CN109061612B - A Novel Combination Search Method for Sparse Cone Array in Shallow Water - Google Patents

Abstract

The invention discloses a novel combination search method in shallow water area of sparse circular frustum array, which relates to the technical field of sonar array. The present invention first establishes a global space Cartesian coordinate system based on a circular platform array, and introduces the pitch angle θ, azimuth angle

Set the position distribution parameters of each array element in the global coordinate system, and lay out the circular array; perform sparse processing on each layer of the circular array, and construct a new sparse multi-layer circular table array; calculate the position of each array element relative to the reference point O The phase difference of the received signal is used to perform phase control compensation and beamforming on each array element of the new-type circular table array; use the circular array of each layer of the new-type circular table array and the bus array to fuse and combine search in the vertical direction; change the number of layers, height, and bus slope of the new-type circular table array and other parameters to obtain the optimized search area range and search target results. The present invention enables the acoustic base array of the three-dimensional circular platform sitting on the bottom in shallow sea to have better search range at the top, save the cost of array arrangement, resist incoming interference from the bottom of the sea, and the like, and has good application prospects.

Description

A Novel Combination Search Method for Sparse Cone Array in Shallow Water

technical field

The invention relates to the technical field of sonar base arrays, in particular to a novel combination search method for shallow water area of sparse circular platform arrays.

Background technique

As the situation of marine rights and interests and security becomes more and more serious, the demand for underwater early warning of river ports is increasing, and the traditional planar array monitoring platform is increasingly unable to meet the actual needs. A new sparse circular platform array shallow water combined search method has emerged pregnancy.

The search range of the top half space of the traditional circular array is very limited, and it also has high defects such as beam side lobe level. How to improve the search range of the top space of the traditional circular array has attracted widespread attention of scientific researchers. In recent years, research on traditional planar arrays has gradually shifted to research on volumetric arrays. He Ming proposed two circular array array layout methods, symmetrical distribution of each array element and spiral distribution of each array element, in "Analysis of Directional Performance of Circular Platform Array Antennas". However, the two traditional conical volume array element distribution methods both face the defect that the array element spacing decreases with the radius and does not satisfy the spatial sampling theorem. There are also some underwater platforms that are used by sitting on the seabed or suspended in the water. Under shallow sea conditions, the underwater platform has little search requirements for the seabed and will be interfered by incoming signals from the seabed, affecting the top half space of the underwater platform. Search performance. To sum up, at present, the traditional circular array has the disadvantage of a small vertical search range; the array elements of each layer of the traditional volume array are redundant, the array is complex, and the energy consumption is high; the platform sitting on the bottom of the shallow sea is vulnerable to incoming signals from the seabed. interference.

Contents of the invention

The purpose of the present invention is to overcome: the shortcoming of the traditional circular array in the vertical direction of the search range; the redundancy of array elements in each layer of the traditional volumetric array, the array is complex, and the energy consumption is high; the shallow sea bottom platform is vulnerable to signals from the seabed interference etc. The invention proposes a novel sparse circular table array combined search method in shallow water, which is simple in array arrangement, can effectively expand the search range of the top half space and effectively suppress the interference of incoming signals from the seabed.

A novel combined search method in shallow waters with a sparse frustum of circular array, comprising the following steps:

Step 1: Establish the global space Cartesian coordinate system O-XYZ, deploy a new sparse multi-layer conical array, obtain the position distribution of each array element in the global space Cartesian coordinate system, and receive signals from the search target;

r_m表示第m层圆环阵的半径，m＝1,2,…,M；The new thinning multi-layer conical array is a three-dimensional array formed by stacking M layers of circular arrays with different radii. The radii of the circular arrays decrease successively from bottom to top, and the array element spacing of the lowest layer circular array is the receiving signal The half-wavelength λ/2 of the new sparse multi-layer circular table array is the half-wavelength λ/2 of the received signal, and the height of each layer is h ₁ , h ₂ , h ₃ ... h _M , and the array elements of each layer The number N _m is

r _m represents the radius of the m-th layer circular array, m=1,2,...,M;

When laying out the new sparse multi-layered conical array, the center of the bottom circular array is arranged at the origin O of the Cartesian coordinate system O-XYZ in the global space, so that the Z-axis points directly above the conical array; the array elements are in the global space The position distribution in the Cartesian coordinate system refers to the cylindrical coordinates of each array element in the global space Cartesian coordinate system; the cylindrical coordinates of the nth array element in the mth layer are expressed as

Step 2: Obtain the received signal phase difference of each array element in the new sparse multi-layer circular table array relative to the reference point O, and perform phase control compensation and beamforming on each array element of the new sparse multi-layer circular table array to obtain each Spatial filtering results of layer ring array and side busbar array;

When m=1 means the bottom ring, the phase difference of the array element n on the bottom ring relative to the reference point O is:

When m=2,3...M, the phase difference of array element n on each ring relative to the reference point O is:

Therefore, the total array pattern function formed by all array elements on all m circular arrays with different radii is:

Among them, θ _m =tg ^-1 (r _m /h _m ); ψ _mn is the initial phase difference of the nth array element in the mth layer;

方向，则有：In order to direct the main beam to the selected

direction, there are:

Then the pattern function of the corresponding symmetrically distributed circular table array is:

Step 3: Use the new sparse multi-layer circular platform array and the busbar array to conduct decision-level fusion combination search in the vertical direction to obtain the search area and search target results;

The decision-level fusion combination search is specifically: when the target comes to the range of θ ₀ ∈ [0°, 45°], use the new sparse multi-layer circular table array to search and output the target, and judge whether the target exists; When the target comes in the range of θ ₀ ∈ [45°,90°], use the new sparse multi-layer conical array side busbar array to search and output the target to judge whether the target exists; when the target comes to θ ₀ ∈ [45°,60 °] belong to two search overlapping areas, the two array search outputs are fused to determine whether there is a target;

Step 4: Change the number of layers, height, and bus slope of the new sparse circular frustum array to obtain the suppression of the half-space search range at the top of the underwater platform and incoming interference from the seabed by the change of formation parameters, and obtain the optimized search area range and search target results.

The beneficial effects of the present invention are:

1. The traditional circular ring array has the defects of relatively limited vertical search range and high beam sidelobe level. This invention proposes a new sparse conical circular array shallow water combined search method, which effectively expands the top of the three-dimensional array based on fusion combined search array processing Half-space search range.

2. The traditional conical circular table array has the same symmetrical distribution of the number of array elements in each layer or the interlacing of different layer array elements at a certain angle to present a spiral distribution, which is faced with the situation that the distance between the array elements does not meet the half-wavelength as the radius decreases. Sparse processing, find out the reasonable matching relationship between array element spacing, radius, and number of array elements to achieve radius matching of the number of array elements, effectively reduce redundant array elements, and reduce array deployment costs and energy consumption.

3. Some underwater platforms are used to sit on the seabed or hang in the water. Under shallow sea conditions, the underwater platform has little search requirements for the seabed and will be interfered by incoming signals from the seabed, affecting the top half space of the underwater platform. Search performance. The novel circular table array fusion combined search array processing method in the present invention can effectively suppress incoming interference from the seabed and improve the stability of the top half-space search.

Description of drawings

Fig. 1 is the flow chart of the combined search method in the shallow water area of the novel sparse conical circular array;

Fig. 2 is a schematic diagram of the three-dimensional formation of the circular table array formed after the array elements are sparsely processed;

Fig. 3(a) is the incoming beam pattern of the circular ring array to the 60° target, and Fig. 3(b) is a schematic diagram of the incoming beam pattern of the three-layer circular table array to the 60° target;

Fig. 4 is a curve diagram of the suppression effect at the bottom of the corresponding complementary angle when different incident signal sources come from;

Fig. 5 is a schematic diagram of the suppressing effect of incoming interference on the seabed of the sparse new circular platform array.

detailed description

The present invention will be further elaborated below in conjunction with the accompanying drawings.

In conjunction with accompanying drawing 1, the present invention comprises the following steps:

设置各阵元在全局坐标系中的位置分布参数，布放圆环阵列；(1) Establish a global space Cartesian coordinate system corresponding to the circular platform array, and introduce the pitch angle θ, azimuth angle

Set the position distribution parameters of each array element in the global coordinate system, and arrange the circular array;

(2) Perform thinning processing on each layer of the circular array, construct a new sparse multi-layer circular table array, draw a new type of circular table array, and the number of layers is 5 to 10 layers;

(3) Obtain the phase difference of the received signal of each array element relative to the reference point O, perform phase control compensation and beamforming on each array element of the new-type circular table array, and obtain the spatial filtering results of the ring array and the side busbar array of the new-type circular table array respectively ;

(4) According to the results of (3) above, use the circular arrays and busbar arrays of each layer of the new circular platform array to fuse and combine search in the vertical direction, and obtain the search area range and search target results at the signal level, parameter level, and decision-making level;

(5) Change parameters such as the number of layers, height, and busbar slope of the new circular platform array, and obtain the suppression of the half-space search range at the top of the underwater platform and the incoming interference from the seabed by the change of array parameters, and obtain the optimized search area and search target results.

同理，第m层第n个阵元的坐标表示为

其中r_m是第m层圆环阵的半径，第n个阵元与圆心之间的连线与X轴夹角为

令m＝1即取圆台阵最底层圆环阵，根据

将第1层圆阵各阵元依次表示出来，进而通过改变第2、3…m层的半径r_m和高度h_m画出任意层的圆阵，最终实现任意层圆台阵立体构建，其中每层圆环阵所含阵元个数相同，半径线性减小以此来保证立体阵母线是直线为圆台阵；信源认为满足远场条件，为平面波入射到各个阵元，信源在全局坐标系中的位置是指信源在全局坐标系下的球坐标，所述波达矢量是信源相对于参考点O的波达矢量

其中θ、

分别是俯仰角和方位角，俯仰角θ∈(0,π)定义为z轴与入射方向的夹角，方位角

是从x轴沿逆时针方向到信号入射方向在阵列平面上投影的夹角。The conical array is a three-dimensional array composed of multiple layers of circular arrays with different radii R. The large circular array is at the bottom, and the radius of the circular array decreases from bottom to top. Circular array) The distance between array elements satisfies half-wavelength λ/2, and the distance between layers also satisfies half-wavelength λ/2, the height of each layer is h ₁ , h ₂ , h ₃ ... h _M in turn, and the number of layers is M; the global coordinate system Take the center of the bottom circular array as the coordinate origin O, and let the Z axis point to the O-XYZ coordinate system directly above the top of the circular platform; the position distribution of each array element in the global coordinate system refers to the position of each array element in the global coordinate system Cylindrical coordinates. To study the circular table array, we must first start to study the uniform circular array. The following takes the reference point O plane circular array as an example: a uniform circular array is formed by N isotropic array elements on the circumference of the radius r. The origin O of the coordinate system is the center of the circle, and the angle between the line between the nth array element and the center of the circle and the X-axis is γ _n = 2πn/N, and its position vector is expressed as

Similarly, the coordinates of the nth array element in the mth layer are expressed as

Where r _m is the radius of the m-th layer circular array, and the angle between the line between the n-th array element and the center of the circle and the X-axis is

Let m=1 to take the circular array at the bottom layer of the table array, according to

The array elements of the circular array on the first layer are shown in turn, and then the circular array of any layer is drawn by changing the radius r _m and the height h _m of the second, third... The number of array elements contained in the layer circular array is the same, and the radius is linearly reduced to ensure that the bus line of the three-dimensional array is a straight line as a circular table array; the source considers that the far-field condition is satisfied, and the plane wave is incident on each array element, and the source is in the global coordinates The position in the system refers to the spherical coordinates of the source in the global coordinate system, and the vector of arrival is the vector of arrival of the source relative to the reference point O

where θ,

They are the pitch angle and the azimuth angle respectively, the pitch angle θ∈(0,π) is defined as the angle between the z axis and the incident direction, and the azimuth angle

is the angle projected on the array plane from the x-axis along the counterclockwise direction to the signal incident direction.

阵元间距半波长λ/2＝0.05m，圆台阵层数m＝5，设最小层圆环阵半径是半波长0.05m，则圆台阵各层圆环阵半径r_m依次是0.5λ,λ,1.5λ,2λ,2.5λ，各层阵元个数N_m确定方式为：

阵元稀疏化处理后形成圆台阵立体阵型如图2所示，层数5到10层。Considering that the number of array elements in each layer is the same, it can be seen from step (1) that the distance between each array element in the bottom circular array satisfies half a wavelength, which will inevitably lead to the decrease of the radius and the constant number of array elements. The spacing is inevitably reduced, which does not satisfy the space sampling theorem, that is, the array element spacing does not meet the requirements of half a wavelength. In this invention, a new idea is provided, that is, based on the premise that the array element spacing is half a wavelength, the phase is determined according to the radius change of each layer of the circular ring array. The number of corresponding array elements is described below in conjunction with specific examples: narrowband signal frequency f = 15kHz, sound velocity c = 1500m/s, then the wavelength

The array element spacing is half wavelength λ/2=0.05m, the number of layers of the conical array is m=5, and the radius of the smallest layer of the circular array is 0.05m, then the radius r _m of each layer of the conical array is 0.5λ,λ , 1.5λ, 2λ, 2.5λ, the number N _m of array elements in each layer is determined as follows:

After the array elements are sparsely processed, the three-dimensional formation of the circular table array is formed, as shown in Figure 2, with 5 to 10 layers.

其方位角为

俯仰角为θ_m＝tg^-1(r_m/h_m)，向量

的坐标为

阵元A到下底面圆心距离

参考点O到远场目标方向的单位向量是

其坐标为

在同一时刻，参考点O与阵元A接收到的信号包络之间相位差是：Let A be an element on the m-th layer circular array, the radius of the circular array is r _m , the height of the circular array from the bottom is h _m , the vector from the reference point O to A is

Its azimuth is

The pitch angle is θ _m ＝tg ^-1 (r _m /h _m ), the vector

The coordinates are

Distance from array element A to the center of the bottom surface

The unit vector from the reference point O to the direction of the far-field target is

Its coordinates are

At the same moment, the phase difference between the reference point O and the signal envelope received by element A is:

的表达式Where k is the wave number, k=2π/λ, λ is the signal wavelength, for the above phase difference

the expression of

When m=1 means the bottom ring, at this time h ₁ =0, r _m =r ₁ , θ _m =2π, then the phase difference of the array element n on the bottom ring relative to the reference point O is:

When m=2,3...M, the phase difference of array element n on each ring relative to the reference point O is:

Therefore, the total array pattern function formed by all array elements on all m circular arrays with different radii is:

方向，则有：where ψ _mn is the initial phase difference of the corresponding array elements, in order to make the main beam point to the selected

direction, there are:

Then the pattern function of the corresponding symmetrically distributed circular table array:

In order to test the pitch angle search range of the circular array and the circular platform array, several groups of sources are selected for analysis, as shown in Figure 3. When the horizontal azimuth angle of the circular array is fixed and only the vertical pitch angle is changed, θ ₀ When ≥60°, the beam width of the main lobe is extremely wide, and it is almost impossible to form a beam, so it is considered to have no spatial directivity. Applying the fusion combination search (signal level, parameter level, decision level) of the new circular frustum array, only 3 layers of the new circular frustum array can realize the search range of half space [0°, 90°]. Further explain the fusion combination search: firstly, the fusion combination refers to the fusion of the output beam information of each layer of ring arrays and side busbar arrays in spatial filtering and target search; Combining the search results of overlapping regional targets within the region, the process of fusion and combination is rich and meaningful. Next, a further explanation of the decision-level fusion combined search is given: when the target comes to the range of θ ₀ ∈ [0°, 45°], use the circular array of each layer of the new circular table array to search and output the target, and judge whether the target exists; similarly , when the target direction θ ₀ ∈ [45°, 90°] range, use the new conical frustum array side busbar array to search and output the target, and judge whether the target exists; when the target direction θ ₀ ∈ [45°, 60°] belongs to When the two searches overlap the area, the two array search outputs are fused to determine whether there is a target. Signal-level and parameter-level fusion combination searches are not listed here one by one, and are still protected by this patent invention.

Select the incident direction of the signal source as θ ₀ = [30°, 45°, 60°], the number of layers of the new circular platform array changes from 5 layers to 10 layers, the distance between the array elements satisfies half a wavelength, and the radius of each layer of the circular ring array increases linearly , and the distance between each layer of the circular array also meets the half-wavelength. According to the above parameter setting requirements, the parameters such as the number of layers, height, and bus slope of the new circular platform array are changed. It can be seen from Figure 4 that when the number of array element layers is the same, the 120° interference direction (that is, the 60° direction of the signal source) has the best suppression effect; when the number of array element layers increases, the 30°, 45°, 60° signal source The suppression effect at the bottom of the incoming signal is enhanced, and the suppression effect at the bottom of the 30° direction changes most obviously with the number of layers.

Select θ ₀ =45° as the incident direction of the signal source, and change the parameters such as the number of layers, the height, and the slope of the bus bar of the new circular platform array, among which, the narrowband signal frequency f = 15kHz, and the sound velocity c = 1500m/s. It can be seen from Fig. 5 that the effect of suppressing incoming interference from the seabed of the sparse new circular platform array is remarkable.

The beneficial effects of the present invention are:

1. The traditional circular ring array has the defects of relatively limited vertical search range and high beam sidelobe level. This invention proposes a new sparse conical circular array shallow water combined search method, which effectively expands the top of the three-dimensional array based on fusion combined search array processing Half-space search range.

2. The traditional conical circular table array has the same symmetrical distribution of the number of array elements in each layer or the interlacing of different layer array elements at a certain angle to present a spiral distribution, which is faced with the situation that the distance between the array elements does not meet the half-wavelength as the radius decreases. Sparse processing, find out the reasonable matching relationship between array element spacing, radius, and number of array elements to achieve radius matching of the number of array elements, effectively reduce redundant array elements, and reduce array deployment costs and energy consumption.

3. Some underwater platforms are used to sit on the seabed or hang in the water. Under shallow sea conditions, the underwater platform has little search requirements for the seabed and will be interfered by incoming signals from the seabed, affecting the top half space of the underwater platform. Search performance. The novel circular table array fusion combined search array processing method in the present invention can effectively suppress incoming interference from the seabed and improve the stability of the top half-space search.

Claims (1)

1. A novel sparse circular truncated cone array shallow water area combined search method is characterized by comprising the following steps:

step 1: establishing a global space rectangular coordinate system O-XYZ, laying a novel sparse multilayer circular array, acquiring the position distribution of each array element of the circular array in the global space rectangular coordinate system, and receiving a signal from a search target;

the novel sparse multilayer circular array is a three-dimensional array formed by stacking M layers of circular arrays with different radiuses, the radiuses of the circular arrays from bottom to top are sequentially reduced, and the array element interval of the lowest layer of circular array is the half-wavelength lambda/2 of a received signal; the interlayer spacing of the novel sparse multilayer circular array is half wavelength lambda/2 of a received signal, and the heights of all layers are h in sequence ₁ ,h ₂ ,h ₃ …h _M Number of array elements of each layer N _m Is composed of

r _m Represents the radius of the circle array of the mth layer, M =1,2, \ 8230;, M;

when the novel sparse multilayer circular array is laid, the circle center of the bottommost circular array is laid at the original point O of a global space rectangular coordinate system O-XYZ, so that the Z axis points to the position right above the circular array; the position distribution of each array element in the global space rectangular coordinate system refers to the column coordinate of each array element in the global space rectangular coordinate system; the column coordinate of the nth array element in the mth layer is expressed as

And 2, step: acquiring a received signal phase difference of each array element in the novel sparse multilayer circular truncated cone array relative to a reference point O, and performing phased compensation and beam forming on each array element of the novel sparse multilayer circular truncated cone array to obtain a spatial filtering result of each layer of circular ring array and a side bus array of the novel circular truncated cone array;

when m =1 represents a bottom ring, the phase difference of the array element n on the bottom ring relative to the reference point O is:

wherein the pitch angle theta epsilon (0, pi) is defined as the included angle between the Z axis and the incident direction; azimuth angle

Is the angle projected on the array plane from the X-axis along the counterclockwise direction to the signal incidence direction;

when M =2,3 \8230M, the phase difference of the array element n on each circular ring relative to the reference point O is as follows:

therefore, the total array directional diagram function formed by all array elements on all the M circular arrays with different radii is as follows:

wherein, theta _m ＝tg ^-1 (r _m /h _m )；ψ _mn The initial phase difference of the nth array element in the mth layer is obtained;

for directing main beam at a selected direction

The directions are as follows:

the directional diagram function of the corresponding symmetric distributed circular array is:

and 3, step 3: carrying out decision-level fusion combination search in the vertical direction by utilizing the ring arrays and the bus arrays of each layer of the novel sparse multilayer circular array to obtain a search area range and a search target result;

the decision-level fusion combination search specifically comprises the following steps: when the target comes to the direction theta ₀ ∈[0°,45°]The range, the novel sparse multilayer circular array is utilized to search and output the target by each layer of circular array, and whether the target exists or not is judged; when the target comes to the direction theta ₀ ∈[45°,90°]The range, the novel sparse multilayer circular array side bus array is utilized to search and output the target, and whether the target exists or not is judged; when the target comes to the direction theta ₀ ∈[45°,60°]When the two search overlapping areas belong to, searching the two arrays, outputting fused judgment targets;

and 4, step 4: the number of layers, the height and the bus slope of the novel sparse circular truncated cone array are changed, the array parameter change is obtained, the semi-space search range of the top end of the underwater platform and the seabed incoming interference suppression are achieved, and the optimized search area range and the search target result are obtained.

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