A verification method for phased array feed combined with dual-focus reflector antenna

Abstract

The present invention discloses a verification method for a phased array feed source in conjunction with a dual-focus reflector antenna, and belongs to the technical field of synthetic aperture radar. The method comprises: step 1, using a metal back frame in conjunction with a satellite vehicle to erect a dual-focus reflector antenna, and adjusting the high-precision posture of the dual-focus reflector antenna through a slide at the bottom of the satellite vehicle and a turntable of the satellite vehicle; step 2, using the dual-focus reflector antenna coordinate system as a reference, using an erection tool to vertically erect the phased array feed source on a six-degree-of-freedom turntable; step 3, optimizing the combination of adaptive excitation coefficients, including: pre-optimization data processing, transmission pattern optimization, and two-way pattern optimization. The method has a high degree of automation, improves optimization efficiency, and reduces computing resources.

Description

Technical Field

[0001] The invention belongs to the technical field of synthetic aperture radar (SAR), and in particular relates to a verification method for a phased array feed source matched with a dual-focus reflector antenna. Background Art

[0002] The phased array feed combined with the dual-focus reflector antenna is a new satellite-borne SAR antenna system. Its characteristics are that the reflector is shaped by the surface equation of two vertical sections (defined as the range direction and the azimuth direction) with different parabolic focal lengths as the reflector, and the phased array feed arranged along the range direction is located at the focus position of the parabola in the azimuth direction and the virtual focus position of the parabola in the range direction. The advantage of this system is that it takes advantage of the low sidelobe of the reflector antenna in the azimuth direction, and at the same time meets the continuous scanning and shaping capabilities of the beam within a certain angle range in the range direction, so that the important imaging index of azimuth blur is optimized while meeting the imaging mode of the system.

[0003] Antenna testing and verification is an important part of the design of spaceborne SAR antennas. Reasonable verification methods and precise testing methods can not only verify the design principle of the antenna and evaluate the errors generated during the processing and assembly of the antenna, but also simulate the antenna's on-orbit state and ensure the antenna's on-orbit performance. Antenna testing and verification methods include antenna test process design, antenna installation methods, and antenna performance optimization methods.

[0004] The existing testing method and process of the phased array feed with the dual-focus reflector antenna are as follows: Step 1: Set up the reflector antenna and phased array feed. The position and attitude of the phased array feed relative to the reflector antenna will directly affect the antenna performance. To ensure that the test verification state of the antenna can reflect the on-orbit state of the antenna, the attitude of the feed relative to the reflector must be as close to the on-orbit attitude as possible. Step 2: Test the secondary radiation pattern of the antenna. The secondary radiation pattern of the antenna is the radiation pattern of a unit in the phased array feed that is excited individually after being reflected by the reflector. Step 3: Optimize the excitation coefficient combination. The excitation coefficient combination is the amplitude and phase combination of all units in the phased array feed. Step 4: Test the synthetic radiation pattern. The synthetic radiation pattern is the radiation pattern after all units of the phased array feed are excited according to the optimized excitation coefficient and reflected by the reflector.

[0005] The above method has the following shortcomings: in the stage of setting up the dual-focus reflector antenna and the phased array feed, the posture adjustment flexibility of the reflector antenna and the phased array feed is insufficient; in the stage of optimizing the combination of excitation coefficients, there is a situation where the two-way pattern after the combination of the transmitting and receiving patterns that meet the pattern indicators does not meet the indicators. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a verification method for a phased array feed source combined with a dual-focus reflector antenna, which adopts a method of directly optimizing the two-way pattern, and brings in the transmission pattern data when optimizing the receiving pattern, so as to ensure that the optimized combined two-way pattern Figure 1 The indicators are determined to be met; in view of the problem that if the optimization result cannot be optimized during the optimization process of the excitation coefficient, the optimization fails, and the only option is to manually re-optimize or try to modify the indicators, and the optimization program cannot be used for adaptive adjustment. The present invention adopts an adaptive excitation coefficient combination optimization method. When the optimal solution cannot be found after repeated optimization, the indicators can be automatically reduced within the acceptable range of the system without manual intervention again; the existing optimization excitation coefficient adopts the method of finding the optimal combination under the condition of known excitation coefficient combination, so each optimization iteration needs to be found in a huge excitation coefficient database, which has a large amount of calculation and a long calculation time. The present invention adopts the method of first optimizing the ideal excitation coefficient, and then finding the excitation coefficient close to the ideal excitation coefficient in the actual excitation coefficient database for verification, thereby improving the optimization efficiency and saving computer resources.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0008] A verification method for a phased array feed source in combination with a dual-focus reflector antenna comprises the following steps:

[0009] Step 1: Use a metal back frame to cooperate with the satellite vehicle to set up a dual-focus reflector antenna, and adjust the high-precision posture of the dual-focus reflector antenna through the bottom slide and turntable of the satellite vehicle;

[0010] Step 2: Using the dual-focus reflector antenna coordinate system as a reference, vertically mount the phased array feed on a six-degree-of-freedom turntable using a mounting fixture;

[0011] Step 3: Optimizing the adaptive excitation coefficient combination, including: pre-optimization data processing, transmission pattern optimization and two-way pattern optimization.

[0012] The beneficial effects of the present invention are:

[0013] (1) The dual-focus reflector antenna is installed with high precision using a satellite vehicle and a metal back frame, so that the attitude angle accuracy of the reflector is controlled within a range of less than 0.015° and can be maintained for a long time;

[0014] (2) Use a six-degree-of-freedom turntable in conjunction with a mounting tool to complete the high-precision posture mounting of the phased array feed source relative to the dual-focus reflector antenna, so that the relative displacement between the two is less than 1 mm, the relative rotation angle is less than 0.015°, and can be maintained for a long time;

[0015] (3) The method of directly optimizing the two-way pattern avoids the situation where the combination of the transmit and receive patterns does not meet the two-way pattern index, thereby improving the optimization efficiency of the satellite-borne phased array feed combined with the dual-focus reflector antenna;

[0016] (4) Improving the genetic algorithm so that it first optimizes the ideal excitation coefficient of the phased array feed source and then searches for the real excitation coefficient can effectively reduce the amount of calculation of the genetic algorithm and improve the optimization efficiency of the excitation coefficient;

[0017] (5) A method for adaptively changing the directivity coefficient index and the sidelobe index in the optimization is proposed. The directivity index can be automatically changed according to the difficulty of optimization in the directivity pattern optimization, thereby optimizing the excitation coefficient with the best directivity pattern index. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a flow chart of the installation and attitude adjustment of the dual-focus reflector antenna according to an embodiment of the present invention;

[0019] Figure 2 This is a flow chart of phased array feed installation and attitude adjustment according to an embodiment of the present invention;

[0020] Figure 3 This is a schematic diagram of the optimization principle of adaptive directional pattern indicators according to an embodiment of the present invention;

[0021] Figure 4 A flow chart of optimizing the transmission pattern according to an embodiment of the present invention;

[0022] Figure 5 The present invention is a two-way directional diagram optimization flow chart according to an embodiment of the present invention. DETAILED DESCRIPTION

[0023] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0024] The present invention proposes a verification method for a phased array feed source in combination with a dual-focus reflector antenna. The method uses a metal back frame in combination with a satellite vehicle to set up the dual-focus reflector antenna, uses a bottom slide and a turntable of the satellite vehicle to achieve high-precision attitude adjustment of the dual-focus reflector antenna, and uses a vertical rod to support the back frame to achieve long-term attitude maintenance of the antenna; uses a six-degree-of-freedom turntable in combination with a support rod to adjust the attitude of the phased array feed source, so as to achieve rapid high-precision adjustment and long-term attitude maintenance of the phased feed source; when optimizing the phased array feed source, first optimize the ideal excitation coefficient, and then find an excitation coefficient combination close to its amplitude and phase in the real excitation coefficient, which can effectively reduce the optimization calculation amount and improve the optimization efficiency; proposes an adaptive directional pattern index adjustment method, according to the priority specified by the system, when multiple repeated optimizations cannot obtain an excitation coefficient combination, reduce the directivity coefficient or the sidelobe level index; when the excitation coefficient combination has been optimized, improve the directivity coefficient or the sidelobe level index, to ensure that the optimal excitation coefficient combination is optimized under existing conditions; directly optimize the two-way directional pattern, that is, when optimizing the receiving directional pattern, bring in the optimized best transmitting directional pattern, so that the optimized two-way directional pattern Figure 1 Must meet the index requirements.

[0025] Example

[0026] The present invention is introduced step by step from the perspective of solving technical problems.

[0027] First, follow the steps below to solve the problem of high-precision attitude adjustment and attitude maintenance of the reflector and phased array feed.

[0028] 1. High-precision installation, attitude adjustment and maintenance of reflector antenna

[0029] The relative attitude of the reflection surface coordinate system and the test coordinate system (near-field test scanning frame coordinate system) is defined by three indicators, and the indicator requirements are Rx≤0.015° (relative rotation angle around the X-axis), Ry≤0.015° (relative rotation angle around the Y-axis), and Rz≤0.015° (relative rotation angle around the Z-axis). Among them, Rx affects the beam pointing of the antenna distance; Ry affects the beam pointing of the antenna azimuth; Rz affects the cross-polarization of the antenna. Based on the existing metal back frame support reflector solution, the present invention uses a connecting tool to connect the back frame to the satellite vehicle turntable. The above three attitude adjustment quantities are respectively adjusted by adjusting the satellite vehicle support platform, the two-dimensional slide under the ground, and the satellite vehicle turntable to achieve high-precision adjustment. This method makes full use of the precise adjustment function of the satellite vehicle platform while making the three attitude adjustment quantities Rx, Ry, and Rz relatively independent, avoiding mutual coupling during adjustment to increase the complexity of adjustment.

[0030] like Figure 1 As shown in the figure, the installation and attitude adjustment process of the dual-focus reflector antenna is given:

[0031] Step 1.1, fix the dual-focus reflector antenna on a metal back frame with the same back surface as the unfolded dual-focus reflector antenna, and adjust the surface shape of the metal back frame;

[0032] Step 1.2, hoist the metal back frame together with the dual-focus reflector antenna to the satellite vehicle turntable tooling and connect them;

[0033] Step 1.3: After driving the satellite vehicle to the designated location, flip the satellite vehicle turntable 90 degrees to a vertical position;

[0034] Step 1.4, add a two-dimensional slide under the ground of the satellite vehicle to complete the initial installation of the dual-focus reflector antenna, and calibrate the initial posture of the reflector antenna coordinate system relative to the test coordinate system, including the rotation angle components around the three directions of x, y, and z, which are Rx, Ry, and Rz respectively;

[0035] Step 1.5: Calculate the two-dimensional slide translation D under the ground foot of the satellite vehicle based on the rotation angle component Ry of the initial attitude of the reflector antenna coordinate system calibrated in step 1.4 about the y direction. 滑台 During adjustment, the satellite vehicle is rotated with its front foot as the axis, driving the dual-focus reflector antenna to rotate, so that the rotation angle component Ry of the initial attitude of the reflector antenna coordinate system around the y direction meets the requirement;

[0036] D 滑台 =-Ry×L 卫星车 ,

[0037] Where, L 卫星车 is the side length of the satellite vehicle;

[0038] Step 1.6, adjusting the rotation angle component Rx of the initial attitude of the reflector antenna coordinate system around the x direction through the support angle of the satellite vehicle support platform, the satellite vehicle support platform is located at the top of the satellite vehicle, and the satellite vehicle support platform is flipped forward and backward through electronic control;

[0039] Step 1.7, adjusting the rotation angle component Rz of the initial attitude of the reflector antenna coordinate system in the z direction of the satellite vehicle through the rotation angle of the satellite vehicle turntable, the satellite vehicle turntable is located on the satellite vehicle support platform at the top of the satellite vehicle, and realizes clockwise or counterclockwise rotation through electronic control;

[0040] Step 1.8, recalibrate the attitude of the reflector antenna coordinate system and the test coordinate system. If the attitude accuracy of the reflector antenna coordinate system does not meet the index requirements, repeat steps 1.5 to 1.7;

[0041] Step 1.9: If the attitude accuracy meets the index requirements, two vertical rods are supported at the bottom of the tooling connected to the satellite vehicle turntable to effectively maintain the reflector attitude and prevent the back frame and the reflector from changing position over time.

[0042] Through the above steps, the high-precision installation, adjustment and attitude maintenance of the dual-focus reflector antenna can be completed to meet the test requirements of the space-borne SAR antenna.

[0043] 2. High-precision installation, attitude adjustment and maintenance of phased array feed

[0044] After the attitude of the reflector antenna is determined, the reflector antenna coordinate system can be used as a reference to adjust the phased array feed coordinate system. There are six parameters for calibrating the phased array feed relative to the reflector antenna coordinate system, which are three displacements and three rotation angle variables: Dx (displacement along the X axis), Dy (displacement along the Y axis), Dz (displacement along the Z axis) and Rx (rotation around the X axis), Dy (rotation around the Y axis), and Dz (rotation around the Z axis). According to the attitude accuracy requirements of the spaceborne SAR antenna, the attitude accuracy requirements of the phased array feed coordinate system relative to the reflector antenna coordinate system are: displacement accuracy (Dx, Dy, Dz) is ≤±1mm, and rotation angle accuracy (Rx, Ry, Rz) is ≤±0.015°. Among them, Rx and Dy affect the antenna range beam pointing; Ry and Dx affect the antenna azimuth beam pointing; Dz affects the antenna beam width; Rz affects the cross-polarization of the antenna. The method adopted by the present invention is to use the erection tool to vertically erect the phased array feed on the six-degree-of-freedom turntable for attitude adjustment. The six-degree-of-freedom turntable is a mechanical mechanism composed of two upper and lower mounting discs and six hydraulic support rods in the discs. The three translation actions along the XYZ axis and the three actions around the XYZ axis are converted into the length changes of the six hydraulic rods through the internal calculation program, thereby realizing the displacement and attitude change of the top disc of the six-degree-of-freedom turntable relative to the bottom disc. This method makes full use of the relatively independent characteristics of the six variables (three translation amounts and three rotation angle amounts) of the six-degree-of-freedom turntable. When adjusting one variable, the remaining five variables can be kept unchanged, which greatly reduces the complexity of the phased array feed attitude adjustment; at the same time, its displacement adjustment accuracy is 0.001mm, and the rotation angle adjustment accuracy is 0.001°, which meets the accuracy requirements of attitude adjustment. Compared with the method of adjusting the attitude of the phased array feed source by the support height and translation of the support structure ground angle, this method is faster, more accurate and safer.

[0045] like Figure 2 As shown in the figure, the installation and attitude adjustment process of the phased array feed is given:

[0046] Step 2.1, connecting the phased array feed to the feed installation tooling;

[0047] Step 2.2, install the lower disc of the six-degree-of-freedom turntable to the ground support structure;

[0048] Step 2.3, hang the phased array feed and feed installation tooling on the six-degree-of-freedom turntable and connect them to the upper disc of the six-degree-of-freedom turntable;

[0049] Step 2.4, move the ground support structure-six-degree-of-freedom turntable-feed source erection tooling-phased array feed to the specified position as a whole, fix it with the support angle, complete the initial erection of the phased array feed, and calibrate the initial posture of the phased array feed source coordinate system relative to the reflector antenna coordinate system;

[0050] Step 2.5, determine the correspondence between the phased array feed coordinate system and the six-degree-of-freedom turntable coordinate system. The six-degree-of-freedom turntable coordinate system is customized by the system, and the phased array feed coordinate system is specified by the SAR antenna protocol. After confirmation, the correspondence between the phased array feed coordinate system and the six-degree-of-freedom coordinate system is shown in Table 1.

[0051] Table 1

[0052]

[0053] Step 2.6, move the initial origin of the six-degree-of-freedom turntable to the origin of the phased array feed source. The initial origin of the six-degree-of-freedom turntable is the center of the upper disk, and the origin of the phased array feed source is the physical center point of the aperture surface;

[0054] Step 2.7. Adjust the six-degree-of-freedom turntable according to the deviation corresponding to the initial attitude of the calibrated phased array feed coordinate system relative to the reflector antenna coordinate system. Determine the adjustment amount according to the correspondence between the phased array feed coordinate system and the six-degree-of-freedom turntable coordinate system determined in step 2.5, and convert it into the adjustment amount required for the six-degree-of-freedom turntable. Table 2 gives the conversion relationship of the phased array feed attitude adjustment variables.

[0055] Table 2

[0056]

[0057] Step 2.8: Recalibrate the attitude of the phased array feed source coordinate system relative to the reflector antenna coordinate system. If the index requirements are not met, repeat step 2.7. If the index requirements are met, shut down the six-degree-of-freedom turntable and turn off the power.

[0058] This method can adjust the phased array feed source attitude accurately and quickly, which can effectively reduce the attitude adjustment time and improve work efficiency. At the same time, the six-freedom turntable is relatively stable during movement, which can ensure the safety of the attitude adjustment process. The power-off attitude is well maintained, which can ensure that the attitude remains unchanged, facilitating long-term antenna testing.

[0059] Second, solve the problem of efficient and adaptive optimization of the combination of excitation coefficients in the following steps:

[0060] The phased array feed source cooperates with the dual-focus reflector antenna to have the ability to scan and shape the range pattern beam, and the azimuth pattern is a low sidelobe normal beam. According to the imaging requirements of the system, the two-way range pattern and azimuth pattern synthesized by the antenna must meet a set of pattern indicators (including beam pointing, beam width, sidelobe level, etc.). Each set of two-way pattern indicator requirements is called a wave position, which contains a transmit synthesis pattern and a receive synthesis pattern. The two-way pattern = (transmit pattern + receive pattern) / 2. The transmit synthesis pattern is determined by the transmit secondary pattern and the transmit excitation coefficient; the receive pattern is determined by the receive secondary pattern and the receive excitation coefficient. The range section and azimuth section of the synthesis pattern are independent of each other. The range synthesis pattern is the range secondary pattern section pattern superimposed with the excitation coefficient, and the azimuth synthesis pattern is the same. Therefore, a set of two-way patterns needs to optimize a transmit excitation coefficient and a receive excitation coefficient.

[0061] (1)

[0062] (2)

[0063] In the formula, F AZ (θ), F EL (θ) is the composite direction pattern of azimuth and range, Fn AZ (θ), Fn EL (θ) is the azimuth and range tangent planes of the secondary pattern when the nth unit in the phased array feed is excited individually, A n e jPn is the excitation coefficient of the nth unit in the phased array feed.

[0064] The number of combinations of excitation coefficients of the phased array feed is determined by the number of combined control states of active components in the phased array feed. Each unit of the phased array feed has three control states: attenuation, phase shift, and delay. The attenuation control state is only valid for the receiving channel. Phase shift and delay control the unit phase, and attenuation control the unit amplitude. The attenuation control is divided into 6 control bits (0.5dB / 1dB / 2dB / 4dB / 8dB / 16dB / ), and the 6 bits can be freely combined into 64 attenuation states to achieve a maximum amplitude attenuation of 31.5dB; the phase shift control is divided into 6 control bits (5.625 degrees, 11.25 degrees, 22.5 degrees, 45 degrees, 90 degrees and 180 degrees), and the 6 bits can be freely combined into 64 phase shift states to achieve a maximum phase lag of 354.375 degrees; the delay control is divided into 3 control bits (0.25 wavelengths / 0.5 wavelengths / 1 wavelength), and the 3 bits can be freely combined into 8 delay states, with a maximum delay of 1.75 wavelengths. When receiving, attenuation, delay and phase shift control can be combined into 16384 (64×64×8=16384 states) control states; when transmitting, delay and phase shift can be combined into 512 (64×8=512 states) control states. The synthetic pattern optimization is to find the control state combination that meets the synthetic pattern index requirements in all the control states of each phased array feed unit.

[0065] The optimization algorithm in the present invention is based on the existing genetic algorithm for optimizing the directional pattern, combined with the characteristics of the phased array feed source and the dual-focus reflector antenna, and has the following improvements:

[0066] First, the number of units in a phased array feed with a dual-focus reflector antenna is generally small, so the excitation coefficient error of each unit will have a certain impact on the composite pattern. The error of the excitation coefficient is determined by the difference between the actual value and the ideal value of the amplitude and phase of each control state of the unit. The control bits of the amplitude modulation and phase modulation of the active components in the phased array feed have precision errors. At the same time, the amplitude modulation control will introduce parasitic phase modulation, and the phase modulation control will also introduce parasitic amplitude modulation. Therefore, a vector network analyzer is used in conjunction with an automated test system to test the true amplitude and phase of 16,384 receiving control states and 512 transmitting control states, respectively, and establish the amplitude phase true value matrix of each channel and each control state, which can ensure that the optimized composite pattern is closer to the true composite pattern.

[0067] Second, in the optimization algorithm, the ideal excitation coefficient that meets the index requirements is first optimized, and then multiple combinations close to the ideal excitation coefficients are found in the amplitude and phase real value matrix of each channel and each control state, and finally it is verified whether the real excitation coefficient meets the index requirements. Compared with other optimization algorithms that directly traverse the 512 control states of the transmitter and the 16384 control states of the receiver to find the optimal solution, this method can effectively reduce the optimization calculation amount and improve the optimization efficiency.

[0068] Third, the method of optimizing the transmit pattern first (so it is generally difficult to optimize the transmit pattern) and then directly optimizing the two-way pattern with the transmit pattern can ensure that the transmit and receive pattern combinations corresponding to the optimized transmit excitation number and receive excitation coefficient must meet the two-way pattern index. This avoids the two-way pattern after the two-way pattern after the transmit pattern and the receive pattern are optimized separately not meeting the index, resulting in repeated optimization and reduced optimization efficiency.

[0069] Fourth, an adaptive directional pattern index optimization method is used. Figure 3 As shown in the figure, the principle diagram of adaptive pattern index optimization is given. In the pattern optimization of spaceborne SAR antenna, based on the specified scanning angle and beam width, it is generally required that the directivity coefficient is as high as possible and the sidelobe level is as low as possible, which can improve the imaging index of spaceborne SAR. Therefore, in the optimization, the directivity coefficient and the sidelobe level can be set as indicators that are adaptively adjusted according to the optimization results. For example, in the first round of pattern optimization, the estimated directivity coefficient and sidelobe level can be input first. If the indicator can optimize the excitation coefficient, the directivity coefficient or sidelobe index is increased according to the system priority requirements (directivity coefficient priority or sidelobe priority); if the indicator still fails to optimize the excitation coefficient after multiple rounds of optimization, the directivity coefficient or sidelobe index is reduced according to the system priority. This method can ensure the optimization of the optimal result within the antenna capability and optimize the system imaging index.

[0070] The efficient and adaptive excitation coefficient combination optimization method is divided into three steps: pre-optimization data processing, transmission pattern optimization and two-way pattern optimization.

[0071] First, data processing before optimization:

[0072] First, the range and azimuth sections of the secondary patterns of all wave positions are processed. After the near-field data of the tested transmitted and received secondary patterns (the patterns reflected by the reflector antenna when each unit of the feed source is excited separately) are Fourier transformed, the azimuth and range section patterns are intercepted according to the radar coordinate system at the pointing angles of the range and azimuth patterns of the beam, and saved as secondary pattern data matrices.

[0073] Secondly, the amplitude and phase of all combinations of excitation coefficients are processed. The real amplitude and phase data of the transmitting 512 state and receiving 16384 state of the M units of the phased array feed are normalized relative to the base state (phase shift, attenuation and delay control states are not in effect) and saved as the real excitation amplitude phase data matrix.

[0074] Second, the transmission pattern optimization:

[0075] like Figure 4 As shown in the figure, the specific transmission pattern optimization process is given:

[0076] Step 1: Set the genetic algorithm parameters and excitation coefficient range. The genetic algorithm parameters that need to be initially set include:

[0077] Gene length (2M): represents the number of elements of each individual. If the number of units in the phased array feed is M, the gene length is 2M, representing the amplitude and phase variables of the M units respectively;

[0078] Population size (N 种群 ): the number of individuals in a generation;

[0079] Number of crossovers (N 交叉 ): The number of crossovers between two individuals in each generation;

[0080] The number of crossover individuals (M 交叉 ): The probability of individuals in a population being able to exchange genes;

[0081] The probability of mutation individual (P 变异 ): The probability of an individual in a population undergoing genetic mutation;

[0082] Single index optimization times (T 优化 ): The maximum number of times to repeat the optimization for a set of directional pattern indicators;

[0083] The number of single optimization iterations (T 迭代 ): The number of times the population can evolve in sequential optimization;

[0084] Whether the parameter setting is appropriate determines the diversity and convergence speed of the genetic algorithm population, and needs to be adjusted according to the actual optimization process. Since there is no attenuator in the transmission channel, only the phase variable of the excitation coefficient is optimized, and the optimization range of the phase is set to 0 to 2 pi (radian value), set the amplitude value to 1.

[0085] Step 2: Input the transmission pattern index requirements and determine the adaptability parameters and judgment parameters. The pattern index requirements include: range beam pointing (SA_EL 目标 ), range beam width (BW_EL 目标 ), range sidelobe level (SLL_EL 目标 ), azimuth beam pointing (SA_AZ 目标 ), azimuth beam width (BW_AZ 目标 ), azimuth sidelobe level (SLL_AZ 目标 ) and directivity coefficient (D 目标 ), etc., and set reasonable weights according to the indicator values ​​(distance weight W EL , azimuth weight W AZ , directivity coefficient weight W D). According to the index requirements, set the adaptability function to determine the adaptability of the pattern to the index. The smaller the adaptability function value, the closer it is to the index. Define the azimuth adaptability parameter (Q AZ ), distance adaptability parameter (Q EL ), azimuth adaptability parameter (Q D ), the sum of the three is the total adaptability parameter (Q 总 ).

[0086] Q AZ =W AZ (1) |SA_AZ- SA_AZ 目标 |+ W AZ (2) |BW_AZ - BW_AZ 目标 |

[0087] + W AZ (3) (SLL_AZ- SLL_AZ 目标 )

[0088] Q EL =W EL (1) |SA_EL-SA_EL 目标 |+ W EL (2) |BW_EL - BW_EL 目标 |

[0089] + W EL (3) (SLL_EL- SLL_EL 目标 )

[0090] Q D= W D ( D 目标 -D )

[0091] Q 总 = Q AZ + Q EL + Q D

[0092] When setting the target value of each indicator, you also need to set the error tolerance range of each indicator: range beam pointing error (SA_EL 误差 ), range beam width (BW_EL 误差 ), azimuth beam pointing (SA_AZ 误差 ), azimuth beam width (BW_AZ 误差), that is, when the optimized directional pattern parameters are within the allowable range of the indicator, the optimization is considered successful. Set the judgment parameters of each indicator according to the allowable range of each indicator: Distance direction directional pattern judgment parameter (J EL ), azimuth direction pattern judgment parameters (J AZ ) and directivity coefficient judgment parameter (J D ), if all the judgment parameters are valid, the optimization is successful.

[0093] J AZ =( |SA_AZ- SA_AZ 目标 |≤SA_AZ 误差 )&( |BW_AZ- BW _AZ 目标 |≤BW _AZ 误差 )&( SLL_AZ≤SLL_AZ 目标 )

[0094] J EL =( |SA_EL- SA_EL 目标 |≤SA_EL 误差 )&( |BW_EL- BW _EL 目标 |≤BW _EL 误差 )&( SLL_EL≤SLL_EL 目标 )

[0095] J D =D≥D 目标

[0096] Step 3: Use genetic algorithm to optimize the ideal excitation coefficient.

[0097] First, the population is randomly initialized, the fitness parameters of individuals in the population are calculated, and they are sorted according to the fitness parameter values.

[0098] Secondly, three methods are used to generate the next generation of individuals in the population: mutation, crossover, and crossover and mutation. The individuals generated by the three methods together with the individuals of the previous generation form the candidate pool of the next generation of individuals, which can greatly enrich the diversity of individuals and improve the convergence rate.

[0099] (a) Mutation: Randomly select N from the population 种群 ×P 变异 Genetic variation occurs in individuals,

[0100] (b) Crossover: M with the highest ranking in fitness parameter 交叉 Randomly select two individuals from the individuals to perform gene crossover and repeat M 交叉 Second-rate

[0101] (c) Crossover and mutation: N individuals are also selected after crossover 种群×P 变异 Genetic variation in individuals

[0102] Step 4: Calculate the adaptability parameters for the new generation of individuals, and use the judgment parameters to determine whether the synthetic range and azimuth direction diagrams of the top 5 individuals with the adaptability parameters meet the requirements. If they meet the requirements, proceed to the next step. If not, repeat steps 3 to 4.

[0103] Step 5: Find the real excitation coefficient based on the ideal excitation coefficient. For example, the phase of each unit of each phased array feed source is optimized to be 0 after normalization relative to the first unit, P 2…… P M-1 , P M Since the phase is relative, at 0, P 2…… P M-1 , P M On the basis of the ideal phase, each unit adds the same phase value and the superposition effect is the same. Therefore, 64 phase combinations with the same effect can be generated by stepping with the minimum phase shift accuracy:

[0104] 0,P 2…… P M-1 , P M

[0105] 5.625°, P2+5.625° …… P M-1 +5.625°, P M +5.625°

[0106] 11.25°, P2+11.25° …… P M-1 +11.25°, P M +11.25°

[0107] …

[0108] 348.75°, P2+348.75° …… P M-1 +348.75°, P M +348.75°

[0109] 354.375°, P2+354.375° …… P M-1 +354.375°, P M +354.375°

[0110] Since the phase is periodic, 0, P 2…… P M-1 , P MOn the basis of the ideal phase, each unit can add or subtract an integer multiple of 360 from the existing phase, and the superposition effect is the same. Therefore, multiple permutations and combinations can be generated. To reduce the amount of calculation, each unit only adds or subtracts a cycle of 360. For example:

[0111] 360,P 2…… P M-1 , P M

[0112] 0, P2+360 …… P M-1 , P M

[0113] …

[0114] 0,P 2…… P M-1 , P M +360 etc.

[0115] Find a real excitation combination similar to it in all the above phase combinations, and verify whether the synthesized range and azimuth synthetic patterns and directivity coefficients meet the indicators. If they meet the indicators, the loop is exited and the transmission pattern optimization ends; if not, the optimization is performed according to the number of single indicator optimizations set initially according to the optimization T 优化 wheel.

[0116] Step 6: If you repeatedly optimize T 优化 If the true excitation coefficient can be optimized after the round, the directivity coefficient or sidelobe level is increased according to the priority specified by the SAR system, and the second to fifth steps are repeated; if the optimization T 优化 If the real excitation coefficient can be optimized after the round, the directivity coefficient or the sidelobe level is reduced according to the priority specified by the SAR system, and the second to fifth steps are repeated.

[0117] Thirdly, two-way directional pattern optimization:

[0118] like Figure 5 As shown in the figure, the specific two-way pattern optimization process is given. The two-way pattern optimization steps are basically the same as the transmission pattern optimization steps. The difference is that when calculating the individual adaptability parameters and difference parameters, the optimized transmission pattern is brought into the calculation of the two-way pattern before calculation. Since the receiving channel has an attenuator, the optimization of the excitation coefficient requires the optimization of the amplitude variable and the phase variable at the same time, and the optimization range of the phase is set to 0 to 2 pi (radian value), set the amplitude value to 0 to 1. In the fifth step, when finding the real excitation coefficient based on the ideal excitation coefficient, it is also necessary to consider that the attenuation parameters of each unit are relative. 2…… A M-1 , A MOn the basis of the ideal amplitude, each unit adds the same attenuation value, and the superposition effect is the same. Therefore, multiple phase combinations with the same effect can be produced by taking the minimum attenuation as a step, until the maximum attenuation value exceeds 31.5 (the maximum attenuation value of the attenuator):

[0119] A1, A 2…… A M-1 , A M

[0120] 5.625°, P2+5.625° …… P M-1 +5.625°, P M +5.625°

[0121] 11.25°, P2+11.25° …… P M-1 +11.25°, P M +11.25°

[0122] …

[0123] 348.75°, P2+348.75° …… P M-1 +348.75°, P M +348.75°

[0124] 354.375°, P2+354.375° …… P M-1 +354.375°, P M +354.375°

[0125] According to the above steps, the phased array feed source can be used with the dual-focus reflector antenna to optimize the best combination of transmit and receive excitation coefficients, and this combination of excitation coefficients must make the two-way pattern meet the index requirements. The synthetic pattern test results verify that this method is indeed feasible and has a high optimization efficiency.

[0126] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A verification method for a phased array feed source combined with a dual-focus reflector antenna, characterized in that: The steps include: Step 1: Use a metal back frame to cooperate with the satellite vehicle to set up a dual-focus reflector antenna, and adjust the high-precision posture of the dual-focus reflector antenna through the bottom slide and turntable of the satellite vehicle; Step 2: Using the dual-focus reflector antenna coordinate system as a reference, vertically mount the phased array feed on a six-degree-of-freedom turntable using a mounting fixture; Step 3: Optimizing the adaptive excitation coefficient combination, including: pre-optimization data processing, transmission pattern optimization and two-way pattern optimization; wherein, the transmission pattern optimization includes: Step 3.21, setting the parameters of the genetic algorithm, the parameters of the genetic algorithm include gene length, population number, number of crossover individuals, probability of mutation individuals, number of single index optimizations, and number of single optimization iterations; Step 3.22, input the index requirements of the transmission pattern, and determine the adaptability parameters and judgment parameters; Step 3.23, optimize the ideal incentive coefficient using genetic algorithm: randomly initialize the population, calculate the fitness parameters of individual individuals, and sort them according to the fitness parameter values, and generate a new generation of individuals through mutation, crossover, and crossover and mutation, that is, a new generation of individual ideal incentive coefficients; Step 3.24, calculate the adaptive parameter value for the new generation individuals, and determine whether the synthetic direction diagrams in the range and azimuth directions of the new generation individuals with the top five adaptive parameter values ​​meet the determination parameters. If so, proceed to the next step. If not, repeat steps 3.23 to 3.

24. Step 3.25, find the real excitation coefficient based on the ideal excitation coefficient, verify whether the synthesized distance and azimuth direction synthetic directional patterns and directivity coefficients meet the indicators, if they do, exit the loop and the transmission directional pattern optimization ends; if not, continue to optimize according to the single indicator optimization times initially set; Step 3.26, if the true excitation coefficient is obtained after repeating the optimization of the single index optimization times, the directivity coefficient or the sidelobe level is increased according to the priority specified by the SAR system, and steps 3.22 to 3.25 are repeated; if the true excitation coefficient is not obtained after repeating the optimization of the single index optimization times, the directivity coefficient or the sidelobe level is reduced according to the priority specified by the SAR system, and steps 3.22 to 3.25 are repeated; The two-way pattern optimization includes directly bringing the optimized transmission pattern into the two-way pattern for further calculation.

2. According to claim 1, a verification method for a phased array feed source combined with a dual-focus reflector antenna is characterized in that: The step 1 comprises: Step 1.1, fix the dual-focus reflector antenna on a metal back frame with the same back surface as the unfolded dual-focus reflector antenna, and adjust the surface shape of the metal back frame; Step 1.2, hoist the metal back frame together with the dual-focus reflector antenna to the satellite vehicle turntable tooling and connect them; Step 1.3: After driving the satellite vehicle to the designated location, flip the satellite vehicle turntable 90 degrees to a vertical position; Step 1.4, add a two-dimensional slide under the ground of the satellite vehicle to complete the initial installation of the dual-focus reflector antenna, and calibrate the initial posture of the reflector antenna coordinate system relative to the test coordinate system, including the rotation angle components around the three directions of x, y, and z, which are Rx, Ry, and Rz respectively; Step 1.5: Calculate the two-dimensional slide translation D under the ground foot of the satellite vehicle based on the rotation angle component Ry of the initial attitude of the reflector antenna coordinate system calibrated in step 1.4 about the y direction. 滑台 During adjustment, the satellite vehicle is rotated with its front foot as the axis, driving the dual-focus reflector antenna to rotate, so that the rotation angle component Ry of the initial attitude of the reflector antenna coordinate system around the y direction meets the requirement; D 滑台 =-Ry×L 卫星车 , Where, L 卫星车 is the side length of the satellite vehicle; Step 1.6, adjusting the rotation angle component Rx of the initial attitude of the reflector antenna coordinate system around the x direction through the support angle of the satellite vehicle support platform, the satellite vehicle support platform is located at the top of the satellite vehicle, and the satellite vehicle support platform is flipped forward and backward through electronic control; Step 1.7, adjusting the rotation angle component Rz of the initial attitude of the reflector antenna coordinate system in the z direction of the satellite vehicle through the rotation angle of the satellite vehicle turntable, the satellite vehicle turntable is located on the satellite vehicle support platform at the top of the satellite vehicle, and realizes clockwise or counterclockwise rotation through electronic control; Step 1.8, recalibrate the attitude of the reflector antenna coordinate system and the test coordinate system. If the attitude accuracy of the reflector antenna coordinate system does not meet the index requirements, repeat steps 1.5 to 1.7; Step 1.9: If the attitude accuracy meets the index requirements, support two vertical rods at the bottom of the tooling connected to the satellite vehicle turntable.

3. The verification method of a phased array feed source combined with a dual-focus reflector antenna according to claim 2 is characterized in that: The step 2 comprises: Step 2.1, connecting the phased array feed to the feed installation tooling; Step 2.2, install the lower disc of the six-degree-of-freedom turntable to the ground support structure; Step 2.3, hang the phased array feed and feed installation tooling on the six-degree-of-freedom turntable and connect them to the upper disc of the six-degree-of-freedom turntable; Step 2.4, move the ground support structure-six-degree-of-freedom turntable-feed source erection tooling-phased array feed to the specified position as a whole, fix it with the support angle, complete the initial erection of the phased array feed, and calibrate the initial posture of the phased array feed source coordinate system relative to the reflector antenna coordinate system; Step 2.5, determine the correspondence between the phased array feed coordinate system and the six-degree-of-freedom turntable coordinate system. The six-degree-of-freedom turntable coordinate system is customized by the system, and the phased array feed coordinate system is specified by the SAR antenna protocol; Step 2.6, move the initial origin of the six-degree-of-freedom turntable to the origin of the phased array feed source. The initial origin of the six-degree-of-freedom turntable is the center of the upper disk, and the origin of the phased array feed source is the physical center point of the aperture surface; Step 2.7, according to the deviation corresponding to the initial posture of the calibrated phased array feed source coordinate system relative to the reflector antenna coordinate system, adjust the six-degree-of-freedom turntable, and determine the adjustment amount according to the corresponding relationship between the phased array feed source coordinate system and the six-degree-of-freedom turntable coordinate system determined in step 2.5; Step 2.8: Recalibrate the attitude of the phased array feed source coordinate system relative to the reflector antenna coordinate system. If the index requirements are not met, repeat step 2.

7. If the index requirements are met, shut down the six-degree-of-freedom turntable and turn off the power.

4. The verification method of a phased array feed source combined with a dual-focus reflector antenna according to claim 3 is characterized in that: In step 3, the data processing before optimization includes: Step 3.11, after Fourier transforming the near-field data of the tested transmitted and received secondary patterns, intercept the range-direction tangent pattern and the azimuth-direction tangent pattern according to the radar coordinate system with the pointing angles of the range-direction and azimuth-direction patterns of the beam, and save them as a secondary pattern data matrix; Step 3.12: Normalize the real amplitude phase data of all transmitting and receiving states of the M feed sources of the phased array feed source relative to the ground state, and save them as a real excitation amplitude phase data matrix.

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