A method for calibrating an active digital phased array using aperture field inversion iteration

Abstract

The application provides a kind of active digital phased array calibration method using aperture field inversion iteration, and relates to the field of antenna measurement. It includes: in the range of planar near field, the near field data of the active digital phased array to be calibrated is obtained by scanning sampling once, including the near field data of each channel and the near field data synthesized by all channels of the phased array;The aperture field distribution of the measured phased array is obtained by introducing the aperture field inversion technology, and the calibration coefficient of each channel is obtained;The near field data of the phased array is synthesized again using the obtained channel calibration coefficient as the weight;The calculation process of the "near field data-aperture field distribution-channel calibration coefficient-synthetic near field data" is iterated until the channel calibration coefficient meets the error requirement, and the calibration of the active digital phased array is completed.The application realizes the rapid calibration of the active digital phased array, and improves the calibration efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of antenna measurement. BACKGROUND

[0002] Active digital phased array is composed of multiple antenna units, and the beam scanning in a specific direction is realized by controlling the amplitude and phase of each antenna unit. The performance of the active digital phased array depends on the amplitude and phase accuracy of each antenna unit and its link, and the calibration of the phased array is needed to ensure its stable performance. The calibration of the active digital phased array is the channel calibration of the complete link including the antenna and the transmitting / receiving components. In the existing calibration technology of the active digital phased array, the probe is placed in front of the channel to be calibrated, the channel to be calibrated is turned on and the remaining channels to be measured are turned off, and the amplitude and phase data are collected as the calibration coefficients of the channel. This method cannot eliminate the coupling between the probe and the channel to be measured and the coupling between the channels to be measured, and for a phased array with a large number of channels, a large amount of time is needed. SUMMARY

[0003] In order to solve the above technical problems, the present application is realized by the following technical scheme:

[0004] An active digital phased array calibration method using aperture field inversion iteration, comprising the following three steps:

[0005] Step 1, sampling step: obtaining the initial amplitude and phase data of the measured phased array under the condition of planar near field, including the near field data synthesized by all channels of the phased array and the near field data of each channel;

[0006] Step 2, calibration coefficient calculation step: obtaining the aperture field distribution of the phased array by performing aperture field inversion on the planar near field data, extracting the corresponding excitation amplitude and phase according to the physical position of each channel, and calculating the channel calibration coefficient;

[0007] Step 3, iterative inversion step: using the obtained channel calibration coefficient as the weight and the near field data of each channel of the phased array to perform digital beam forming, synthesizing the "new" near field data of the calibrated phased array, and iterating the calculation process of "near field data-aperture field distribution-channel calibration coefficient-synthesized near field data" until the error of the channel calibration coefficients before and after is less than a given error, i.e. the calibration of the phased array is completed.

[0008] Further, the iterative calculation process of "near field data-aperture field distribution-channel calibration coefficient-synthesized near field data" further comprises:

[0009] determining the initial amplitude calibration coefficient of each channel of the phased array as the initial phase calibration coefficient is determining the channel calibration coefficient error requirement of the phased array, the amplitude error requirement is less than ∈ A, phase error requirement is less than ∈ P ; for the first calculation, the initial near-field data of phased array is obtained by scanning the probe on the plane z=d, E 0 (x, y, z=d), the coupling formula measured by the antenna plane can be obtained:

[0010]

[0011] Wherein, the meaning of the parameters are wave vector: Wave number: Antenna plane wave spectrum vector A, probe plane wave spectrum vector S; the plane wave spectrum of the phased array to be measured can be calculated by using formula 301 using the known pattern of the probe; using the relationship between the electric field and the plane wave spectrum:

[0012]

[0013] Wherein, Indicates the aperture field amplitude and phase distribution of the phased array obtained by the first calculation; by comparing the physical position of each channel of the phased array with the position of the aperture field distribution, the excitation amplitude and phase of the channel is obtained and the amplitude and phase calibration coefficient of the corresponding channel is calculated The channel calibration coefficient of the first calculation is compared with the initial channel calibration coefficient, if the error requirement is met, the phased array calibration is completed; if the error requirement is not met, the channel calibration coefficient is applied to the channel near-field data, and the "new" phased array near-field data E 1 (x, y, z=d) is synthesized by using digital beam forming algorithm; thus, the first calculation process is completed; the "new" near-field data obtained is repeated in the process of "near-field data-aperture field distribution-channel calibration coefficient-synthesized near-field data", until the channel calibration coefficients obtained twice are less than the given error A , ∈ P , the iterative process is ended, and the channel calibration coefficient calculated in the last time is taken As the channel calibration coefficient of the phased array. In the aperture field inversion calculation process, the sampling interval of the plane near-field of the phased array to be measured in x and y directions is Δx, Δy (Δx, Δy), and the corresponding sampling point number is M, N. The specific steps of calculating the plane wave spectrum from the near-field data are:

[0014]

[0015] Wherein, the parameters m∈[1, M], n∈[1, N], p∈[1, M], q∈[1, N], are the numbers corresponding to the sampling points;

[0016] The steps of calculating the aperture field amplitude and phase from the plane wave spectrum are:

[0017]

[0018] Since the planar near-field sampling interval is Δx, Δy(Δx, Δy), according to formulas 203 and 204, the resolution of the calculated aperture field distribution is still Δx, Δy. The excitation amplitude and phase of each channel of the phased array are obtained by the one-to-one correspondence between the physical position of the channel and the position of the aperture field distribution. In the specific implementation process, Fourier interpolation formula is introduced to improve the resolution.

[0019]

[0020] According to Equation 205, the aperture field amplitude and phase data of the phased array at any position (x, y) on the aperture plane can be calculated. Attached Figure Description

[0021] Fig. 1 This is a flowchart of the calibration method for active digital phased array antennas according to the present invention.

[0022] Fig. 2 The normalized amplitude calibration coefficient is the result of five iterations of calculation using the phased array of this invention.

[0023] Fig. 3 The normalized phase calibration coefficients are obtained from each iteration of the phased array calculated using the embodiment of the present invention after five iterations. Detailed Implementation

[0024] The following combination Figs. 1-3 The following describes a preferred embodiment of the present invention in detail.

[0025] A preferred embodiment of the present invention is a working P-band horizontally polarized active digital phased array comprising 1×16 channels, with 16 channels in the horizontal direction, a channel spacing of 20 cm, and 1 channel in the vertical direction. Fig. 1 As shown, a preferred embodiment of the present invention includes the following steps:

[0026] Step 1, Sampling Step: Acquire the initial amplitude and phase data of the phased array under test within the planar near-field range, including the near-field data synthesized from all channels of the phased array and the near-field data of each channel;

[0027] Step 2, Calibration coefficient calculation steps: Perform aperture field inversion on the planar near-field data to obtain the aperture field distribution of the phased array, extract the corresponding excitation amplitude and phase according to the physical position of each channel, and calculate the channel calibration coefficient;

[0028] Step 3, iterative inversion step: using the obtained channel calibration coefficient as weight and the near-field data of each channel of the phased array to do digital beam forming, synthesizing the "new" near-field data of the calibrated phased array, iterating the calculation process of "near-field data - aperture field distribution - channel calibration coefficient - synthesized near-field data" until the error of the channel calibration coefficient of the previous and the next time is less than the given error, and the calibration of the phased array is completed.

[0029] The iterative calculation process of "near-field data - aperture field distribution - channel calibration coefficient - synthesized near-field data" specifically includes:

[0030] Determine the initial channel calibration coefficient of the phased array, and the amplitude calibration coefficient is The phase calibration coefficient Determine the error requirement ∈ of the amplitude calibration coefficient A <0.2dB, and the error requirement ∈ of the phase calibration coefficient P <5deg. The distance between the probe and the phased array to be measured is z=1m, and the initial plane near-field amplitude and phase of the phased array obtained by the probe is E 0 (x,y,z=1m), the superscript of the parameter E indicates the number of iterative calculations, and 0 indicates the amplitude and phase obtained by initial sampling. The coupling formula measured by the antenna plane can be obtained:

[0031]

[0032] Wherein, the meanings of the parameters are respectively wave vector: Wave number: Plane wave spectrum vector A of the antenna, and plane wave spectrum vector S of the probe. The plane wave spectrum data of the probe can be obtained by the known pattern of the probe, and the plane wave spectrum of the phased array to be measured can be calculated by using formula 401. Then, the aperture field distribution is calculated by using the relationship between the electric field and the plane wave spectrum:

[0033]

[0034] Wherein, Indicates the aperture field distribution obtained by the first calculation. The physical positions of the channels are one-to-one corresponding to the physical positions of the aperture field distribution, the excitation amplitude and phase of each channel are extracted, and the calibration coefficient Parameter Indicates the amplitude calibration coefficient obtained by the first calculation, Indicates the phase calibration coefficient obtained by the first calculation. It is judged whether the amplitude and phase calibration coefficients meet the error requirement, and if not, iterative calculation is performed. The obtained amplitude and phase calibration coefficients are used as weight factors acting on the near-field data of each channel of the phased array, and the "new" near-field data E of the calibrated phased array is synthesized by using the digital beam forming algorithm. 1(x, y, z = 1m); enter the second calculation, and calculate the aperture field distribution according to the aperture field inversion algorithm of formula 401 and formula 402 , obtain the channel calibration coefficient Compare the calibration coefficient obtained in the first calculation with the error, if the error is not satisfied, the channel calibration coefficient of this time is taken as the weight factor to synthesize the new phased array near-field data E after calibration 2 (x, y, z = 1m) Enter the next calculation process; until the calibration coefficients obtained in the previous and next two times satisfy the error condition, that is, end the iterative calculation process, and take the last calibration coefficient The channel calibration coefficient of the to-be-tested active digital phased array.

[0035] The aperture field inversion calculation step is further specifically implemented as:

[0036] The specific implementation mode of the mutual conversion between the plane wave spectrum and the amplitude and phase distribution of the radiation field of the to-be-tested phased array is:

[0037] The plane near-field sampling interval of the to-be-tested phased array in the x and y directions is Δx, Δy (Δx, Δy), and the corresponding sampling point number is MxN. The specific steps of calculating the plane wave spectrum from the near-field amplitude and phase are:

[0038]

[0039] Wherein, the parameters m ∈ [1, M], n ∈ [1, N], p ∈ [1, M], q ∈ [1, N] are the corresponding numbers of the sampling points.

[0040] The steps of calculating the radiation field amplitude and phase from the plane wave spectrum are:

[0041]

[0042] Specifically, in the calculation of the calibration coefficient step, the physical positions of the channels of the phased array and the physical positions of the aperture field distribution are one-to-one corresponding, so as to extract the excitation amplitude and phase of the corresponding channel, and the further specific implementation mode is:

[0043] Since the plane near-field sampling interval is Δx, Δy, according to formula 403 and formula 404, the resolution of the calculated aperture field distribution is still Δx, Δy, and the Fourier interpolation formula is introduced to improve the resolution so that the physical positions of the channels and the positions of the aperture field amplitude and phase distribution are one-to-one corresponding, and the specific implementation is:

[0044]

[0045] Wherein, the parameter E x,y (x, y) represents the aperture field data of the to-be-tested phased array at any position on the aperture plane.

[0046] Fig. 2 and Fig. 3 The channel normalization amplitude and phase calibration coefficient obtained by the preferred embodiment of the present application after 5 iterations are shown in the following table. It can be seen that the iterative method of aperture field inversion is used to calibrate the active digital phased array, the iterative calculation process converges rapidly, and converges within the error range after the 3rd and 4th calculation, which can quickly meet the error condition to end the iteration process, and the FFT algorithm is further used to improve the calculation efficiency.

[0047] The above examples are only used to illustrate the technical solutions of the present application and not to limit. Those skilled in the art should understand that the technical solutions of the present application can be modified or equivalently replaced without departing from the spirit and scope of the present application, and all should be covered in the scope of the claims of the present application.

Claims

1. An active digital phased array calibration method utilizing aperture field inversion iteration, characterized in that: Step 1, Sampling Step: Acquire the initial data of the phased array under planar near-field conditions, including near-field data synthesized from all channels of the phased array and near-field data of each channel; Step 2, Calibration coefficient calculation steps: Perform aperture field inversion on the planar near-field data to obtain the aperture field distribution of the phased array, extract the corresponding excitation amplitude and phase according to the physical location of each channel, and calculate the channel calibration coefficient; Step 3, Iterative Inversion Step: Using the obtained channel calibration coefficients as weights and the near-field data of each channel of the phased array, perform digital beamforming to synthesize new phased array near-field data after calibration. Iterate the calculation process of "near-field data - aperture field distribution - channel calibration coefficients - synthesized near-field data" until the error between the two channel calibration coefficients is less than the given error, and the calibration of the phased array is completed. Step 3 also includes: The initial amplitude calibration coefficients of the phased array channels are determined to be: The initial phase calibration coefficient is The required channel calibration coefficient error for the phased array is determined, and the amplitude error is required to be less than ∈ A The phase error is required to be less than ∈ P ; For the first calculation, the probe scans the z=d plane to obtain the initial near-field data of the phased array as E. 0 (x,y,z=d), can be obtained from the coupling formula of the antenna plane measurement: Among them, wave vector Wave number The antenna's plane spectrum vector A, and the probe's plane spectrum vector S; the probe's plane spectrum data can be obtained from the probe's known radiation pattern, and the plane spectrum of the phased array under test can be calculated using formula 201; using the relationship between the electric field and the plane spectrum: in, This represents the amplitude and phase distribution of the aperture field of the phased array under test obtained after the first calculation; by comparing the physical position of each channel of the phased array with the position of the aperture field distribution, the excitation amplitude and phase of the channel are obtained, and the amplitude and phase calibration coefficient of the corresponding channel is calculated. The channel calibration coefficients calculated in the first step are compared with the initial channel calibration coefficients. If the error requirements are met, the phased array calibration is completed; otherwise, the channel calibration coefficients are applied to the channel near-field data, and a new phased array near-field data E is synthesized using a digital beamforming algorithm. 1 (x,y,z=d); This concludes the first calculation process; Repeat the process of "near-field data—aperture field distribution—channel calibration coefficients—synthesized near-field data" with the obtained new phased array near-field data until the channel calibration coefficients obtained in the two acquisitions are less than the given error ∈ A ,∈ P End the iteration process and take the channel calibration coefficient from the last calculation. These are the channel calibration coefficients for the phased array.

2. The active digital phased array calibration method using aperture field inversion iteration according to claim 1, characterized in that: The aperture field inversion process in the iterative calculation of "near-field data - aperture field distribution - channel calibration coefficient - synthetic near-field data" also includes: The methods for converting between the plane spectrum and the amplitude and phase distribution of the radiation field of the phased array under test include: The planar near-field sampling intervals of the phased array under test in the x and y directions are Δx and Δy, respectively, and the corresponding number of sampling points are M and N. The specific steps for calculating the planar spectrum from the near-field data are as follows: Where the parameters m∈[1,M], n∈[1,N], p∈[1,M], q∈[1,N] are the numbers corresponding to the sampling points; The steps for calculating the aperture field distribution from a plane wave spectrum are as follows:

3. The active digital phased array calibration method using aperture field inversion iteration according to claim 2, characterized in that: The aperture field inversion process also includes: The excitation amplitude and phase of each channel of the phased array are obtained by a one-to-one correspondence between the physical location of the channel and the location of the aperture field distribution, and the resolution is improved by using Fourier interpolation formula: The aperture field amplitude and phase data of the phased array at any position (x, y) are calculated according to Equation 401.

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