CN111505611A - Broadband Fishing Sonar Receiving Beamforming Method Based on Cylindrical Transducer Array - Google Patents

Abstract

The invention provides a wideband fishing sonar receiving beamforming method based on a cylindrical transducer array, which is realized by using the cylindrical transducer array. In this method, a cylindrical transducer array is used to divide the detection area into multiple sectors, and each sector corresponds to a partial arc-surface array of the cylindrical transducer. To realize the detection of the entire horizontal 360°, considering the computing capability of the device, multiple arrays are involved in a multi-channel receiver for processing, and the processing program of each multi-channel receiver is the same, which improves the maintainability of the system. The invention adopts the broadband beam forming method based on complex envelope, reduces the requirement of the sampling rate of the system, and realizes the high beam forming performance under the condition of lower sampling.

Description

Broadband Fishing Sonar Receiving Beamforming Method Based on Cylindrical Transducer Array

technical field

The invention relates to the field of fishery equipment, in particular to a beamforming method for wideband fishing sonar based on a cylindrical transducer array.

Background technique

As the most typical marine fishery fishing instrument, fishing sonar is an important means to obtain information on the quantity and spatial distribution of marine fish resources, and plays an important role in improving the efficient, precise and selective fishing of marine fisheries. In order to obtain higher spatial detection resolution and fish species identification ability, marine fishery detection is developing rapidly in the direction of bandwidth, multi-beam and other technologies. Especially with the development of microelectronic technology and artificial intelligence technology in recent years, it has brought a new technical development direction for the development of fishing sonar, and large-scale signal processors continue to emerge as more complex and higher-performance fish finder signals. The use of processing technology provides hardware conditions, which brings opportunities for the development of higher-performance fishing sonars.

Multi-beam fishing sonar usually uses plane transducer array and cylindrical transducer array. The plane transducer array can only scan the sea area with a certain opening angle (generally less than 90°) of the fishing boat heading; the cylindrical transducer array The horizontal 360° scan and the vertical 60° scan with the fishing boat as the center can be realized. As shown in Figure 1, the working process of the multi-beam fishing sonar first sets a certain inclination angle according to the operating environment, and then performs periodic repeated horizontal scanning. Multi-angle stereo detection of fish.

Fishing sonar often uses two signal forms: narrowband signal and wideband signal. The beamforming of narrowband signal can be realized by phase shifting, but its anti-reverberation ability, especially the interface reverberation ability caused by sea surface and seabed reflection, is poor. Limit the detection distance of systems using narrowband signals. Fishing sonar adopts the form of broadband signal, which can effectively reduce the influence of interface reverberation and improve the detection distance of fishing sonar. However, the broadband signal has phase modulation, so it cannot be achieved by simple phase shifting. The traditional method is unified by multi-channel signal. It is sent to the main control machine, and the method of delaying and accumulating in the main control machine completes beamforming, which requires high sampling phase deviation of the system, requires a high sampling frequency, and also brings a large amount of calculation to subsequent signal processing. , increasing the complexity of the system and increasing the overall cost.

SUMMARY OF THE INVENTION

In view of the defects in the prior art, the purpose of the present invention is to provide a broadband fishing sonar receiving beamforming method based on a cylindrical transducer array, which adopts the broadband beamforming method based on the complex envelope and reduces the system sampling rate requirement. , achieving higher beamforming performance under the condition of lower sampling, and solving the complex problem of the broadband signal fishing sonar system in the prior art.

The technical scheme provided by the present invention is:

A broadband fishing sonar receiving beamforming method based on a cylindrical transducer array is realized by using a cylindrical transducer array, wherein the cylindrical transducer array includes a large number of elements distributed on a cylindrical surface, so The cylindrical transducer array is divided into a large number of physical sectors along the axis direction; at least two adjacent physical sectors form a receiving sector for receiving beams, and the arc length of the receiving sector is the same as that of the cylinder. The perimeter ratio of the transducer array is 1:3 to 1:6; at least one of the physical sectors participates in the beamforming process of at least two of the receiving sectors, and the receiving sectors are used to simultaneously receive multiple The beamforming process for each beam includes the following steps:

(S1) calculate the sound path between each array element in each described receiving sector and the origin of described cylindrical transducer array;

(S2) sampling the signals received by each of the arrays;

(S3) obtain the complex envelope of the sampled signal;

(S4) phase compensation is performed on the complex envelope of the received signal of each of the arrays;

(S5) performing delay compensation on the complex envelope after the phase compensation;

(S6) weighted accumulation is performed on the complex envelopes after the delay compensation of each element in each physical sector to form a partial beam;

(S7) Perform weighted addition of partial beams of each physical sector in the receiving sector to obtain an output beam.

A further improvement of the present invention is that the cylindrical transducer array includes 32 linear arrays distributed along the direction of the generatrix of the cylindrical surface; each linear array includes 8 arrays, and the linear arrays are distributed at equal intervals on the cylindrical surface; Each physical sector includes 4 linear arrays, and each receiving sector is composed of two physical sectors; the arc length of the receiving sector is the same as the perimeter of the cylindrical transducer array The ratio is 1:4.

A further improvement of the present invention is that the signal received by the receiving element of each physical sector is processed by a multi-channel receiver, and after obtaining the partial beam, the multi-channel receiver sends the partial beam to the main control computer , the main control machine performs weighted addition on part of the beams to obtain an output beam.

A further improvement of the present invention is that, in the above step S1, the expression for calculating the sound path between the array element i and the origin of the cylindrical transducer array is:

为待接收波束的入射方向。Where: [x _i , y _i , z _i ] is the Cartesian coordinate of the array element i in the cylindrical transducer array,

is the incident direction of the beam to be received.

A further improvement of the present invention is that, in step S2, the sampling frequency is 1Mhz, and the signal expression obtained by sampling is:

s _i (n)=cos(2πf ₀ n-2πf ₀ τ _i +γ(n-τ _i ))+v _i (n)

Among them: f ₀ is the signal carrier frequency, γ(t) is the phase modulation function, v _i (n) is the superimposed noise of the received signal, and τ _i is the sound path difference.

A further improvement of the present invention is, in above-mentioned step S3:

Multiply the sampled signal _si (n) by cos(2πf ₀ n) and low-pass filter the multiplied result to get the real part of the complex envelope:

Xer _i (t)=[cos(2πf ₀ τ _i +γ(n-τ _i ))]/2+w _i (n)

Multiply the sampled signal s _i (n) by sin(2πf ₀ n) and low-pass filter the multiplied result to get the imaginary part of the complex envelope:

Xim _i (t)=[sin(2πf ₀ τ _i +γ(n-τ _i ))]/2+ _wi (n)

where w _i (n) is the noise signal.

A further improvement of the present invention is that the complex envelope of the received signal of the element i participates in the beamforming process of the multiple beams received by the receiving sector where it is located.

波束的相位常值

其表达式为：A further improvement of the present invention is that, in the above step S4: performing a phase-shift operation on the complex envelope through a trigonometric function formula to remove the corresponding pointing to be

Phase constant of the beam

Its expression is:

Expanding the above expression yields:

波束相对的声程差

对复包络进行延时处理，其表达式为：A further improvement of the present invention is that, in the process of performing delay compensation in the above step S5, according to the array i, the direction is

beam relative sound path difference

The complex envelope is delayed and its expression is:

为阵子i对于指向为

波束的复包络。

for a while i for the point to be

The complex envelope of the beam.

波束的复包络进行加权，其表达式为：A further improvement of the present invention is that, in the above-mentioned step S6, each array in the physical sector is directed to

The complex envelope of the beam is weighted, and its expression is:

Among them, weight_total _i is the weight in the weighted accumulation process, and its expression is:

weight_total=weight_line(:)*weight_column(1,:)

Wherein, weight_line(:) is the weight in the vertical line array where the period i is located, and weight_column(1,:) is the weight in the physical sector of the line array where the period is located.

Compared with the prior art, the present invention has the following beneficial effects:

(1) The fishing sonar of the present invention adopts a cylindrical transducer array to divide the detection area into a plurality of sectors, and each sector corresponds to a partial arc-surface array of the cylindrical transducer. Beam receiving, to achieve 360° detection of the entire level, considering the computing capability of the device, multiple arrays are involved in a multi-channel receiver for processing, so that each multi-channel receiver has the same processing procedure, which improves the maintainability of the system;

(2) The present invention adopts the broadband beamforming method based on the complex envelope, which reduces the requirement of the sampling rate of the system, and realizes higher beamforming performance under the condition of lower sampling.

Description of drawings

Other features, objects and advantages of the present invention will become more apparent by reading the detailed description of non-limiting embodiments with reference to the following drawings:

Fig. 1 is the working process schematic diagram of multi-beam fishing sonar in the prior art;

Fig. 2 is the hardware architecture diagram of the omnidirectional broadband fishing sonar system adopted by the present invention;

3 is a schematic diagram of a coordinate system of a cylindrical transducer array in this embodiment;

4 is a schematic diagram of physical sector division of a cylindrical transducer array in this embodiment;

5 is a schematic diagram of a receiving sector;

6 is a schematic diagram of a beam combining process between two multi-channel receivers;

7 is a schematic diagram of a beamforming process;

Figure 8 is a waveform diagram of a 20kHz-30kHz linear frequency modulation signal;

Fig. 9 is the waveform schematic diagram of the real part of the complex envelope of a plurality of quadrants;

Figure 10 is a waveform diagram of the complex envelopes of the three quadrants after phase compensation;

Fig. 11 is the waveform diagram of the complex envelope after phase compensation;

Fig. 12 The output result of multi-array weighted accumulation of single and multi-channel receivers;

Figure 13. The final output result of beamforming performed by the receiving sector on a certain receiving beam.

Detailed ways

The present invention will be described in detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that, for those skilled in the art, several changes and improvements can be made without departing from the inventive concept. These all belong to the protection scope of the present invention.

The present invention provides a broadband fishing sonar receiving beamforming method based on a cylindrical transducer array, which is implemented based on the omnidirectional broadband fishing sonar system shown in FIG. 2 . The omnidirectional broadband fishing sonar includes a 256-channel cylindrical transducer array, a signal processing host and a host controller.

In the cylindrical transducer array, each element is distributed on the cylindrical surface of the cylindrical transducer array, and each element works independently to complete the electro-acoustic conversion when the underwater acoustic signal is transmitted and the acoustic-electric conversion when it is received.

The signal processing host is composed of several multi-channel receivers (for multi-channel reception and transmission, signal processors, transceiver switches, etc.), switches, backplanes, etc., which are responsible for generating transmission signals and driving transmission circuits during transmission to achieve large Power signal transmission; analog and digital processing of the signal received by the transducer array during reception, including filtering, amplification, down-conversion, beamforming, etc.

The main control computer is responsible for the host control process such as the setting of the entire sonar operating parameters, the setting of the operating mode, and the processing of the acoustic echo image; other peripheral modules include the display, the keyboard (including the mouse) and the signal processing host to complete the sonar detection image. Display and set parameter input, control, etc.

In order to transmit and receive multiple beams at the same time, the array elements of the cylindrical transducer array in the present invention are designed to be multiplexed according to sectors. The arrays are distributed on the cylindrical surface, and the axis of the cylindrical surface is set along the vertical direction during use. The sector is divided into a plurality of physical sectors according to the transducer along its axis, and each physical sector includes a large number of elements distributed on the arc-shaped sector.

The division of physical sectors is not unique. For example, a physical sector with a smaller arc length can be used in the key detection direction and more dense arrays can be installed, and a sector with a larger arc length can be used in the non-critical direction and the arrays can be arranged more sparsely. The physical sector can also be divided in the form of an equally divided cylindrical surface. For example, the cylindrical transducer array is equally divided into 12 physical sectors (30° each radian), 45° per arc), 6 physical sectors (60° per arc).

In a cylindrical transducer array, at least two adjacent physical sectors form a receive sector for receiving beams. Each receive sector is used to receive multiple waveforms. Each physical sector participates in at least two receiving sectors, thereby realizing the multiplexing design. For the above-mentioned division manners of the various physical sectors, the receiving sector may also adopt corresponding division manners. For example, for a cylindrical transducer array divided into 12 physical sectors, any 2 or 3 adjacent physical sectors can be divided into a receiving sector, in this case, the arc length of the physical sector The ratio to the circumference of the cylindrical transducer array is 1:6 or 1:4. For a cylindrical transducer array divided into 6 physical sectors, any 2 adjacent physical sectors can be divided into a receiving sector. In this case, the arc length of the physical sector is the same as the cylindrical transducer array. The perimeter ratio of the transducer array is 1:3.

As shown in Figures 3 and 4, in a specific embodiment, the cylindrical transducer array is equally divided into 8 physical sectors along its axis, each physical sector has an arc length of 45°, and each physical sector has an arc length of 45°. The district has 32 rounds. In the signal processing host, the signal received by the element of each physical sector is processed by a 32 receiver/transmitter (hereinafter referred to as a multi-channel receiver). In each physical sector, 32 array elements are divided into four columns, and each array element is parallel to the axis direction of the cylindrical transducer array.

In order to facilitate signal processing, a coordinate system needs to be established in the cylindrical transducer array, so as to clarify the coordinate position of each array. In the above embodiment, the origin of the transducer coordinate system is the transducer center. Take the sailing direction of the ship as the X-axis direction, take the horizontal and vertical directions of the heading direction as the Y-axis direction, take the vertical and vertical directions of the heading direction as the Z-axis direction, and the Z-axis origin is in the middle of the transducer height.

In the above embodiment, the cylindrical transducer array has M rows and N columns, where M is 8 and N is 32. A column is arranged in a straight line to form a line array. The linear arrays are arranged along the busbar direction of the cylindrical transducer array, and the linear arrays are distributed at equal intervals on the cylindrical surface.

The adjacent linear arrays are vertically dislocated up and down. The up-and-down dislocation distribution means that in any three adjacent line arrays, the line arrays on both sides have the same height, while the middle line array is higher or lower than the other two line arrays. In a cylindrical transducer array, a row of quadrants forms a circle with two adjacent quadrants displaced up and down. Column numbers are numbered counterclockwise from the right side of the X-axis, 1, 2, 3…..31, 32. The row numbers are 1, 2, 3...7, 8 from bottom to top. Corresponding to the spherical coordinate system, it is 0 to 180° counterclockwise from the X axis, and 0 to -180° clockwise. The positive half-axis of the Z-axis in the vertical direction is -90° to 90° from top to bottom. As shown in FIG. 4 , eight multi-channel receivers numbered 1# to 8# are respectively responsible for the signal reception of each cell in one physical sector.

As shown in Figures 4 and 5, the above cylindrical transducer array has 8 receiving sectors in total. Among them, the physical sectors corresponding to the multi-channel receiver 8# and the multi-channel receiver 1# constitute the first receiving sector; the physical sectors corresponding to the multi-channel receiver 1# and the multi-channel receiver 2# constitute the second receiving sector area; the physical sectors corresponding to the multi-channel receiver 2# and the multi-channel receiver 3# constitute the third receiving sector; and so on. Eight physical sectors constitute eight receiving sectors with an arc length of 90°, and each physical sector has an arc length of 45°, participating in two receiving sectors.

For each receiving sector, its independent coordinate system needs to be determined, and each receiving sector includes a coordinate system in the same form. For a receiving sector, the independent coordinate system takes the coordinate origin of the cylindrical transducer array as the coordinate origin of the receiving sector, the normal direction of the sector arc passing through the origin as the X axis, and the horizontal and vertical lines passing through the origin as the Y axis axis, take the Z axis of the cylindrical array as the Z axis. The vertical angle definition in the spherical coordinate system is consistent with the cylindrical transducer array, and the horizontal angle is defined by its own X-axis, which is 0 to 180° counterclockwise from the X axis, and 0 to 180° clockwise. That is, the horizontal angle of the sector is the horizontal angle in the coordinate system of the cylindrical transducer array minus the rotation angle of the sector.

In the above embodiment, the cylindrical transducer array has 8 receiving sectors, and each receiving sector completes 20 beams, covering an area of -22.5° to 22.5° in front of the respective receiving sector (in the independent coordinates of the receiving sector). tie down), the beam spacing is 2.25°. The horizontal angles for 20 beams per receive sector are: -21.375°, -19.125°, -16.875°, -14.625°, -12.375°, -10.125°, -7.875°, -5.625°, -3.375° , -1.125°, 1.125°, 3.375°, 5.625°, 7.875°, 10.125°, 12.375°, 14.625°, 16.875°, 19.125°, 21.375°.

As shown in Figures 4 and 5, in the above embodiment, since there is one physical sector in common between two receiving sectors, the multi-channel receiver corresponding to a single physical sector needs to participate in the shaping of 40 beams; For the multi-channel receiver of a single physical sector, the left half beam or the right half beam of a certain beam that it participates in receiving can be obtained through each element connected to it. After the left/right half beams are obtained, the multi-channel receiver sends them to the main controller through the switch, and the main controller can perform weighted superposition of the left half beam and the right half beam of each beam received to obtain each beam. output beam.

As shown in Figures 6 and 7, specifically, the shaping process of each beam includes the following steps:

(S1) Calculate the sound path between each element in the receiving sector and the origin of the cylindrical transducer array; the calculation process is carried out in the independent coordinate system of the receiving sector; it is assumed that the rectangular coordinates of the element in this coordinate system is [x _i , y _i , z _i ], then the expression of the sound path between the period i and the origin of the cylindrical transducer array is:

为待接收波束的入射方向；对于不同的待接收波束，阵子i与坐标系原点之间具有不同的声程差。in,

is the incident direction of the beam to be received; for different beams to be received, there are different sound path differences between the element i and the origin of the coordinate system.

(S2) Sampling the signals received by each array; under the condition that each multi-channel receiver is synchronized, adopt 1Mhz sampling frequency to digitally sample the underwater acoustic echo signal, and the wideband signal to be received is:

s(t)=cos(2πf ₀ t+γ(t))

Where f ₀ is the signal carrier frequency, γ (t) phase modulation function. FIG. 8 shows a chirp signal with a carrier frequency signal of 20 kHz and a bandwidth of 10 kHz in this embodiment.

For the signal received by any array i, there is a certain delay τ _i due to the sound path difference, and the size of the delay is related to the beam direction. At the same time, the received signal is superimposed with noise v _i (n). Then the expression of the received signal of period i is:

s _i (n)=cos(2πf ₀ n-2πf ₀ τ _i +γ(n-τ _i ))+v _i (n)

Among them: f ₀ is the signal carrier frequency, γ(t) is the phase modulation function, v _i (n) is the superimposed noise of the received signal, and τ _i is the sound path difference. Expanding the above equation, we can get

s _i (n)=cos(2πf ₀ n-2πf ₀ τ _i +γ(n-τ _i ))+v _i (n)

Since the carrier frequency does not contain useful signal information, beamforming can be performed by obtaining the phase modulation function θ(n) to improve the output signal-to-noise ratio of the system.

In order to facilitate your understanding, the following is an explanation of the process of simple trigonometric function operation. In the above formula, 2πf ₀ n, -2πf ₀ τ _i , -τ _i are three characteristic quantities, of which the latter two are related to a given period of time and a given If the beam direction is related, we need to remove these three quantities through signal processing to obtain the complex envelope cos(θ(n)) of the received signal of each element, and finally sum the complex envelopes of the received signals of all elements of the sector, then Get beamforming results. In the next steps, we will remove 2πf ₀ n by down-conversion + low-pass filtering, -2πf ₀ τ _i by phase shifting, and -τ _i by time delay.

(S3) Obtain the complex envelope of the sampled signal; by obtaining the complex envelope, carrier frequencies that do not contain useful information can be removed. Using the envelope signal for beamforming can reduce the influence of the phase error of the sampled signal. Specifically, obtaining the complex envelope specifically includes the following steps:

(S31) Multiply the sampled signal _si (n) by cos(2πf ₀ n), and perform low-pass filtering on the multiplied result to obtain the real part of the complex envelope: Xer _i (t)=[ cos(2πf ₀ τ _i +γ(n-τ _i ))]/2+ _wi (n).

The expression after multiplying the sampled signal _si (n) by cos(2πf ₀ n) is:

s _i (n).*cos(2πf ₀ n)=cos(2πf ₀ n-2πf ₀ τ _i +γ(n-τ _i )).*cos(2πf ₀ n)+v _i (n)*cos( 2πf ₀ n)

According to the trigonometric function formula, the above formula can be obtained as:

=[cos(2πf ₀ τ _i +γ(n-τ _i ))+cos(2π*2f ₀ n-2πf ₀ τ _i +γ(n-τ _i ))]/2+v _i (n)*cos (2πf ₀ n)

Low-pass filtering, the real part of the complex envelope of the signal can be obtained

Xer _i (t)=[cos(2πf ₀ τ _i +γ(n-τ _i ))]/2+w _i (n)

(S32) Multiply the sampled signal _si (n) by sin(2πf ₀ n), and perform low-pass filtering on the multiplied result to obtain the imaginary part of the complex envelope:

Xim _i (t)=[sin(2πf ₀ τ _i +γ(n-τ _i ))]/2+ _wi (n)

where w _i (n) is the noise signal.

The complex envelope obtained in this step includes the information of all beams that array element i needs to receive, so the complex envelope of array element i obtained in step (S3) needs to participate in multiple beamforming processes. In the process of forming multiple beams by a certain receiving sector, the complex envelope of each beam element of the receiving sector only needs to be taken once. FIG. 9 is a schematic diagram of waveforms of the real part of the complex envelope of a plurality of quadrants.

其为每个阵子对应指向为

波束的相位常值，通过三角函数公式进行移相运算予以去除；其表达式为：(S4) Perform phase compensation on the complex envelope of the received signal of each of the arrays. Variables are included in the expressions for the real part Xer _i (n) and the imaginary part Xim _i (n) of the complex envelope

It corresponds to the point for each period of time as

The constant value of the phase of the beam is removed by the phase shift operation of the trigonometric function formula; its expression is:

Expanding the above expression yields:

Figure 10 is a waveform diagram of the complex envelopes of the three arrays after phase compensation. After the phase compensation, for any receiving beam, the difference between the received signals of each array is only a fixed time delay.

波束相对的声程差

对复包络进行延时处理，其表达式为：(S5) Delay compensation is performed on the complex envelope after phase compensation. The purpose of delay compensation is to eliminate the above-mentioned fixed delay. In the process of delay compensation, according to the period i, the direction is

beam relative sound path difference

The complex envelope is delayed and its expression is:

为阵子i对于指向为

波束的复包络。从图11可知，补偿后，对于任意以一个接收波束，各阵子的接收信号近乎重叠。

for a while i for the point to be

The complex envelope of the beam. It can be seen from Fig. 11 that after compensation, for any received beam, the received signals of each array are almost overlapped.

(S6) Weighted accumulation is performed on the complex envelopes after the delay compensation of each element in each physical sector to form partial beams; for any receiving beam, the complex envelopes are weighted and accumulated by the two physical sectors to obtain respectively Left half beam and right half beam.

In this embodiment, the expression for the weighted accumulation process of the complex envelope of each element in a physical sector of a certain receiving beam is:

Among them, weight_total _i is the weight in the weighted accumulation process, and its expression is:

weight_total=weight_line(:)*weight_column(1,:)

Wherein, weight_line(:) is the weight in the vertical line array where the period i is located, and weight_column(1,:) is the weight in the physical sector of the line array where the period is located.

The above weighted accumulation process can be understood as the joint weighting of a linear array and an arc. The above process can suppress side lobes and achieve better beamforming directivity. The same phase modulation signal can be obtained through step S5, but in practice, there are differences in the signal due to the influence of noise. Using the incoherent characteristics of noise to accumulate multiple sub-signals can also partially cancel the noise and make the received signal pass through the weighted Enhanced for better directivity gain.

In the above process, the complex envelope of each element includes signals of a plurality of beams to be received, but after phase compensation and delay compensation are performed for a specific beam to be received, the complex envelope of each element in the complex envelope of a specific beam to be received The phase of the signal is consistent, while the phases of other beams are randomly distributed, similar to noise. Therefore, in the above weighted accumulation process, the amplitudes of the specific beams to be received that are consistent in phase are highlighted, while the beams of other signals are randomly distributed due to the phase, and the weighted accumulation will be cancelled in the process. Therefore, in this embodiment, a specific to-be-received beam is extracted from a plurality of to-be-received beams by performing phase compensation and delay compensation for the specific to-be-received beam.

It can be seen from Fig. 12 that, for a certain receiving beam, the amplitude of the signal increases significantly after the complex envelopes of each array in a single physical sector are accumulated.

(S7) Perform weighted addition of partial beams of each physical sector in the receiving sector to obtain an output beam. In this embodiment, one receiving sector includes two physical sectors. After the multi-channel receiver corresponding to the physical sector obtains part of the beam, the part of the beam is sent to the main control machine through the switch, and each receiver is sent to the main control machine in the main control machine. Each partial beam of the beam is weighted and added to obtain the signal of each receiving beam. Its expression is:

Fig. 13 shows the signal waveform after the weighted addition of each part of a receiving beam. In this embodiment, each multi-channel receiver independently generates partial beams, which avoids transmitting the received signals of each beam to the main control computer. This distributed processing method can make full use of the computing resources of the system and reduce the communication bandwidth of the system. .

In the description of this application, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", The orientation or positional relationship indicated by "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, which is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying the indicated device. Or elements must have a particular orientation, be constructed and operate in a particular orientation, and therefore should not be construed as a limitation of the present application.

Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above-mentioned specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essential content of the present invention. The embodiments of the present application and features in the embodiments may be combined with each other arbitrarily, provided that there is no conflict.

Claims (10)

1. A broadband sonar receiving beam forming method for fishing based on a cylindrical transducer array is realized by using the cylindrical transducer array, wherein the cylindrical transducer array comprises a plurality of arrays distributed on a cylindrical surface, and the cylindrical transducer array is divided into a plurality of physical sectors along the axis direction; at least two adjacent physical sectors form a receiving sector for receiving beams, and the ratio of the arc length of the receiving sector to the perimeter of the cylindrical transducer array is 1:3 to 1: 6; at least one of the physical sectors is involved in a beamforming process for at least two of the receiving sectors, the receiving sectors being configured to simultaneously receive a plurality of beams, the beamforming process for each beam comprising the steps of:

(S1) calculating a sound path between each array and the origin of the cylindrical transducer array;

(S2) sampling signals received by each of the elements;

(S3) finding a complex envelope of the sampled signal;

(S4) performing phase compensation on the complex envelope of the received signal of each of the arrays;

(S5) performing delay compensation on the phase-compensated complex envelope;

(S6) carrying out weighted accumulation on the complex envelope after each array delay compensation in each physical sector to form partial wave beams;

(S7) performing weighted addition on the partial beams of each physical sector in the reception sector to obtain an output beam.

2. The broadband sonar receiving beam forming method based on the cylindrical transducer array for the fishing is characterized by comprising 32 linear arrays distributed along the generatrix direction of a cylindrical surface; each linear array comprises 8 arrays, and the linear arrays are distributed on the cylindrical surface at equal intervals; each physical sector comprises 4 linear arrays, and each receiving sector comprises two physical sectors; the ratio of the arc length of the receiving sector to the perimeter of the cylindrical transducer array is 1: 4.

3. The broadband sonar receiving beam forming method based on the cylindrical transducer array for the fishing is characterized in that signals received by a receiving array of each physical sector are processed by a multi-channel receiver, after the partial beams are obtained, the multi-channel receiver sends the partial beams to a main control computer, and the main control computer performs weighted addition on the partial beams to obtain output beams.

4. The method according to claim 1, wherein in step S1, the expression for calculating the acoustic path from the array i to the origin of the cylindrical transducer array is:

wherein: [ x ] of_i，y_i，z_i]Is the rectangular coordinate of the array i in the cylindrical transducer array,

is the incident direction of the beam to be received.

5. The broadband sonar receiving beam forming method based on the cylindrical transducer array for the fishing use according to claim 4, wherein in step S2, the sampling frequency is 1Mhz, and the signal expression obtained by sampling is as follows:

s_i(n)＝cos(2πf₀n-2πf₀τ_i+γ(n-τ_i))+v_i(n)

wherein: f. of₀For the carrier frequency of the signal, gamma (t) is the phase modulation function, v_i(n) noise superimposed on the received signal, τ_iIs the path difference.

6. The method according to claim 5, wherein in step S3:

the sampled signal s_i(n) and cos (2 π f)₀n) multiplying and low-pass filtering the result of the multiplication to obtain the real part of the complex envelope:

Xer_i(t)＝[cos(2πf₀τ_i+γ(n-τ_i))]/2+w_i(n)

the sampled signal s_i(n) and sin (2 π f)₀n) multiplication and low-pass filtering the result of the multiplication to obtain the imaginary part of the complex envelope:

Xim_i(t)＝[sin(2πf₀τ_i+γ(n-τ_i))]/2+w_i(n)

wherein, w_iAnd (n) is a noise signal.

7. The cylindrical transducer array-based broadband sonar receiving beam forming method for fishing is characterized in that the complex envelope of the received signal of the array i participates in the beam forming process of a plurality of beams received by the receiving sector where the array i is located.

8. According to claim 6, the broadband sonar receiving beam forming based on the cylindrical transducer arrayThe method of type i, wherein in step S4: the complex envelope is subjected to phase shift operation by a trigonometric function formula to remove the corresponding direction as

Constant phase of beam

The expression is as follows:

the above expression is developed to obtain:

9. the method according to claim 8, wherein the delay compensation is performed in step S5 according to the orientation of the array i

Relative path difference of wave beam

And carrying out time delay processing on the complex envelope, wherein the expression is as follows:

for array i to point

The complex envelope of the beam.

10. The method according to claim 9, wherein in step S6, each array pair in the physical sector is pointed to

The complex envelope of the beam is weighted, which is expressed as:

wherein weight _ total_iThe expression of the weight in the weighted accumulation process is as follows:

weight_total＝weight_line(：)*weight_column(1，：)

wherein, weight _ line (: is the weight of the first array i in the vertical linear array where the array is located, and weight _ column (1): is the weight of the linear array where the array is located in the physical sector.

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