Highly-integrated cylindrical surface near-far field transformation rapid calculation method and highly-integrated cylindrical surface near-far field transformation rapid calculation system

Abstract

The invention discloses a highly-integrated cylindrical surface near-far field transformation rapid calculation method and system, and the method comprises the following steps: S1, determining a mode for carrying out the cylindrical surface near-far field transformation of near-field measurement data, and carrying out the representation through a far-field electric field calculation formula; s2, according to the near-field measurement data, calculating to obtain a weighting coefficient compensated by the probe, performing acceleration processing by using FFT Fourier transform in the calculation process, and substituting the obtained weighting coefficient into a far-field electric field calculation formula to obtain a far-field result of the measured antenna; s3, the phase center of the antenna is obtained through calculation according to the far-field result in the S2, phase deviation caused by the phase center is compensated to the far-field result obtained through calculation in the S2, and finally the accurate far-field result of the tested antenna is obtained. The method comprises the processes of probe compensation, phase center calculation and compensation, FFT acceleration and the like, near-far field transformation simulation calculation of the tested antenna can be powerfully supported, and the accuracy of a calculation result is improved.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic simulation calculation, specifically to a highly integrated method and system for fast calculation of near-field and far-field transformations of cylindrical surfaces. Background Technology

[0002] In the field of antenna measurement, accurately obtaining the far-field radiation pattern of an antenna is crucial for evaluating its performance. Traditional far-field measurement methods face many limitations in practical applications, such as large test site requirements and susceptibility to environmental interference. With technological advancements, near-field measurement techniques have emerged. These techniques collect data from a region relatively close to the antenna under test and then use near-far-field transformation algorithms to deduce the far-field radiation pattern, effectively overcoming some of the shortcomings of far-field measurement. Among these, the near-far-field transformation algorithm based on mode expansion has received widespread attention and in-depth research in recent years due to its unique advantages.

[0003] The challenges and difficulties currently faced in calculating near-field and far-field transformations of cylindrical surfaces based on pattern expansion are as follows:

[0004] The cylindrical near-field and far-field transformation algorithm based on mode expansion involves a large number of mathematical operations, such as series summation and calculation of special functions (e.g., Bessel functions). Determining the weighting coefficients requires numerical calculations of complex integrals, which is not only computationally intensive but also demands high precision. As antenna size increases and measurement accuracy requirements rise, the number of modes to be processed increases, leading to an exponential increase in computational complexity. For example, for electrically large antennas, hundreds or even thousands of modes may need to be considered, making the calculation process extremely time-consuming, even exceeding the processing capabilities of ordinary computers.

[0005] The characteristics of probes used in practice are complex and diverse, and even after calibration, their characteristic parameters may still have some uncertainty. Different types of probes behave differently at different frequencies and under different measurement environments, which increases the difficulty of probe compensation. Moreover, the mutual coupling between the probe and the antenna under test also affects the measurement results, making the probe compensation model more complex. When performing near-field measurements on cylindrical surfaces, the unique characteristics of cylindrical scanning cause the probe response to vary at different positions, further increasing the complexity of compensation. If the probe characteristics are not accurately compensated, it will lead to large errors in the near-field data, thus seriously affecting the accuracy of the far-field radiation pattern.

[0006] As mentioned earlier, accurately determining the phase center is crucial for near-field and far-field transformation of cylindrical antennas. However, for complex antenna structures, the calculation method for the phase center is complicated and easily affected by various factors, such as the antenna geometry, material properties, and operating frequency. In actual measurements, the measured phase data may contain errors due to measurement noise, environmental interference, and other factors, which can affect the accuracy of the phase center calculation. Moreover, the phase center may not be fixed in different directions, exhibiting dynamic characteristics, which brings great difficulties to the determination of the phase center and its application in near-field and far-field transformation. If the phase center is not accurately determined, it will lead to the incorrect transmission of phase information during the near-field and far-field transformation process, resulting in a serious deviation in the final far-field radiation pattern.

[0007] Meanwhile, commercially available near-field and far-field transformation algorithms for cylindrical antennas are relatively mature and can effectively calculate near-field and far-field transformations. However, integrated functional modules for probe compensation, phase center calculation and compensation, and FFT acceleration are still lacking. This is because probe compensation algorithms are inherently complex, and the calculation and compensation of the phase center of the antenna under test are susceptible to interference from various factors, making accurate calculation difficult. Therefore, most current solutions offer only single functions and often fail to achieve a highly integrated functionality encompassing probe compensation, phase center calculation and compensation, and FFT acceleration. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a highly integrated method and system for fast calculation of near-field and far-field transformation of cylindrical surfaces.

[0009] The objective of this invention is achieved through the following technical solution: a highly integrated method for fast calculation of near-field and far-field transformations of cylindrical surfaces, comprising the following steps:

[0010] S1. Determine the method for cylindrical near-field and far-field transformation of near-field measurement data, and characterize it using the far-field electric field calculation formula;

[0011] S2. Based on the near-field measurement data, calculate the weighting coefficients after probe compensation, and use FFT Fourier transform for accelerated processing during the calculation process. Then, substitute the obtained weighting coefficients into the far-field electric field calculation formula to obtain the far-field result of the antenna under test.

[0012] S3. Calculate the phase center of the antenna based on the far-field results of S2, and compensate the phase offset caused by the phase center to the far-field results calculated in S2, so as to obtain the accurate far-field results of the antenna under test.

[0013] A highly integrated fast computation system for near-field and far-field transformation of cylindrical surfaces, comprising:

[0014] The cylindrical near-field data import module is used to import near-field measurement data;

[0015] The probe pattern data import module is used to import the far-field pattern of the probe.

[0016] The phase center compensation calculation module is used to calculate the phase center of the antenna under test and to achieve far-field phase compensation. It also supports outputting and displaying the XYZ axis coordinate values ​​of the phase center.

[0017] The normalization module is used to normalize the far-field calculation pattern.

[0018] The probe compensation module is used to compensate the input cylindrical near-field data and eliminate the far-field influence of the probe on the antenna under test.

[0019] The data export module is used to export the far-field calculation results;

[0020] The cylindrical near-field and far-field transformation module is used to perform cylindrical near-field and far-field transformation on the imported near-field measurement data to obtain the far-field calculation results.

[0021] The cylindrical near-field data display module is used to display the imported near-field measurement data;

[0022] The far-field calculation result display module is used to display the far-field calculation results;

[0023] The general parameter setting module is used to set general parameters.

[0024] The beneficial effects of this invention are:

[0025] This invention allows for setting corresponding parameters or options based on imported cylindrical near-field data, thereby enabling rapid simulation and calculation of the far-field radiation pattern of the antenna under test. The software highly integrates phase center calculation and compensation algorithms, probe compensation algorithms, FFT acceleration algorithms, etc., and supports functions such as phase center calculation and compensation, probe compensation, normalization settings, and near-field data viewing. It can effectively meet the needs of near-field and far-field transformation calculation and result viewing under different requirements.

[0026] Furthermore, this invention integrates multiple modules, including: a Fourier Transform (FFT) acceleration algorithm module, a cylindrical near-field data import module, a probe pattern data import module, a phase center compensation calculation module, a normalization module, a probe compensation module, a data export module, a cylindrical near-field and far-field transformation module, a cylindrical near-field data display module, a far-field calculation result display module, and a conventional parameter setting module. By inputting relevant calculation parameters, the cylindrical near-field and far-field transformation of the antenna under test can be quickly achieved. Attached Figure Description

[0027] Figure 1 This is a flowchart of the method of the present invention;

[0028] Figure 2 The far-field radiation patterns of the E-plane and H-plane of the cylindrical near-far field transformation without probe compensation and phase compensation are shown in the embodiment.

[0029] Figure 3 The far-field radiation patterns of the E-plane and H-plane of the cylindrical near-far field transformation without probe compensation, with phase center calculation and compensation, are shown in the embodiment.

[0030] Figure 4 The far-field radiation patterns of the E-plane and H-plane of the cylindrical near-far field transformation with probe compensation and without phase compensation are shown in the embodiment.

[0031] Figure 5 The far-field radiation patterns of the E-plane and H-plane of the cylindrical near-far field transformation with probe compensation, phase center calculation and compensation are shown in the embodiment. Detailed Implementation

[0032] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings, but the scope of protection of the present invention is not limited to the following description.

[0033] This invention will focus on a cylindrical near-field and far-field transformation calculation method based on pattern expansion, including near-field and far-field transformation algorithms based on pattern expansion, probe compensation, and phase center calculation;

[0034] (1) Planar near-field and far-field transformation

[0035] In early near-field and far-field transformation research, the plane transformation algorithm was a relatively basic one. Based on the plane wave expansion theory, it represents the field distribution of the antenna under test in the near-field plane as a superposition of plane waves. In a Cartesian coordinate system, by performing a Fourier transform on the measured electric or magnetic field data, the field can be decomposed into plane wave components of different wave numbers.

[0036] The basic principle is as follows: Assuming the electric field measured at a near-field plane distance z = z0 is E(x,y,z0), with units of volts per meter, it can be expressed as follows based on the properties of the Fourier transform:

[0037]

[0038] Where E p (k x k y z0) is the plane spectrum (unit: volt-meter), k x and k y It represents the wavenumber components in the x and y directions, measured in meters. Using the propagation factor, the plane wave spectrum can be extrapolated to the far field, thus obtaining the far-field radiation pattern.

[0039] Planar transformation algorithms played a crucial role in early antenna near-field measurements, providing relatively accurate far-field estimations for simple antenna structures and specific application scenarios. However, this algorithm has limitations: it is only applicable to directional high-gain antennas, and it suffers from truncation errors during near-field and far-field transformations, failing to capture omnidirectional far-field radiation characteristics. Because the radiation field of a real antenna is not entirely composed of plane waves, the accuracy of the planar transformation algorithm is significantly affected for complex antenna structures and non-planar field distributions.

[0040] (2) Near-field and far-field transformation of spherical surface

[0041] With increasing demands for accuracy and comprehensiveness in antenna measurements, spherical near-field and far-field transformation algorithms have gradually gained attention. Based on the theory of spherical wave mode expansion, this algorithm expands the field established by the antenna under test in space into a sum of spherical wave functions.

[0042] With the origin as the center, construct a minimum sphere with radius R that can enclose the antenna under test. min (Unit is meters). In space outside the sphere, the antenna field can be represented as a spherical vector wave function. and The weighted sum, i.e.

[0043]

[0044] For a typical antenna, m and n have finite bandwidths, where 0 ≤ m ≤ N, m ≤ n ≤ N, and N ≈ k(R). min +λ); λ is the wavelength, measured in meters. Weighting coefficients. and It contains complete information about the antenna field. Once the weighting coefficients are determined, the antenna field and many characteristic parameters can be calculated.

[0045] The weighting coefficients determined from near-field measurement data are generally related to the probe characteristics. A rigorous solution can be obtained by deriving the coupling equation between the probe and the antenna through Lorentz's reciprocity theorem or antenna scattering matrix analysis. Since the probe is always directly facing the antenna under test during spherical scanning, its directivity is minimally affected. Generally, only the probe's response needs to be corrected to accurately calculate the far-field.

[0046] The advantage of the spherical near-field and far-field transformation algorithm lies in its applicability to all types of antennas and its ability to obtain omnidirectional far-field radiation characteristics, which is unmatched by planar transformation algorithms. However, this algorithm also suffers from high computational complexity. Due to the complexity of the calculation formula, which involves a large number of series summations and special function operations, the calculation is time-consuming and requires significant computing resources. For example, when calculating electrically large targets, a large number of mode coefficients need to be processed, making the calculation process extremely cumbersome and prone to numerical instability.

[0047] (3) Near-field and far-field transformation of cylindrical surfaces

[0048] The cylindrical near-field and far-field transformation algorithm is developed based on the planar and spherical transformation algorithms. It expands and transforms the field on the cylindrical scanning surface. In the cylindrical coordinate system, the near-field data of the antenna under test on the cylindrical surface is represented as a superposition of cylindrical wave functions. By processing the near-field measurement data and determining the weighting coefficients, the far-field radiation pattern is obtained by using propagation relationships to extrapolate the outside field to the far field.

[0049] Cylindrical transformation algorithms have unique application scenarios. They are suitable for small sector-beam antennas, and in some specific engineering applications, such as measuring antennas with cylindrical symmetry, they can provide a more accurate and convenient method for far-field estimation. However, similar to planar and spherical transformation algorithms, cylindrical transformation algorithms also face some challenges. For example, determining the weighting coefficients requires calculating complex integrals, which increases the difficulty and complexity of the computation.

[0050] Secondly, regarding probe compensation:

[0051] In near-field antenna measurements, the probe's role is to receive the near-field signal radiated by the antenna under test. However, the probe itself has certain characteristics, such as directivity and gain, which can affect the measurement results, causing the measured signal to be inconsistent with the true near-field signal of the antenna under test. To obtain accurate near-field data and thus achieve precise near-field to far-field transformation, it is necessary to compensate for the probe's influence, i.e., probe compensation.

[0052] When an ideal dipole probe is used to sample on a virtual sphere, the electric or magnetic field of the antenna can be directly obtained. This electric or magnetic field can then be expanded using modes, and the coefficients of each mode can be obtained by utilizing the orthogonality between modes, leading to a probe-free compensation formula for near-field and far-field transformations. However, in practical applications, ideal dipole probes are difficult to implement; directional probes are typically used instead.

[0053] For directional probes, their form is generally limited for ease of testing and calculation, such as using probes with azimuth symmetry. Through mathematical model derivation, a differential operator can be obtained to describe the probe's influence, thus enabling probe compensation. Taking spherical near-field measurement as an example, when using a directional probe, the difference between the probe compensation formula and the formula without probe compensation lies only in the coefficients. Probe compensation requires knowledge of the probe's detailed characteristic parameters, such as its radiation pattern function and gain. These parameters are typically obtained through experimental calibration or precise theoretical calculations.

[0054] The accuracy of probe compensation is crucial for the precision of near-field and far-field transformation. Inaccurate probe compensation can lead to deviations in near-field data, resulting in significant errors between the far-field pattern obtained through near-field and far-field transformation and the true values. In actual measurements, probe characteristics may change due to factors such as manufacturing processes and environmental conditions. Therefore, it is necessary to periodically calibrate and re-evaluate the probe's characteristic parameters to ensure the effectiveness of probe compensation.

[0055] Regarding the phase center and compensation:

[0056] The phase center is an important parameter of an antenna, playing a crucial role in accurately understanding its radiation characteristics and performing near-field and far-field transformations. During radiation, the phase distribution of an antenna is not uniform; the phase center can be understood as the equivalent phase reference point when the antenna radiates in a certain direction.

[0057] Determining the phase center of a complex antenna structure is no easy task. During near-field to far-field transformation, the position of the phase center affects the calculation of the propagation factor, thus impacting the accuracy of the far-field radiation pattern. If the phase center position is not accurately determined, phase information will deviate during the near-field to far-field transformation, resulting in a far-field radiation pattern that differs from the true values ​​in both phase and amplitude.

[0058] In practical measurements, there are various methods to determine the phase center. One common method is to measure the phase distribution of the antenna in different directions, and then use specific algorithms to fit and calculate the data to determine the location of the phase center. For example, the phase of the antenna radiation field can be measured at multiple different angular positions. By using optimization algorithms such as the least squares method, a point can be found that minimizes the fitting error between the phase distribution referenced to that point and the measurement data. This point is the phase center of the antenna.

[0059] Accurate calculation of the phase center is crucial for improving the accuracy of cylindrical near-field and far-field transform calculations based on mode expansion. In cylindrical near-field and far-field transforms, it is necessary to consider the relative positional relationship between the phase center and the cylindrical scanning surface, as well as the impact of phase center movement on field propagation and transformation. Only by accurately determining the phase center and reasonably considering its factors in the near-field and far-field transform algorithm can more accurate far-field radiation pattern results be obtained.

[0060] like Figure 1 As shown, a highly integrated method for fast calculation of near-field and far-field transformations of cylindrical surfaces includes the following steps:

[0061] S1. Determine the method for cylindrical near-field and far-field transformation of near-field measurement data, and characterize it using the far-field electric field calculation formula;

[0062] S101. Let the minimum cylindrical radius surrounding the antenna under test be R, in meters. In the region where the distance r > R, the electromagnetic field generated by the antenna under test satisfies the electromagnetic wave equation for the passive region:

[0063]

[0064] The passive region is the region without electric charge. For Hamiltonian operators, The electric field generated by the antenna under test is expressed in volts per meter. The magnetic field generated by the antenna under test is expressed in amperes per meter, and k is the wave number, expressed in radians per meter.

[0065] Let ψ be the solution to the scalar wave equation in cylindrical coordinates, then we have:

[0066]

[0067] S102. Taking the geometric center of the antenna as the origin of the coordinate axis, the area within the cylinder enclosing the antenna under test is the active region, and the area outside this region is the passive region. Therefore, the passive region satisfies the condition that the cylinder radius ρ ≠ 0. The scalar wave equation in the cylindrical coordinate system is:

[0068]

[0069] Where ρ is the radius of the cylinder, in meters. Z represents the azimuth angle in radians, and Z represents the height of the cylinder in meters.

[0070] By using the method of separation of variables, the fundamental solution of the scalar wave equation is:

[0071]

[0072] in, For the second type of Hankel function with independent variable k ρ The expression at ρ, k ρ It is the wave number in the ρ direction, with units of radians per meter (k). z The wave number in the Z direction is expressed in radians per meter, and j is an imaginary number with no unit.

[0073] S103. Let... Let be a constant unit vector. For any solution ψ of the scalar wave equation in a source-free region, the following three vectors are defined:

[0074]

[0075] All solutions to the wave equation in the source-free region constitute a discrete and complete function set, and the nth solution in the function set is denoted as ψ. n According to ψ n Three wave vector functions are derived.

[0076] In this context, any two wave vector functions are orthogonal. Since these three wave vector functions are orthogonal and complete, any vector function can be linearly combined from these three vectors. Furthermore, if this vector is divergent-free, then the expansion contains only vector functions. If the divergence of the vector is not zero, then the expansion must contain By Gauss's theorem:

[0077]

[0078] In the linear passive region, we have Let represent the electric displacement vector, ε be a constant, and ρ2 = 0, where ρ2 is the total charge in joules; then electric field strength It is non-dispersion, a vector. and Only use Linear combination representation:

[0079]

[0080] Among them, a n and b n It is a weighting function, where ω is the angular frequency in radians per second, μ is the permeability in Henry per meter, and n is the number of accumulations;

[0081] S104. The electromagnetic waves radiated by the antenna under test in free space can be expanded into a sum of cylindrical wave functions. The weighting function a in the expansion is... n and b n Including far-field radiation pattern information, a weighting function is calculated based on near-field measurement data to determine the antenna's far-field radiation pattern:

[0082] Before calculating the weighting function, it is necessary to first obtain the two basic vectors according to the above formula.

[0083]

[0084] in, It is the unit vector in the Z direction. It is the unit vector in the ρ direction. yes The unit vector of direction;

[0085] because All are k z It is a function of n, therefore its weighting coefficients are also k. z A function of and n; due to k zIt is continuous, and n is an integer. When calculating the electric field, for k... z It is an integral, and with respect to n it is a summation, therefore:

[0086]

[0087] in, It is the spherical coordinate position vector of the observation point, calculated using the stationary phase method. The internal integral in the calculation formula yields:

[0088]

[0089] Where θ is the pitch angle, and the unit is radians. It is the unit vector in the θ direction;

[0090] S105. Let the distance between the probe and the antenna under test be ρ0, in meters. In near-field measurements, a rectangular waveguide is used as the probe. The rectangular waveguide vertically polarized the data collected from the antenna under test. The directional component is then scanned by rotating the probe 90°. Directional component; therefore, the tangential electric field measured at ρ = ρ0 in actual measurements The unit is volts per meter, denoted as:

[0091]

[0092] in, for The electric field in the direction of the field, measured in volts per meter (E). z The electric field in the Z direction is expressed in volts per meter.

[0093] Then use vector functions Cross-multiply the above expression, then dot-multiply. The directional components are then integrated to obtain:

[0094]

[0095] in, For the second type of Hankel function with independent variable k ρ The expression that is differentiated at ρ0;

[0096] Similarly, we can obtain:

[0097]

[0098] in, For the second type of Hankel function with independent variable k ρ The expression at ρ0.

[0099] Get a n (kz ) and b n (k z After that, calculate At an angle, the far-field electric field E θ and Quantity, measured in volts per meter:

[0100]

[0101] in, These represent the pitch angle and azimuth angle, respectively.

[0102] S2. Based on the near-field measurement data, calculate the weighting coefficients after probe compensation, and use FFT Fourier transform for accelerated processing during the calculation process. Then, substitute the obtained weighting coefficients into the far-field electric field calculation formula to obtain the far-field result of the antenna under test.

[0103] Known far-field radiation pattern The far-field radiation pattern and azimuth angle can be obtained from the pitch angle θ component. The far-field radiation pattern of the component is used to represent it:

[0104]

[0105] in, and θ and A unit vector in direction.

[0106] Then let This is the representation of the probe's far-field radiation pattern. If P is 1, it indicates horizontal polarization of the probe aperture electric field; if P is 2, it indicates vertical polarization. Therefore, the probe's far-field radiation pattern can be expressed using the probe's E-plane far-field radiation pattern and H-plane far-field radiation pattern.

[0107]

[0108] Where θ0 and These represent the pitch and azimuth angles in the corresponding directions, respectively.

[0109] Therefore, by combining the far-field radiation patterns of the probe's E-plane and H-plane, the overall far-field radiation pattern of the probe can be obtained, which can then be decomposed into... and Quantity.

[0110] Next, combining the stationary phase method, the probe characteristic correction coefficient is... and (Where P represents the number of measurements, and n is an integer) can be expressed as:

[0111]

[0112] in, R is the stationary phase point. R is the distance from the probe to the normal direction of the antenna under test, in meters. k is the wave number. n is an integer.

[0113] In actual testing, the weighting function 'a' of the antenna under test with probe compensation is calculated. n and b n Two measurements need to be performed using the same probe in two orthogonal directions (considering that the probe needs to be aligned with the polarization direction of the antenna under test to obtain a voltage signal, the voltage in the other direction can often be set to 0 when performing two measurements in two orthogonal directions). Let the voltage obtained from each measurement be denoted as V. (p) (δ, z) (voltage received by the probe in the near field region), where P represents the number of measurements and (δ, z) represents the cylindrical coordinate system during the measurement.

[0114]

[0115] Among them, Z m b represents the Z-axis in the cylindrical coordinate system. n (θ) and a n (θ) is the weighting function a of the antenna under test. n and b n .and and This is the probe characteristic correction factor.

[0116] Therefore, by using the same probe to perform two measurements in two orthogonal directions, a system of linear equations can be established to obtain the weighting function 'a' of the antenna under test. n and b n .

[0117]

[0118] in, The voltage V received by the probe in the near field region can be measured. (p) (δ,z) is obtained by replacing the two-dimensional integral operation with FFT Fourier transform to accelerate the calculation.

[0119] By solving the two equations above, we can obtain:

[0120]

[0121] Fourier Acceleration Algorithm:

[0122] The Fast Fourier Transform (FFT) is the most important fast solution technique in near-field and far-field transform algorithms. FFT is a fast algorithm for calculating the Discrete Fourier Transform (DFT). For integration or summation operations in near-field and far-field transforms, the data is first discretized and transformed into a form convenient for FFT calculation, and then programmed and computed using a computer language. To facilitate program implementation, the FFT algorithm is chosen in this near-field and far-field transform algorithm to further improve data processing efficiency.

[0123] Thus, by using the FFT acceleration algorithm, the efficiency of computation can be effectively improved, and the problem of slow computation speed caused by the loop of dependent variables can be shortened.

[0124] S3. Calculate the phase center of the antenna based on the far-field results of S2, and compensate the phase offset caused by the phase center to the far-field results calculated in S2, so as to obtain the accurate far-field results of the antenna under test.

[0125] S301. Will and Vector synthesis is performed to obtain the far-field radiation pattern, which can be represented as follows:

[0126]

[0127] By decomposing the far-field radiation pattern into amplitude and phase, we obtain the far-field radiance pattern and phase pattern; among them, This is the amplitude direction diagram. The phase pattern is given, where k is the wavenumber. For the antenna, different phase centers exist on different observation planes. On one observation plane, an arbitrary point is selected as a reference point, and the phase within the antenna's 3dB beamwidth is calculated. When the value is a constant, the selected point is the phase center of the antenna;

[0128] The observation planes refer to the H-plane and V-plane of the antenna, which are determined by the far-field electric field of the antenna. and After vector synthesis, the cross-sectional results with azimuth angles of 0 degrees and 90 degrees are obtained;

[0129] S302. When the reference point of the skyline deviates from the origin of the measurement system, the far-field expression for calculating the new reference point is:

[0130]

[0131] Where r′ is the radius vector of the new reference point in the measurement coordinate system, expressed by the following formula:

[0132]

[0133] (Δx, Δy, Δz) represent the coordinates of the new reference point in the measurement coordinate system, in meters; therefore, the phase pattern function corresponding to the new reference point is further expressed as:

[0134]

[0135] If the calculated Δx, Δy, and Δz make the phase If the coordinates are equal to a constant, then the coordinates (Δx, Δy, Δz) represent the position of the phase center.

[0136] S303. Considering that the phase center of the antenna far-field observation section must be within this section, only calculate the two-dimensional coordinates of the phase center, and set the other dimension coordinate value to 0;

[0137] Therefore, the phase pattern functions of the antenna H-plane and V-plane are expressed as follows:

[0138] ψ H ′(θ)=ψ H (θ)-k(Δxsinθ+Δzcosθ)

[0139] ψ V ′(θ)=ψ V (θ)-k(Δysinθ+Δzcosθ)

[0140] In the formula, ψ H (θ), ψ V (θ), ψ H ′(θ), ψ V ′(θ) are the phase patterns of the antenna H-plane and V-plane in the measurement coordinate system and the new reference point coordinate system, respectively, thus obtaining the correct far-field phase pattern.

[0141] A highly integrated fast computation system for near-field and far-field transformation of cylindrical surfaces, comprising:

[0142] The cylindrical near-field data import module is used to import near-field measurement data;

[0143] The probe pattern data import module is used to import the far-field pattern of the probe.

[0144] The phase center compensation calculation module is used to calculate the phase center of the antenna under test and to achieve far-field phase compensation. It also supports outputting and displaying the XYZ axis coordinate values ​​of the phase center.

[0145] The normalization module is used to normalize the far-field calculation pattern.

[0146] The probe compensation module is used to compensate the input cylindrical near-field data and eliminate the far-field influence of the probe on the antenna under test.

[0147] The data export module is used to export the far-field calculation results;

[0148] The cylindrical near-field and far-field transformation module is used to perform cylindrical near-field and far-field transformation on the imported near-field measurement data to obtain the far-field calculation results.

[0149] The cylindrical near-field data display module is used to display the imported near-field measurement data;

[0150] The far-field calculation result display module is used to display the far-field calculation results;

[0151] The general parameter setting module is used to set general parameters.

[0152] The standard parameters include: frequency, minimum bounding radius, near-field measurement radius, and highest-order mode amplification factor.

[0153] The system also includes a Fourier acceleration algorithm module, which replaces the double integral calculation step of probe compensation, to achieve efficient calculation and shorten the calculation speed caused by the dependent variable loop.

[0154] In the embodiments of the application, the above scheme is integrated into a software, and the main calculation operation flow of the software is as follows:

[0155] (1) Importing cylindrical near-field data: Simply click the "Import cylindrical near-field data" button in the software to quickly import near-field measurement data.

[0156] (2) Standard Parameter Settings: In the software's standard parameter settings interface, you can easily set four parameters: frequency, minimum encirclement radius, near-field measurement radius, and highest-order mode amplification factor. The first three parameters are mainly determined by the measurement frequency, size, and test range of the antenna under test. As for the highest-order mode amplification factor, it can be set to an integer between 7 and 10 based on experience.

[0157] (3) Determine the normalization option: The software selects the normalization option by default. This option mainly normalizes the far-field calculation pattern, which is convenient for subsequent comparison with the measured results.

[0158] (4) Determine if probe compensation is enabled: Probe compensation is disabled by default. This option primarily compensates for the input cylindrical near-field data, eliminating the probe's influence on the far-field of the antenna under test. If this function is enabled, the probe's E-plane and H-plane radiation patterns must be imported beforehand. The specific import paths can be achieved using the software's "Import Probe E-plane Far-field Radiation Pattern" and "Import Probe H-plane Far-field Radiation Pattern" buttons.

[0159] (5) Determine whether the probe far-field pattern is imported: Whether the probe far-field pattern is imported depends on whether probe compensation is enabled in step (4).

[0160] (6) Enable Phase Center Calculation and Compensation: This option is mainly used to calculate the phase center and compensate the phase of the antenna under test. When this option is enabled, the software will automatically derive the phase center based on the far-field radiation pattern obtained by the near-field and far-field transformation of the cylinder (and display the XYZ axis coordinates of the phase center in the software interface). Finally, the phase offset caused by the phase center will be compensated to the far-field data result.

[0161] (7) Click Simulation Calculation: Simply click the "Simulation Calculation" button in the software to quickly perform near-field and far-field transformation calculations of the cylinder.

[0162] (8) Data export: This function supports exporting the calculated far-field results, which is convenient for subsequent linkage debugging or analysis in third-party software.

[0163] Figures 2-5 Here are the results for each case, including and without probe compensation, phase center calculation, and compensation:

[0164] In the embodiments of this application, the advantages of the above-described software are:

[0165] 1) The software has a certain degree of versatility.

[0166] The software allows users to set / select corresponding parameters or options based on imported cylindrical near-field data, enabling rapid simulation and calculation of the far-field radiation pattern of the antenna under test. Currently, the software highly integrates phase center calculation and compensation algorithms, probe compensation algorithms, and FFT acceleration algorithms, supporting functions such as phase center calculation and compensation, probe compensation, normalization settings, and near-field data viewing. This effectively meets the needs of near-field and far-field transformation calculations and result viewing under various requirements.

[0167] 2) The software has a high degree of integration.

[0168] The software integrates multiple modules, including: a Fourier Transform (FFT) acceleration algorithm module, a cylindrical near-field data import module, a probe pattern data import module, a phase center compensation calculation module, a normalization module, a probe compensation module, a data export module, a cylindrical near-field and far-field transformation module, a cylindrical near-field data display module, a far-field calculation result display module, and a general parameter setting module. By inputting relevant calculation parameters, the cylindrical near-field and far-field transformation of the antenna under test can be quickly achieved.

[0169] 3) Strong format compatibility

[0170] For external cylindrical near-field files / probe far-field files, the software supports input in Excel, DAT, and TxT formats, demonstrating strong format compatibility and effectively meeting the application needs of practical engineering.

[0171] 4) Wide coverage frequency band

[0172] It supports near-field and far-field transformation of cylindrical surfaces at arbitrary frequencies, which greatly improves the simulation calculation and data analysis of test devices at different frequencies in real-world environments.

[0173] The foregoing description illustrates and describes a preferred embodiment of the present invention. However, as previously stated, it should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the inventive concept described herein through the foregoing teachings or techniques or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A highly integrated method for fast calculation of near-field and far-field transformations of cylindrical surfaces, characterized in that: Includes the following steps: S1. Determine the method for cylindrical near-field and far-field transformation of near-field measurement data, and characterize it using the far-field electric field calculation formula; S2. Based on the near-field measurement data, calculate the weighting coefficients after probe compensation, and use FFT Fourier transform for accelerated processing during the calculation process. Then, substitute the obtained weighting coefficients into the far-field electric field calculation formula to obtain the far-field result of the antenna under test. S3. Calculate the phase center of the antenna based on the far-field results of S2, and compensate the phase offset caused by the phase center to the far-field results calculated in S2, so as to obtain the accurate far-field results of the antenna under test.

2. The highly integrated method for fast calculation of near-field and far-field transformation of a cylindrical surface according to claim 1, characterized in that: In step S1, the method of performing cylindrical near-far field transformation on the near-field measurement data is expressed by the far-field electric field calculation formula as follows: Where θ is the pitch angle. The azimuth angle is given by j, where j is the imaginary unit and k is the azimuth angle. z Let k be the wave number in the Z direction. z = k cosθ, where k represents the wave number. Represents the long-range component in the θ direction; express The far-field component of the direction, a n (k z b n (k z The symbol represents the cylindrical spectrum obtained from near-field measurement data, which is also called the weighting coefficient for far-field pattern calculation.

3. The highly integrated method for fast calculation of near-field and far-field transformation of a cylindrical surface according to claim 2, characterized in that: Step S2 includes: S201. Given far-field radiation pattern Far-field radiation pattern and azimuth angle using the pitch angle θ component The far-field radiation pattern of the component is used to represent it: in, and θ and The unit vector of direction; make This is the representation of the probe's far-field radiation pattern. If P is 1, it indicates horizontal polarization of the probe aperture electric field; if P is 2, it indicates vertical polarization of the probe aperture electric field. Therefore, the probe's far-field radiation pattern is expressed through the probe's E-plane and H-plane far-field radiation patterns. Where θ0 and These represent the pitch and azimuth angles in the corresponding directions, respectively. S202. By combining the far-field radiation patterns of the probe's E-plane and H-plane, the overall far-field radiation pattern of the probe is obtained, and then it is decomposed into... and Quantity; Next, combining the stationary phase method, the probe characteristic correction coefficient is... and Represented as: Where P represents the number of measurements, and n is an integer. R is the stationary phase point, R is the distance from the probe to the normal direction of the antenna under test in meters, k is the wave number, and n is an integer; S202. Calculate the weighting function a of the antenna under test with probe compensation. n and b n Two measurements need to be taken in two orthogonal directions using the same probe: Considering that the probe needs to be aligned with the polarization direction of the antenna under test to obtain a voltage signal, when performing two measurements in two orthogonal directions, the voltage in the other direction is set to 0. Let the voltage obtained from each measurement be denoted as V. (p) (δ, z) represents the voltage received by the probe located in the near field region, where P represents the number of measurements and (δ, z) represents the cylindrical coordinate system during the measurement. Among them, b n (θ) and a n (θ) is the weighting function a of the antenna under test. n and b n ,and and This is the probe characteristic correction factor; Therefore, by using the same probe to perform two measurements in two orthogonal directions, a system of linear equations is established to obtain the weighting function 'a' of the antenna under test. n and b n ; S203. In calculation At that time, the voltage V received by the probe in the near field region is... (p) (δ, z) is transformed using FFT Fourier transform, replacing the step S202. Two-dimensional integral operations of the calculation formula are used to accelerate the calculation process; By solving the two equations above, we obtain: S204. Calculate a n (θ) is a in step S1 n (k z ), calculate the b n (θ) is b in step S1 n (k z Substituting this into the formula of step S1, we can calculate... and 4. The highly integrated method for fast calculation of near-field and far-field transformation of a cylindrical surface according to claim 1, characterized in that: Step S3 includes: S301. Will and Vector synthesis is performed to obtain the far-field radiation pattern, which can be represented as follows: By decomposing the far-field radiation pattern into amplitude and phase, we obtain the far-field radiance pattern and phase pattern; among them, This is the amplitude direction diagram. The phase pattern is given, where k is the wavenumber. For the antenna, different phase centers exist on different observation planes. On one observation plane, an arbitrary point is selected as a reference point, and the phase within the antenna's 3dB beamwidth is calculated. When the value is a constant, the selected point is the phase center of the antenna; The observation plane refers to the H-plane and V-plane of the antenna, which are determined by the far-field electric field of the antenna. and After vector synthesis, the cross-sectional results with azimuth angles of 0 degrees and 90 degrees are obtained; S302. When the reference point of the skyline deviates from the origin of the measurement system, the far-field expression for calculating the new reference point is: Where r′ is the radius vector of the new reference point in the measurement coordinate system, expressed by the following formula: (Δx, Δy, Δz) represent the coordinates of the new reference point in the measurement coordinate system, in meters; therefore, the phase pattern function corresponding to the new reference point is further expressed as: If the calculated Δx, Δy, and Δz make the phase If the coordinates are equal to a constant, then the coordinates (Δx, Δy, Δz) represent the position of the phase center. S303. Considering that the phase center of the antenna far-field observation section must be within this section, only calculate the two-dimensional coordinates of the phase center, and set the other dimension coordinate value to 0; Therefore, the phase pattern functions of the antenna H-plane and V-plane are expressed as follows: ψ H ′(θ)=ψ H (θ)-k(Δx sinθ+Δz cosθ) ψ V ′(θ)=ψ V (θ)-k(△y sinθ+△z cosθ) In the formula, ψ H (θ), ψ V (θ), ψ H ′(θ), ψ V ′(θ) are the phase patterns of the antenna H-plane and V-plane in the measurement coordinate system and the new reference point coordinate system, respectively, thus obtaining the correct far-field phase pattern.

5. A highly integrated fast calculation system for near-field and far-field transformation of cylindrical surfaces, based on the method described in any one of claims 1 to 4, characterized in that: include: The cylindrical near-field data import module is used to import near-field measurement data; The probe pattern data import module is used to import the far-field pattern of the probe. The phase center compensation calculation module is used to calculate the phase center of the antenna under test and to achieve far-field phase compensation. It also supports outputting and displaying the XYZ axis coordinate values ​​of the phase center. The normalization module is used to normalize the far-field calculation pattern. The probe compensation module is used to compensate the input cylindrical near-field data and eliminate the far-field influence of the probe on the antenna under test. The data export module is used to export the far-field calculation results; The cylindrical near-field and far-field transformation module is used to perform cylindrical near-field and far-field transformation on the imported near-field measurement data to obtain the far-field calculation results. The cylindrical near-field data display module is used to display the imported near-field measurement data; The far-field calculation result display module is used to display the far-field calculation results; The general parameter setting module is used to set general parameters.

6. The highly integrated cylindrical near-field and far-field transformation fast calculation system according to claim 5, characterized in that: The standard parameters include: frequency, minimum bounding radius, near-field measurement radius, and highest-order mode amplification factor.

7. The highly integrated cylindrical near-field and far-field transformation fast calculation system according to claim 6, characterized in that: The system also includes a Fourier acceleration algorithm module, which replaces the double integral calculation step of probe compensation, to achieve efficient calculation and shorten the calculation speed caused by the dependent variable loop.

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