A method for designing low sidelobe pattern of array antenna

Abstract

The invention discloses a method for designing a low sidelobe pattern of an array antenna, comprising the following steps: obtaining an array antenna model of a low sidelobe pattern to be designed; performing simulation configuration in FEKO software; simulating the array antenna through the FEKO software and exporting an ffe file; adding sampling points in the sidelobe region according to the position of the main lobe, designing a window, and constructing a low sidelobe radiation pattern; constructing an antenna radiation efficiency model based on circuit theory, and calculating the array element excitation of the low sidelobe pattern of the array antenna; calculating the optimal solution of the antenna radiation efficiency model as the excitation vector of the array antenna, and then obtaining a radiation pattern with the minimum radiation efficiency and the lowest radiation energy in the area where the sampling points are placed. The invention is based on the circuit port network theory, takes the efficiency of antenna radiation energy and input energy as the optimization target, minimizes the radiation efficiency of the antenna sidelobe region, constructs a calculation model, and obtains the array antenna unit excitation by deriving the analytical solution of the calculation model equation. The excitation is input into the array antenna to obtain a low sidelobe radiation pattern, which can greatly improve the calculation efficiency.

Description

Technical Field

[0001] The invention relates to a method for designing a low sidelobe pattern of an array antenna, and belongs to the technical field of low sidelobe array antenna design. Background Art

[0002] The antenna pattern is used to reflect the distribution of the ability of an antenna system (such as an antenna, antenna array, antenna element, etc.) to transmit or receive electromagnetic waves in the space around it. The antenna pattern describes how the antenna concentrates or disperses electromagnetic wave energy in three-dimensional space. The antenna pattern contains many important indicators for evaluating antenna performance, such as main lobe, side lobe, etc. The radiation lobe in the antenna pattern, except for the main lobe, has weak energy but cannot be ignored. The side lobe may interfere with neighboring cells or increase noise. Low sidelobe antennas can significantly improve the signal-to-noise ratio of wireless communication signals, reduce the risk of signal crosstalk in neighboring cells of antenna base stations, and enhance the efficiency of antenna systems. Low sidelobe array antennas have broad application prospects in wireless communication systems, radar systems, satellite communications and other fields. Therefore, it is necessary to study a low sidelobe pattern design method for array antennas to quickly generate low sidelobe radiation patterns.

[0003] At present, the main approach to the synthesis of low sidelobe patterns of array antennas is to select a type of optimization algorithm, combine the low sidelobe conditions with optimization constraints, gradually make the antenna pattern approach the expected pattern in multiple iterations, and terminate the constraint when the error threshold is less than a certain value. This type of method has certain limitations: for example, the optimization algorithm requires a large number of cycles and iterations, and the optimization results are often accompanied by a decrease in computational efficiency; when the optimization algorithm is operating, the optimization result may converge to a certain extreme point rather than the global minimum point, resulting in a decrease in algorithm capability. Summary of the invention

[0004] In order to solve the above-mentioned problems existing in the prior art, the present invention provides a method for designing a low sidelobe pattern of an array antenna. Based on the circuit port network theory, the efficiency of antenna radiation energy and input energy is taken as the optimization target, the radiation efficiency of the antenna sidelobe area is minimized, and a calculation model is constructed. By deriving the analytical solution of the calculation model equation, the array antenna unit excitation can be obtained. The excitation is input into the array antenna to obtain a low sidelobe radiation pattern, which can greatly improve the calculation efficiency.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] A method for designing a low sidelobe pattern of an array antenna is provided, comprising the following steps:

[0007] Step 1: Obtain an array antenna model with a low sidelobe pattern to be designed;

[0008] Step 2: In the FEKO software simulation configuration, insert the far-field sphere and select the spherical coordinate system; set the θ angle to start at 0, end at 180, and increment at 1; set The angle starts at 0, ends at 360, and the increment is 1; set the ffe file of the exported field;

[0009] Step 3: Use FEKO software to simulate the array antenna and export the ffe file;

[0010] Step 4: According to the position of the main lobe, add sampling points in the side lobe area, design the window, and construct a low side lobe radiation pattern;

[0011] Step 5: Construct an antenna radiation efficiency model based on circuit theory:

[0012] S51. Synthesize the Etheta and Ephi data vectors in the ffe file to obtain Etotal data;

[0013] S52. Set sampling points in the preset low radiation area;

[0014] S53. Extract the radiation pattern containing the sampling points to form a matrix G n =[G n (θ1),G n (θ2),...,G n (θ m )] T , the matrix G n is a subset of the nth array element pattern, G = [G1, G2, ..., G N ] is a matrix composed of the sampled radiation patterns of all array elements; [a t ]=[a1,a2,…,a n ], Matrix[a t ] is the array antenna excitation vector; construct the matrix [A], the element A in the matrix [A] ij =G j (θ i );

[0015] S54. To minimize the antenna radiation efficiency in the radiation area of ​​the sampling point, let [B] = [A] H [A];

[0016] Step 6. Calculate the eigenvalues ​​and eigenvectors of the matrix [B], take the eigenvector corresponding to the smallest non-zero eigenvalue as the excitation vector of the array antenna, and then find the radiation pattern with the minimum radiation efficiency and the lowest radiation energy in the area where the sampling points are placed.

[0017] Furthermore, in the step 1, the array antenna model includes the size, spacing, material of the antenna radiation unit, the material, thickness, and number of array elements of the antenna substrate; in the electromagnetic simulation software FEKO, a simulation model of the array antenna is established, and the network size is automatically segmented.

[0018] Furthermore, the step three comprises:

[0019] S31. Load an excitation with an amplitude of 1V and a phase of 0 degrees to the port of the array element to be simulated;

[0020] S32. Remove the excitation source of other array element ports;

[0021] S33. The simulation between array elements should keep the far-field sampling points and reference coordinate system settings the same.

[0022] Furthermore, in step S51, the FEKO generated FE file contains all the information about the electric field distribution in the far field of the antenna, with the center of the reference spherical coordinate system as the origin, and each Each coordinate point has a set of real and imaginary parts of Etheta and real and imaginary parts of Ephi.

[0023] Furthermore, in step S52, M sampling points are placed on a certain tangent plane of the spherical coordinate system, and all of the M sampling points are located in a preset low radiation area.

[0024] Further, the step S53 includes: the input power of the antenna system is The radiated power of the antenna system is P out =[a t ] H [A] H [A][a t ], its efficiency is:

[0025]

[0026] To minimize the antenna radiation efficiency in the radiation area of ​​the sampling point, let [B] = [A] H [A], that is, to calculate the Rayleigh quotient The minimum value of .

[0027] Furthermore, in the step 4, when placing the sampling point window, if the window is placed outside the normal direction of the antenna, the oblique beam radiation pattern is obtained after the steps 5 and 6.

[0028] Furthermore, in the step 4, when placing the sampling points and opening the windows, if two or more windows are set and the weighting values ​​are adjusted, a dual-beam or multi-beam radiation pattern is formed after the steps 5 and 6.

[0029] The present invention has the following beneficial effects:

[0030] In order to avoid the time-consuming iteration problem caused by the optimization algorithm and to reduce the complexity of the array antenna pattern synthesis, the present invention uses circuit theory instead of electromagnetic field theory to realize antenna pattern design, which has better practicality. Based on the circuit port network theory, the present invention takes the efficiency of antenna radiation energy and input energy as the optimization target, minimizes the radiation efficiency of the antenna sidelobe area, and constructs a calculation model. At this time, by deriving the analytical solution of the model equation, the array antenna unit excitation can be obtained. This method can quickly obtain the array antenna port excitation, which is of great significance for realizing real-time pattern synthesis and low sidelobe antenna design.

[0031] The low sidelobe pattern design method for array antenna proposed in the present invention can quickly calculate the array antenna excitation without iterative optimization. The low sidelobe radiation pattern can be obtained by inputting the set of excitations into the array antenna, thereby reducing the complexity and calculation time of the array antenna low sidelobe pattern synthesis algorithm. The method can be applied to the low sidelobe radiation pattern design of various array antennas, and greatly reduce the calculation performance requirements of the array antenna pattern synthesis algorithm.

[0032] At the same time, based on the improvement of algorithm efficiency, this method can be used to construct low-sidelobe scanning beams in array radars, which can effectively improve the signal-to-noise ratio of the radar system. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings used in the description of the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the contents of the embodiments of the present invention and these drawings without paying any creative work.

[0034] Figure 1 A flow chart of a method for designing a low sidelobe pattern of an array antenna according to an embodiment of the present invention;

[0035] Figure 2 Schematic diagram of an eight-element array antenna in an embodiment of the present invention;

[0036] Figure 3 is a schematic diagram of a polar coordinate system used in an embodiment of the present invention;

[0037] Figure 4 Schematic diagram of sampling point arrangement and window in an embodiment of the present invention;

[0038] Figure 5 A low sidelobe antenna radiation pattern generated for an embodiment of the present invention;

[0039] Figure 6 A low sidelobe slant beam pattern generated by an embodiment of the present invention. DETAILED DESCRIPTION

[0040] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention.

[0041] Example

[0042] like Figure 1 As shown, a method for designing a low sidelobe pattern of an array antenna comprises the following steps:

[0043] Step 1: Obtain the array antenna model with low sidelobe pattern to be designed:

[0044] The array antenna model includes necessary parameters such as antenna radiation unit size, spacing, material, antenna substrate material, thickness, number of array elements, etc. In the electromagnetic simulation software FEKO, a simulation model of the array antenna is established and the network size is automatically divided.

[0045] In this embodiment, a 1×8 uniformly arranged linear array antenna is used, and its operating frequency is 2.45 GHz. The model of the antenna in the FEKO software is as follows: Figure 2 As shown, the blue line is the X-axis, the green line is the Y-axis, and the red line is the Z-axis. The antenna array element port uses a line port, the red positive pole is in the positive direction of the Z axis, the line port radius is 0.25mm, and the excitation source is a voltage source.

[0046] Step 2: In the FEKO software simulation configuration, insert the far field sphere (Far fields), and select the spherical coordinate system. The definition of the spherical coordinate system is as follows: Figure 3 As shown; set the θ angle to start at 0, end at 180, and increment at 1; set The angle starts at 0, ends at 360, and the increment is 1; set the ASCII file of the exported field, that is, the *.ffe file (hereinafter referred to as the ffe file). In the Workplane tab, modify the reference system of the far-field sphere to offset 215.25mm along the Y axis, that is, move the reference system of the far-field sphere to the geometric center of the array antenna radiation surface.

[0047] Step 3: Use the electromagnetic simulation software FEKO to simulate the array antenna and export the ffe file:

[0048] The array antenna model is divided into 8 simulation projects. The array antenna elements are simulated one by one as follows. Each time a simulation is started, an ffe file generated by the FEKO software can be obtained, a total of 8 ffe files:

[0049] S31. Load an excitation with an amplitude of 1V and a phase of 0 degrees to the port of the array element to be simulated;

[0050] S32. Remove the excitation source of other array element ports;

[0051] S33. The simulation between array elements needs to keep the far-field sampling points and the reference coordinate system settings the same.

[0052] Step 4: According to the position of the main lobe, add sampling points in the side lobe area, design the window, and construct a low side lobe radiation pattern:

[0053] In order to obtain a beam with the main lobe of the antenna radiation pattern located in the normal direction, it is usually necessary to add sampling points in the side lobe areas on both sides of the main lobe to construct a radiation pattern with low side lobes. The cross-section of the array is used to construct a matrix [A] composed of the sampled radiation patterns of all array elements. 140 sampling points are placed in the range of θ∈[-90°,-20°)∪(20°,90°]. The sampling point arrangement and window diagram are shown in the figure. Figure 4 As shown in the figure, the area with a value of 1 needs to place sampling points, and the area with a value of 0 does not need to place sampling points. The area with a value of 0 is the window area.

[0054] Step 5: Construct an antenna radiation efficiency model based on circuit theory and calculate the element excitation of the array antenna with low sidelobe pattern:

[0055] The ffe file generated by S51.FEKO contains all the information about the electric field distribution in the far field of the antenna. The center of the reference spherical coordinate system is taken as the origin. Each coordinate point has a set of real and imaginary parts of Etheta and real and imaginary parts of Ephi. Use Python to write a program to read out the vector data of Etheta and Ephi in the 8 ffe files according to the corresponding coordinate points, synthesize the electric field vectors of Etheta and Ephi, obtain the Etotal vector data, and merge the 8 sets of radiation pattern data into variables.

[0056] S52. To simplify the design conditions, M sampling points may be placed on a certain plane of the spherical coordinate system, and all of the M sampling points are located in a preset low radiation area.

[0057] S53. Extract the radiation patterns of all sampling points from the pattern data variable, and construct a matrix [A] consisting of the sampled radiation patterns of all array elements.

[0058] Extract the radiation pattern containing the sampling points to form the matrix G n =[G n (θ1),G n(θ2),...,G n (θ m )] T , the matrix G n is a subset of the nth array element pattern. G=[G1,G2,...,G N ] is a matrix consisting of the sampled radiation patterns of all array elements. Matrix[a t ] is the array antenna excitation vector. Construct matrix [A], the element A in matrix [A] ij =G j (θ i ), the matrix [A] is a [M×N]-dimensional matrix. In this embodiment, the dimension of the matrix [A] is [140,8].

[0059] S54. The input power of the antenna system is The radiated power of the antenna system is P out =[a t ] H [A] H [A][a t ], and its efficiency is

[0060]

[0061] To minimize the antenna radiation efficiency in the radiation area of ​​the sampling point, let [B] = [A] H [A], that is, to calculate the Rayleigh quotient The minimum value of .

[0062] Step 6: Calculate the eigenvalues ​​and eigenvectors of the matrix [B], and take the eigenvector corresponding to the smallest non-zero eigenvalue as the excitation vector of the array antenna, so as to obtain the radiation pattern with the smallest radiation efficiency and the lowest radiation energy in the area where the sampling points are placed. In this embodiment, in FEKO, the array antenna is simulated with this group of excitations, and the radiation pattern obtained is as follows: Figure 5 As shown, the side lobes are all below -30 dB, indicating that the present invention effectively realizes the construction of low side lobe radiation pattern.

[0063] As an extension, by changing the window position or increasing the number of windows, array excitation with oblique beams or multiple beams can be obtained:

[0064] When placing the sampling point window, if the window is placed outside the normal direction of the antenna, an oblique beam radiation pattern can be obtained.

[0065] If two or more windows are set and the weighting values ​​are adjusted, dual-beam and multi-beam radiation patterns can be formed.

[0066] Taking the oblique beam as an example, in step 4, at intervals of 1°, 140 sampling points are placed in the range of θ∈[-90°,0°)∪(40°,90°]. At this time, the window moves 20 degrees in the positive direction of the θ axis. Steps 5 and 6 are completed in sequence. The array antenna is simulated with the newly calculated excitation vector. The radiation pattern obtained is as follows Figure 6 As shown, at this time, the main lobe beam of the array antenna points to 18°, completing the construction of a low sidelobe slant beam.

[0067] The method is used to construct a low sidelobe radiation pattern of an array antenna, and can be used for the design of an array antenna requiring a low sidelobe radiation pattern, as well as for the real-time generation of a low sidelobe radiation beam of an array antenna radar.

[0068] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for designing a low sidelobe pattern of an array antenna, characterized in that: The following steps are involved: Step 1: Obtain an array antenna model with a low sidelobe pattern to be designed; Step 2: In the FEKO software simulation configuration, insert the far-field sphere and select the spherical coordinate system; set the θ angle to start at 0, end at 180, and increment at 1; set The angle starts at 0, ends at 360, and the increment is 1; set the ffe file of the exported field; Step 3: Use FEKO software to simulate the array antenna and export the ffe file; Step 4: According to the position of the main lobe, add sampling points in the side lobe area, design the window, and construct a low side lobe radiation pattern; Step 5: Construct an antenna radiation efficiency model based on circuit theory: S51. Synthesize the Etheta and Ephi data vectors in the ffe file to obtain Etotal data; S52. Set sampling points in the preset low radiation area; S53. Extract the radiation pattern containing the sampling points to form a matrix G n =[G n (θ1),G n (θ2),...,G n (θ m )] T , the matrix G n is a subset of the nth array element pattern, G = [G1, G2, ..., G N ] is a matrix composed of the sampled radiation patterns of all array elements; [a t ]=[a1,a2,…,a n ], Matrix[a t ] is the array antenna excitation vector; construct the matrix [A], the element A in the matrix [A] ij =G j (θ i ); S54. To minimize the antenna radiation efficiency in the radiation area of ​​the sampling point, let [B] = [A] H [A]; Step 6. Calculate the eigenvalues ​​and eigenvectors of the matrix [B], take the eigenvector corresponding to the smallest non-zero eigenvalue as the excitation vector of the array antenna, and then find the radiation pattern with the minimum radiation efficiency and the lowest radiation energy in the area where the sampling points are placed.

2. A method for designing a low sidelobe pattern of an array antenna as claimed in claim 1, characterized in that: In the step 1, the array antenna model includes the size, spacing, and material of the antenna radiation unit, the material, thickness, and number of array elements of the antenna substrate; in the electromagnetic simulation software FEKO, a simulation model of the array antenna is established, and the network size is automatically segmented.

3. A method for designing a low sidelobe pattern of an array antenna as claimed in claim 1, characterized in that: The step three comprises: S31. Load an excitation with an amplitude of 1V and a phase of 0 degrees to the port of the array element to be simulated; S32. Remove the excitation source of other array element ports; S33. The simulation between array elements should keep the far-field sampling points and reference coordinate system settings the same.

4. The method for designing a low sidelobe pattern of an array antenna according to claim 1, characterized in that: In step S51, the ffe file generated by FEKO contains all the information about the electric field distribution in the far field of the antenna, with the center of the reference spherical coordinate system as the origin, and each relative to the origin in space. Each coordinate point has a set of real and imaginary parts of Etheta and real and imaginary parts of Ephi.

5. The method for designing a low sidelobe pattern of an array antenna according to claim 1, characterized in that: In the step S52, M sampling points are placed on a certain tangent plane of the spherical coordinate system, and all of the M sampling points are located in a preset low radiation area.

6. A method for designing a low sidelobe pattern of an array antenna as claimed in claim 1, characterized in that: The step S53 includes: the input power of the antenna system is The radiated power of the antenna system is P out =[a t ] H [A] H [A][a t ], its efficiency is: To minimize the antenna radiation efficiency in the radiation area of ​​the sampling point, let [B] = [A] H [A], that is, to calculate the Rayleigh quotient The minimum value of .

7. A method for designing a low sidelobe pattern of an array antenna as claimed in claim 1, characterized in that: In the step 4, when placing the sampling point window, if the window is placed outside the normal direction of the antenna, the oblique beam radiation pattern is obtained after the steps 5 and 6.

8. The method for designing a low sidelobe pattern of an array antenna according to claim 1, wherein: In the step 4, when placing the sampling points and opening the windows, if two or more windows are set and the weighting values ​​are adjusted, a dual-beam or multi-beam radiation pattern is formed after the steps 5 and 6.

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