A method for amplitude and phase probe compensation and spectral filtering of antenna near-field measurements

Abstract

The application belongs to the technical field of antenna measurement and communication antenna, and discloses an amplitude-phase probe compensation and spectrum filtering method for antenna near-field measurement, which comprises the following steps: selecting the type, frequency band and size parameter of a target antenna, and obtaining the planar near-field data of the target antenna through simulation; setting necessary parameters of the target antenna, and performing adaptive processing on the planar near-field data to obtain the planar near-field data after the adaptive processing; performing operation on the planar near-field data after the adaptive processing to obtain the planar spectrum of the target antenna; setting appropriate parameters for the planar spectrum, removing the high-frequency physical characteristics and high-frequency noise in K space, and obtaining the transverse spatial frequency component; calculating the wave number grid and performing phase compensation based on the necessary parameters; importing the probe far-field directional diagram data used for testing and simulation, establishing a binary first-order matrix equation set, and solving the matrix equation set by using the Cramer rule to obtain a solution; performing drawing analysis on the solution, analyzing the error, and judging the data quality.

Description

Technical Field

[0001] This invention belongs to the field of antenna measurement and communication antenna technology, specifically relating to a method for amplitude and phase probe compensation and spectrum filtering in near-field antenna measurement. Background Technology

[0002] Precise measurement of antenna radiation characteristics plays a fundamental and crucial role in modern wireless communication, radar detection, and aerospace engineering. With the rapid development of complex base station antennas and large phased array antenna systems, traditional far-field testing, limited by large test sites and stringent distance requirements, is no longer sufficient to meet the growing engineering testing demands. Planar near-field measurement technology, with its advantages of small site requirements, large information acquisition capacity, and good confidentiality, has become the mainstream solution in the current antenna testing field. Its essence is to collect amplitude and phase distribution data of the electromagnetic field on a plane close to the antenna, and then derive the far-field radiation characteristics of the antenna under test using rigorous mathematical and physical transformations (such as plane wave expansion).

[0003] It is worth noting that in actual planar near-field measurement engineering, ideal theoretical test conditions are often difficult to fully meet, inevitably introducing significant errors into the final reconstructed far-field data. On the one hand, the measurement probe is not an ideal isotropic point source; its own geometric dimensions and radiation pattern receiving characteristics will produce a strong spatial modulation effect on the acquired near-field electromagnetic waves. If the probe characteristics are not eliminated in the near-field-to-far-field transformation, the calculation accuracy of the far-field radiation pattern (especially the main lobe width and gain) will be directly reduced. On the other hand, due to the physical dimensions of the mechanical scanning frame, the actual scanning plane is necessarily finite, and this finite area data truncation will cause a significant truncation effect. At the same time, multipath reflection interference in the anechoic chamber environment and the inherent high-frequency electrical noise of the test system will also be superimposed on the sampled data. Existing conventional near-field-to-far-field transformation algorithms often lack a systematic and refined calibration and filtering mechanism when dealing with the above-mentioned probe coupling and environmental compound errors, resulting in an insurmountable accuracy bottleneck when evaluating the low sidelobe level or wide-angle radiation characteristics of the antenna; or they introduce complex matrix operations in the solution process, significantly increasing the consumption of computational resources.

[0004] Notably, introducing modern signal processing theory into the electromagnetic field plane spectrum (K-space) domain provides a superior technical approach for solving the aforementioned error coupling problem. By constructing a rigorous electromagnetic coupling model between the probe and the antenna under test in the frequency domain, complex spatial convolution can be decoupled, thus providing a theoretical basis for implementing precise amplitude and phase compensation. Simultaneously, relying on the physical aperture distribution characteristics of the antenna, setting a reasonable spectral truncation threshold in K-space can effectively separate and filter out useless evanescent waves and high-frequency spatial noise from a physical mechanism perspective. Furthermore, the entire mathematical calculation is performed in the spectral domain or on a uniform sampling surface of the far-field sphere, transforming it into more regular spectral domain multiplication, pruning, or interpolation, reducing computational complexity, facilitating debugging, and improving computational speed. Based on this, the present invention constructs a novel near-field and far-field transformation algorithm system that deeply integrates amplitude and phase probe compensation and K-space spectrum filtering mechanism. By establishing a calculation paradigm of "probe decoupling compensation - spectrum threshold filtering - far-field accurate reconstruction", it effectively suppresses probe modulation, truncation effect and multipath noise, and realizes high-precision, high-fidelity, high-computation speed and low-resource consumption far-field performance evaluation of complex antennas. Summary of the Invention

[0005] This invention aims to address the shortcomings of existing technologies and provides the following solutions:

[0006] A method for amplitude and phase probe compensation and spectrum filtering in near-field antenna measurement includes the following steps:

[0007] Select the type, frequency band, and size parameters of the target antenna, and obtain the planar near-field data of the target antenna through simulation experiments;

[0008] Set the necessary parameters for the target antenna and perform adaptation processing on the planar near-field data to obtain the adapted planar near-field data;

[0009] Mathematical operations are performed on the adapted planar near-field data to obtain the planar spectrum of the target antenna;

[0010] By setting appropriate window functions, cutoff wavenumbers, and transition bands for the plane wave spectrum, and using K-space filtering according to the evanescent wave to remove the high-frequency physical characteristics in K-space, while also removing high-frequency noise, a pure transverse spatial frequency component that will be transmitted to the far field is obtained.

[0011] Based on the necessary parameters, the wavenumber grid is calculated, and phase compensation is performed according to the physical offset in the three axes of x, y, and z.

[0012] Import the far-field radiation pattern data of the probe used for testing and simulation, then perform probe compensation calculation based on the far-field radiation pattern data, and then construct a system of two linear matrix equations. Finally, use Cramer's rule to solve the system of matrix equations and obtain the solution results.

[0013] The solution results are plotted and analyzed, and errors are analyzed to determine the data quality.

[0014] Preferably, the planar near-field data is formatted as columns, with the first row being a file header indicating the data type of the current column, the first two columns being x and y coordinates or θ and φ data recording the data location information, and subsequent columns being electric field information columns, where θ and φ are angle information on the far-field sphere with a step of dθ.

[0015] Preferably, the necessary parameters include: wavelength, distance between the antenna aperture and the probe, elevation and azimuth step, polarization direction, and probe data characteristics.

[0016] Preferably, the adapted planar near-field data is subjected to a fast Fourier transform, and zero-padding is performed around the original data. The frequency domain sampling density is increased by expanding the sampling window, thereby realizing the interpolation expression of the diagonal spectrum. At the same time, the smoothness of the far-field radiation pattern and the peak positioning accuracy are improved, but the actual spatial resolution or information content of the system is not increased, thus obtaining the planar spectrum.

[0017] Preferably, the K-space filter uses k0 as the cutoff wavenumber, which is the wavenumber corresponding to a 90° scan angle, and sets an adjustable transition start point. At this time, the window function created will completely preserve the effective frequency components below the transition start point, so that the frequency components gradually decrease and decay to 0 in the transition band.

[0018] Preferred methods for obtaining the solution include:

[0019] By rotating the measuring probe 90° around the physical axis, two sets of near-field sampling data under orthogonal polarization states are acquired, and two sets of corresponding plane wave spectrum data are obtained through Fourier transform. The relationship between the probe and the object under test pattern and the probe received data is then applied:

[0020] ,

[0021] in, The θ component represents the far-field radiation pattern of the antenna under test. This represents the θ component of the probe's far-field radiation pattern. The φ component represents the far-field radiation pattern of the antenna under test. The φ component represents the far-field radiation pattern of the probe, C represents the constant factor, j represents the imaginary unit, k represents the wavenumber, and d represents the distance between the antenna and the probe. This indicates the probe's receive output;

[0022] Using the known far-field pattern reception characteristics of the probe in the corresponding orthogonal state as coefficients, a system of two-variable linear matrix equations is constructed regarding the true plane wave spectrum of the antenna under test:

[0023] ,

[0024] in, This represents the θ component of the far-field pattern of the probe under common polarization. c1 represents the φ component of the far-field pattern of the probe under co-polarization, and c1 represents the constant factor. This represents the θ component of the far-field radiation pattern of the probe under crossover conditions. I represents the φ component of the far-field radiation pattern of the probe under cross-sectional conditions. H I represents the integral independent of the chosen variable in the case of common polarization. V This represents the integral that is independent of the chosen variable in the case of vertical polarization;

[0025] By using Cramer's rule to solve the system of two linear matrix equations point by point and calculating the ratio of the determinants of each matrix, the orthogonal components of the true plane spectrum of the antenna under test after eliminating the directional modulation effect of the probe can be analytically obtained, where Δ is:

[0026] ;

[0027] The final solution is as follows:

[0028] ,

[0029] .

[0030] Preferably, the solution results are stored and represented in the form of a two-dimensional data matrix:

[0031] The variables to be solved in the two-dimensional data matrix correspond to the data of the complete far-field spherical space sampling points. The spherical sampling points are uniformly or non-uniformly divided in space according to the preset θ and φ step resolution.

[0032] The two-dimensional data matrix adopts a dimension of 61×61, and the pitch and azimuth angle steps are both 3 degrees.

[0033] Preferably, the two-dimensional data matrix can also be a data matrix with a dimension of 181×181 and a step of 1 degree for both pitch and azimuth angles.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] (1) It breaks through the accuracy bottleneck of traditional planar near-field testing. This invention deeply combines the plane wave expansion theory and Cramer's law to solve the probe compensation matrix equation, and realizes accurate amplitude and phase decoupling of probe influence in K space; at the same time, it introduces a spectrum filtering mechanism based on physical truncation threshold, which eliminates the high-frequency truncation effect and high-frequency noise interference caused by multipath reflection in the anechoic chamber from the underlying logic of signal processing, realizes high-fidelity reconstruction of low sidelobe and wide-angle radiation characteristics, and significantly improves the measurement accuracy of antenna near-field and far-field transformation.

[0036] (2) Significantly improves the computational efficiency and engineering applicability of the algorithm. This invention abandons complex spatial domain integration and non-uniform grid iteration, enabling mathematical calculations to be performed entirely on a uniform sampling surface in the spectral domain or far-field sphere, successfully transforming near-field and far-field transformations and error calibration into more regular spectral domain multiplication, matrix pruning, or numerical interpolation. This processing mechanism not only greatly reduces computational complexity and memory consumption, but also provides highly structured data (such as a standard two-dimensional data matrix format), which is extremely convenient for modular debugging and hardware / software deployment, greatly improving the overall system's computational speed.

[0037] (3) This invention fills the gap in the implementation of probe compensation technology from pure theoretical derivation to engineering application, and provides a highly operable discretized numerical solution architecture. Current research on probe compensation in the field of electromagnetic field theory is mostly limited to complex analytical formulas in the continuous domain, lacking specific implementation paths to guide the development of underlying code. This invention deconstructs the continuous plane wave expansion and spatial decoupling theory into a discrete data execution process that can be efficiently processed by a computer—from the generation of the near-field sampling matrix and grid zero-padding under the discrete Fourier transform, to the construction of a discrete matrix equation system in K-space and point-by-point analysis using Cramer's rule. This systematic engineering implementation plan successfully breaks down the barrier between pure theoretical formulas and actual program development, providing a standardized and transparent implementation template for the core algorithm development of antenna automated testing systems, and significantly reducing the R&D threshold and algorithm reproduction difficulty of the underlying software of complex antenna testing systems. Attached Figure Description

[0038] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a schematic diagram of the method flow according to an embodiment of the present invention;

[0040] Figure 2 This is a schematic diagram of a method for zero-filling the near-field sampling plane and improving the smoothness and peak positioning accuracy of the far-field radiation pattern according to an embodiment of the present invention.

[0041] Figure 3 This is a schematic diagram of the spatial surface enclosed by the antenna under test and the probe in the probe compensation algorithm of this embodiment of the invention;

[0042] Figure 4 In this embodiment of the invention, the same probe is rotated 90° to perform two measurements with different orientations to obtain information about E. θ and E φ A schematic diagram of the two equations;

[0043] Figure 5 The simulation examples of this invention use a circular horn antenna and a pyramidal horn antenna. The circular horn antenna has an aperture radius of 0.12m and a height of 0.22m, while the pyramidal horn antenna has an aperture of 0.28×0.36m and a height of 0.5m.

[0044] Figure 6 For the simulation verification of the near-far field transformation in this embodiment of the invention, a schematic diagram comparing the near-far field transformation results of the simulated near-field data on the H-plane with the theoretical far-field data is shown.

[0045] Figure 7 For the simulation verification of the near-far field transformation in this embodiment of the invention, a schematic diagram comparing the near-far field transformation results of the simulated near-field data on the E-plane with the theoretical far-field data is shown.

[0046] Figure 8 A schematic diagram of the comparison curves before and after probe compensation on the E plane is shown for the actual measurement verification of amplitude and phase compensation in this embodiment of the invention.

[0047] Figure 9 For the experimental verification of amplitude and phase compensation in this embodiment of the invention, a schematic diagram of the comparison curves of probe H before and after compensation is shown.

[0048] Figure 10 The above are comparison images of the H-plane far-field direction before and after high-frequency spatial noise filtering in an embodiment of the present invention, where (a) is before filtering and (b) is after filtering.

[0049] Figure 11 This is a flowchart illustrating the execution of the amplitude and phase probe compensation and spectrum filtering system for near-field measurement of the antenna mentioned in this embodiment of the invention. Detailed Implementation

[0050] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0051] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0052] Example 1:

[0053] In this embodiment, as Figure 1 As shown, a method for amplitude and phase probe compensation and spectrum filtering in near-field antenna measurement includes the following steps:

[0054] S1. Select the type, frequency band, and size parameters of the target antenna, and obtain the planar near-field data of the target antenna through simulation experiments.

[0055] The format of planar near-field data is composed of columns. The first row is the file header indicating the data type of the current column. The first two columns are the x and y coordinates or θ and φ data that record the data position information. The subsequent columns are electric field information columns, where θ and φ are the angle information on the far-field sphere with a step of dθ.

[0056] In this embodiment, the planar near-field data of the antenna is obtained by modeling and simulating using commercial electromagnetic simulation software or by actual measurement in a microwave anechoic chamber. Measurements in a microwave anechoic chamber naturally involve various noises and coupling between the probe antenna and the antenna under test, which can be directly compensated and denoised using the algorithm mentioned in this invention. Since the simulation assumes an ideal environment, the probe antenna can be modeled outside the antenna under test, and the S-parameters at each sampling point can be collected according to the Nyquist sampling theorem, thereby completing the simulation verification of compensation and denoising.

[0057] S2. Set the necessary parameters for the target antenna and perform adaptation processing on the planar near-field data to obtain the adapted planar near-field data.

[0058] Essential parameters include: wavelength, distance between antenna aperture and probe, elevation and azimuth step, polarization direction, and probe data characteristics.

[0059] In this embodiment, necessary parameters are set and data preprocessing is completed, such as wavelength, distance between antenna aperture and probe, elevation and azimuth step size, polarization direction, and probe data characteristics. Since electric field data obtained by different methods have different formats, the planar near-field data needs to be adapted using a script so that it can be directly input into the algorithm for solution. This format has four columns: "x(m), y(m), Ex". real Ex imag ", that is, the coordinates on the plane and the real and imaginary parts of the electric and magnetic fields, and divided into E x and E y(Common polarization and cross-plan) Two raw data files are used, where x(m) and y(m) are the x and y coordinates of each sampling point on the near-field sampling plane, as shown in Table 1. The first row is the file header indicating the data type of the current column. The first two columns are the x and y coordinates or θ and φ data recording the data location information, and the subsequent columns are the electric field information columns. This storage method facilitates debugging by engineers and allows for easy adjustment of the current data matrix composition as needed, such as filling the data matrix with inner and outer loops according to any column order. In actual antenna measurement, some objects under test in microwave anechoic chambers cannot be rotated across the entire spherical surface (they can only perform a complete circular rotation at a specific angle). This requires the probe compensation algorithm to perform near-field and far-field transformation and probe compensation only on a specific angular section. In this case, the far-field spherical data of the specific section after near-field data transformation can be selected for one-dimensional interpolation to solve the above problem.

[0060] Table 1

[0061] .

[0062] S3. Perform mathematical operations on the adapted planar near-field data to obtain the planar spectrum of the target antenna.

[0063] The adapted planar near-field data is subjected to a fast Fourier transform, and zero-padding is performed around the original data. The sampling density in the frequency domain is increased by expanding the sampling window, and the diagonal spectrum is interpolated to improve the smoothness of the far-field radiation pattern and the peak positioning accuracy, without increasing the actual spatial resolution or information content of the system, thus obtaining the planar spectrum.

[0064] In this embodiment, a Fourier transform is performed on the near-field data in a uniform format to obtain the plane wave spectrum of the antenna under test. The detailed calculation steps of this process are as follows:

[0065] Starting from the near-field electric field data, it satisfies the Helmholtz equation:

[0066] ,

[0067] Where k is the wave number and E represents the near-field electric field. From the constitutive equations, we know that only two components of k exist independently, in which case we have:

[0068] ,

[0069] Where, k x k represents the wavenumber component in the x-direction. y k represents the wavenumber component in the y-direction. z This represents the wavenumber component in the z-direction.

[0070] Solving the Helmholtz equation, we get:

[0071] ,

[0072] Where A(k) x ,k y ) represents the complex amplitude of a plane wave.

[0073] Performing a Fourier transform, we get:

[0074] ;

[0075] At this point, by simplifying the method of stationary phases, we can obtain:

[0076] ,

[0077] Where r represents the straight-line distance between the antenna under test and the observation point.

[0078] This formula is an approximate expression for the far field, where θ and φ are the polar angle and azimuth angle of the observation point, respectively. The actual test yields the tangential component E of the electric field on the sampling surface. x and E y Converted to spherical coordinate system components E θ and E φ From the above formula, we can obtain:

[0079] ,

[0080] The far-field vector pattern is then represented as follows:

[0081] ,

[0082] During the Fourier transform process, zero-padding is applied to the near-field data, such as... Figure 2 As shown. The zero-padding strategy improves frequency domain sampling, interpolation performance, and numerical results, enhances the smoothness of the far-field radiation pattern and peak localization accuracy, without increasing the system's actual spatial resolution or information content.

[0083] S4. Set appropriate window functions, cutoff wavenumbers, and transition bands for the plane wave spectrum. According to the evanescent wave, use K-space filtering to remove the high-frequency physical characteristics in K-space, and at the same time remove high-frequency noise, to obtain a relatively pure transverse spatial frequency component that will be transmitted to the far field.

[0084] K-space filtering uses k0 as the cutoff wavenumber, which is the wavenumber corresponding to a 90° scan angle. An adjustable transition start point is set. The window function created at this time will completely preserve the effective frequency components below the transition start point, so that the frequency components gradually decrease and decay to 0 in the transition band.

[0085] In this embodiment, a suitable window function, cutoff wavenumber, and transition band are set for the aforementioned plane wave spectrum. The evanescent wave is removed according to its higher-frequency physical characteristics in K-space, while simultaneously removing high-frequency noise, resulting in a relatively pure transverse spatial frequency component that will propagate to the far field. Based on k... z From the formula, we can see that in the k-space spectral domain, for The real solution guarantees that the electromagnetic wave propagates along the +z direction. At this point, the spectral components can be transmitted to the far field, serving as components of the far-field radiation pattern; these are the transverse components that need to be retained. The solution is a complex number, representing an evanescent wave component, which needs to be zeroed out in the window function. To avoid the Gibbs phenomenon of spatial oscillations caused by hard truncation, the window function created here will gradually reduce the frequency component to zero in the transition band.

[0086] S5. Based on the necessary parameters, calculate the wavenumber grid and perform phase compensation according to the physical offsets in the x, y, and z axes.

[0087] S6. Import the far-field radiation pattern data of the probe used for testing and simulation, then perform probe compensation calculation based on the far-field radiation pattern data, and then construct a system of two linear matrix equations. Solve the system of matrix equations using Cramer's rule to obtain the solution results.

[0088] In this embodiment, far-field radiation pattern data of the probe used for testing and simulation is imported. This radiation pattern data needs to be 6 columns, given in the following order: θ, φ, Re(E) θ ), Im(E θ ), Re(E φ ), Im(E φ ), where θ and φ are required to be angle information on the far-field sphere with dθ as the step, and each set of angle information corresponds to a set of real and imaginary part data formats of the electric field of pitch and azimuth angles, as shown in Table 2. This format can be generated by script processing.

[0089] Table 2

[0090] .

[0091] Methods for obtaining the solution results include:

[0092] Mathematical calculations for probe compensation are performed based on the above data. The Lorentz reciprocity theorem is applied to the spatially enclosing surface V of the probe, such as... Figure 3 As shown:

[0093] ,

[0094] Where S0 represents the probe aperture surface, S1 represents the probe enclosure surface, and S ∞ S represents a surface at infinity. PE represents the sampling plane. A E represents the electric field received by probe A. B H represents the electric field received by probe B. A H represents the electric field received by probe A. B Let n represent the electric field received by probe B, n represent the normal of the sampling plane, and s represent the integration region.

[0095] After integration and simplification, and considering the relationship between the antenna coordinate system and the probe coordinate system, based on the sampling properties of the Dirichlet function, it can be simplified using vector operation rules as follows:

[0096] ,

[0097] Among them, P B The output received by the probe is represented by ω, ω represents the angular frequency, μ represents the permeability, G represents the plane spectrum of the probe, and F represents the plane spectrum of the antenna under test.

[0098] By rotating the measuring probe 90° around the physical axis, two sets of near-field sampling data under orthogonal polarization states are acquired, and two sets of corresponding plane wave spectrum data are obtained through Fourier transform. The relationship between the probe and the object under test pattern and the probe received data is then applied:

[0099] ,

[0100] in, This represents the θ component of the far-field radiation pattern of the antenna under test. This represents the θ component of the probe's far-field radiation pattern. This represents the φ component of the far-field radiation pattern of the antenna under test. The θ component represents the far-field radiation pattern of the probe, C represents the constant factor, j represents the imaginary unit, k represents the wavenumber, and d represents the straight-line distance between the aperture surface of the antenna under test and the probe. This indicates the output received by the probe.

[0101] Using the known far-field radiation pattern reception characteristics of the probe in the corresponding orthogonal state as coefficients, a system of two-variable linear matrix equations is constructed regarding the true plane wave spectrum of the antenna under test (Method: Perform two measurements with the same probe rotated 90° and in different orientations, such as...). Figure 4 As shown, where AUT represents the antenna under test and Probe represents the probe:

[0102] ,

[0103] in, This represents the θ component of the far-field pattern of the probe under co-polarization. c1 represents the φ component of the far-field pattern of the probe under co-polarization, and c1 represents the constant factor. This represents the θ component of the far-field radiation pattern of the probe under crossover conditions. I represents the φ component of the far-field radiation pattern of the probe under cross-sectional conditions. H I represents the integral independent of the chosen variable in the case of common polarization. V This represents the integral that is independent of the chosen variable in the case of vertical polarization;

[0104] I H and I V The expression is:

[0105] ,

[0106] .

[0107] By using Cramer's rule to solve the system of two linear matrix equations point by point and calculating the ratio of the determinants of each matrix, the orthogonal components of the true plane spectrum of the antenna under test after eliminating the directional modulation effect of the probe can be analytically obtained, where Δ is:

[0108] ;

[0109] The final solution is as follows:

[0110] ,

[0111] .

[0112] The solution results are stored and represented in the form of a two-dimensional data matrix:

[0113] The variables to be solved in the two-dimensional data matrix correspond to the data of complete far-field spherical spatial sampling points. The spherical sampling points are uniformly or non-uniformly divided in space according to preset θ and φ step resolutions. The two-dimensional data matrix used is a 61×61 dimension data matrix with a pitch and azimuth step of 3 degrees. Alternatively, a 181×181 dimension data matrix with a pitch and azimuth step of 1 degree can also be used.

[0114] S7. Perform plot analysis on the solution results, analyze the errors, and judge the data quality.

[0115] In this embodiment, the above solution results are plotted and analyzed, including plotting: far-field radiation patterns of each cross-section (such as the E-plane and H-plane), far-field phase patterns, radiation patterns before and after probe compensation and comparison curves with reference data, radiation pattern data before and after K-space filtering and comparison curves with reference data, and analyzing errors and judging data quality, etc.

[0116] Two simulation and test examples are designed to verify the correctness of the method mentioned in this paper.

[0117] For the simulation verification of near-field and far-field transformation, a circular horn antenna with an aperture radius of 0.12m and a height of 0.22m is designed, along with a pyramidal horn antenna with an aperture of 0.28×0.36m and a height of 0.5m. Figure 5 As shown. In the simulation environment, the sampling plane size is 2×3m, the sampling interval is 0.06m, and there are a total of 34×50 sampling points. Near-field transformation is performed on the near-field data obtained under the simulation conditions without probe interference, and the results are as follows. Figure 6 and Figure 7 As shown, it achieves a very high degree of agreement with the commercial simulation software FEKO within the confidence interval.

[0118] The measured sampling was performed using a C-band pyramidal horn (5.85-8.2 GHz) and a WR-137 rectangular open waveguide probe from the NSI system. The probe was 3λ away from the object under test, and the sampling interval was 0.3λ. A total of 70×70 near-field data sampling points were collected on a sampling plane with x and y axes ranging from -0.42 to 0.42.

[0119] After compensation using the algorithm proposed in this invention, the simulation and measured amplitude and phase compensation curves of the pyramidal horn antenna at 7.5 GHz are shown below in the E-plane and H-plane. Figure 8 and Figure 9 As shown, NF2FF represents the near-field to far-field transformation, NF2FF_COMP represents the probe compensation function of the near-field to far-field transformation algorithm, and NSI-MI is an RF measurement solutions company, with the corresponding curve representing the solution proposed by that company. It is readily apparent that the compensation algorithm and optimization method proposed in this paper can correctly compensate for the level reduction introduced by coupling. Under this measurement configuration, the compensated far-field pattern achieves good agreement with the simulation and measured results under the NSI-MI system within the confidence interval.

[0120] After introducing high-frequency spatial noise into the spectral space under a simulation environment, the far-field radiation patterns of the H-plane before and after filtering by the algorithm proposed in this invention are as follows: Figure 10 As shown, (a) is before filtering and (b) is after filtering. This method significantly removes the influence of evanescent waves and high-frequency spatial noise on the far-field radiation pattern.

[0121] Example 2:

[0122] In this embodiment, corresponding to Embodiment 1, the present invention also provides an amplitude and phase probe compensation and K-space spectrum filtering system for antenna near-field measurement. This system is based on the same inventive concept as the method in Embodiment 1 and is used to implement the above-mentioned high-precision near-field and far-field transformation algorithm. Its process is as follows: Figure 11 As shown, the system includes:

[0123] The near-field data acquisition and analysis module is used to import and analyze the raw measurement data acquired by the planar near-field scanning system. This module supports reading the near-field amplitude and phase distribution matrix data of the antenna under test under two orthogonal polarization states acquired by the probe with the probe physically rotated 90 degrees or using a dual-polarized probe, and simultaneously extracts and loads the calibration far-field radiation pattern data of the measurement probe itself;

[0124] The spectral domain transformation and preprocessing module is used to perform boundary expansion and zero-filling (zero padding) strategies on the acquired near-field spatial sampling data, and to perform two-dimensional fast Fourier transform (FFT) to improve the frequency domain sampling density and interpolation effect, transforming the near-field distribution data in the spatial domain into preliminary plane wave spectrum data modulated by the probe characteristics in K space (plane wave spectrum domain).

[0125] The amplitude and phase probe decoupling compensation module is used to accurately separate the spatial modulation effect caused by the probe's directivity in K-space. This module combines the receiving characteristics of the probe in orthogonal polarization state to automatically construct a system of orthogonal two-dimensional linear matrix equations about the true plane spectrum of the antenna under test, and uses a built-in Cramer's rule matrix solver to perform point-by-point algebraic analysis, efficiently extracting the true spectral response components of the antenna under test.

[0126] The K-space spectrum filtering and optimization module is used to eliminate composite errors caused by the test environment. Based on the physical size, operating frequency, and actual geometric position of the antenna under test, this module dynamically sets the K-space truncation threshold and performs two-dimensional mask clipping and noise reduction processing on the probe-compensated data in the spectral domain. This physically filters out evanescent wave components that do not contribute radiation and high-frequency spatial interference caused by multipath reflections in the anechoic chamber.

[0127] The far-field radiation characteristics reconstruction module is used to perform the mapping of clean data from the spectral domain to the far-field sphere. Based on the filtered and optimized clean planar spectral data, this module calculates and reconstructs the accurate radiation characteristics of the antenna under test on the complete far-field sphere (such as the main polarization / cross-polarization pattern and gain parameters) through coordinate transformation, polarization matching and numerical interpolation.

[0128] The data storage and visualization post-processing module is used to structurally save and display the calculated far-field radiation characteristics. This module discretizes the far-field spherical sampling point data to be solved according to preset elevation and azimuth angles, and generates a three-dimensional surface visualization image and a two-dimensional polar coordinate profile of the antenna far-field radiation pattern based on the matrix data.

[0129] Example 3:

[0130] This embodiment provides an electronic device, including a memory and a processor. The memory stores a computer program, and the processor runs the computer program to enable the electronic device to perform the amplitude and phase probe compensation and K-space spectrum filtering method for antenna near-field measurement of Embodiment 1.

[0131] Alternatively, the aforementioned electronic device may be a server.

[0132] In addition, embodiments of the present invention also provide a computer-readable storage medium storing a computer program that, when executed by a processor, implements the amplitude and phase probe compensation and K-space spectrum filtering method for antenna near-field measurement of Embodiment 1.

[0133] Embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0134] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0135] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0136] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0137] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for amplitude and phase probe compensation and spectral filtering in near-field antenna measurement, characterized in that, Includes the following steps: Select the type, frequency band, and size parameters of the target antenna, and obtain the planar near-field data of the target antenna through simulation experiments; Set the necessary parameters for the target antenna and perform adaptation processing on the planar near-field data to obtain the adapted planar near-field data; Mathematical operations are performed on the adapted planar near-field data to obtain the planar spectrum of the target antenna; By setting appropriate window functions, cutoff wavenumbers, and transition bands for the plane wave spectrum, and using K-space filtering according to the evanescent wave, the high-frequency physical characteristics in the K-space are removed, while high-frequency noise is also removed, resulting in a pure transverse spatial frequency component that will be transmitted to the far field. Based on the necessary parameters, the wavenumber grid is calculated, and according to... x , y , z Phase compensation is performed for physical offsets in three axes; Import the far-field radiation pattern data of the probe used for testing and simulation, then perform probe compensation calculation based on the far-field radiation pattern data, and then construct a system of two linear matrix equations. Finally, use Cramer's rule to solve the system of matrix equations and obtain the solution results. Analyze the solution results graphically, identify errors, and assess data quality. Methods for obtaining the solution include: By rotating the measuring probe 90° around the physical axis, two sets of near-field sampling data under orthogonal polarization states are acquired, and two sets of corresponding plane wave spectrum data are obtained through Fourier transform. The relationship between the probe and the object under test pattern and the probe received data is then applied: ， in, Represents the far-field radiation pattern of the antenna under test. θ Quantity, Represents the far-field radiation pattern of the probe θ Quantity, Represents the far-field radiation pattern of the antenna under test. φ Quantity, Represents the far-field radiation pattern of the probe φ Quantity, C Indicates a constant factor. j Represents the imaginary unit. k Indicates wave number, d This indicates the distance between the antenna and the probe. This indicates the probe's receive output; Using the known far-field pattern reception characteristics of the probe in the corresponding orthogonal state as coefficients, a system of two-variable linear matrix equations is constructed regarding the true plane wave spectrum of the antenna under test: ， in, This represents the far-field pattern of the probe under co-polarization. θ Quantity, This represents the far-field pattern of the probe under co-polarization. φ Quantity, c 1 represents a constant factor. This indicates the far-field radiation pattern of the probe under cross conditions. θ Quantity, This indicates the far-field radiation pattern of the probe under cross conditions. φ Quantity, I H This represents the integral in the common polarization case that is independent of the chosen variable. I V This represents the integral that is independent of the chosen variable in the case of vertical polarization; By using Cramer's rule to solve the system of two linear matrix equations point by point and calculating the ratio of the determinants of each matrix, the orthogonal components of the true plane spectrum of the antenna under test after eliminating the directional modulation effect of the probe can be analytically obtained, where Δ is: ； The final solution is as follows: ， 。 2. The amplitude and phase probe compensation and spectrum filtering method for near-field antenna measurement according to claim 1, characterized in that, The format of planar near-field data is column-based. The first row is a file header indicating the data type of the current column, and the first two columns record the data location information. x , y coordinates or θ , φ The data, followed by the electric field information column, includes... θ and φ For the far-field sphere with d θ This is the angle information for the stepping.

3. The amplitude and phase probe compensation and spectrum filtering method for near-field antenna measurement according to claim 1, characterized in that, Essential parameters include: wavelength, distance between antenna aperture and probe, elevation and azimuth step, polarization direction, and probe data characteristics.

4. The amplitude and phase probe compensation and spectrum filtering method for near-field antenna measurement according to claim 1, characterized in that, The adapted planar near-field data is subjected to a fast Fourier transform, and zero-padding is applied around the original data. The sampling density in the frequency domain is increased by expanding the sampling window, thereby achieving interpolation of the diagonal spectrum. At the same time, the smoothness of the far-field radiation pattern and the peak positioning accuracy are improved without increasing the actual spatial resolution or information content of the system, thus obtaining the planar spectrum.

5. The amplitude and phase probe compensation and spectral filtering method for near-field antenna measurement according to claim 1, characterized in that, K-space filtering uses k0 as the cutoff wavenumber, which is the wavenumber corresponding to a 90° scan angle. An adjustable transition start point is set. The window function created at this time will completely preserve the effective frequency components below the transition start point, so that the frequency components gradually decrease and decay to 0 in the transition band.

6. The amplitude and phase probe compensation and spectrum filtering method for near-field antenna measurement according to claim 1, characterized in that, The solution results are stored and represented in the form of a two-dimensional data matrix: The unsolved variables in the two-dimensional data matrix correspond to the data of complete far-field spherical space sampling points, which are located in space according to a preset... θ and φ Step resolution is used to divide the data into uniform or non-uniform sections; The two-dimensional data matrix adopts a dimension of 61×61, and the pitch and azimuth angle steps are both 3 degrees.

7. The amplitude and phase probe compensation and spectrum filtering method for near-field antenna measurement according to claim 6, characterized in that, Two-dimensional data matrices can also be data matrices with dimensions of 181×181 and pitch and azimuth steps of 1 degree.

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