without forming the transducer in the oil-immersed structure.

[0029]

The first effect of the present invention is that it is possible to maintain a constant target searching ability from a shallow depth to a deep depth without increasing the hardware of the receiving section. The reason is that the transmission / reception frequency is changed based on the depth information, and the beam pattern is controlled to be constant without increasing the number of reception beams of the reception unit.

The second effect is that the wave transmitter / receiver need not be soaked in oil and the performance of the wave transmitter / receiver can be fully exhibited. The reason is that the transmission / reception frequency is changed by following the resonance frequency due to the depth pressure of the transmitter / receiver.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

2 is a block diagram showing an example of the wave transmitter (FIG. 1A), the wave receiver, and the phasing circuit (FIG. 2B) shown in FIG.

FIG. 3A is a depth characteristic diagram of a wave transmitter and a wave receiver, and FIG. 3B is a resonance frequency characteristic table of the wave transmitter and the wave receiver.

FIG. 4 is a block diagram showing a second embodiment of the present invention.

FIG. 5 is a block diagram of an example of a conventional active sonar.

[Explanation of symbols]

 1 Wave Transmitter 2 Power Amplifier Circuit 3 Transmission Signal Generation Circuit 4 Depth Sensor 5 Frequency Setting Circuit 6 Receiver 7 Phaser Circuit 8 Band Pass Filter 9 Display Processing Circuit 10 Display 1a Transmitter Element 6a Receiver Element 7a Shading module 7b Phase adjusting module 7c Addition module 11 Transducer 12 Switching circuit 22 Transmission / reception switch 33 Transmitter 44 Receiver 55 Controller 66 Transmit frequency control circuit 77 Depth detector

Claims (4)

[Claims] 1. A transmission signal generating means for generating a transmission signal, a transmission means for converting the transmission signal into a sound wave and transmitting the sound wave in water, and a reception signal by receiving the sound wave reflected by an underwater object. The generated wave receiving means, the detecting means for detecting the water depth, the frequency setting means for setting the transmission frequency and the receiving frequency based on the depth information from the detecting means, and the received signal from the wave receiving means for the frequency setting. Based on the frequency information from the means, it comprises a phasing means for phasing while controlling the reception beam width to be a constant value, the transmission signal generating means, the transmission signal generating means, of the transmission signal according to the water depth. An active sonar characterized in that the frequency is changed and the phasing means keeps the reception beam width constant. 2. The active sonar according to claim 1, wherein the frequency setting means stores transmission frequencies and reception frequencies corresponding to the depth information individually in a table format. 3. The wave-receiving means has a plurality of wave-receiving elements, and the phasing means receives a plurality of wave-receiving element outputs and adjusts the amplitude of the wave-receiving elements. A plurality of phasing module groups provided corresponding to the plurality of shading module groups for performing phasing processing, and signals of the respective phasing module groups provided corresponding to the plurality of sets are added. The active sonar according to claim 1 or 2, further comprising: an addition module for controlling the shading module group and a shading controller for changing each weighting coefficient of the shading module group based on the frequency information. 4. The wave transmitting means and the wave receiving means are integrally provided as wave transmitting / receiving means, and the transmission signal is transmitted only during a period in which the transmission signal should be transmitted by a signal from the transmission signal generating means. 4. A switching means for outputting the received signal from the wave receiving means to the phasing means during a period in which the sound wave is to be received, and is output to the wave transmitting means.
Active sonar described in any of.