A 30-meter microwave anechoic chamber high-precision calibration device optimization algorithm

Abstract

The present application relates to a kind of 30 meters microwave darkroom high-precision calibration device optimization algorithm, belong to microwave darkroom measurement calibration technical field.The present application eliminates the coupling interference caused by mechanical jitter of calibration device, environmental stray reflection by adaptive error decoupling algorithm, optimizes the effective test area determination logic of quiet zone, substantially improves the calibration precision and operation efficiency of 30 meters microwave darkroom far-field test, effectively solves the technical problem of poor consistency of large-size microwave darkroom global calibration, can be widely applied to radar antenna, microwave device, wireless terminal far-field performance test calibration scene.

Description

Technical Field

[0001] This invention relates to the field of microwave anechoic chamber metrology and calibration technology, and more specifically, to an optimized algorithm for a high-precision calibration device for a 30-meter microwave anechoic chamber. Background Technology

[0002] A 30-meter microwave anechoic chamber is a core infrastructure for testing the far-field performance of large antennas, radar systems, and high-power microwave devices. Its calibration accuracy directly determines the validity and reliability of electromagnetic test data. Compared to small and medium-sized microwave anechoic chambers, 30-meter-class large-size anechoic chambers are characterized by a large test space span, a wide quiet zone coverage, superposition of stray reflections from multiple interfaces, and significant accumulation of three-dimensional scanning travel errors. This places higher demands on the global adaptability, error suppression capability, and real-time performance of calibration algorithms. Currently, the industry commonly uses the traditional free-space standing wave ratio (VSWR) method for 30-meter microwave anechoic chamber calibration, combined with a fixed-parameter calibration device, to complete the detection of basic parameters such as quiet zone reflection level and spatial attenuation. This technical solution has several inherent flaws: First, the traditional VSWR algorithm only analyzes the VSWR amplitude in a single dimension, failing to decompose the vector components of direct signals and multipath reflected signals, and making it difficult to isolate stray reflection interference from side walls, ground, and top surfaces, resulting in large calibration errors for quiet zone reflection levels. Second, the calibration process does not fully consider the amplitude-phase error coupling problem caused by the three-dimensional scanning frame pose deviation, antenna phase center offset, and environmental temperature and humidity fluctuations, leading to the superposition of multi-dimensional errors and poor consistency in spatial attenuation calibration over a 30-meter distance. Third, the traditional calibration algorithm uses a fixed iteration threshold and a static calculation model, which cannot adapt to the nonlinear distribution characteristics of electromagnetic parameters across the entire 30-meter anechoic chamber, resulting in insufficient calibration accuracy in local areas, and requiring numerous iterations and low efficiency. Fourth, the existing algorithm lacks a bidirectional coordinate system correction mechanism, and the conversion deviation between the anechoic chamber test coordinate system and the coordinate system of the device under test cannot be effectively corrected, further reducing the calibration accuracy of the far-field radiation pattern and RCS parameters of large antennas.

[0003] Existing technologies primarily focus on single-parameter calibration or hardware improvements for small and medium-sized anechoic chambers. Dedicated algorithm systems for multi-parameter coupled calibration, global error decoupling, and efficient computational optimization for 30-meter wide-span microwave anechoic chambers are largely lacking, failing to meet the testing and calibration requirements of high-precision radar and aerospace microwave equipment. Therefore, there is an urgent need to develop a calibration device optimization algorithm that is adaptable to the 30-meter microwave anechoic chamber scenario, offering high precision, high efficiency, and excellent global consistency. Summary of the Invention

[0004] This invention aims to provide an optimized algorithm for a high-precision calibration device in a 30-meter microwave anechoic chamber, addressing the problems of weak reflection interference suppression, multi-dimensional error coupling, uneven global calibration accuracy, and low computational efficiency in existing calibration algorithms for large-size microwave anechoic chamber scenarios. It achieves integrated high-precision calibration of the quiet zone performance, spatial electromagnetic parameters, and coordinate system pose of a 30-meter microwave anechoic chamber, improving the accuracy and stability of far-field testing of large microwave equipment. To solve the above technical problems, the first aspect of this invention provides an optimized algorithm for a high-precision calibration device in a 30-meter microwave anechoic chamber, comprising the following specific steps: S1. Calibration system parameter initialization and data acquisition: Build a three-dimensional scanning calibration device adapted to a 30-meter microwave anechoic chamber, and complete the initialization of scanning stroke, antenna gain, test frequency band, and coordinate system reference parameters; collect standing wave test data, spatial attenuation data, and amplitude and phase characteristic data of the quiet zone of the entire anechoic chamber, construct the original calibration dataset, and simultaneously collect environmental temperature and humidity and scanning frame mechanical pose parameters to establish an environmental-mechanical coupling parameter library; S2. Multipath Reflection Signal Vector Decomposition Modeling: Based on the spatial structure characteristics of a 30-meter anechoic chamber, a vector superposition model of direct signal and multipath reflection signal is constructed. The standing wave data is vector decomposed to separate the effective direct electromagnetic signal and stray reflection signal. The amplitude weight and phase offset of each path reflection signal are calculated to complete the quantitative identification of stray reflection interference. S3. Multi-dimensional error decoupling and parameter correction: Based on the principle of rigid transformation of spatial coordinate system, construct homogeneous transformation matrices of darkroom test coordinate system, scanning frame coordinate system and device under test coordinate system to realize bidirectional pose transformation of three coordinate systems; establish a multi-parameter error coupling model, and use iterative sequence quadratic optimization algorithm to solve the optimal solution of nonlinear error to complete the decoupling compensation and correction of coupling error. S4. Adaptive Judgment and Global Calibration Optimization of Quiet Zone Performance: Based on the quiet zone size and electromagnetic parameter distribution characteristics of the 30-meter anechoic chamber, an adaptive iteration threshold is set; combined with the reflectivity level calculation model, the electromagnetic parameters of the entire anechoic chamber are corrected point by point, the effective quiet zone range is selected, and the global calibration parameter optimization is completed. S5. Calibration result verification and data output: Compare the optimized calibration data with the standard anechoic chamber reference data. If the deviation is less than the preset threshold, output the final calibration parameters. If the deviation exceeds the standard, iterate and optimize until the accuracy meets the standard.

[0005] Preferably, the standing wave in the anechoic chamber is equivalent to the vector sum of the direct signal and the multipath reflected signal. By performing operations on the real and imaginary parts in the complex domain, the electromagnetic signal parameters of different propagation paths are extracted to distinguish between the effective test signal and the stray interference signal.

[0006] Preferably, in step S3, a nonlinear least squares optimization objective function is constructed, and the optimal amplitude and phase calibration coefficients and pose correction parameters are iteratively solved to eliminate calibration deviations caused by the three-dimensional travel error of the scanning frame and the offset of the antenna phase center.

[0007] Preferably, in step S4, the adaptive iteration threshold is dynamically adjusted according to the reflection intensity of different areas of the darkroom. The iteration accuracy is improved in areas with high reflection interference, and the calculation process is simplified in areas with low interference, thus balancing calibration accuracy and calculation efficiency.

[0008] Preferably, it is compatible with the 1GHz-120GHz microwave test frequency band and can achieve integrated calibration of reflection level, spatial attenuation, antenna amplitude and phase parameters, and coordinate system pose in a 30-meter microwave anechoic chamber quiet zone.

[0009] Preferably, in step S1, the process of constructing the environment-mechanical coupling parameter library includes: synchronously collecting environmental temperature and humidity data and encoder readings of each axis of the scanning frame at preset time intervals, establishing a temperature and humidity-mechanical deformation mapping table, and using a moving average filter to remove abnormal data points to form a coupling parameter library.

[0010] Preferably, the vector superposition model represents the total field strength at any test point in the anechoic chamber as the sum of the complex amplitudes of the direct wave and N reflected waves. The standing wave data is sparsely decomposed using the MUSIC algorithm or compressed sensing algorithm based on spatial spectrum estimation to separate the amplitude weights and phase offsets of each reflection path.

[0011] Preferably, the homogeneous transformation matrix consists of a 3×3 rotation matrix and a 3×1 translation vector, which are used to describe the attitude and position deviations of the scanning frame coordinate system relative to the darkroom coordinate system and the coordinate system of the device under test relative to the scanning frame coordinate system, respectively. The iterative sequence quadratic optimization algorithm solves the quadratic programming subproblem in each iteration and terminates when the gradient norm of the objective function is less than the set threshold or the number of iterations exceeds the upper limit.

[0012] Preferably, in step S4, the reflectivity level calculation model calculates the theoretical reflectivity level at each scanning point based on the reflectivity coefficient of the absorbing material in the anechoic chamber and the test distance, and compares it with the measured standing wave data to obtain the error correction factor; the adaptive iterative threshold is dynamically adjusted according to the root mean square value of the current correction residual, decreasing the threshold step size when the residual is large and increasing the threshold step size when the residual is small.

[0013] Preferably, in step S5, the deviation comparison uses normalized root mean square error and maximum absolute error as evaluation indicators. When both indicators are less than the preset threshold, it is determined to meet the standard. If the deviation exceeds the standard, the initial iteration point of the optimization algorithm is updated according to the deviation direction, and steps S3 to S5 are re-executed until the standard is met or the preset maximum number of iterations is reached.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. High precision and strong anti-interference capability: This invention uses vector decomposition technology to remove multi-path stray reflection interference in a 30-meter anechoic chamber, and eliminates mechanical, environmental, and pose coupling errors through a multi-parameter error decoupling algorithm. Compared with the traditional VSWR calibration algorithm, the calibration accuracy of the quiet zone reflection level is improved by more than 40%, and the spatial attenuation calibration error is controlled within ±0.2dB, making it suitable for the complex electromagnetic environment of a 30-meter large-size anechoic chamber.

[0015] 2. Excellent consistency in global calibration: For the 30-meter span of the anechoic chamber and the nonlinear distribution of parameters, an adaptive threshold iterative optimization strategy is adopted to achieve accurate and differentiated calibration of the entire anechoic chamber. This solves the problems of insufficient accuracy in local areas and poor consistency in the entire region of traditional algorithms, and effectively expands the effective quiet zone test range.

[0016] 3. Significantly improved computational efficiency: The integrated sequence secondary optimization algorithm optimizes the iteration logic, abandons the traditional fixed iteration mode, reduces invalid computation steps, and improves the calibration data processing efficiency by more than 30%, enabling rapid integrated calibration of all parameters in a 30-meter microwave anechoic chamber.

[0017] 4. Wide adaptability and strong practicality: It can be compatible with the calibration requirements of different test frequency bands and different sizes of test equipment, and realize the integrated calibration of quiet zone performance, spatial attenuation, antenna amplitude and phase parameters, and coordinate system attitude. It is widely applicable to the far-field test calibration of radar antennas, microwave devices, and aerospace electromagnetic equipment, and has extremely high engineering application value. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort. In the drawings: Figure 1 This is a flowchart of the optimization algorithm for a 30-meter microwave anechoic chamber high-precision calibration device according to an embodiment of the present invention. Detailed Implementation

[0019] Hereinafter, exemplary embodiments according to the present invention will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of the present invention, and not all embodiments of the present invention. It should be understood that the present invention is not limited to the exemplary embodiments described herein.

[0020] As stated in the background section above, the present invention aims to overcome the problem that existing related technologies mostly focus on single-parameter calibration or hardware device improvement for small and medium-sized anechoic chambers, and lack a dedicated algorithm system for multi-parameter coupling calibration, global error decoupling, and efficient computation optimization for 30-meter large-span microwave anechoic chambers, which cannot meet the testing and calibration requirements of high-precision radar and aerospace microwave equipment.

[0021] Example 1 Figure 1 This is a flowchart of an optimization algorithm for a 30-meter microwave anechoic chamber high-precision calibration device according to an embodiment of the present invention, including the following specific steps: S1. Calibration system parameter initialization and data acquisition: Build a three-dimensional scanning calibration device adapted to a 30-meter microwave anechoic chamber, and complete the initialization of scanning stroke, antenna gain, test frequency band, and coordinate system reference parameters; collect standing wave test data, spatial attenuation data, and amplitude and phase characteristic data of the quiet zone of the entire anechoic chamber, construct the original calibration dataset, and simultaneously collect environmental temperature and humidity and scanning frame mechanical pose parameters to establish an environmental-mechanical coupling parameter library; S2. Multipath Reflection Signal Vector Decomposition Modeling: Based on the spatial structure characteristics of a 30-meter anechoic chamber, a vector superposition model of direct signal and multipath reflection signal is constructed. The standing wave data is vector decomposed to separate the effective direct electromagnetic signal and stray reflection signal. The amplitude weight and phase offset of each path reflection signal are calculated to complete the quantitative identification of stray reflection interference. S3. Multi-dimensional error decoupling and parameter correction: Based on the principle of rigid transformation of spatial coordinate system, construct homogeneous transformation matrices of darkroom test coordinate system, scanning frame coordinate system and device under test coordinate system to realize bidirectional pose transformation of three coordinate systems; establish a multi-parameter error coupling model, and use iterative sequence quadratic optimization algorithm to solve the optimal solution of nonlinear error to complete the decoupling compensation and correction of coupling error. S4. Adaptive Judgment and Global Calibration Optimization of Quiet Zone Performance: Based on the quiet zone size and electromagnetic parameter distribution characteristics of the 30-meter anechoic chamber, an adaptive iteration threshold is set; combined with the reflectivity level calculation model, the electromagnetic parameters of the entire anechoic chamber are corrected point by point, the effective quiet zone range is selected, and the global calibration parameter optimization is completed. S5. Calibration result verification and data output: Compare the optimized calibration data with the standard anechoic chamber reference data. If the deviation is less than the preset threshold, output the final calibration parameters. If the deviation exceeds the standard, iterate and optimize until the accuracy meets the standard.

[0022] Specifically, the vector decomposition modeling in step S2 involves: equating the standing wave in the anechoic chamber space to the vector sum of the direct signal and the multipath reflected signal; extracting the electromagnetic signal parameters of different propagation paths through the separation operation of the real and imaginary parts in the complex domain; accurately distinguishing the effective test signal from the stray interference signal; and solving the problem of difficulty in distinguishing the superposition of multiple reflected signals under a long-distance propagation of 30 meters.

[0023] Furthermore, the standing wave in the anechoic chamber is equivalent to the vector sum of the direct signal and the multipath reflected signal. By performing operations on the real and imaginary parts in the complex domain, the electromagnetic signal parameters of different propagation paths are extracted to distinguish between the effective test signal and the stray interference signal.

[0024] Furthermore, in step S3, a nonlinear least squares optimization objective function is constructed, and the optimal amplitude and phase calibration coefficients and pose correction parameters are iteratively solved to eliminate calibration deviations caused by the three-dimensional travel error of the scanning frame and the offset of the antenna phase center.

[0025] The error decoupling process described in step S3 involves constructing a nonlinear least squares optimization objective function and iteratively solving for the optimal amplitude and phase calibration coefficients and pose correction parameters to eliminate calibration deviations caused by X / Y / Z three-dimensional travel errors of the scanning frame and antenna phase center offset.

[0026] Furthermore, in step S4, the adaptive iteration threshold is dynamically adjusted according to the reflection intensity of different areas of the darkroom. The iteration accuracy is improved in high-reflection interference areas, and the calculation process is simplified in low-interference areas, thus balancing calibration accuracy and calculation efficiency.

[0027] In step S4, the adaptive iteration threshold dynamically adjusts the number of iterations based on the reflection intensity of different areas in the darkroom. This increases the iteration accuracy in areas with high reflection interference and simplifies the calculation process in areas with low interference, thus balancing overall calibration accuracy and computational efficiency.

[0028] Furthermore, it is compatible with the 1GHz-120GHz microwave test frequency band and can achieve integrated calibration of reflection level, spatial attenuation, antenna amplitude and phase parameters, and coordinate system pose in a 30-meter microwave anechoic chamber quiet zone.

[0029] Furthermore, in step S1, the construction process of the environment-mechanical coupling parameter library includes: synchronously collecting environmental temperature and humidity data and encoder readings of each axis of the scanning frame at preset time intervals, establishing a temperature and humidity-mechanical deformation mapping table, and using a moving average filter to remove abnormal data points to form a coupling parameter library.

[0030] Furthermore, in step S2, the vector superposition model represents the total field strength at any test point in the anechoic chamber as the sum of the complex amplitudes of the direct wave and N reflected waves. The standing wave data is sparsely decomposed using the MUSIC algorithm based on spatial spectrum estimation or the compressed sensing algorithm to separate the amplitude weights and phase offsets of each reflection path.

[0031] Furthermore, in step S3, the homogeneous transformation matrix consists of a 3×3 rotation matrix and a 3×1 translation vector, which are used to describe the attitude and position deviations of the scanning frame coordinate system relative to the darkroom coordinate system and the coordinate system of the device under test relative to the scanning frame coordinate system, respectively; the iterative sequence quadratic optimization algorithm solves the quadratic programming subproblem in each iteration and terminates when the gradient norm of the objective function is less than a set threshold or the number of iterations exceeds the upper limit.

[0032] Furthermore, in step S4, the reflectivity level calculation model calculates the theoretical reflectivity level at each scanning point based on the reflection coefficient of the anechoic chamber absorbing material and the test distance, and compares it with the measured standing wave data to obtain the error correction factor; the adaptive iterative threshold is dynamically adjusted according to the root mean square value of the current correction residual, decreasing the threshold step size when the residual is large and increasing the threshold step size when the residual is small.

[0033] Furthermore, in step S5, the deviation comparison uses normalized root mean square error and maximum absolute error as evaluation indicators. When both indicators are less than the preset threshold, it is determined to meet the standard. If the deviation exceeds the standard, the initial iteration point of the optimization algorithm is updated according to the deviation direction, and steps S3 to S5 are re-executed until the standard is met or the preset maximum number of iterations is reached.

[0034] Example 2 This embodiment discloses an optimized algorithm for a high-precision calibration device in a 30-meter microwave anechoic chamber, applied to a fully automated three-dimensional scanning calibration system for a 30-meter far-field microwave anechoic chamber, and adapted to the 1GHz-120GHz microwave test frequency band. The specific implementation steps are as follows: The first step is system initialization and data acquisition. The 30-meter microwave anechoic chamber calibration device is activated, and the maximum X / Y / Z travel parameters of the 3D scanning frame, the standard horn antenna gain, and the test frequency band parameters are initialized. The anechoic chamber reference coordinate system is calibrated, and standard environmental parameters of 25℃ and 50% humidity are acquired. Fully automatic scanning is initiated, traversing the entire quiet zone of the anechoic chamber, acquiring spatial standing wave data, multi-point spatial attenuation data, and antenna amplitude and phase test data to construct the original calibration dataset. The number of sampling points is set to 1024 points evenly distributed throughout the entire area to ensure complete data coverage.

[0035] The second step is multipath reflection signal vector decomposition. The original calibration dataset is imported, and the standing wave signal is decomposed in the complex domain. The amplitude and phase parameters of the direct effective signal, the reflected signal from the anechoic chamber sidewall, and the stray reflected signals from the ground and top surface are extracted respectively. The weight ratio of each interference signal is calculated to complete the quantization and separation of stray interference and eliminate the test interference caused by the superposition of multiple reflection signals in a large space.

[0036] The third step is multi-dimensional error decoupling and correction. A homogeneous transformation matrix of three coordinate systems is constructed to complete the bidirectional pose transformation of the anechoic chamber coordinate system, the scanning gantry coordinate system, and the coordinate system of the device under test. A coupled model of amplitude and phase error, mechanical travel error, and environmental error is built. An iterative sequence quadratic optimization algorithm is used to iterate 20 times to solve for the optimal calibration coefficients, and to complete the compensation and correction of various coupled errors, correcting the cumulative deviation of the scanning gantry during long-distance travel and the antenna phase center offset error.

[0037] The fourth step is adaptive global calibration and optimization. Iteration thresholds are dynamically set based on the reflection intensity of different areas within the anechoic chamber. High-precision iterative calculations are used for high-reflection areas at the edges of the anechoic chamber, while conventional iterative calculations are used for low-interference areas in the central quiet zone. The global quiet zone reflectivity level, spatial attenuation uniformity, and amplitude-phase consistency parameters are calculated to select the effective quiet zone range for the 30-meter anechoic chamber, thus completing the global parameter optimization and calibration.

[0038] The fifth step is result verification and output. The optimized calibration parameters are compared with the national metrological standard anechoic chamber reference data. In this embodiment, the calibration deviation is less than 0.2dB, which meets the high-precision calibration requirements. Finally, the anechoic chamber quiet zone performance parameters, spatial attenuation parameters, amplitude and phase calibration parameters, and coordinate system correction parameters are output, completing the entire calibration process.

[0039] Tests have shown that, compared to traditional calibration algorithms, the algorithm in this embodiment significantly improves global calibration accuracy and reduces calibration time by 28%. It effectively solves the problems of uneven calibration accuracy and insufficient interference suppression in a large space like a 30-meter microwave anechoic chamber, and fully meets the requirements for high-precision electromagnetic testing and measurement.

[0040] Those skilled in the art will readily conceive of embodiments of the invention upon consideration of the specification and practice of the methods disclosed herein. The invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein.

[0041] It should be understood that the present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. An optimization algorithm for a high-precision calibration device for a 30-meter microwave anechoic chamber, characterized in that, Includes the following steps: S1. Calibration system parameter initialization and data acquisition: Build a three-dimensional scanning calibration device adapted to a 30-meter microwave anechoic chamber, and complete the initialization of scanning stroke, antenna gain, test frequency band, and coordinate system reference parameters; collect standing wave test data, spatial attenuation data, and amplitude and phase characteristic data of the quiet zone of the entire anechoic chamber, construct the original calibration dataset, and simultaneously collect environmental temperature and humidity and scanning frame mechanical pose parameters to establish an environmental-mechanical coupling parameter library; S2. Multipath Reflection Signal Vector Decomposition Modeling: Based on the spatial structure characteristics of a 30-meter anechoic chamber, a vector superposition model of direct signal and multipath reflection signal is constructed. The standing wave data is vector decomposed to separate the effective direct electromagnetic signal and stray reflection signal. The amplitude weight and phase offset of each path reflection signal are calculated to complete the quantitative identification of stray reflection interference. S3. Multi-dimensional error decoupling and parameter correction: Based on the principle of rigid transformation of spatial coordinate system, construct homogeneous transformation matrices of darkroom test coordinate system, scanning frame coordinate system and device under test coordinate system to realize bidirectional pose transformation of three coordinate systems; establish a multi-parameter error coupling model, and use iterative sequence quadratic optimization algorithm to solve the optimal solution of nonlinear error to complete the decoupling compensation and correction of coupling error. S4. Adaptive Judgment and Global Calibration Optimization of Quiet Zone Performance: Based on the quiet zone size and electromagnetic parameter distribution characteristics of the 30-meter anechoic chamber, an adaptive iteration threshold is set; combined with the reflectivity level calculation model, the electromagnetic parameters of the entire anechoic chamber are corrected point by point, the effective quiet zone range is selected, and the global calibration parameter optimization is completed. S5. Calibration result verification and data output: Compare the optimized calibration data with the standard anechoic chamber reference data. If the deviation is less than the preset threshold, output the final calibration parameters. If the deviation exceeds the standard, iterate and optimize until the accuracy meets the standard.

2. The optimization algorithm for the 30-meter microwave anechoic chamber high-precision calibration device according to claim 1, characterized in that... In step S2, the standing wave in the anechoic chamber is equivalent to the vector sum of the direct signal and the multipath reflected signal. By performing operations on the real and imaginary parts in the complex domain, the electromagnetic signal parameters of different propagation paths are extracted to distinguish between the effective test signal and the stray interference signal.

3. The optimized algorithm for the 30-meter microwave anechoic chamber high-precision calibration device according to claim 1, characterized in that, In step S3, a nonlinear least squares optimization objective function is constructed, and the optimal amplitude and phase calibration coefficients and pose correction parameters are iteratively solved to eliminate calibration deviations caused by scanning frame three-dimensional travel error and antenna phase center offset.

4. The optimized algorithm for the 30-meter microwave anechoic chamber high-precision calibration device according to claim 1, characterized in that, In step S4, the adaptive iteration threshold is dynamically adjusted according to the reflection intensity of different areas of the darkroom. The iteration accuracy is improved in high-reflection interference areas, and the calculation process is simplified in low-interference areas, taking into account both calibration accuracy and calculation efficiency.

5. The optimized algorithm for the 30-meter microwave anechoic chamber high-precision calibration device according to claim 1, characterized in that, It is compatible with the 1GHz-120GHz microwave test frequency band and can achieve integrated calibration of reflection level, spatial attenuation, antenna amplitude and phase parameters, and coordinate system pose in a 30-meter microwave anechoic chamber quiet zone.

6. The optimized algorithm for the 30-meter microwave anechoic chamber high-precision calibration device according to claim 1, characterized in that, In step S1, the construction process of the environment-mechanical coupling parameter library includes: synchronously collecting environmental temperature and humidity data and encoder readings of each axis of the scanning frame at preset time intervals, establishing a temperature and humidity-mechanical deformation mapping table, and using a moving average filter to remove abnormal data points to form a coupling parameter library.

7. The optimized algorithm for the 30-meter microwave anechoic chamber high-precision calibration device according to claim 1, characterized in that, In step S2, the vector superposition model represents the total field strength at any test point in the darkroom space as the sum of the complex amplitudes of the direct wave and N reflected waves. The standing wave data is sparsely decomposed using the MUSIC algorithm based on spatial spectrum estimation or the compressed sensing algorithm to separate the amplitude weights and phase offsets of each reflection path.

8. The optimized algorithm for the 30-meter microwave anechoic chamber high-precision calibration device according to claim 1, characterized in that, In step S3, the homogeneous transformation matrix consists of a 3×3 rotation matrix and a 3×1 translation vector, which are used to describe the attitude and position deviations of the scanning frame coordinate system relative to the darkroom coordinate system and the coordinate system of the device under test relative to the scanning frame coordinate system, respectively. The iterative sequence quadratic optimization algorithm solves the quadratic programming subproblem in each iteration and terminates when the gradient norm of the objective function is less than a set threshold or the number of iterations exceeds the upper limit.

9. The optimized algorithm for the 30-meter microwave anechoic chamber high-precision calibration device according to claim 1, characterized in that, In step S4, the reflectivity level calculation model calculates the theoretical reflectivity level at each scanning point based on the reflection coefficient of the anechoic chamber absorbing material and the test distance, and compares it with the measured standing wave data to obtain the error correction factor; the adaptive iterative threshold is dynamically adjusted according to the root mean square value of the current correction residual, decreasing the threshold step size when the residual is large and increasing the threshold step size when the residual is small.

10. The optimization algorithm for the 30-meter microwave anechoic chamber high-precision calibration device according to claim 1, characterized in that, In step S5, the deviation comparison uses normalized root mean square error and maximum absolute error as evaluation indicators. When both indicators are less than the preset threshold, it is determined to meet the standard. If the deviation exceeds the standard, the initial iteration point of the optimization algorithm is updated according to the deviation direction, and steps S3 to S5 are re-executed until the standard is met or the preset maximum number of iterations is reached.

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