A fast method for obtaining the radiation field of a large-scale array antenna

Abstract

This invention proposes a method for obtaining the radiation field of a large-scale array antenna, mainly addressing the problems of low computational efficiency and long computation time in existing technologies for obtaining the radiation field of large-scale array antennas. The implementation scheme is as follows: 1) Construct a subarray model and obtain subarray radiation field data; 2) Translate the subarray and perform spherical wave expansion on the translated radiation field; 3) Calculate the radiation field of the i-th antenna element in the subarray model according to the spherical expansion formula; 4) Repeat steps 2) and 3) to obtain the radiation fields of all antenna elements in the subarray; 5) Calculate the radiation field of each element of the large-scale array antenna based on the radiation fields of the subarray elements and superimpose the radiation fields of all elements to obtain the total radiation field of the large-scale array antenna. This invention uses subarray radiation field data, obtains the radiation field of each element of the subarray through mode filtering, and extrapolates to the large-scale array antenna, improving computational efficiency and shortening computation time, and can be used for obtaining the radiation field of large-scale array antennas.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic technology, and specifically relates to a method for rapidly acquiring electromagnetic radiation fields, which can be used to study the far-field radiation characteristics of large-scale array antennas. Background Technology

[0002] Large-scale array antennas are widely used in various fields due to their high gain, controllable directivity, and narrow beamwidth. However, the increasing array size and the complexity of array element structures pose challenges to their design and evaluation. Currently, research on the radiation characteristics of large-scale array antennas mainly relies on measurements and calculations using various electromagnetic simulation software or microwave anechoic chambers. Developing rapid methods for acquiring the radiation characteristics of large-scale array antennas is of significant engineering importance for solving the simulation and measurement challenges of shipborne and airborne radars with hundreds or thousands of elements, and for reducing project development cycles and research costs.

[0003] As the array size increases, on the one hand, the classic pattern product method, by neglecting the mutual coupling between elements, yields results that differ significantly from the actual results; on the other hand, both the increase in the number of array elements and the complexity of the array element structure require existing simulation software to consume a large amount of computer resources and computation time, causing the project's progress to be severely hampered by working conditions and development cycles. Even in actual testing, the large space occupied by the array size often makes it difficult to find a suitable anechoic chamber for experiments.

[0004] Patent application CN104992001B, authorized for publication, discloses a "precise and fast calculation method for the far-field radiation field of a large-scale MIMO array antenna." This method utilizes the structural parameters of an M×N element planar array antenna, solving for the relationship between the incident and scattered fields of the antenna elements using spherical vector wave functions and iterative scattering principles. Based on the mutual coupling between antenna elements, it selects and extracts antenna subarrays within the array environment, solves for the far-field radiation field of the elements in the subarray, and finally calculates the far-field radiation field of the array antenna based on the field superposition principle. However, the accuracy of this method in calculating the radiation field of antenna elements within the array environment is limited by the number of scattering iterations. It only reduces some of the computation through subarray strategies, and the computational load increases dramatically with the number of iterations and the size of the subarray. Therefore, obtaining the radiation field of a large-scale array antenna remains limited by computer resources, resulting in long computation cycles and low efficiency. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of the prior art by proposing a rapid method for acquiring the radiation field of a large-scale array antenna, thereby reducing computation time and improving the efficiency of acquiring the far-field radiation field of a large-scale array antenna.

[0006] To achieve the above technical objectives, the present invention provides a method for rapidly acquiring the radiation field of a large-scale array antenna, comprising the following steps:

[0007] (1) From the large-scale array antenna to be calculated in row A and column B, select the adjacent row a and column b as a subarray, collect the far-field data of the subarray, and obtain the far-field radiation pattern of the subarray under test. Where A, B, a, and b are all integers, and 1 ≤ a ≤ A, 1 ≤ b ≤ B, and θ represents the pitch angle. Represents spatial azimuth;

[0008] (2) Far-field pattern of the subarray to be measured Perform coordinate translation to obtain the subarray far-field radiation pattern with the center of the aperture of the i-th radiating element as the origin of the coordinate system.

[0009] (3) Far-field pattern of the subarray at the origin of the coordinate system Perform a spherical wave expansion, filter out the higher-order mode terms of the spherical wave, and obtain the radiation field of the i-th radiating element in the subarray under test.

[0010] (4) Repeat (2) to (3) to obtain the radiation field data of all antenna elements in the subarray;

[0011] (5) Expand the subarray of row a and column b to row A and column B, obtain the phase difference between each element of the subarray and each element of the large-scale array antenna, and calculate the radiation field of each element of the large-scale array antenna.

[0012] (6) Based on the principle of field superposition, the radiation fields of each element of the large-scale array antenna are superimposed to obtain the total radiation field of the large-scale array antenna.

[0013] Compared with the prior art, the present invention has the following advantages:

[0014] First, this invention reduces the difficulty of extracting the far-field radiation field of each antenna element in the subarray by performing spherical wave expansion on the far-field radiation field of the subarray and using mode filtering.

[0015] Second, this invention eliminates the multipath effect in the environment by filtering out the multipath effect in the environment, thereby eliminating the influence of environmental clutter on the far-field radiation field of the subarray, so that the acquisition of the subarray radiation field is not limited to the microwave anechoic chamber.

[0016] Third, by expanding the subarray, the present invention uses the subarray radiation field to calculate the radiation field of the large-scale array antenna, which greatly simplifies the calculation process and shortens the calculation time while ensuring the accuracy of the results.

[0017] Fourth, this invention only requires measuring the total radiation field of the subarray to obtain the radiation field of a large-scale array antenna. Its accuracy is not affected by the complexity of the antenna element structure of the array antenna, and it has a wide range of applications. Attached Figure Description

[0018] Figure 1 This is a flowchart illustrating the implementation of the present invention;

[0019] Figure 2 This is a schematic diagram of the neutron array element model and a schematic diagram of the |S11| parameters in this invention;

[0020] Figure 3 This is a diagram of a large-scale antenna array from which the radiation field to be acquired is to be obtained in this invention;

[0021] Figure 4 This is a schematic diagram of the large-scale array antenna subarray model of the present invention;

[0022] Figure 5 This is a comparison chart of the simulation results of this invention and existing full-wave simulation results. Detailed Implementation

[0023] To more clearly describe the technical solution and effects of the present invention, the following description is provided in conjunction with specific embodiments and accompanying drawings.

[0024] Reference Figure 1 The implementation steps of this invention are as follows:

[0025] Step 1: Construct a large-scale array antenna and subarray model and obtain the subarray radiation field pattern.

[0026] (1.1) Constructing a large-scale array antenna model:

[0027] This example utilizes Altair Feko simulation software, selecting, but not limited to, the following: Figure 2 (a) The dipole antenna shown in the structure is used as an array element of a large-scale array antenna. The array element is a half-wave dipole antenna with an antenna arm length of 5 cm and an operating frequency of 3 GHz.

[0028] The antenna element was fed using a voltage source, and the element's frequency sweep range was set to 2 GHz - 4 GHz with a sweep interval of 0.01 GHz. The |S11| parameters of the antenna element at each frequency point were obtained, as shown in the figure. Figure 2 As shown in (b);

[0029] The antenna elements are evenly placed in a rectangular xyz coordinate system, with rows along the positive x-axis. Each row contains 50 antenna elements, with an element spacing of 0.7λ. A total of 50 rows are formed, with a row spacing of 0.7λ, creating a 50*50 large-scale array antenna model. Figure 3 As shown;

[0030] (1.2) Construct the subarray model and obtain the radiation field pattern of the subarray.

[0031] Using Altair Feko simulation software, the row and column spacing of a large-scale array antenna were selected. Figure 3 The subarray model formed by 7 adjacent rows and 7 columns of data, with a size of 7*7, is as follows: Figure 4 As shown;

[0032] All antenna elements of the subarray are fed using a voltage source. Sampling parameters are set, and data is collected at 1° intervals within the spatial elevation angle θ of 0° to 180° and the spatial azimuth angle θ of 0° to 360° to obtain the radiation field pattern of the subarray.

[0033] In this example, A = 50, B = 50, a = 7, b = 7.

[0034] Step 2: Radiation field pattern of the subarray Perform a translation to obtain the radiation field pattern of the subarray after translation.

[0035] (2.1) Translate the geometric center point of the subarray to the origin of the rectangular coordinate system and calculate the radiation pattern of the subarray after translation. phase difference δ i :

[0036]

[0037] Where, d x d y These represent the row spacing and column spacing of the array antenna, respectively. In this example, d x =0.7λ, d y =0.7λ;

[0038] (2.2) Calculate the radiation field pattern of the translated subarray

[0039]

[0040] Where j represents the imaginary unit and k represents the wave number.

[0041] Step 3: Analyze the radiation field pattern of the translated subarray. Perform spherical wave expansion and obtain the radiation field of the i-th radiating element.

[0042] (3.1) The far-field pattern of the subarray with the center of the aperture of the i-th antenna element as the origin of the coordinate system is calculated according to the following formula. Perform spherical wave expansion:

[0043]

[0044] Where m = 0, ±1, ±2, ..., ±n and n = 1 to ∞ represent different mode terms, a represents the incident wave, b represents the outgoing wave, TE represents the transverse electric wave, TM represents the transverse magnetic wave, and m and n are limited mode indices, with n taking values ​​from 1 to ∞ and m taking values ​​from 0 to ∞. These represent the transverse electric wave (TE) output mode, the transverse electric wave (TE) incident mode, the transverse magnetic wave (TM) output mode, and the transverse magnetic wave (TM) incident mode, respectively. for The expansion coefficients, for The expansion coefficients, for The expansion coefficients, for The expansion coefficients, where j represents the imaginary unit.

[0045] (3.2) Filter out the higher-order spherical wave mode terms in (3.1) and calculate the radiation field of the i-th antenna element in the subarray.

[0046]

[0047] Where N is the number of truncated modes of the spherical wave function, N = [kR] + c, k is the wave number, R is the radius of the smallest sphere surrounding the i-th element in the subarray to be tested, [kR] represents the smallest integer greater than kR, and c is an integer greater than or equal to 0 and less than or equal to 10; in this example, the number of truncated modes of the spherical wave function can be obtained as N = 2 from the operating frequency and the structure of the radiating element.

[0048] Step 4: Obtain radiation field data for all elements of the subarray.

[0049] Ah

[0050] Repeat steps two and three 49 times to obtain the radiation field data of all elements of the subarray, i.e., the 49 antenna elements of the 7x7 subarray.

[0051] Where t is an integer, t = 1, 2, ..., i, ... 49.

[0052] Step 5: Calculate the phase difference and radiation field of each element of the large-scale array antenna.

[0053] (5.1) Calculate the phase difference of each element in a large-scale array antenna:

[0054] (5.1.1) Calculate the first row to the second row of the subarray. Rows and large-scale array antennas, row 1 to row 2 Phase difference δ of each row of cells l :

[0055]

[0056] in,

[0057] (5.1.2) Calculate the subarray of the first... Linear and large-scale array antennas Arriving at the Phase difference δ of each row of cells p :

[0058]

[0059] Among them, p=1,2,3,…,[(A-a+1)×B], m=1,2,3,…,[(A-a+1)×B]

[0060] (5.1.3) Calculate the subarray of the first... Reaching row a and the large-scale array antenna The phase difference δ between the cells in row A and the cells in row A q :

[0061]

[0062] in,

[0063] (5.2) Calculate the radiation field of each element of the large-scale array antenna:

[0064] (5.2.1) Calculate the first row to the second row of the large-scale array antenna. Radiation field of each unit in the row

[0065]

[0066] Where j represents the imaginary unit, k represents the wave number, u and n are integers, n = 1, 2, 3, ..., B, δ l The phase difference obtained in (5.1.1);

[0067] (5.2.2) Calculate the first... Arriving at the Radiation field of each unit in the row

[0068]

[0069] Among them, p=1,2,3,…,[(Aa)×B], δ pThe phase difference obtained in (5.1.2);

[0070] (5.2.3) Calculate the first... and the radiation fields of each unit in row A

[0071]

[0072] in, δ q The phase difference is obtained in (5.1.3).

[0073] In this example, A = 50, B = 50, a = 7, b = 7, l = 1, 2, 3, ..., 150, n = 1, 2, 3, ..., 50, m = 1, 2, 3, ..., 44, p = 1, 2, 3, ..., 2200, q = 1, 2, 3, ..., 150.

[0074] Step 6: Calculate the total radiated field of the large-scale array antenna

[0075] By superimposing the element radiation fields obtained in step five, the total radiation field of the large-scale array antenna is obtained.

[0076]

[0077] In this example, (A-a+1)×B=2200.

[0078] The effects of this invention can be further illustrated by the following simulation experiments:

[0079] I. Simulation Experiment Conditions

[0080] Using Altair Feko simulations, dipole antennas were used as the array elements of an array antenna. A 50*50 planar array was established in a Cartesian xyz coordinate system as a large-scale array antenna for calculating the radiation field. The antenna elements were uniformly distributed, with rows along the positive x-axis and a row spacing of 0.7λ, and columns along the positive y-axis and a column spacing of 0.7λ. The spatial elevation angle θ ranged from 0° to 180°, and the spatial azimuth angle... Data is collected at 1° intervals within the range of 0° to 360° to obtain radiation field data of a large-scale array antenna.

[0081] II. Simulation Experiment Content

[0082] Simulation Experiment 1: Under the above experimental conditions, the results obtained by extrapolating the total radiation field of a large-scale array antenna using the method of this invention through the far-field radiation field of the subarray are compared with the results obtained by simulating a large-scale array antenna using the existing Altair Feko simulation software. Figure 5 As shown.

[0083] from Figure 5 (a) It can be seen that in the plane where the spatial angle Phi is 0° and the elevation angle Theta is -90° to 90°, the radiation field of the large-scale array antenna obtained in this invention is basically consistent with the FEKO simulation results in the range of -70° to 70°, showing good agreement. There is an error of about 2dB in other regions. Figure 5 (b) It can be seen that in the plane with a spatial angle Phi of 90° and an elevation angle Theta of -90° to 90°, the radiation field of the large-scale array antenna obtained by the present invention is basically consistent with the FEKO simulation results in the range of -45° to 45°, and the degree of agreement is good, indicating that the present invention can successfully calculate the far-field radiation field of the large-scale array antenna.

[0084] Simulation Experiment 2: Under the above experimental conditions, the total time required to obtain the total radiated field of the large-scale array antenna by the method of the present invention and the time required to perform the simulation using Altair Feko simulation software were recorded. The results are shown in Table 1.

[0085] Table 1

[0086] method Calculate time (seconds) Method of the present invention 11 Altair Feko Simulation 73

[0087] As shown in Table 1, it takes 11 seconds to calculate the total radiation field of a large-scale array antenna using the method of this invention, while it takes 73 seconds using AltairFeko simulation software. Compared with simulation software, this method can obtain the total radiation field of a large-scale array antenna faster and more efficiently.

Claims

1. A method for obtaining the radiation field of a large array antenna, characterized in that: Comprise: (1) from the A row B column of the large-scale array antenna to be calculated, select its adjacent a row b column as a subarray, collect the far-field data of the subarray, and obtain the far-field pattern of the measured subarray Wherein, A, B, a, b are all integers, and 1≤a≤A, 1≤b≤B, θ represents the spatial elevation angle, represent the spatial azimuth angle; (2) far field pattern of the subarray to be tested Coordinate translation is performed to obtain the far field pattern of the subarray with the center of the aperture of the i-th radiating element as the origin of the coordinate system (3) the subarray far-field pattern of the coordinate system origin Carrying out spherical wave expansion, filtering out high-order mode items of the spherical wave, obtaining a radiation field of the i-th radiation unit in the to-be-measured subarray (4) repeating (2) to (3) to obtain the radiation field data of all antenna elements in the subarray where t = 1, 2, …, i, …, 49; (5) the sub-array of a row b column is expanded to A row B column, the phase difference between each unit of the sub-array and each unit of the large-scale array antenna is obtained, and the radiation field of each unit of the large-scale array antenna is calculated; (6) According to the field superposition principle, the radiation fields of each unit of the large-scale array antenna are superposed to obtain a total field of the large-scale array antenna 2. The method of claim 1, wherein, (2) The subarray radiation pattern after mid-translation is represented as follows: wherein is the subarray radiation pattern phase difference after translation, d x , d y are the array antenna row and column spacing, respectively, j represents the imaginary unit, and k represents the wave number.

3. The method of claim 1, wherein, The (3) is implemented as follows: (3a) The following formula is used to measure the far-field pattern of the subarray with the center of the i-th radiation unit aperture as the coordinate system origin Carry out spherical wave expansion: Wherein, m and n represent different mode terms, m takes the value range of 0~±n, n takes the value range of 1~∞, a represents incident wave, b represents outgoing wave, TE represents transverse electric wave, and TM represents transverse magnetic wave; Respectively represent the transverse electric wave TE outgoing wave mode, the transverse electric wave TE incident wave mode, the transverse magnetic wave TM outgoing wave mode and the transverse magnetic wave TM incident wave mode of the spherical wave; For The expansion coefficient of For The expansion coefficient of For The expansion coefficient of For The expansion coefficient of j represents the imaginary unit; (3b) filtering out the high order mode terms in the spherical wave expansion in (3a) to obtain the element radiation field of the i-th antenna element in the subarray under test Wherein, N is the truncated mode number of spherical wave function, N=[kR]+c, k is wave number, R is the minimum spherical radius surrounding the i th unit in the sub-array to be measured, [kR] represents the minimum integer greater than kR, and c is an integer greater than or equal to 0 and less than or equal to 10.

4. The method of claim 1, wherein, The phase difference between each unit of the sub-array and each unit of the large-scale array antenna is obtained in (5), and the implementation is as follows: (4a) the phase difference δ of each element of the first row to the last row of the subarray is obtained (4b) the phase difference δ of each element of the first row to the last row of the large-scale array antenna is obtained l :​ wherein d x , d y are the array antenna row and column spacing, respectively, n = 1, 2, 3,..., B. (4b) obtaining the phase difference δ of each element in the first row to the first row of the large array antenna p : Wherein, p=1,2,3,…,[(A-a)×B], m=1,2,3,…,A (4c) obtaining a sub-array of the first up to the a-th row and the first phase difference δ of the elements of the a-th row q : wherein 5. The method of claim 1, wherein, The radiation field of each unit of the large-scale array antenna is calculated in (5), and the implementation is as follows: (5a) calculating the radiation field of each element of the first to the row of the large scale array antenna wherein j represents the imaginary unit, k represents the wave number, u, n are integers, n = 1, 2, 3,..., B; δ l is the phase difference obtained in (4a); (5b) calculating the element radiation field of the large scale array antenna up to the element radiation field of the large scale array antenna up to the element radiation field of the large scale array antenna where p = 1, 2, 3,..., [(A-a+1)xB], δ p is the phase difference obtained in (4b); (5c) calculating the radiation field of the large scale array antenna and the radiation field of each element in row A wherein δ q is the phase difference obtained in (4c).

6. The method of claim 1, wherein, (6) The total radiation field of large-scale array antenna is obtained by field superposition is expressed as: wherein, l = 1, 2, 3, …, [(a-1) / 2] x B, p = 1, 2, 3, …, [(A-a) x B], q = 1, 2, 3, …, [(a-1) / 2] x B.

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