Waveguide slot phased array antenna with low far-field sidelobes and its design method

Abstract

The present invention discloses a waveguide slot phased array antenna with low far-field sidelobes and its design method, which mainly solves the problems that the far-field sidelobes of the scanning beam of the existing waveguide slot phased array antenna increase, resulting in a decrease in the radar anti-jamming ability, and that the far-field sidelobe suppression method is difficult to be applied to the design of the waveguide slot phased array antenna. The waveguide slot phased array antenna with low far-field sidelobes of the present invention is composed of two types of radiation elements with the same slot parameters except for the phase inversion of the radiation slots, and the positions and numbers of the two types of radiation elements in the antenna array are determined by a global optimization algorithm. The present invention reduces the far-field sidelobe level of the scanning beam of the waveguide slot phased array antenna and improves the radar anti-jamming ability. The simulation results show that the far-field sidelobe levels of the scanning beams of the waveguide slot phased array antenna in the embodiments of the present invention are on average decreased by 12.22 dB.

Description

Technical Field

[0001] The present invention belongs to the technical field of radar communication, and further relates to a waveguide slot phased array antenna with low far-field sidelobes and its design method in the technical field of antennas. The present invention can be used to design a waveguide slot phased array antenna for phased array radar. Background Art

[0002] High-gain, low-sidelobe antennas are the core components of phased array radars. High gain enables the radar to achieve long-distance monitoring, an extremely narrow beamwidth enables high resolution, and low sidelobes can reduce background clutter and improve the radar's anti-jamming ability. Beam scanning can be achieved by changing the antenna feed phase. Waveguide slot antennas have the advantages of low insertion loss, high gain, and high radiation efficiency, and it is easy to control the amplitude distribution of the internal field of the antenna aperture, making it easier to achieve low sidelobes. Therefore, waveguide slot antennas have more advantages in terms of high gain, high efficiency, and low sidelobes. The traditional design method of waveguide slot phased array antennas is to extract the conductance value and set different slot parameters for each slot to achieve low sidelobe performance in the azimuth plane, and to achieve antenna elevation plane beam scanning by reasonably setting the array spacing in the elevation plane. However, when the traditional waveguide slot phased array antenna performs beam scanning, relatively high far-field sidelobes will be generated outside 30° of the main beam. These far-field sidelobes will move with the main beam and increase as the scanning angle increases, resulting in a decrease in the radar's anti-jamming ability and affecting the overall performance of the radar.

[0003] Shenzhen Kuang-Chi Institute of Advanced Technology disclosed an array antenna in its patent document "An Array Antenna" (application number 201410605379.9, publication number CN 105633593 A). By setting a high-impedance surface reflector around the antenna reflector, it suppresses the transmission of surface waves, blocks surface currents, reduces the far-field sidelobes of the antenna, and improves the gain, directivity, and anti-jamming ability of the antenna. However, there are still two deficiencies in this antenna: First, for the high-gain phased array radar antenna, due to its large antenna array surface, the role of the high-impedance surface reflector is weakened, and it cannot effectively reduce the far-field sidelobes. Second, this antenna introduces additional structures, increasing the complexity of antenna design, raising the antenna cost, and increasing the installation difficulty.

[0004] The University of Electronic Science and Technology of China discloses a low-sidelobe waveguide slot array antenna and a design method in its patent document "A Low-Sidelobe Waveguide Slot Array Antenna and Design Method" (application number 202210643586.8, publication number CN 115189150 A). All radiation slot parameters of the low-sidelobe waveguide slot phased array antenna disclosed in this patent are the same, which simplifies the antenna design difficulty. This antenna design method divides the internal radiation slot units into in-phase units and anti-phase units. By optimizing the positions of the in-phase units and anti-phase units, two-dimensional low-sidelobe shaping of the waveguide slot array antenna in the plane parallel to the electric field direction and the plane parallel to the magnetic field direction is achieved simultaneously. Although this method simplifies the antenna design difficulty, there are still two deficiencies: Firstly, since the offset and slot length of each radiation slot are the same and the excitation amplitude of each unit is consistent, although the maximum sidelobe is optimized compared with the sidelobe of equal-amplitude excitation, the overall sidelobe level is still relatively high. Secondly, this method performs two-dimensional low-sidelobe shaping on the normal beam of the antenna and does not optimize the sidelobes of the scanning beam and other 3D pattern cross-sections in other directions. Since the phased array radar antenna has relatively high requirements for sidelobes, this method cannot meet the low-sidelobe performance requirements of the radar antenna. Summary of the Invention

[0005] The purpose of the present invention is to propose a design method for a low far-field sidelobe waveguide slot phased array antenna in view of the deficiencies of the above-mentioned prior art, aiming to solve the problem that the far-field sidelobe of the scanning beam of the waveguide slot phased array antenna increases, resulting in a reduction in the radar anti-jamming ability, and the problem that the far-field sidelobe suppression method is difficult to be applied to the design of the waveguide slot phased array antenna.

[0006] The idea for achieving the purpose of the present invention is as follows: In view of the above problems, the waveguide slot phased array antenna of the present invention uses two radiation units with the same radiation slot parameters except for the reverse phase of the radiation slots to form an array. By feeding an inverse phase at the antenna feed point, the radiation phases of the two radiation units can be made consistent. Since the radiation slot parameters of the two radiation units are the same, the radiation performance of the waveguide slot phased array antenna will not affect important phased array radar antenna parameters such as gain, near-field sidelobe, beam width, and beam pointing except for the far-field sidelobe, and no other additional structures are introduced, which simplifies the antenna design process and solves the problem that the far-field sidelobe suppression method is difficult to be applied to the design of the waveguide slot phased array antenna. The design method of the present invention optimizes the number and positions of the two radiation units in the array, changes the elevation position and number of the far-field sidelobes, and realizes the far-field sidelobe suppression of the waveguide slot phased array antenna at each scanning angle, thus solving the problem of the elevation of the far-field sidelobe of the scanning beam of the waveguide slot phased array antenna.

[0007] To achieve the above object, the waveguide slot phased array antenna of the present invention includes N waveguide slot antenna radiation units composed of a waveguide joint, radiation slots, and shorting plates / loads that are arrayed in the beam scanning plane, where N≥4. The waveguide slot antenna radiation units are divided into two types of radiation units with the same slot parameters except for the opposite phase of the radiation slots. The positions and numbers of the two types of radiation units in the antenna array are determined by a global optimization algorithm.

[0008] The steps of the design method of the waveguide slot phased array antenna of the present invention are as follows:

[0009] Step 1, extract the radiation pattern in the radiation element array:

[0010] Establish a simulation model composed of M waveguide slot antenna radiation units with the same slot parameters except for the opposite phase of the radiation slots, where M≥4, and the value of M is less than N and at least includes two types of radiation units with the same slot parameters except for the opposite phase of the radiation slots located in the antenna array. Simulate the simulation model and extract the antenna radiation patterns corresponding to the two types of radiation units located in the antenna array respectively.

[0011] Step 2, use the global optimization algorithm to calculate the positions and numbers of the two types of radiation units in the antenna array:

[0012] Step 2.1, set the initial values of the numbers and positions of the two types of radiation units in the waveguide slot phased array antenna, and substitute the initial values, the radiation pattern in the radiation element array, and the phase values of each unit corresponding to the scanned beam into the antenna array synthesis calculation formula to obtain the antenna radiation pattern of the waveguide slot phased array antenna scanned beam corresponding to the initial values. Calibrate the maximum level outside the 30° range of the main beam on the antenna radiation pattern corresponding to the initial values as the far-field sidelobe level of the waveguide slot phased array antenna scanned beam.

[0013] Step 2.2, take the far-field sidelobe level of the waveguide slot phased array antenna scanned beam as the optimization target, take the numbers and positions of the radiation units in the waveguide slot phased array antenna as the optimization variables, and set the maximum number of iterations corresponding to the global optimization algorithm.

[0014] Step 2.3, substitute the optimization target and optimization variables into the global optimization algorithm for iterative calculation until the maximum number of iterations is reached, and obtain the numbers and positions of the radiation units in the waveguide slot phased array antenna corresponding to the lowest far-field sidelobe level of the waveguide slot phased array antenna scanned beam.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] First, since the slot parameters of the two radiation elements that make up the waveguide slot phased array antenna of the present invention are the same, the waveguide slot phased array antenna of the present invention has no impact on important radar antenna indicators such as gain, near sidelobes, beam width, and beam pointing. Moreover, without introducing any additional structures, only the far sidelobes are suppressed, enhancing the radiation ability of the radar waveguide slot phased array antenna and reducing the complexity of antenna design.

[0017] Second, the design method of the present invention can reduce the far sidelobe level of the waveguide slot phased array antenna by 12.22 dB at each scanning angle by optimizing the number and position of the two radiation elements with the same slot parameters except for the reverse phase of the radiation slots in the waveguide slot phased array antenna. Thus, the problem that the radiation ability of the waveguide slot phased array antenna is reduced due to the increase of the far sidelobes of the scanning beam of the waveguide slot phased array antenna is overcome, and the anti-interference ability of the phased array radar is improved in the present invention. Brief Description of the Drawings

[0018] Figure 1 is a schematic diagram of the division of each region of the 3D radiation pattern of the embodiment of the present invention; Figure 1 (a) is a schematic diagram of the main section; where Figure 1 (b) is a schematic diagram of the far region and the near region;

[0019] Figure 2 is a flowchart of the antenna design method of the embodiment of the present invention;

[0020] Figure 3 is a top view of the simulation model of the embodiment of the present invention;

[0021] Figure 4 is a side view of the simulation model of the embodiment of the present invention;

[0022] Figure 5 is the 3D radiation pattern of the existing waveguide slot phased array antenna scanning at 45° in the UV coordinate system in the embodiment of the present invention; where Figure 5 (a) is a top view; Figure 5 (b) is a side view;

[0023] Figure 6 is the 3D radiation pattern of the waveguide slot phased array antenna scanning at 45° in the UV coordinate system in the embodiment of the present invention; where Figure 6 (a) is a top view; Figure 6 (b) is a side view;

[0024] Figure 7 is a curve graph showing the change of the far sidelobe level of the existing waveguide slot phased array antenna and the waveguide slot phased array antenna of the embodiment of the present invention with the scanning angle in the embodiment of the present invention. Detailed Embodiments

[0025] The application scenario of the embodiments of the present invention is a waveguide slot phased array antenna, and the number N of radiation units is determined by the actual use of the antenna. To improve the calculation accuracy, the number M of radiation units included in the simulation model established by extracting the radiation pattern in the radiation unit array should be as large as possible, at least 4. When extracting the radiation pattern in the radiation unit array, the radiation units closest to the middle of the array should be selected as much as possible for extraction.

[0026] The waveguide slot phased array antenna of the embodiments of the present invention is a waveguide slot phased array antenna composed of, but not limited to, 64 waveguide slot antenna radiation unit arrays with inclined slots opened on the narrow side.

[0027] To illustrate the implementation effect of the present invention, first, Figure 1 the schematic diagram of the division of each region of the 3D radiation pattern in the shown UV coordinate system will be described. As Figure 1 (a), first, the 3D radiation pattern can be divided into an azimuth plane section D, an elevation plane section E, and an outer radiation region I of the main beam section according to whether it is in the main beam section. As Figure 1 (b), it can also be divided into a near region F and a far region G according to the angle from the main beam, where the near region F is the radiation region within 30° from the main beam C, and the far region G is the radiation region outside 30° from the main beam C. The waveguide slot phased array antenna will generate relatively high far side lobes in the region H, and the region G includes the region H. This patent mainly aims to suppress the far side lobes in the region H.

[0028] Next, in combination with the drawings and embodiments, the implementation steps and effects of the present invention will be further described.

[0029] In combination with Figure 2 , the implementation steps of the embodiments of the present invention will be further described.

[0030] Step 1: First, a waveguide slot antenna radiation unit composed of a waveguide joint 1, a radiation slot 2, and a load 3 is established, and this antenna radiation unit is called radiation unit A. The radiation slot 2 and the waveguide joint 1 of radiation unit A are phase-inverted, and other slot parameters remain unchanged, and the obtained antenna radiation unit is called radiation unit B. Radiation unit A and radiation unit B are arranged alternately at an interval of d to form a simulation model composed of four radiation units as shown in Figure 3 and Figure 4 , where d = 18 mm. The simulation model is simulated, and the in-array radiation patterns of radiation unit A and radiation unit B in the array are extracted in sequence.

[0031] Step 2, in the embodiment of the present invention, the population size NP = 100, the crossover rate Pc = 0.8, the mutation rate Pm = 0.05, the maximum number of convergence generations G = 1000, and the chromosome length L is equal to the number of radiating elements, which is 64. Randomly generate NP chromosomes as the first-generation population. Here, a chromosome is a sequence of length L composed of A and B, representing the positions and quantities of radiating element A and radiating element B in the array.

[0032] Step 3, substitute the NP chromosomes corresponding to the first-generation population, the in-array radiation patterns of radiating element A and radiating element B, and the phases of each radiating element corresponding to a 45° scan into the array synthesis calculation formula, and calculate the antenna radiation pattern of the waveguide slot phased array antenna scanning at 45° corresponding to the NP chromosomes. Calibrate the maximum level outside the 30° range of the main beam of the antenna radiation pattern as the far-field sidelobe level of the waveguide slot phased array antenna scanning at 45° corresponding to the chromosome.

[0033] Step 4, define the fitness function of the genetic algorithm as the negative value of the maximum level outside the 30° of the main beam of the antenna radiation pattern of the waveguide slot phased array antenna corresponding to the chromosome, which is obtained by substituting the corresponding chromosome, the in-array radiation patterns of radiating element A and radiating element B, and the phases of each radiating element corresponding to a 45° scan into the array synthesis calculation formula.

[0034] Step 5, substitute the first-generation population, the fitness function, the crossover rate Pc, the mutation rate Pm, and the maximum number of convergence generations G into the genetic algorithm to perform fitness function calculation, selection, crossover, and mutation operations in sequence. After iteration until the maximum number of convergence generations is reached, obtain the chromosome with the highest fitness value in the output population. The sequence corresponding to this chromosome is the positions and quantities of the two types of radiating elements of the waveguide slot phased array in the array in the embodiment of the present invention.

[0035] Step 6, the waveguide slot phased array antenna in the embodiment of the present invention is composed of two types of radiating elements, and the existing waveguide slot phased array is composed of one of the 64 above-mentioned two types of radiating elements. Substitute the radiation pattern of radiating element A and the phases of each radiating element corresponding to scans of 0°, 18°, 30°, 36°, and 45° into the array synthesis calculation formula, and calculate the antenna radiation patterns of the existing waveguide slot phased array antenna at each scan angle. Calibrate the maximum level outside the 30° range of the main beam on the antenna radiation pattern as the far-field sidelobe level of the existing waveguide slot phased array antenna at each scan angle.

[0036] Figure 5 is the 3D radiation pattern of the existing waveguide slot phased array antenna scanning at 45° in the UV coordinate system in the embodiment of the present invention; where Figure 5 (a) is the top view; Figure 5 (b) is the side view. From Figure 5It can be seen in (a) that the elevation of the far - field sidelobes is obvious. In Figure 5 the far - field sidelobe level is calibrated in (b), and the far - field sidelobe level is obtained as - 27.39 dB.

[0037] Step 7: Substitute the positions and quantities of the two radiation units of the waveguide slot phased array in the embodiment of the present invention in the array, the radiation patterns in the center of the array of radiation unit A and radiation unit B, and the phases of each radiation unit corresponding to the scanning angles of 0°, 18°, 30°, 36°, and 45° into the array synthesis calculation formula to calculate the antenna radiation patterns of the waveguide slot phased array at each scanning angle. Calibrate the maximum level outside the 30° range of the main beam on the antenna radiation pattern as the far - field sidelobe level of the waveguide slot phased array antenna of the present invention at each scanning angle.

[0038] Figure 6 is the 3D radiation pattern of the waveguide slot phased array antenna of the embodiment of the present invention at a scanning angle of 45° in the UV coordinate system; where Figure 6 (a) is the top view; Figure 6 (b) is the side view. From ​ it can be seen in (a) that the far - field sidelobes are greatly suppressed. In ​ the far - field sidelobe level is calibrated in (b), and the far - field sidelobe level is obtained as - 41.05 dB. Compared with the far - field sidelobe performance of the existing waveguide slot phased array antenna at a beam scanning angle of 45°, it is improved by 13.66 dB.

[0039] The variation trends of the far - field sidelobe levels of the existing waveguide slot phased array antenna and the waveguide slot phased array antenna of the embodiment of the present invention with the scanning angle are as ​ shown. From ​ it can be seen that, compared with the existing waveguide slot phased array antenna, the far - field sidelobes of the waveguide slot phased array antenna of the embodiment of the present invention are improved by 9.29 - 15.05 dB at different scanning angles.

[0040] The above results show that when the waveguide slot phased array antenna of the embodiment of the present invention performs beam scanning, the far - field sidelobe performance at each scanning angle is improved by an average of 12.22 dB.

[0041] The above description is only an example of the present invention and does not constitute any limitation to the present invention. Any person skilled in the art can think of making possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above when not departing from the ideological content of the present invention. Therefore, any simple modification, equivalent change, and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for designing a waveguide slot phased array antenna with low far-field sidelobes, characterized in that: The global optimization algorithm is used to calculate the positions and quantities of the two radiating elements in the antenna array by introducing the radiation patterns of the two radiating elements. The steps of this method include the following: Step 1: Extract the radiation pattern of the radiation element array: A simulation model is established, consisting of M radiating elements of two types with identical slot parameters except for the phase inversion of the radiating slots, where M is greater than or equal to 4, the value of M is less than N, and at least two radiating elements with phase inversion of the radiating slots are located in the antenna array. The simulation model is simulated and the antenna radiation patterns corresponding to the two radiating elements in the antenna array are extracted. Step 2: Use a global optimization algorithm to calculate the position and number of the two radiating elements in the antenna array: Step 2.1: Set the initial values for the number and position of the two radiating elements in the waveguide slot phased array antenna. Substitute these initial values, the radiation pattern of the radiating element array, and the phase value of each element corresponding to the scanning beam into the antenna array synthesis calculation formula to obtain the antenna radiation pattern of the scanning beam of the waveguide slot phased array antenna corresponding to these initial values. Calibrate the maximum level outside the 30° range of the main beam on the antenna radiation pattern corresponding to this initial value as the far-field sidelobe level of the scanning beam of the waveguide slot phased array antenna. Step 2.2: Set the far-field sidelobe level of the waveguide slot phased array antenna scanning beam as the optimization target, the number and position of the radiating elements in the waveguide slot phased array antenna as the optimization variables, and set the maximum number of iterations of the corresponding global optimization algorithm; In step 2.3, the optimization objective and optimization variables are brought into the global optimization algorithm for iterative calculation until the maximum number of iterations is reached, and the number and position of the radiating elements in the waveguide slot phased array antenna corresponding to the lowest far-field sidelobe level of the waveguide slot phased array antenna scanning beam are obtained.

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