Low-orbit satellite oversized folded array antenna beam and polarization adaptive calibration system

Abstract

The invention belongs to the technical field of satellite communication and antenna arrays, and relates to a low-orbit satellite ultra-large folded array antenna beam and polarization adaptive calibration system. According to the system, through a feed network of an antenna and a coupler of a satellite-borne detection path, a Jones matrix of each array element is obtained by adopting time division multiplexing excitation, and amplitude and phase calibration in a substrate is realized by utilizing least square pseudo-inverse compensation. Self-adaptive fusion is carried out according to the energy of the left-hand and right-hand circular polarization channels, the residual error of a fusion signal and an ideal signal is calculated, and abnormal array elements are removed in combination with amplitude outlier and phase jump detection. Performing low-rank denoising and sparse correction processing on the phase residual error, calculating the plane coefficient of each substrate through weighted least square plane fitting, and realizing smoothing and compensation iteration by using Kalman filtering and phase updating constraint. And finally, correcting each array element by the spaceborne digital beam forming unit according to the calibration coefficient, thereby realizing accurate calibration of the antenna beam and polarization.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of satellite communication and antenna array technology, and particularly relates to a low-orbit satellite super-large folding array antenna beam and polarization adaptive calibration system, which is used for in-board calibration and inter-board calibration of an antenna with folding deformation between boards caused by insufficient unfolding between boards due to factors such as light and radiation, thereby improving the on-orbit satellite antenna pattern performance and polarization purity. BACKGROUND

[0002] With the development of low-orbit satellite communication, super-large folding array antennas with a multi-board and multi-subarray structure have become mainstream. However, such antennas may have the following problems in actual manufacturing, assembly and on-orbit operation:

[0003] (1) Subarray board-to-board error: Satellite antennas now mostly use deployable satellite antenna technology, which refers to a satellite payload component that is stored in a folded configuration in a launch vehicle during launch, and is deployed into a working configuration through a driving mechanism after entering a predetermined orbit to achieve communication, remote sensing, navigation and other functions. However, there may be a situation where the antenna subarray boards are not fully deployed, resulting in an included angle between the subarray boards, which in turn causes beam distortion and side lobe rise of the antenna;

[0004] (2) Subarray board internal error: Since satellite antennas work in a complex space environment, they may be affected by high and low temperatures, radiation and other adverse factors, resulting in physical deformation such as protrusions in the subarray board, causing deformation of the antenna board structure and affecting the normal use of the antenna;

[0005] (3) Polarization purity is reduced: Since the subarrays cannot maintain strict phase consistency, the right-handed / left-handed circular polarization (RHCP / LHCP) channels are coupled, and the cross-polarization ratio (XPI) is reduced;

[0006] The traditional satellite antenna calibration method mainly relies on an angle measuring device outside the antenna and ground cooperative calibration, and has many deficiencies: first, there is a lack of hierarchical modeling and independent compensation mechanism, the existing calibration method usually uniformly compensates the amplitude and phase of the entire array, and cannot model and correct the internal error of the subarray panel and the connection error between the subarray panels in layers, when the subarray panel has assembly deviation or inconsistent unfolding angle, uniform compensation cannot simultaneously consider local accuracy and overall consistency, and is prone to cause the problem of main lobe recovery but insufficient sidelobe suppression; second, the polarization channel coupling is not effectively compensated, the existing technology is generally based on single polarization assumption, and only the co-polarization channel is corrected, ignoring the cross-coupling effect between right-handed / left-handed circular polarization channels, and the subarray unfolding error and inconsistent feeding will cause polarization signal aliasing, reduce polarization isolation, and affect the polarization purity and communication performance of the system; third, the calibration process relies on ground measurement or complex star-ground loop, and some methods need to rely on ground direction finding system or high signal-to-noise ratio link signal for feedback estimation, which is complex in hardware and occupies a lot of resources, and is not suitable for low-orbit satellite scenarios with limited on-board computing power and communication resources.

[0007] Therefore, it is urgent to develop a new adaptive calibration system and method with hierarchical in-panel and inter-panel compensation, adaptive polarization calibration and on-orbit independent implementation, to improve the antenna performance and make up for the deficiencies of the existing technology. SUMMARY

[0008] The present application aims to solve the problems of insufficient calibration accuracy caused by subarray panel interconnection error, subarray panel internal structure deformation and polarization channel coupling in the process of manufacturing, assembly and on-orbit operation of the low-orbit satellite on-board super large folding array antenna in the prior art, and provides a low-orbit satellite super large folding array antenna beam and polarization adaptive calibration system to realize hierarchical modeling of array errors, joint calibration of polarization channels and on-orbit independent compensation.

[0009] The low-orbit satellite super large folding array antenna beam and polarization adaptive calibration system provided by the present application comprises:

[0010] The time-sharing self-measurement on-orbit data acquisition module is used for exciting and measuring the left-handed circular polarization and right-handed circular polarization channel outputs of each array element with left-handed circular polarization and right-handed circular polarization signals in different calibration time slots, acquiring Jones matrix data of each array element, and being used for subsequent calibration process;

[0011] The in-panel calibration module is connected with the time-sharing self-measurement on-orbit data acquisition module, and is used for compensating and calibrating the amplitude and phase errors of the array elements caused by the physical deformation such as bulging in the substrate and the polarization coupling errors existing in the substrate according to the measured Jones matrix;

[0012] An adaptive channel fitting module is connected with the in-board calibration module, and calculates adaptive fitting weights according to the calibrated two-polarization channel data, so as to realize optimal synthesis of the two-polarization channels and provide data required by inter-board calibration;

[0013] A residual phase calculation module is connected with the adaptive channel fitting module, and calculates a phase residual according to the adaptively fused complex response and an ideal reference phase, and performs abnormality detection to eliminate bad elements and obtain a residual phase distribution of normal elements;

[0014] An inter-board phase calibration module is connected with the residual phase calculation module, and establishes an actual phase distribution structure model of elements of the same board according to the residual phase distribution of normal elements, performs error calibration in steps, performs low-rank denoising on high-frequency noise and random jitter, performs plane fitting according to the denoised phase, calculates a coefficient residual existing in the plane fitting, modifies the original phase according to the modified phase, and performs board error plane coefficient fitting again according to the modified phase;

[0015] A Kalman filter smoothing module is connected with the inter-board phase calibration module, and performs dynamic estimation and smoothing on the plane coefficients obtained for each subarray board, so as to reduce the influence of random fluctuations caused by measurement noise, element error and numerical fitting error on fitting sparseness, and make the plane parameters keep continuity and physical consistency in time sequence;

[0016] A soft-limit phase updating module is connected with the Kalman filter smoothing module, calculates a phase compensation amount according to the final plane coefficients obtained by Kalman filter smoothing, and suppresses excessive updates by using a nonlinear compression function, and iteratively calculates and accumulates the phase compensation amount;

[0017] A convergence judgment module is connected with the soft-limit phase updating module and the adaptive channel fitting module, and after each round of plane fitting and phase compensation updating, calculates a maximum absolute value of phase updating amounts of all elements, and compares the maximum absolute value with a set convergence threshold, if the termination condition is not met, data is transmitted to the adaptive channel fitting module for iteration, if the termination condition is met, amplitude and phase calibration coefficients obtained by in-board calibration and inter-board calibration are saved, and iteration is terminated;

[0018] A spaceborne digital beam forming module is connected with the convergence judgment module, and compensates and calibrates each element according to the amplitude and phase calibration coefficients obtained by in-board calibration and inter-board calibration.

[0019] Preferably, the time-division self-test in-orbit data acquisition module comprises:

[0020] A spaceborne coupler is connected with the element feed path, and is used for realizing time-division excitation and collection of element signals in different calibration time slots;

[0021] A switching control unit controls the excitation sequence according to the space-borne time synchronization pulse;

[0022] A signal acquisition and processing unit acquires the Jones matrix of each array element through synchronous sampling, for subsequent calibration processing.

[0023] As a preferred, the in-board calibration module comprises:

[0024] A least square pseudo-inverse compensation approximates the off-diagonal elements to 0, and matrix calculates the array element Jones matrix to obtain the amplitude and phase compensation coefficients of the array element: Wherein is the Jones matrix of the i-th array element and its conjugate transpose, λ is a damping coefficient, and I is a unit matrix.

[0025] As a preferred, the adaptive fusion channel module comprises:

[0026] A calculation energy distribution and weight unit calculates the fusion weight based on the energy ratio of the polarization channel, and obtains the fusion weight through And

[0027] A fusion output complex response unit fuses the two polarization channel signals according to the calculated fusion weight.

[0028] As a preferred, the residual phase calculation module comprises:

[0029] A calculation residual phase unit calculates the phase residual according to the adaptive fused complex response and the ideal reference phase;

[0030] An amplitude outlier detection unit performs amplitude outlier detection based on the median absolute deviation MAD, and calculates the median and median absolute deviation based on the complex equivalent response of each array element after fusion, and performs amplitude anomaly detection: ||C i |-med m |>τ m ·mad m , wherein C i is the complex equivalent response of each array element after fusion, med m is the median, mad m is the median absolute deviation, τ m is the amplitude empirical value.

[0031] A phase jump detection unit calculates the difference module length of adjacent array element residual phases, and calculates the median and median absolute deviation, and performs phase jump detection: d i >τ d ·mad d , wherein d i is the difference module length of adjacent array elements, τ d is the phase empirical value, and mad​d is the median absolute deviation;

[0032] The subarray protection eliminates bad element units, prevents the entire substrate from being determined as bad, calculates the proportion of bad points in each substrate, and if it exceeds the empirical threshold p, the bad point marks in the substrate are removed, and then the units marked as bad elements are eliminated.

[0033] As preferred, the inter-plate phase calibration module comprises:

[0034] The error model analysis unit establishes an actual phase distribution structure model of the same substrate element according to the residual phase distribution of the normal elements;

[0035] The low-rank denoising unit performs low-rank denoising on high-frequency noise and random jitter;

[0036] The plane fitting unit calculates the plane residual coefficient in the phase residual according to the amplitude weight of different elements by weighted least squares fitting;

[0037] The ISTA sparse correction unit uses the iterative shrinkage threshold algorithm ISTA to calculate and eliminate the non-smooth part of the residual phase, thereby realizing higher precision plane calibration.

[0038] As preferred, the soft limit phase update module comprises:

[0039] The phase compensation amount calculation unit calculates the phase compensation amount according to the final plane coefficient smoothed by Kalman filtering;

[0040] The excessive update suppression unit uses the hyperbolic tangent function to perform soft limiting on the obtained phase compensation amount: Δφ soft = φ max tanh(Δφ / φ max ), where Δφ is the calculated phase compensation amount, φ max is the limit maximum empirical value.

[0041] The low-orbit satellite super large folding array antenna beam and polarization adaptive calibration system comprises the following steps:

[0042] The starboard coupler, switching control unit and signal acquisition unit of the array antenna are controlled to acquire the Jones matrix of each element;

[0043] The least squares pseudo-inverse is calculated for the Jones matrix of each element, the in-plate calibration is performed on the internal physical deformation of the substrate, and the calibrated amplitude and phase coefficients are obtained;

[0044] The adaptive fusion weight is calculated according to the energy of the calibrated two-polarization channel data, and the two signals are fused;

[0045] The phase residual of the complex equivalent response of the fused signal and the ideal reference phase is calculated, and amplitude outlier detection and phase jump detection based on median absolute deviation (MAD) and subarray protection are performed to remove bad elements, so that the phase residual of normal elements is obtained;

[0046] The phase residual of the elements is subjected to low-rank decomposition to filter out high-frequency noise and random jitter, and then weighted least square plane fitting is performed to obtain a smooth phase error, and then an iterative shrinkage threshold algorithm is used for sparse correction to remove non-smooth errors, and then the baseboard error plane coefficient is calculated based on the corrected phase and the weighted least square fitting baseboard error plane coefficient;

[0047] The baseboard error plane coefficient is subjected to Kalman filter smoothing to reduce random fluctuations that may occur in iteration;

[0048] The compensation phase is calculated based on the smoothed baseboard error plane coefficient, the hyperbolic tangent nonlinear compression function is used to suppress excessive updates, and the cumulative phase compensation amount is calculated;

[0049] The maximum absolute value of the new round of iteration update amount is calculated based on the cumulative phase compensation amount, and the convergence threshold is compared to determine whether the current antenna state is input to the adaptive channel fusion module for iteration calculation, or the iteration is exited when the convergence is reached;

[0050] The amplitude and phase calibration coefficients obtained by the in-board calibration and the phase calibration coefficients obtained by the inter-board calibration are loaded into the complex weight control module of the on-board digital beam forming module, the in-board calibration coefficients are in the form of a matrix and act on the complex I / Q signals of each polarization channel to realize element-level decoupling and amplitude and phase equalization, and the inter-board phase compensation amount is in the form of a scalar and is superimposed on the beam forming weight vector to realize phase reference alignment between subarrays and overall wavefront flattening.

[0051] The present application has the following advantages:

[0052] 1. The on-orbit self-calibration capability of the on-board super large array antenna is realized, and the on-board autonomous amplitude and phase measurement and calibration can be realized without relying on ground test signals, so that the on-orbit adaptive maintenance capability of the low-orbit satellite is significantly improved;

[0053] 2. The adaptive polarization fusion capability is provided, the left and right circular polarization channel energy adaptive fusion algorithm is adopted, the fusion weight can be dynamically calculated according to the actual channel state, the optimal synthesis of the two polarization signals is realized, and the robustness and precision of the calibration process are improved;

[0054] 3. The bad element interference can be suppressed and intelligent removal can be realized, the abnormal elements are automatically identified and removed by combining the residual phase calculation with the amplitude outlier detection and phase jump detection, and the pollution of the bad element response to the overall calibration precision is avoided;

[0055] 4. Significantly reduce the influence of inter-plate deformation and folding error, while considering the calibration of internal deformation of the substrate and inter-plate folding deformation, and realize effective compensation for the performance of the antenna;

[0056] 5. Comprehensive improvement of the on-orbit performance of the antenna, the cross-polarization isolation of the left and right circularly polarized channels is significantly improved, and after calibration, it is greater than 35dB, completely realizing polarization isolation, the antenna sidelobe level is significantly reduced, the sidelobe direction energy leakage is reduced, and the main lobe pointing is more concentrated, accurate and stable. BRIEF DESCRIPTION OF DRAWINGS

[0057] Figure 1 The overall architecture diagram of the low-orbit satellite super large folding array antenna beam and polarization adaptive calibration system of the application

[0058] Figure 2 The flowchart of time-sharing excitation and Jones matrix acquisition

[0059] Figure 3 The flowchart of adaptive channel fitting and anomaly detection

[0060] Figure 4 The inter-plate phase calibration flowchart

[0061] Figure 5 The Kalman filter smoothing and soft limit phase update iteration block diagram DETAILED DESCRIPTION

[0062] Please refer to Figures 1-5 , the specific embodiments of the application will be described in detail below with reference to the drawings.

[0063] As Figure 1 shown, the low-orbit satellite super large folding array antenna beam and polarization adaptive calibration system provided by the application includes a time-sharing self-test on-orbit data acquisition module 1, a plate-in calibration module 2, an adaptive channel fusion module 3, a residual phase calculation module 4, an inter-plate phase calibration module 5, a Kalman filter smoothing module 6, a soft limit phase update module 7, a convergence judgment module 8, a satellite digital beam forming module 12. Among them, the time-sharing self-test on-orbit data acquisition module 1 needs to use the feed network 9 and the coupler 10, the modules 2-8 are realized on the satellite processor 11, and the final result is transmitted to the satellite digital beam forming module 12 to control the antenna unit 13 to complete the calibration.

[0064] The time-sharing self-test on-orbit data acquisition module 1 is used to acquire the Jones matrix of each array element. The in-board calibration module 2 is connected with the time-sharing self-test on-orbit data acquisition module 1 and is used to perform in-board calibration to solve the array element amplitude and phase errors caused by physical deformation such as protrusion in the substrate and the existing polarization coupling errors. The adaptive channel fusion module 3 is connected with the in-board calibration module 2 and is used to realize the optimal synthesis of two channel signals according to the two polarization channel information. The residual phase calculation module 4 is connected with the adaptive channel fusion module 3 and is used to calculate the residual phase distribution according to the fused complex equivalent response and ideal phase and perform abnormal array element detection and elimination on the result. The inter-board phase calibration module 5 is connected with the residual phase calculation module 4 and is used to perform inter-board phase calibration according to the residual phase distribution to acquire the inter-board phase error plane coefficient and solve the influence caused by the folding deformation between the substrates. The Kalman filter smoothing module 6 is connected with the inter-board phase calibration module 5 and is used to smooth the inter-board phase error plane coefficient to reduce the influence of random fluctuations. The soft limit phase update module 7 is connected with the Kalman filter smoothing module 6 and is used to calculate the compensation phase and suppress the excessive update. The convergence judgment module 8 is connected with the soft limit phase update module 7 and the adaptive channel fusion module 3 and is used to perform threshold judgment on the array element phase update amount of each round: if the termination condition is met, the amplitude and phase coefficients after calibration are output; if the termination condition is not met, the antenna state after update is transmitted to the adaptive channel fusion module 3 for iterative operation. The on-board digital beam forming module 12 is connected with the convergence judgment module 8 and is used to control the antenna unit 13 to perform calibration output according to the received amplitude and phase calibration coefficients.

[0065] In the preferred embodiment of the application, the in-board calibration module 2 compensates by using the least square pseudo-inverse according to the acquired Jones matrix to obtain the amplitude and phase compensation coefficients of each array element: wherein is the Jones matrix of the i th array element and its conjugate transpose, λ is a damping coefficient, and I is a unit matrix. The non-diagonal elements can be approximated to 0 by using the amplitude and phase compensation coefficients to autonomously complete the in-board decoupling and amplitude and phase calibration.

[0066] As shown in Figure 2 , the time-sharing self-test on-orbit data acquisition module 1 process includes initialization 14, loading excitation sequence 15, coupling detection signal acquisition 16, signal preprocessing 17, acquiring Jones matrix 18, and storing Jones matrix 19.

[0067] Initialization 14 initializes the calibration time slot allocation, assigning different time slots to each array element for excitation to prevent mutual interference between elements. Loading the excitation sequence 15 controls different array elements to be excited with different polarization signals in different time slots. Coupled detection signal acquisition 16 synchronously receives signals from each array element through the onboard detection path. Signal preprocessing 17 performs preliminary amplitude normalization and noise filtering on the acquired signals to obtain signals at specified frequencies. Obtaining the Jones matrix 18 integrates the acquired data into a Jones matrix.

[0068]

[0069] in, The RHCP input and RHCP output are for the i-th array element; The i-th array element receives RHCP input and receives LHCP output. The i-th array element is input to LHCP and output to RHCP. The LHCP input and LHCP output are for the i-th array element.

[0070] The stored Jones matrix 19 provides the Jones matrix for subsequent intra-board decoupling and inter-board plane fitting calibration.

[0071] like Figure 3 As shown, in a preferred embodiment of the present invention, the process of the adaptive channel fusion module 3 and the residual phase calculation module 4 includes: inputting data 20 to obtain the Jones matrix after on-board calibration, calculating the energy distribution and weights 21 to obtain the complex response c of the array element in the RHCP channel. R and the complex response c of the LHCP channel L And calculate their respective energies: Calculate the adaptive fusion weights based on the results: The final composite signal of the fused output complex response 22 is calculated as: C i =α i c R (i)+(1-α i )c L (i) can achieve balanced compensation of the two polarization channels in the amplitude and phase domains, thereby realizing robust adaptive polarization synthesis; the residual phase is calculated based on the fused signal and the ideal reference phase: Φ resid,i =∠(exp(j(∠C)) i -kr i ·s0)));Subsequent anomaly detection is performed, firstly by amplitude outlier detection 24, then the median and median absolute deviation are calculated: med m =median({|C i |}), mad m =median(|Ci |-med m )+ε, judge amplitude anomaly: mag_out i =||C i |-med m |>τ m ·mad m , where τ m is amplitude empirical value, if the above formula is satisfied, it is marked as an abnormal point, then phase jump detection 25 is performed, and 2π jump is processed for residual phase distribution: Calculate difference amplitude of adjacent elements: d1=0, the median and MAD are also used for judgment: med d =median({d i}), mad d =median(|d i -med d )+ε, phase_out i =d i >τ d ·mad d , where τ d is phase empirical value, if the above formula is satisfied, it is marked as an abnormal point, and the subarray protection removes bad elements 26 in order to prevent the entire substrate from being determined as bad, the proportion of bad points in each substrate s is calculated: f s =|B∩S S | / S S , where B is the number of bad elements in a substrate, S s is the total number of elements in the same substrate, if f s >ρ, the bad element mark in the substrate is cancelled, where ρ is a probability threshold; output normal element residual phase distribution 27 output the residual phase distribution after removing bad points, as the input of subsequent subarray plane fitting, sparse correction and Kalman smoothing, so as to ensure the robust convergence and on-orbit implementability of inter-plate phase calibration process.

[0072] As Figure 4 shown, in the preferred embodiment of the application, the inter-plate phase calibration module 5 process includes: input residual phase matrix 28 to obtain the residual phase distribution after removing bad elements, error model analysis 29 to construct the actual phase residual distribution structure model of the present element: φ res (x,y)=ax+by+c+r s (x,y)+n, where x and y are the coordinates of the element in the plate, a and b correspond to the tilt coefficients of the substrate plane, c is the global phase offset, ax+by+c belongs to the plane tilt term, r s(x,y) represents diluted local anomalies, and n is random noise. Based on the error model, low-rank denoising is performed on the residual phase data matrix. The residual phase vectors of the current subarray are reconstructed into matrix M according to spatial arrangement, and singular value decomposition is performed: M = USV T By retaining the first k singular values, a low-rank approximation is achieved: M rec =US k V T After filtering out high-frequency noise and random disturbances, the denoised phase is obtained: φ = vec(M rec ); Plane fitting 31: On the low-rank denoised phase, perform weighted least squares plane fitting: The solution is: [a; b; c] = (A T WA) -1 A T Wφ, where A=[x m ,y m ,1],x m y m The x, y coordinates of all array elements on the m-th substrate, W = diag(w i The magnitude weights are obtained; ISTA sparse correction 32 calculates local anomalies based on the calculated plane coefficients [a; b; c]: r0 = φ - A * [a; b; c], using the L1 norm-constrained sparse reconstruction model: The ISTA iterative shrinkage threshold algorithm is used to solve the problem. The original phase can be corrected based on the calculated sparse residual: φ corr =φ-r s ; Plane fitting 33 Based on the sparse correction results, perform weighted least squares plane fitting to obtain new [a; b; c]; Output substrate phase error plane coefficients 34 Save the obtained new fitting coefficients for later use.

[0073] like Figure 5 As shown, in a preferred embodiment of the present invention, the Kalman filter smoothing module 6, the soft-limited phase update module 7, and the convergence judgment module 8 include the following processes: inputting plane coefficients 35 to obtain the previously calculated fitted substrate phase error plane coefficients; Kalman filter smoothing 36 dynamically estimating and smoothing the coefficient sequence so that the plane parameters maintain temporal continuity and physical consistency, and the plane coefficient state is: x k =[a k ,b k ,c k ] T The process model that changes with iteration is: x k =Fx k-1 +w k Where F is the state transition matrix, I is the identity matrix, and w k~N(0,Q) represents process noise, and the observation equation is: z k =Hx k +v k Where H is the observation matrix, v k ~N(0,R) represents the measurement noise. Prediction steps: P k|k-1 =FP k-1|k-1 F T +Q, Update steps: K k =P k|k-1 H T HP k|k-1 H T +R) -1 , P k|k =(IK k H)P k|k-1 The final output The subarray plane coefficients are smoothed; soft-constrained phase update 37 first calculates the compensated phase: Δφ(x,y)=-γ plane (ax+by+c), where γ plane It involves adding amplitude limiting weights, and then using a soft limiting function to suppress excessive updates: Δφ soft =φ max tanh(Δφ / φ max ), where φ max If the maximum update value is set, then the cumulative phase compensation amount is: φ cum (i)=φ cum (i)+Δφ soft (i); Convergence criterion 38 After each round of plane fitting and phase compensation update, calculate the maximum absolute value of the phase update amount of all array elements: and the set convergence threshold ε φ The algorithm is compared, and when the maximum single-step compensation amount is lower than the threshold, it is automatically determined that the algorithm has converged and the iteration is terminated. Otherwise, the current antenna state is input to the adaptive channel fusion module for iterative calculation. The onboard digital beamforming module 12 receives the intra-board calibration coefficient and the inter-board calibration phase compensation result for compensation: the intra-board calibration coefficient is applied to the complex I / Q signal of each polarization channel in matrix form to achieve array element-level decoupling and amplitude-phase equalization; the inter-board phase compensation amount is superimposed on the beamforming weight vector in scalar form to achieve inter-array phase reference alignment and overall wavefront flattening.

[0074] The low-Earth orbit satellite ultra-large folded array antenna beam and polarization adaptive calibration system of this invention has good engineering applicability and can be applied to satellites for antenna pattern calibration and performance compensation. The system is implemented using existing mature on-board hardware components, making it suitable for large-scale deployment. The core algorithm of the system has low computational complexity, enabling implementation and deployment on resource-constrained satellite platforms.

[0075] The low-orbit satellite ultra-large folded array antenna beam and polarization adaptive calibration system of the present invention has many beneficial effects:

[0076] 1. Effectively compensates for folding errors between substrates. The system utilizes an iterative joint optimization algorithm based on plane fitting to estimate the orientation deviation of each substrate and dynamically correct surface distortion caused by unfolding errors.

[0077] 2. Significantly improved on-orbit pattern performance; the main lobe direction of the array after calibration... Figure 1 The consistency is significantly improved. The cross-polarization isolation is increased from 0.63dB before calibration to more than 50dB, the sidelobe level is reduced from -6dB to below -13dB, and the main lobe pointing error is reduced to within 0.001°, thus ensuring the high-precision shaping capability of the star carrier beam.

[0078] 3. Enhanced system adaptability and anti-interference capability: Through energy fusion, adaptive weighting and abnormal array element removal mechanisms, this invention can maintain stable calibration performance when there are partial array element failures, noise interference or link drift, ensuring the robustness of the antenna pattern.

[0079] 4. Comprehensive improvement of satellite on-orbit performance: In typical spaceborne communication scenarios, this invention significantly improves beam pointing accuracy and polarization purity, and achieves precise compensation for internal antenna deformation and folding errors, thereby ensuring high gain, high fidelity and high stability of the spaceborne communication system.

[0080] In summary, the low-orbit satellite ultra-large folded array antenna beam and polarization adaptive calibration system of the present invention realizes autonomous on-orbit independent calibration, which not only calibrates the main lobe direction of the echo beam and reduces side lobe energy leakage, but also improves the polarization isolation between channels. It integrates intra-board calibration and inter-board calibration, providing strong technical support for on-orbit operation calibration of satellite antennas.

[0081] The embodiments described above are merely illustrative of specific implementations of the present invention, and while the descriptions are detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A beam and polarization adaptive calibration system for a low-orbit satellite ultra-large folded array antenna, characterized in that, include: The time-division self-test on-orbit data acquisition module is used to measure the left-hand and right-hand circular polarization channel outputs of each array element by excitation with left-hand and right-hand circular polarization signals in different calibration time slots, and to acquire the Jones matrix data of each array element for subsequent calibration processes. The in-board calibration module is connected to the time-division self-test on-orbit data acquisition module and is used to compensate for the amplitude and phase errors of the array elements caused by physical deformations such as protrusions inside the substrate and the existing polarization coupling errors based on the measured Jones matrix. An adaptive channel fitting module, connected to the in-board calibration module, calculates adaptive fitting weights based on the calibrated bipolar channel data to achieve optimal synthesis of the bipolar channels and subsequently provides the data required for inter-board calibration. The residual phase calculation module is connected to the adaptive channel fitting module. Based on the complex response of the adaptive fusion and the ideal reference phase, it calculates the phase residual, performs anomaly detection to remove bad elements, and obtains the residual phase distribution of normal array elements. The inter-board phase calibration module is connected to the residual phase calculation module. Based on the residual phase distribution of the normal array elements, it establishes the actual phase distribution structure model of the array elements of the same substrate, performs error calibration step by step, performs low-rank denoising for high-frequency noise and random jitter, performs plane fitting based on the denoised phase, calculates the existing coefficient residual, corrects the original phase, and performs substrate error plane coefficient fitting based on the corrected phase. The Kalman filter smoothing module, connected to the inter-board phase calibration module, dynamically estimates and smooths the planar coefficients obtained for each subarray substrate, reducing the impact of random fluctuations caused by measurement noise, array element errors and numerical fitting errors on the sparse fitting, so that the planar parameters maintain continuity in time and physical consistency. The soft-limited phase update module is connected to the Kalman filter smoothing module. It calculates the phase compensation amount based on the final plane coefficients of the Kalman filter smoothing, and uses a nonlinear compression function to suppress excessive updates and iteratively calculates the cumulative phase compensation amount. The convergence judgment module is connected to the soft-limited phase update module and the adaptive channel fitting module. After each round of plane fitting and phase compensation update, it calculates the maximum absolute value of the phase update of all array elements and compares it with the set convergence threshold. If the termination condition is not met, the data is transmitted to the adaptive channel fitting module for iteration. If the termination condition is met, the amplitude and phase calibration coefficients obtained from the in-board calibration and inter-board calibration are saved and the iteration is terminated. The onboard digital beamforming module is connected to the convergence judgment module and performs compensation calibration on each array element based on the amplitude and phase calibration coefficients obtained from in-plane calibration and inter-plane calibration.

2. The low-orbit satellite ultra-large folded array antenna beam and polarization adaptive calibration system according to claim 1, characterized in that, The time-sharing self-test on-orbit data acquisition module includes: The spaceborne coupler, connected to the array element feed path, is used to realize time-division excitation and acquisition of array element signals in different calibration time slots; The switching control unit controls the excitation sequence of left-hand and right-hand circular polarization signals according to the onboard time synchronization pulse; The signal acquisition and processing unit obtains the Jones matrix of each array element by synchronously sampling and measuring the left-hand and right-hand circular polarization channel data, which is then used for subsequent calibration processing.

3. The low-orbit satellite ultra-large folded array antenna beam and polarization adaptive calibration system according to claim 1, characterized in that, The on-board calibration module includes: Least squares pseudo-inverse compensation approximates off-diagonal elements to 0, performs matrix calculations on the Jones matrix of the array elements, and obtains the amplitude and phase compensation coefficients of the array elements: in Let I be the Jones matrix of the i-th element and its conjugate transpose, λ be the damping coefficient, and I be the identity matrix.

4. The low-orbit satellite ultra-large folded array antenna beam and polarization adaptive calibration system according to claim 1, characterized in that, The adaptive fusion channel module includes: Calculate the energy distribution and weighting units, and calculate the fusion weights based on the energy ratio of the polarization channels. and The fusion weights can be obtained; The fusion output complex response unit fuses the two polarization channel signals according to the calculated fusion weights.

5. The low-orbit satellite ultra-large folded array antenna beam and polarization adaptive calibration system according to claim 1, characterized in that, The residual phase calculation module includes: Calculate the residual phase unit, and calculate the phase residual based on the adaptively fused complex response and the ideal reference phase; The amplitude outlier detection unit performs amplitude outlier detection based on the median absolute deviation (MAD). It calculates the median and median absolute deviation from the complex equivalent response of each fused array element and then performs amplitude anomaly detection: ||C i |-med m |>τ m ·mad m C i It is the complex equivalent response of each array element after fusion, med m It is the median, MACD m It is the median absolute deviation, τ m It is an empirical value of the amplitude; The phase jump detection unit calculates the differential modulus of the residual phase of adjacent array elements, and calculates its median and median absolute deviation to perform phase jump detection: d i >τ d ·mad d , where d i It is the difference modulus of adjacent array elements, τ d It is the phase empirical value, mad d It is the absolute deviation of the median; The subarray protection removes defective cells to prevent the entire substrate from being judged as defective. The proportion of defective cells in each substrate is calculated. If it exceeds the empirical threshold ρ, the defective cell marking in the substrate is removed, and then the cells marked as defective cells are removed.

6. The low-orbit satellite ultra-large folded array antenna beam and polarization adaptive calibration system according to claim 1, characterized in that, The inter-board phase calibration module includes: The error model analysis unit establishes the actual phase distribution structure model of the array elements on the same substrate based on the residual phase distribution of the normal array elements. The low-rank denoising unit performs low-rank denoising on high-frequency noise and random jitter. The planar fitting unit calculates the planar residual coefficients in the phase residual by performing weighted least squares fitting based on the amplitude weights of different array elements. The ISTA sparse correction unit uses the Iterative Shrink Threshold Algorithm (ISTA) to calculate and remove the non-smooth parts of the residual phase during sparse correction, thereby achieving higher-precision planar calibration.

7. The low-orbit satellite ultra-large folded array antenna beam and polarization adaptive calibration system according to claim 1, characterized in that, The soft-limited phase update module includes: The phase compensation calculation unit calculates the phase compensation amount based on the final plane coefficients smoothed by the Kalman filter. To suppress excessively large update units, a soft limit is applied using the hyperbolic tangent function and the resulting phase compensation: Δφ. soft =φ max tanh(Δφ / φ max ), where Δφ is the calculated phase compensation amount, φ max It limits the maximum experience points.

8. The low-Earth orbit satellite ultra-large folded array antenna beam and polarization adaptive calibration system as described in any one of claims 1-7, characterized in that, Includes the following steps: The satellite coupler, switching control unit, and signal acquisition unit of the control array antenna are used to acquire the Jones matrix of each array element. For the Jones matrix of each array element, the least squares pseudo-inverse is obtained, and the physical deformation inside the substrate is calibrated within the substrate to obtain the calibrated amplitude and phase coefficients. The adaptive fusion weight is calculated based on the energy of the calibrated two-polarization channel data, and the two signals are fused. The phase residual between the complex equivalent response of the fused signal and the ideal reference phase is calculated, and amplitude outlier detection, phase jump detection and subarray protection are performed based on the median absolute deviation (MAD). Bad elements are removed to obtain the phase residual of the normal array elements. Low-rank decomposition is performed on the phase residual of the pair to filter out high-frequency noise and random jitter. Then, weighted least squares plane fitting is performed to obtain smooth phase error. Then, sparse correction is performed using an iterative shrinking threshold algorithm to remove non-smooth error. Based on the corrected phase, weighted least squares is used to fit the substrate error plane coefficient. The obtained substrate error plane coefficients are smoothed by Kalman filtering to reduce random fluctuations that may occur during iteration; The compensation phase is calculated based on the smoothed substrate error plane coefficient, and the excessive update is suppressed by the nonlinear compression function of hyperbolic tangent. The cumulative phase compensation amount is then calculated. Based on the cumulative phase compensation amount, calculate the maximum absolute value of the new round of iteration update amount, compare it with the convergence threshold, and if convergence fails, input the current antenna state into the adaptive channel fusion module for iterative calculation; if convergence occurs, exit the iteration. The amplitude and phase calibration coefficients obtained from the in-plane calibration and the phase calibration coefficients obtained from the inter-plane calibration are loaded into the complex weight control module of the spaceborne digital beamforming module. The in-plane calibration coefficients are applied to the complex I / Q signals of each polarization channel in matrix form to achieve array element-level decoupling and amplitude and phase equalization. The inter-plane phase compensation is superimposed on the beamforming weight vector in scalar form to achieve phase reference alignment between subarrays and overall wavefront flattening.

Images