Active phased array calibration method based on far-field pattern

Abstract

The invention provides an active phased array calibration method based on a far-field pattern. The method comprises the following steps: initializing parameters; calculating a scattering matrix, an impedance matrix, an actual feed amplitude and a phase of the active phased-array antenna to be calibrated; and obtaining a calibration result of the active phased array. According to the invention, an impedance matrix of the active phased-array antenna is calculated through a scattering matrix calculated by a far-field pattern in an array of each phased-array antenna unit and a far-field pattern of a single phased-array antenna unit, and a diagonal matrix formed by inherent impedance of an active phased-array antenna transmitter; the influence on calculation errors caused by the fact that only near-field data is used and a calculation result is a non-analytical solution is avoided, and the calibration precision is improved; and meanwhile, calibration feed amplitudes and phases of the active phased-array antenna in different phase shifter states can be obtained through the impedance matrix, and calibration results in all phase shifter states can be obtained at the same time without multiple iterations, so that the calibration efficiency is effectively improved.

Description

Technical Field

[0001] The invention belongs to the field of electromagnetic technology and relates to a phased array calibration method, in particular to an active phased array calibration method based on a phased array unit pattern. Background Art

[0002] Since the beginning of the 21st century, phased array antenna technology has become an important hotspot in this field. Phased array antennas are widely used in communications, radar and other fields due to their fast scanning speed, strong directivity and high precision. Phased array antennas are divided into passive phased array antennas and active phased array antennas. Compared with passive phased array antennas, active phased arrays receive and transmit electromagnetic waves through their unique T / R components, and each T / R component is connected to a corresponding antenna unit, so that each antenna unit can independently realize the function of receiving and transmitting electromagnetic waves. By modifying the phase information on each antenna unit, the beam scanning function of the active phased array is completed.

[0003] Due to various factors in the manufacturing and installation process, such as differences in antenna unit size and position deviations, the actual radiation pattern of the active phased array antenna may deviate from the theoretical design. Active phased array antenna calibration can adjust these deviations to make the phased array antenna radiation pattern more accurate. Active phased array antenna calibration first requires obtaining the test data of the phased array antenna, calculating the feed phase and amplitude of the phased array antenna unit, and adjusting the input feed according to the calculation results to ensure that the actual radiation pattern of the active phased array antenna meets the design requirements. For example, a patent application with application publication number CN116170089A and titled “A method for calibrating an active digital phased array using aperture field inversion iteration” discloses a method for calibrating an active digital phased array using aperture field inversion iteration. The invention scans and samples the active digital phased array to be calibrated once within the planar near field range to obtain near-field data, which includes the near-field data of each channel and the near-field data synthesized by all channels of the phased array; introduces aperture field inversion technology to obtain the aperture field distribution of the phased array to be measured, and obtains the calibration coefficient of each channel; uses the obtained channel calibration coefficient as a weight to re-synthesize the near-field data of the phased array; iterates the calculation process of “near-field data—aperture field distribution—channel calibration coefficient—synthesized near-field data” until the channel calibration coefficient meets the error requirement, thereby completing the calibration of the active digital phased array. This invention realizes rapid calibration of active digital phased arrays and improves calibration efficiency. However, when calculating channel calibration coefficients, that is, calibrating the feed amplitude and phase, it only uses near-field data without considering the inherent impedance of the phased array antenna transmitter, resulting in large calibration errors. In addition, multiple iterations are required when calculating the calibration feed amplitude and phase, and only one phase shifter state can be calibrated at a time, which affects the further improvement of calibration efficiency. Summary of the invention

[0004] The purpose of the present invention is to address the shortcomings of the above-mentioned prior art and propose a phased array calibration method based on far-field radiation pattern to solve the technical problems of low calibration accuracy and efficiency in the prior art.

[0005] To achieve the above object, the technical method adopted by the present invention includes the following steps:

[0006] (1) Initialization parameters:

[0007] The initialization active phased array antenna to be calibrated includes N phased array antenna units with a spacing of D. The far-field pattern of the nth phased array antenna unit is E n (θ); Initialize the phase factor of the active phased array antenna to be calibrated to P, and the phase delay of the nth phased array antenna unit to P n ; Initialize the far-field pattern of a single phased array antenna unit to E s (θ); Initialize the active phased array antenna to be calibrated. There are I phase shifter states. The initial feed of the active phased array antenna to be calibrated corresponding to the i-th phase shifter state is V i , V i The amplitude and phase are V i_mag 、V i_ph ; Initialize the inherent impedance of the active phased array antenna transmitter to be calibrated as z net ; The maximum initialization amplitude and phase errors are ε A , ε P , where N ≥ 2 and θ represents E n (θ) and E s (θ) the pitch angle;

[0008] (2) Calculate the scattering matrix of the active phased array antenna to be calibrated:

[0009] The distance D between adjacent phased array antenna units and the far-field pattern E of the phased array antenna unit to be calibrated n (θ) and phase delay P n , and the far-field pattern E of a single phased array antenna element s (θ), calculate E n (θ) corresponds to the scattering parameter S n , and construct a scattering matrix S with a dimension of N×N, with the number of phase factor P as rows and the number of phased array antenna units as columns;

[0010] (3) Calculate the impedance matrix of the active phased array antenna to be calibrated:

[0011] Build with z net The N×N diagonal matrix Z is a matrix with diagonal elements. net , and through Z netCalculate the N×N dimensional impedance matrix Z of the active phased array antenna to be calibrated with the scattering matrix S;

[0012] (4) Calculate the actual feeding amplitude and phase of the active phased array antenna to be calibrated:

[0013] Through the i-th initial feed V of the active phased array antenna to be calibrated i And the impedance matrix Z, calculate the actual feeding amplitude I of the active phased array antenna to be calibrated i_mag And the actual feeding phase I i_ph ;

[0014] (5) Obtain the calibration results of the active phased array:

[0015] Judgment | V i_mag -I i_mag |≤ε A And |V i_ph -I i_ph |≤ε P Is it true? If so, set the initial feed amplitude V of the active phased array antenna to be calibrated i_mag , Phase V i_ph are respectively used as the calibration feed amplitude C of the active phased array antenna to be calibrated i_mag , Phase C i_ph , otherwise, the active phased array antenna to be calibrated is initially fed with V i And the impedance matrix Z, calculate the calibration feed amplitude C of the active phased array antenna to be calibrated i_mag And calibrate the feed phase C i_ph .

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] First, the present invention calculates the scattering matrix of the active phased array antenna to be calibrated through the far-field radiation pattern of each antenna unit in the active phased array antenna and the far-field radiation pattern of a single phased array antenna unit, and calculates the impedance matrix of the active phased array antenna through a diagonal matrix composed of the scattering matrix and the inherent impedance of the active phased array antenna transmitter, thereby avoiding the defect of the prior art that only near-field data is used when calculating the feed amplitude and phase, resulting in a non-analytical solution, reducing the calculation error, and thus improving the calibration accuracy.

[0018] Second, the impedance matrix calculated by the present invention through the inherent impedance of the active phased array antenna transmitter can obtain the calibration feed amplitude and phase of the active phased array antenna in different phase shifter states without multiple iterations. The calibration results under all phase shifter states can be obtained simultaneously, and the defect of the prior art that only one phase shifter state can be calibrated per iteration is avoided, thereby effectively improving the calibration efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is an implementation flow chart of the present invention.

[0020] Figure 2 1 is a graph of actual feeding amplitude and actual feeding phase in an embodiment of the present invention.

[0021] Figure 3 It is a simulation diagram of the calibration result in the embodiment of the present invention. DETAILED DESCRIPTION

[0022] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0023] Reference Figure 1 , the present invention comprises the following steps:

[0024] Step 1) Initialize parameters:

[0025] The initialization active phased array antenna to be calibrated includes N phased array antenna units with a spacing of D. The far-field pattern of the nth phased array antenna unit is E n (θ); Initialize the phase factor of the active phased array antenna to be calibrated to P, and the phase delay of the nth phased array antenna unit to P n ; Initialize the far-field pattern of a single phased array antenna unit to E s (θ); Initialize the active phased array antenna to be calibrated. There are I phase shifter states. The initial feed of the active phased array antenna to be calibrated corresponding to the i-th phase shifter state is V i , V i The amplitude and phase are V i_mag 、V i_ph ; Initialize the inherent impedance of the active phased array antenna transmitter to be calibrated as z net ; The maximum initialization amplitude and phase errors are ε A , ε P , where N ≥ 2 and θ represents E n (θ) and E s (θ) the pitch angle;

[0026] The phased array antenna unit used in this embodiment is a half-wave dipole antenna. In this embodiment, N=7, D=0.05m, and the inherent impedance z of the active phased array antenna transmitter to be calibrated is net =50Ω, maximum amplitude error ε A =0.5dB, maximum phase error ε P =5°, feed a single phased array antenna unit with an amplitude of 1v and a phase of 0°; obtain the far-field pattern E of a single phased array antenna unit through simulation s(θ); feed each unit of the phased array antenna in turn with an amplitude of 1v and a phase of 0°, and obtain the far-field pattern E of the phased array antenna unit through simulation n (θ).

[0027] Step 2) Calculate the scattering matrix of the active phased array antenna to be calibrated:

[0028] In order to obtain the impedance matrix of the active phased array antenna to be calibrated, it is necessary to first calculate the scattering matrix of the active phased array antenna to be calibrated. The far-field pattern E of the nth phased array antenna unit of the active phased array antenna n (θ) can be expanded as:

[0029]

[0030] in,[·] nm represents the element in the nth row and mth column of the matrix, U N represents the N×N dimensional unit diagonal matrix, j represents the imaginary unit, e represents the natural constant, π represents the circumference of a circle, f represents the operating frequency of the phased array antenna, and c represents the speed of light.

[0031] The distance D between adjacent phased array antenna units and the far-field pattern E of the phased array antenna unit to be calibrated n (θ) and phase delay P n , and the far-field pattern E of a single phased array antenna element s (θ), calculate E n (θ) corresponds to the scattering parameter S n , and construct a scattering matrix S with a dimension of N×N, with the number of phase factor P as rows and the number of phased array antenna elements as columns:

[0032] S=[S1,S2,...,S n ,...,S N ]

[0033]

[0034] Among them, P -1 represents the inverse result of P, Y n represents an N×1 dimensional matrix where all elements except the nth row are 1 and all other elements are 0. n It represents the phase delay of the electromagnetic wave radiated by the nth phased array antenna unit relative to the first phased array antenna unit at an angle of θ.

[0035] In this embodiment, the phased array antenna operating frequency f = 3 GHz, in order to improve the calculation efficiency, only the E when θ = 0° ~ 30° is used. n (θ) and E s (θ) is calculated.

[0036] Step 3) Calculate the impedance matrix of the active phased array antenna to be calibrated:

[0037] In order to calculate the actual, calibrated feed amplitude and phase of the active phased array antenna to be calibrated, it is necessary to first calculate the impedance matrix of the phased array antenna. net is a diagonal matrix Z with dimension N×N for the diagonal elements net , and through Z net The impedance matrix Z of the active phased array antenna to be calibrated is calculated with the scattering matrix S:

[0038] Z=Z net (U N +S)(U N -S) -1

[0039] Among them, U N represents the N×N dimensional unit diagonal matrix, (U N -S) -1 Represents the matrix (U N -S) is the inverse result.

[0040] The present invention calculates the scattering matrix of the active phased array antenna to be calibrated through the far-field radiation pattern of each antenna unit in the active phased array antenna and the far-field radiation pattern of a single phased array antenna unit, and calculates the impedance matrix of the active phased array antenna through a diagonal matrix composed of the scattering matrix and the inherent impedance of the active phased array antenna transmitter, thereby avoiding the defect of the prior art that only near-field data is used when calculating the feed amplitude and phase, resulting in a non-analytical solution, reducing the calculation error, and thus improving the calibration accuracy.

[0041] Step 4) Calculate the actual feed amplitude and phase of the active phased array antenna to be calibrated:

[0042] Through the i-th initial feed V of the active phased array antenna to be calibrated i And the impedance matrix Z, calculate the actual feeding amplitude I of the active phased array antenna to be calibrated i_mag And the actual feeding phase I i_ph :

[0043] I i_mag =abs(Z -1 V i )

[0044] I i_ph =angle(Z -1 V i )

[0045] Where abs(·) represents the absolute value function, angle(·) represents the complex phase angle function, and Z -1Represents the inverse result of Z.

[0046] Step 5) Obtain the calibration results of the active phased array:

[0047] Judgment | V i_mag -I i_mag |≤ε A And |V i_ph -I i_ph |≤ε P Is it true? If so, set the initial feed amplitude V of the active phased array antenna to be calibrated i_mag , Phase V i_ph are respectively used as the calibration feed amplitude C of the active phased array antenna to be calibrated i_mag , Phase C i_ph , otherwise, the active phased array antenna to be calibrated is initially fed with V i And the impedance matrix Z, calculate the calibration feed amplitude C of the active phased array antenna to be calibrated i_mag And calibrate the feed phase C i_ph :

[0048] C i_mag =abs(ZV i )

[0049] C i_ph =angle(ZV i ).

[0050] The present invention can obtain the calibration feed amplitude and phase of the active phased array antenna in different phase shifter states through the impedance matrix calculated by the inherent impedance of the active phased array antenna transmitter, without the need for multiple iterations, and can simultaneously obtain the calibration results in all phase shifter states. It avoids the defect of the prior art that only one phase shifter state can be calibrated per iteration, and effectively improves the calibration efficiency.

[0051] The following is a further description of the technical effects of the present invention in conjunction with the simulation results:

[0052] 1. Experimental conditions and contents:

[0053] The actual feeding amplitude and phase of the active phased array at different phase states and the far-field radiation pattern of the phased array before and after calibration of the active phased array are simulated by FEKO2020 and MATLAB R2021b. The results are as follows: Figure 2 , 3 As shown;

[0054] 2. Experimental results analysis:

[0055] Reference Figure 2 The horizontal axis represents the unit number, and the initial feeding amplitude and phase of each phased array unit are set to 1v and 0°.

[0056] Reference Figure 2 (a), the vertical axis represents the actual feeding amplitude of the phased array antenna, in dB. The dashed line is the actual feeding amplitude of the phased array antenna obtained by this method, and the solid line is the actual feeding amplitude of the phased array antenna obtained by FEKO2020.

[0057] Reference Figure 2 (b), the vertical axis represents the actual feeding phase of the phased array antenna, in degrees. The dashed line is the actual feeding phase of the phased array antenna obtained by this method, and the solid line is the actual feeding phase of the phased array antenna obtained by FEKO2020.

[0058] Reference Figure 3 , the vertical axis represents the phased array antenna pattern, in dB, and the horizontal axis represents the elevation angle, in degrees. When the target beam is pointed at 40°, the initial feeding amplitude of each phased array unit is set to 1v, the initial feeding phase of the first unit is 0°, and each unit increases the initial feeding phase of the previous unit by 115.78° according to the position order. The phased array antenna is fed with the initial feeding amplitude, phase and the calibrated feeding amplitude and phase respectively, and the far-field pattern of the phased array antenna is obtained by simulation. The solid line is the far-field pattern of the phased array antenna when the initial feeding amplitude and phase are used for feeding, and the dashed line is the far-field pattern of the phased array antenna when the calibrated feeding amplitude and phase are used for feeding. The beam pointing of the far-field pattern of the phased array antenna when the initial feeding amplitude and phase are used for feeding is 39°, and the beam pointing of the far-field pattern of the phased array antenna when the calibrated feeding amplitude and phase are used for feeding is 40°.

[0059] In summary, the actual feeding amplitude and phase of the active phased array antenna obtained by the present invention are consistent with the actual feeding amplitude and phase curves obtained by FEKO2020, and the actual feeding amplitude and phase of each unit of the active phased array antenna are accurately calculated. The beam pointing of the phased array antenna pattern fed with the initial feeding amplitude and phase does not reach the target beam pointing. When fed with the calibrated feeding amplitude and phase, the beam pointing of the phased array antenna pattern reaches the target beam pointing, which further illustrates the accuracy of the calibrated feeding amplitude and phase.

Claims

1. A method for calibrating an active phased array based on a far-field pattern, characterized in that: The steps include: (1) Initialization parameters: The initialization active phased array antenna to be calibrated includes N phased array antenna units with a spacing of D. The far-field pattern of the nth phased array antenna unit is E n (θ); Initialize the phase factor of the active phased array antenna to be calibrated to P, and the phase delay of the nth phased array antenna unit to P n ; Initialize the far-field pattern of a single phased array antenna unit to E s (θ); Initialize the active phased array antenna to be calibrated. There are I phase shifter states. The initial feed of the active phased array antenna to be calibrated corresponding to the i-th phase shifter state is V i , V i The amplitude and phase are V i_mag 、V i_ph ; Initialize the inherent impedance of the active phased array antenna transmitter to be calibrated as z net ; The maximum initialization amplitude and phase errors are ε A , ε P , where N ≥ 2 and θ represents E n (θ) and E s (θ) the pitch angle; (2) Calculate the scattering matrix of the active phased array antenna to be calibrated: The distance D between adjacent phased array antenna units and the far-field pattern E of the phased array antenna unit to be calibrated n (θ) and phase delay P n , and the far-field pattern E of a single phased array antenna element s (θ), calculate E n (θ) corresponds to the scattering parameter S n , and construct a scattering matrix S with a dimension of N×N, with the number of phase factor P as rows and the number of phased array antenna units as columns; (3) Calculate the impedance matrix of the active phased array antenna to be calibrated: Build with z net The N×N diagonal matrix Z is a matrix with diagonal elements. net , and through Z net Calculate the N×N dimensional impedance matrix Z of the active phased array antenna to be calibrated with the scattering matrix S; (4) Calculate the actual feeding amplitude and phase of the active phased array antenna to be calibrated: Through the i-th initial feed V of the active phased array antenna to be calibrated i And the impedance matrix Z, calculate the actual feeding amplitude I of the active phased array antenna to be calibrated i_mag And the actual feeding phase I i_ph ; (5) Obtain the calibration results of the active phased array: Judgment | V i_mag -I i_mag |≤ε A And |V i_ph -I i_ph |≤ε P Is it true? If so, set the initial feed amplitude V of the active phased array antenna to be calibrated i_mag , Phase V i_ph are respectively used as the calibration feed amplitude C of the active phased array antenna to be calibrated i_mag , Phase C i_ph , otherwise, the active phased array antenna to be calibrated is initially fed with V i And the impedance matrix Z, calculate the calibration feed amplitude C of the active phased array antenna to be calibrated i_mag And calibrate the feed phase C i_ph .

2. The method according to claim 1, characterized in that E described in step (2) n (θ) corresponds to the scattering parameter S n , the calculation formula is: Among them, P -1 represents the inverse result of the phase factor P, Y n represents an N×1 dimensional matrix where all elements except the nth row are 1 and all other elements are 0. n It represents the phase delay of the electromagnetic wave radiated by the nth phased array antenna unit relative to the first phased array antenna unit at an angle of θ, e represents a natural constant, j represents an imaginary unit, π represents pi, f represents the operating frequency of the phased array antenna, and c represents the speed of light.

3. The method according to claim 1, characterized in that The N×N dimensional impedance matrix Z of the active phased array antenna to be calibrated described in step (3) is calculated as follows: Z=Z net (U N +S)(U N -S) -1 Among them, U N represents the N×N dimensional unit diagonal matrix, (U N -S) -1 Represents the matrix (U N -S) is the inverse result.

4. The method according to claim 1, characterized in that: The actual feed amplitude I of the active phased array antenna to be calibrated in step (4) i_mag And the actual feeding phase I i_ph , the calculation formulas are: I i_mag =abs(Z -1 V i ) I i_ph =angle(Z -1 In i ) Where abs(·) represents the absolute value function, angle(·) represents the complex phase angle function, and Z -1 Represents the inverse result of Z.

5. The method according to claim 4, characterized in that The calibration feed amplitude C of the active phased array antenna to be calibrated in step (5) i_mag And calibrate the feed phase C i_ph , the calculation formula is: C i_mag =abs(ZV i ) C i_ph =angle(ZV i )。

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