Phase-modulated doubly-fed circularly-polarized phased-array antenna and port phase optimization method

Abstract

The invention discloses a phase-modulated doubly-fed circularly-polarized phased-array antenna and a port phase optimization method thereof, a radiation unit of the phase-modulated doubly-fed circularly-polarized phased-array antenna adopts a dual-port polarization multiplexing antenna unit, the dual-port polarization multiplexing antenna unit adopts a double-feed-point structure, signal excitation with equal amplitude and 90-degree phase difference is applied to two feed points of the antenna, and the phase-modulated doubly-fed circularly-polarized phased-array antenna is obtained. Therefore, the electric field vector radiated from the antenna unit rotates in the space along a circular trajectory, thereby forming a circularly polarized wave. According to the port phase optimization method, a genetic algorithm and a simulated annealing algorithm are utilized, and the high axial ratio under phased array large-angle scanning is suppressed only through regulation and control of the phase difference of the array element double ports. The method has the advantages that the mutual coupling effect between the array elements is fully considered, the algorithm complexity is low, and the low axial ratio characteristic of the circularly polarized phased-array antenna at each scanning angle can be rapidly obtained.

Description

Technical Field

[0001] The present invention belongs to the field of radar communication technology, and further relates to a phase-modulated dual-fed circularly polarized phased array antenna and a port phase optimization method in the field of antenna technology. The present invention can be used to design a circularly polarized phased array antenna for a phased array radar. Background Art

[0002] Circularly polarized antennas are widely used in the field of modern wireless communications because of their advantages of reducing the impact of multipath propagation, resisting Faraday rotation effect, and strong anti-interference ability. Circularly polarized phased arrays are widely used in the field of satellite communications because they can achieve large-scale beam scanning. Ideal circularly polarized waves are difficult to achieve in actual situations. At present, sequential rotation technology is mainly used to obtain good matching characteristics and circular polarization characteristics when forming circularly polarized array antennas. Sequential rotation feeding technology reduces the design requirements and difficulty of array elements. Circularly polarized antenna arrays can also be formed using linear polarization units, but it also limits the performance of circularly polarized arrays to a certain extent. When the array scale of the phased array antenna increases and the number of array elements increases, the number of required T / R components increases. Faced with many difficult problems, including complex systems, high costs, large volumes, heavy weights, and high power consumption, its complex feeding structure and T / R module will affect the performance of circularly polarized phased array antennas.

[0003] The 8511 Institute of China Aerospace Science and Industry Corporation disclosed a broadband low-axis ratio circularly polarized phased array antenna based on sequential rotation in its patent application "A broadband low-axis ratio circularly polarized phased array antenna based on sequential rotation" (application number 202311683657.8, application publication number CN 117638498A). It is composed of 16×16 subarrays, each of which includes 2×2 sequentially rotated structures, thereby improving the low-axis ratio characteristics of the antenna in the wide band and the stability of the radiation gain. By superimposing the double-layer dual-circular polarization unit loaded with the metasurface and the sequentially rotated structure, the broadband characteristics of the entire array are realized. The two sets of feeding networks at the bottom layer ensure the amplitude and phase feeding configuration of the sequentially rotated structure, thereby improving the feeding efficiency and amplitude and phase consistency of the system. However, the antenna still has two shortcomings: first, the synthesis of large-spacing subarrays will lead to the mutual coupling effect between antenna units, thereby affecting the radiation performance and beam control of the antenna; second, the design of multi-layer dielectric plates and complex feeding networks increases the complexity of the manufacturing process and production costs.

[0004] The National Space Science Center of the Chinese Academy of Sciences disclosed a circularly polarized microstrip antenna parameter optimization method and system for multi-objective optimization in its patent application "Circularly polarized microstrip antenna parameter optimization method and system for multi-objective optimization" (application number 202211571694.5, application publication number CN116151096A). This optimization method uses the adaptive NSGA-III algorithm to optimize multiple antenna performance indicators, such as return loss, axial ratio, antenna gain, etc. to solve the optimal structural parameters of the antenna, and finally optimize the antenna parameters, maintain the diversity of solutions in high-dimensional space, and further improve the antenna performance. However, this optimization method still has three shortcomings: First, this method uses the NSGA-III algorithm for multi-objective optimization. Although it can ensure the diversity of solutions, it needs to balance and sort between multiple objectives, resulting in high computational complexity. Second, this method needs to use the HFSS-MATLAB-API toolkit to generate scripts and use the HFSS three-dimensional electromagnetic simulation software to complete the modeling and electromagnetic calculation of N groups of antenna structural parameters, resulting in reduced optimization efficiency. Third, this method only optimizes the antenna parameters of a single circularly polarized microstrip antenna, while the performance of an antenna array is not only determined by the performance of a single antenna unit, but also affected by the interaction between the units. The optimization of the antenna parameters of a single unit cannot effectively eliminate the coupling effect between the units. The mutual coupling effect will cause the array gain to decrease and the pattern to distort, thus affecting the overall radiation characteristics of the array. If this method is used to optimize the parameters of each circularly polarized microstrip antenna in the array, the computational complexity will be greatly increased, resulting in a significant reduction in the optimization efficiency. Summary of the invention

[0005] The purpose of the present invention is to address the deficiencies of the above-mentioned prior art and propose a phase-adjustable dual-fed circularly polarized phased array antenna and a port phase optimization method, aiming to solve two problems of antenna structure and its design method. First, the mutual coupling effect caused by the use of sequential rotation structure and large-spacing subarray synthesis structure affects the antenna radiation performance, and the sequential rotation feeding network design is complex and the production cost is high. Second, the use of NSGA-III algorithm for multi-objective optimization leads to high computational complexity, the use of HFSS three-dimensional electromagnetic simulation software to model N groups of antenna structure parameters and electromagnetic calculations leads to reduced optimization efficiency, and only optimizing the antenna parameters of a single circularly polarized microstrip antenna cannot effectively eliminate the coupling effect between units.

[0006] The technical idea to achieve the purpose of the present invention is:

[0007] The radiating unit of the circularly polarized phased array antenna of the present invention adopts a dual-port polarization multiplexing antenna unit, and the dual-port polarization multiplexing antenna unit adopts a dual-feed point structure. By applying equal-amplitude signal excitation with a phase difference of 90° on the two feeding points of the antenna, the electric field vector radiated from the antenna unit rotates along a circular trajectory in space, thereby forming a circularly polarized wave. By changing the phase difference of the signal on the two feeding points to positive 90° or negative 90°, the rotation direction of the circularly polarized wave is dynamically adjusted, thereby realizing right-hand circular polarization or left-hand circular polarization. Without introducing any additional structure, the high axial ratio under large-angle scanning is suppressed only by the phase difference of the dual ports of the array element, thereby solving the problem of complex design of the sequential rotation structure feeding network in the prior art. When the circularly polarized phased array antenna of the present invention is formed, the dual-port polarization multiplexing antenna unit is directly used for uniform array arrangement, thereby ensuring that the spacing between the array antenna units is moderate, so as to reduce the mutual coupling effect caused by the sequential rotation structure and the large-spacing sub-array synthesis structure. The circular polarization phased array antenna port phase optimization method of the present invention first establishes an antenna model in HFSS and performs simulation to obtain the radiation field distribution of each unit, then builds a data interface between MATLAB and HFSS through the MATLAB-HFSS-API function toolkit and a self-compiled API subroutine, automatically and quickly extracts the active unit pattern of each unit in the array by sending a command to HFSS through MATLAB, and uses the active unit pattern of each unit in the array during array synthesis to eliminate the mutual coupling effect between units. The circular polarization phased array antenna port phase optimization method of the present invention adopts a genetic simulated annealing algorithm, which can explore the solution space in a larger range by combining the genetic algorithm group search, crossover and mutation operations, and has the advantages of strong global search capability and the simulated annealing algorithm temperature control and gradual cooling mechanism to achieve the advantages of accurate local search, thereby solving the problem of high computational complexity of the NSGA-III algorithm in the prior art. The circular polarization phased array antenna port phase optimization method of the present invention adopts a genetic simulated annealing algorithm. The advantage of genetic algorithms is that they can perform global searches in a wide range of solution spaces through crossover and mutation operations, thus avoiding falling into local optimal solutions. The simulated annealing algorithm gradually reduces the search range through temperature control, allowing the algorithm to perform local optimization more finely when approaching the optimal solution. The genetic simulated annealing algorithm achieves efficient optimization by combining the population search of genetic algorithms with the local search mechanism of simulated annealing, thereby solving the problem of high computational complexity of the NSGA-III algorithm in the prior art.The optimization method of the present invention uses an array synthesis formula to calculate the fitness function during the optimization process. The array synthesis formula is based on the phase and radiation pattern of each radiation unit. By extracting the active radiation pattern of each unit in the array and calculating the phase corresponding to the scanning angle of each unit, and substituting it into the array synthesis calculation formula, the radiation characteristics of the array can be quickly obtained, thereby solving the problem of low optimization efficiency caused by modeling and electromagnetic calculation of different parameters in the optimization process using HFSS three-dimensional electromagnetic simulation software.

[0008] The technical solution for achieving the purpose of the present invention is as follows:

[0009] The phase-modulated dual-fed circularly polarized phased array antenna of the present invention comprises an antenna array consisting of N×N radiating units, wherein N is an integer greater than or equal to 2; the N×N radiating units are closely arranged at equal intervals, and each antenna unit has two feeding ports, and phase modulation is achieved by adjusting the phase difference of signals on the two feeding ports.

[0010] Furthermore, the N×N radiation units are closely arranged with equal spacing, which means that the N×N radiation units are closely arranged along the x-axis and the y-axis with the unit size as the spacing to ensure that the unit spacing is moderate and reduce the coupling effect between the units.

[0011] Furthermore, each antenna unit has two feeding ports, which means that the two feeding points are used to input radio frequency signals into the antenna structure, adjust the phase difference of each dual-feed point radiating unit in the array antenna, and dynamically adjust the rotation direction of the circularly polarized wave to achieve right-hand circular polarization or left-hand circular polarization.

[0012] Furthermore, adjusting the phase difference of each dual-feed point radiating unit in the array antenna means changing the phase difference of the signals on the two feeding points to positive 90° or negative 90° to compensate for the change in phase path difference caused by large-angle scanning. By reasonably adjusting the phase difference of each antenna unit, the synthesis of the electric field vector can be readjusted, thereby suppressing the high axial ratio of the phased array at a large-angle scanning angle.

[0013] The invention discloses a phase optimization method for a phase-adjusted dual-fed circularly polarized phased array antenna port. The method uses a genetic algorithm to perform a global search on the feeding phase difference of the dual ports of each radiating unit of the dual-fed circularly polarized phased array. The method uses a simulated annealing algorithm to perform a local search on the feeding phase difference of the dual ports of each radiating unit of the dual-fed circularly polarized phased array. By adjusting the feeding phase difference of the dual ports of each radiating unit of the dual-fed circularly polarized phased array, a circularly polarized phased array with low axial ratio characteristics at a large scanning angle is realized.

[0014] Furthermore, the steps of the genetic algorithm are as follows:

[0015] In the first step, an initial population of N×N scale dual-fed circularly polarized phased array dual-port feeding phase differences of each radiating unit is randomly generated to ensure the diversity of the search starting point within the entire possible phase difference value range. The fitness function is calculated for each individual in the initial population. The fitness function is determined according to the inverse of the axial ratio of the circularly polarized phased array antenna at a large scanning angle. The lower the axial ratio, the higher the fitness value.

[0016] The second step is to use the roulette wheel selection method to select some individuals from the initial population to enter the next generation population. In this process, the higher the individual fitness value, the greater the probability of being selected;

[0017] The third step is to perform a crossover operation on the selected individuals, combining the good features of different individuals in different local areas to expand the global search range;

[0018] In the fourth step, some individuals are randomly selected from the population after crossover to perform mutation operations, so that the population jumps out of the local optimum and searches again in the entire value range; in the fifth step, by continuously repeating the above selection, crossover, and mutation operations, the population continues to evolve until a set of feeding phase difference combinations is found so that the axial ratio of the circularly polarized phased array antenna reaches a preset low axial ratio standard at a large-angle scanning angle, thereby determining the optimal solution that satisfies the low axial ratio and excellent circular polarization characteristics at a large-angle scanning angle, where N is an integer greater than or equal to 2.

[0019] Furthermore, the steps of the simulated annealing algorithm are as follows:

[0020] In the first step, after obtaining the feeding phase difference of the dual ports of each radiating unit of the dual-fed circularly polarized phased array through the genetic algorithm, the starting conditions of the simulated annealing algorithm are determined, including setting a higher starting temperature, a cooling ratio less than 1, and a termination temperature value, and the phase difference obtained by the genetic algorithm is used as the initial solution of the simulated annealing algorithm;

[0021] The second step is to perform a change operation on the current phase difference solution under each round of temperature conditions, that is, to make a small random change to the feeding phase difference of the dual ports of each radiating unit to form a new phase difference solution;

[0022] The third step is to evaluate the axial ratio characteristics of the circularly polarized phased array antenna corresponding to the current phase difference solution and the new phase difference solution, and determine whether to accept the new phase difference solution based on the evaluation results and the Metropolis criterion;

[0023] Step 4: If the new solution has better axial ratio characteristics, the new solution must be accepted; if the new solution has worse axial ratio characteristics, the acceptance is decided based on the probability related to temperature. When the temperature is high, the possibility of accepting the worse new solution is greater, and as the temperature decreases, this possibility gradually decreases.

[0024] Step 5: After completing all judgments and solution updates in one round of temperature, lower the temperature according to the cooling ratio, and then enter the next round of temperature cycle;

[0025] In the sixth step, the above process is continued. As the temperature decreases, a detailed search is performed near the optimal solution until the temperature drops to the preset termination temperature value. The final phase difference solution can enable the dual-fed circularly polarized phased array antenna to have a low axial ratio characteristic when scanning at large angles.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] First, the circularly polarized phased array antenna of the present invention uses a dual-port polarization multiplexing radiation unit to form an array, and the antenna structure overcomes the defects of the prior art such as the mutual coupling effect caused by the sequential rotation structure and the large-pitch subarray synthesis structure and the complex design of the sequential rotation feeding network. This makes the present invention have the advantage of suppressing the high axial ratio under large-angle scanning of the phased array without the need to design a complex feeding network structure, and only by adjusting the dual-port phase difference of the array element.

[0028] Second, the design method of the present invention quickly obtains the active unit radiation pattern of each unit in the array by building a data interface between MATLAB and HFSS, eliminates the mutual coupling effect between units, and optimizes the phase difference of each dual-port array element through a genetic simulated annealing algorithm that has both fast global search capabilities and efficient and accurate local search capabilities. It overcomes the defects of the prior art that the NSGA-III algorithm has high computational complexity, the use of HFSS three-dimensional electromagnetic simulation software to model N groups of antenna structure parameters and electromagnetic calculations leads to reduced optimization efficiency, and only the antenna parameters of a single circularly polarized microstrip antenna are optimized to effectively eliminate the coupling effect between units. This makes the present invention have the advantages of fully considering the mutual coupling effect between array elements, low algorithm complexity, and being able to quickly obtain the circularly polarized phased array antenna with low axial ratio characteristics at various scanning angles. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of the structure of a dual-fed circularly polarized phased array antenna according to an embodiment of the present invention;

[0030] FIG. 2 is a schematic diagram of the structure of a dual-fed circularly polarized antenna unit according to an embodiment of the present invention; FIG. 2( a) is a schematic diagram of the overall structure of the dual-fed circularly polarized antenna unit; FIG. 2( b) is a schematic diagram of the ports of the dual-fed circularly polarized antenna unit, where port a and port b are two feeding points of the dual-fed circularly polarized antenna unit;

[0031] Figure 3 It is a flow chart of a dual-fed circularly polarized phased array antenna port phase optimization method according to an embodiment of the present invention;

[0032] Figure 4 is a simulation result diagram of the port phase optimization method of the dual-fed circularly polarized phased array antenna in an embodiment of the present invention; wherein, Figure 4(a) is a phase difference distribution diagram of each unit dual port obtained by optimizing the dual-port polarization multiplexing circularly polarized phased array antenna scanning -60°, phi=0° surface; Figure 4(b) is an axial ratio curve diagram before and after the dual-port polarization multiplexing circularly polarized phased array antenna scanning -60°, phi=0° surface optimization; Figure 4(c) is a main polarization gain and cross-polarization gain curve diagram before the dual-port polarization multiplexing circularly polarized phased array antenna scanning -60°, phi=0° surface optimization; Figure 4(d) is a main polarization gain and cross-polarization gain curve diagram after the dual-port polarization multiplexing circularly polarized phased array antenna scanning -60°, phi=0° surface optimization. DETAILED DESCRIPTION

[0033] The antenna array of the present invention is a dual-fed circularly polarized phased array antenna, and the number N of antenna arrays is determined by the actual use of the antenna. The dual-fed circularly polarized phased array antenna of the embodiment of the present invention uses 8×8 dual-fed circularly polarized antenna radiation units, but those skilled in the art should understand that the dual-fed circularly polarized phased array antenna can also be other combinations, for example, 2×2, 4×4, 6×6, 8×8... The embodiment of the present invention does not limit this.

[0034] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0035] Reference Figure 1 , the structure of the dual-fed circularly polarized phased array antenna array according to an embodiment of the present invention is further described.

[0036] The dual-fed circularly polarized phased array antenna array of the embodiment of the present invention includes 8×8 antennas arranged at uniform intervals along the x-axis and the y-axis, wherein the unit interval d x =d y =7mm dual-fed circularly polarized antenna radiating unit. The embodiment of the present invention suppresses the high axial ratio under large-angle scanning only by the phase difference of the dual ports of 8×8 dual-fed circularly polarized radiating units in the dual-fed circularly polarized phased array antenna without introducing any additional structure, so as to solve the problem of complex design of the sequential rotation structure feeding network in the prior art.

[0037] 2 , the dual-fed circularly polarized antenna unit according to the embodiment of the present invention is further described.

[0038] The overall structure of the dual-fed circularly polarized antenna unit of the embodiment of the present invention is shown in FIG2(a), and the ports of the dual-fed circularly polarized antenna unit are shown in FIG2(b). Port a and port b are two feeding points of the dual-fed circularly polarized antenna unit. By applying equal-amplitude signal excitation with a phase difference of 90° to the two feeding points, the electric field vector radiated from the antenna unit rotates along a circular trajectory in space, thereby forming a circularly polarized wave. By changing the phase difference of the signal at the two feeding points to positive 90° or negative 90°, the rotation direction of the circularly polarized wave is dynamically adjusted to achieve right-hand circular polarization or left-hand circular polarization.

[0039] Reference Figure 3 , the steps of the dual-fed circularly polarized phased array antenna port phase optimization method of an embodiment of the present invention are further described.

[0040] Step 1, simulate the model of the dual-fed circularly polarized phased array antenna composed of 8×8 dual-fed circularly polarized antenna radiating units arranged at uniform intervals along the x-axis direction and the y-axis direction in the embodiment of the present invention, obtain the radiation field distribution of each unit, and extract the AEP of each unit in the array by calling HFSS through MATLAB. That is, through the MATLAB-HFSS-API function toolkit and the self-compiled API subroutine, build a data interface between MATLAB and HFSS, send a command to HFSS through MATLAB to automatically and quickly extract the active unit pattern of each unit in the array, and use the active unit pattern of each unit in the array when synthesizing the array to eliminate the mutual coupling effect between the units.

[0041] Step 2: setting the parameters of the genetic simulated annealing algorithm in the dual-fed circularly polarized phased array antenna port phase optimization method according to the embodiment of the present invention.

[0042] The embodiment of the present invention introduces a hybrid optimization algorithm, combining the genetic algorithm and simulated annealing two optimization algorithms to improve the search efficiency and the quality of the solution. In the embodiment of the present invention, the genetic algorithm parameters are set as follows: population number NP = 200, crossover rate Pc = 0.8, mutation rate Pm = 0.1, maximum convergence number G = 500, elite retention ratio Pe = 0.3, population density threshold R = 0.4. A population density function is introduced into the genetic algorithm to determine the density of the population and adaptively adjust the order of the crossover operator and the mutation operator. Simulated annealing algorithm parameters: initial temperature T_start = 1500, minimum temperature Tmin = 0.01, temperature attenuation rate alpha = 0.99. The chromosome length L is equal to the number of radiation units 64, and NP chromosomes are randomly generated as the first generation population, wherein the chromosome is a sequence of length L composed of dual-port polarization multiplexing circularly polarized radiation units, representing the dual-port feeding phase difference of each radiation unit in the array.

[0043] Step 3, the embodiment of the present invention puts the NP chromosomes corresponding to the first-generation population and the phase of each radiating unit corresponding to the dual-port polarization multiplexing radiating unit scanning -60° into the array synthesis calculation formula, and calculates the directional electric field component ETheta and the pitch electric field component Ephi when the circularly polarized phased array antenna corresponding to the NP chromosomes scans -60°, and then calculates the long axis OA and the short axis OB of the axial ratio through ETheta and Ephi, and finally obtains the axial ratio of the circularly polarized phased array antenna when scanning -60° from the ratio of OA to OB.

[0044] Step 4, construct the objective function, reduce the axial ratio of the array antenna when scanning to various angles by optimizing the phase, and define the fitness function of the genetic algorithm as follows: by bringing the corresponding chromosome, the active unit radiation pattern of the dual-port polarization multiplexing radiation unit, and the phase of each radiation unit corresponding to scanning -60° into the array synthesis calculation formula, the antenna axial ratio of the circularly polarized phased array antenna scanning -60° corresponding to the chromosome is calculated.

[0045] Step 5, bring the first generation population, fitness function, population number NP=200, crossover rate Pc=0.8, mutation rate Pm=0.1, maximum convergence number G=500, elite retention ratio Pe=0.3, population density threshold R=0.4 into the genetic algorithm, and perform fitness function calculation, population density judgment, selection, crossover, mutation, and elite retention operations in sequence. After iteration, until the last 70% of the total number of generations is reached, the simulated annealing algorithm is introduced, and the optimal individual obtained by the genetic operation of the population is used as the object of the simulated annealing operation, thereby improving the local search ability of the algorithm, so as to effectively jump out of the local optimal solution and further improve the global search ability. After multiple iterations until the maximum convergence number G is reached, the chromosome with the highest fitness value in the output population is obtained. The sequence corresponding to the chromosome is the dual-port feeding phase difference of each unit of the circularly polarized phased array in the array of the embodiment of the present invention.

[0046] Step 6, substitute the active unit radiation pattern of the dual-port polarization multiplexing radiation unit and the phase of each radiation unit corresponding to scanning -60° into the array synthesis calculation formula, and calculate the axial ratio of the existing circularly polarized phased array antenna when it scans to -60° when it is not optimized; then substitute the active unit radiation pattern of the dual-port polarization multiplexing radiation unit, the optimal dual-port feeding phase difference of each unit in the circularly polarized phased array optimized by the genetic simulated annealing algorithm, and the phase of each radiation unit corresponding to scanning -60° into the array synthesis calculation formula, and calculate the axial ratio of the existing circularly polarized phased array antenna when it scans to 60° after optimization.

[0047] Step 7, substitute the active unit radiation pattern of the dual-port polarization multiplexing radiation unit and the phase of each radiation unit corresponding to scanning -60° into the array synthesis calculation formula, and calculate the main polarization gain and cross-polarization gain of the existing circularly polarized phased array antenna when scanning to -60° when not optimized; then substitute the active unit radiation pattern of the dual-port polarization multiplexing radiation unit, the optimal dual-port feeding phase difference of each unit in the circularly polarized phased array optimized by the genetic simulated annealing algorithm, and the phase of each radiation unit corresponding to scanning -60° into the array synthesis calculation formula, and calculate the main polarization gain and cross-polarization gain of the existing circularly polarized phased array antenna when scanning to -60° after optimization.

[0048] The effect of the present invention can be further demonstrated through the following simulation.

[0049] 1. Simulation experimental conditions.

[0050] The simulation experiment of the present invention uses the ANASYS Electronics Desktop 2020R1 software platform installed on computer hardware to complete the dual-fed circularly polarized phased array antenna simulation, and uses the Matlab R2022a software platform installed on computer hardware to complete the dual-fed circularly polarized phased array antenna port phase difference optimization simulation.

[0051] 2. Analysis of simulation content and results.

[0052] The simulation experiment of the present invention is to perform a phase difference optimization simulation of the dual-fed circularly polarized phased array antenna port of the dual-fed circularly polarized phased array antenna at a frequency of 21.2G for the dual-fed circularly polarized phased array antenna of the embodiment of the present invention. The simulation results are plotted into curve graphs, as shown in Figure 4. Among them, Figure 4 (a) is a phase difference distribution diagram of each unit dual port obtained by optimizing the dual-fed circularly polarized phased array antenna scanning -60°, phi=0° surface; Figure 4 (b) is a comparison diagram of the axial ratio curves obtained by optimizing the existing dual-fed circularly polarized phased array antenna scanning -60°, phi=0° surface before optimization and by the method of the present invention; Figure 4 (c) is a main polarization and cross-polarization gain curve diagram of the existing dual-fed circularly polarized phased array antenna scanning -60°, phi=0° surface before optimization in the embodiment of the present invention; Figure 4 (d) is a main polarization and cross-polarization gain curve diagram of the existing dual-fed circularly polarized phased array antenna scanning -60°, phi=0° surface after optimization by the method of the present invention in the embodiment of the present invention.

[0053] The effects of the present invention are further described below in conjunction with simulation diagrams.

[0054] The horizontal axis in Figure 4(a) is the number of units in the dual-fed circularly polarized phased array antenna along the x-dimension, and the vertical axis is the number of units in the dual-fed circularly polarized phased array antenna along the y-dimension. The squares marked with different shades of color in Figure 4(a) represent the size of the dual-port feeding phase difference of each radiating unit in the array optimized by the method of the present invention.

[0055] It can be seen from Figure 4(a) that the range of the excitation phase difference of each dual-fed circularly polarized antenna unit port optimized by the dual-fed circularly polarized phased array antenna port phase optimization method in the present invention is [-180°, 180°], indicating that the solution space of the dual-fed circularly polarized phased array antenna port phase difference is complete.

[0056] The horizontal axis in Figure 4(b) is the angle of the Theta plane of the dual-fed circularly polarized phased array antenna, in degrees, and the vertical axis represents the axial ratio of the dual-fed circularly polarized phased array antenna, in dB. The curve marked with a dotted line represents the axial ratio curve of the dual-fed circularly polarized phased array antenna before optimization when the scanning angle is -60°, and the curve marked with a solid line represents the axial ratio curve of the dual-fed circularly polarized phased array antenna after optimization when the scanning angle is -60°.

[0057] It can be seen from Figure 4(b) that under the above conditions, the dual-fed circularly polarized phased array antenna port phase optimization method of the embodiment of the present invention is used to simulate and optimize the excitation phase difference of each dual-fed circularly polarized antenna unit port. The dual-fed circularly polarized phased array antenna in the simulation experiment of the present invention is at a frequency of 21.2 GHz. When not optimized, the axial ratio of the array at -60° is 8.30 dB. After optimization, the axial ratio at -60° is reduced to 0.04 dB, and the axial ratio is reduced by 8.26 dB, thereby realizing the low axial ratio characteristics of the dual-fed circularly polarized phased array under large-angle scanning.

[0058] The horizontal coordinates in Figure 4(c) and Figure 4(d) are the angles of the Theta plane of the dual-fed circularly polarized phased array antenna, in degrees, and the vertical coordinates represent the gain value of the dual-fed circularly polarized phased array antenna, in dB. The curve marked with a dotted line in Figure 4 represents the cross-polarization gain curve of the dual-fed circularly polarized phased array antenna when the scanning angle is -60°, and the curve marked with a solid line represents the main polarization gain curve of the dual-fed circularly polarized phased array antenna when the scanning angle is -60°.

[0059] It can be seen from Figure 4(c) and Figure 4(d) that under the above conditions, the dual-fed circularly polarized phased array antenna port phase optimization method of the embodiment of the present invention is used to simulate and optimize the excitation phase difference of each dual-fed circularly polarized antenna unit port. The dual-fed circularly polarized phased array antenna in the simulation experiment of the present invention is at a frequency of 21.2GHz. Before optimization, the main polarization gain of the array at -60° is 16.61dB. After optimization, the main polarization gain at -60° is 17.03dB, and the main polarization gain is increased by 0.42dB. Before optimization, the cross-polarization gain of the array at -60° is 9.57dB. After optimization, the cross-polarization gain at -60° is -63.67dB, and the cross-polarization gain is significantly reduced. Thereby achieving the goal of improving the main polarization gain and significantly suppressing the cross-polarization gain of the dual-fed circularly polarized phased array under large-angle scanning.

[0060] 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 above disclosed methods and technical contents without departing from the content of the technical solution of the present invention. Therefore, any simple modification, equivalent change and modification made to the above embodiment 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 phase-adjustable dual-fed circularly polarized phased array antenna, comprising an antenna array consisting of N×N radiating elements, wherein: N is an integer greater than or equal to 2; it is characterized in that N×N radiating units are arranged closely and evenly spaced, each antenna unit has two feeding ports, and phase modulation is achieved by adjusting the phase difference of the signals on the two feeding ports.

2. The phase-adjustable dual-fed circularly polarized phased array antenna according to claim 1, characterized in that: The N×N radiation units are closely arranged with equal spacing, which means that the N×N radiation units are closely arranged along the x-axis and the y-axis with the unit size as the spacing to ensure that the unit spacing is moderate and reduce the coupling effect between the units.

3. The phase-adjustable dual-fed circularly polarized phased array antenna according to claim 2, characterized in that: The fact that each antenna unit has two feeding ports means that the two feeding points are used to input radio frequency signals into the antenna structure, adjust the phase difference of each dual-feed point radiating unit in the array antenna, and dynamically adjust the rotation direction of the circularly polarized wave to achieve right-hand circular polarization or left-hand circular polarization.

4. The phase-adjustable dual-fed circularly polarized phased array antenna according to claim 3, characterized in that: Adjusting the phase difference of each dual-feed point radiating unit in the array antenna means changing the phase difference of the signals on the two feeding points to positive 90° or negative 90° to compensate for the change in phase path difference caused by large-angle scanning. By reasonably adjusting the phase difference of each antenna unit, the synthesis of the electric field vector can be readjusted, thereby suppressing the high axial ratio of the phased array at a large-angle scanning angle.

5. The method for optimizing the phase of a dual-fed circularly polarized phased array antenna port by phase adjustment according to claim 1, characterized in that: A genetic algorithm is used to perform a global search for the feeding phase difference of the dual ports of each radiating unit of the dual-fed circularly polarized phased array; a simulated annealing algorithm is used to perform a local search for the feeding phase difference of the dual ports of each radiating unit of the dual-fed circularly polarized phased array. By adjusting the feeding phase difference of the dual ports of each radiating unit of the dual-fed circularly polarized phased array, a circularly polarized phased array with low axial ratio characteristics at a large scanning angle is achieved.

6. The method for optimizing the phase port of a phase-adjustable dual-fed circularly polarized phased array antenna according to claim 5, characterized in that: The genetic algorithm refers to: In the first step, an initial population of N×N scale dual-fed circularly polarized phased array dual-port feeding phase differences of each radiating unit is randomly generated to ensure the diversity of the search starting point within the entire possible phase difference value range. The fitness function is calculated for each individual in the initial population. The fitness function is determined according to the inverse of the axial ratio of the circularly polarized phased array antenna at a large scanning angle. The lower the axial ratio, the higher the fitness value. The second step is to use the roulette wheel selection method to select some individuals from the initial population to enter the next generation population. In this process, the higher the individual fitness value, the greater the probability of being selected; The third step is to perform a crossover operation on the selected individuals, combining the good features of different individuals in different local areas to expand the global search range; The fourth step is to randomly select some individuals from the population after crossover to perform mutation operations, so that the population jumps out of the local optimum and searches again in the entire value range; In the fifth step, by continuously repeating the above selection, crossover, and mutation operations, the population continues to evolve until a set of feed phase difference combinations is found so that the axial ratio of the circularly polarized phased array antenna reaches a preset low axial ratio standard at a large-angle scanning angle, thereby determining the optimal solution that satisfies the low axial ratio and excellent circular polarization characteristics at a large-angle scanning angle, where N is an integer greater than or equal to 2.

7. The method for optimizing the phase port of a phase-adjustable dual-fed circularly polarized phased array antenna according to claim 6, characterized in that: The simulated annealing algorithm refers to: In the first step, after obtaining the feeding phase difference of the dual ports of each radiating unit of the dual-fed circularly polarized phased array through the genetic algorithm, the starting conditions of the simulated annealing algorithm are determined, including setting a higher starting temperature, a cooling ratio less than 1, and a termination temperature value, and the phase difference obtained by the genetic algorithm is used as the initial solution of the simulated annealing algorithm; The second step is to perform a change operation on the current phase difference solution under each round of temperature conditions, that is, to make a small random change to the feeding phase difference of the dual ports of each radiating unit to form a new phase difference solution; The third step is to evaluate the axial ratio characteristics of the circularly polarized phased array antenna corresponding to the current phase difference solution and the new phase difference solution, and determine whether to accept the new phase difference solution based on the evaluation results and the Metropolis criterion; Step 4: If the new solution has better axial ratio characteristics, the new solution must be accepted; if the new solution has worse axial ratio characteristics, the acceptance is decided based on the probability related to temperature. When the temperature is high, the possibility of accepting the worse new solution is greater, and as the temperature decreases, this possibility gradually decreases. Step 5: After completing all judgments and solution updates in one round of temperature, lower the temperature according to the cooling ratio, and then enter the next round of temperature cycle; In the sixth step, the above process is continued. As the temperature decreases, a detailed search is performed near the optimal solution until the temperature drops to the preset termination temperature value. The final phase difference solution can enable the dual-fed circularly polarized phased array antenna to have a low axial ratio characteristic when scanning at large angles.

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