A fast calibration method for phased array antenna system

Abstract

The present invention relates to the field of phased array antennas, and specifically to a system-level rapid calibration method for phased array antennas. When performing midfield calibration, there is no need to calibrate the precise position of the midfield calibration unit. The phase error estimation of the array surface is achieved by utilizing the measured data for two-dimensional phase unwrapping and fitting according to the model. The technical key points are mainly to unwrap the folded phase surface based on the midfield monitoring parameters in two dimensions, and perform surface fitting to achieve the estimation of the array surface phase parameters. High-precision array surface calibration can be achieved without the need for calibration units with high-precision requirements and array surface position calibration. The problem of high dependence on midfield calibration and high difficulty in operation of phased array radars is solved, and the calibration efficiency of phased array antennas is greatly improved.

Description

Technical Field

[0001] The present invention relates to the field of phased array antennas, and in particular to a system-level rapid calibration method for phased array antennas. Background Art

[0002] Phased array radars generally have the characteristics of flexible and agile beams and strong scanning capabilities. Their antenna performance mainly depends on the consistency of the amplitude and phase of each radiation channel and receiving channel. Therefore, after the phased array antenna is integrated, high-precision amplitude and phase calibration is required to meet the system antenna gain, sidelobe and other performance indicators.

[0003] The general calibration methods include near-field calibration, internal monitoring calibration and mid-field calibration.

[0004] Near-field calibration generally needs to be completed in a darkroom. The near-field scanning frame drives the test probe to traverse the antenna array to obtain the amplitude and phase information of each channel. The near-field calibration method has a stable test environment and accurate amplitude and phase information, but the near-field calibration requires a large amount of equipment, the test is complex, and the test cycle is long. At the same time, the near-field calibration method is limited by the size of the radar. For large phased array radars, the antenna diameter is often more than ten meters or even dozens of meters, which is difficult to calibrate in a darkroom.

[0005] The internal monitoring calibration method is to inject or receive monitoring signals through the antenna internal monitoring network to obtain the amplitude and phase information of each channel, so as to achieve the purpose of calibration. This method requires the internal monitoring network to be parallel-fed and unit-level, and requires the internal monitoring network itself to have good amplitude and phase consistency of each channel and high isolation between channels. For large / high-frequency phased array radars, the amplitude and phase consistency of the internal monitoring network is difficult to ensure, and the amplitude and phase characteristics of the internal monitoring network will change with external factors such as radar disassembly, folding, maintenance, and aging. In addition, the internal monitoring network does not pass through equipment such as antenna units, and it is impossible to perform amplitude and phase calibration on the entire link of the radar antenna.

[0006] Midfield calibration is performed by placing an auxiliary antenna at a certain distance in front of the antenna. The placement of the auxiliary antenna should make the angle between the auxiliary antenna and each unit of the radar antenna change within a relatively small angle. The amplitude and phase information of each channel of the antenna array is obtained through the auxiliary antenna. Since the antenna unit is not an isotropic radiator and the observation point is not in the radiation far field, the superposition angle of the amplitude radiation pattern and phase radiation pattern of each antenna unit at the observation point is different, and there is a phase path difference. Therefore, before the traditional midfield calibration, the relative position relationship between the auxiliary antenna and the antenna under test must be accurately calibrated, and the amplitude and phase errors caused by the distance must be deducted in the amplitude and phase calibration. Summary of the invention

[0007] The purpose of the present invention is to propose a method for estimating the amplitude and phase errors of the array surface by using the measured data for two-dimensional phase unwrapping under the condition of mid-field calibration, so as to solve the problems of high calibration accuracy and great difficulty of calibration in the traditional method (which requires accurate calibration of the position of the calibration horn before solving the array surface amplitude and phase errors), optimize the calibration process of the phased array antenna, reduce the dependence of the phased array antenna calibration, and improve the efficiency of the phased array antenna calibration.

[0008] A phased array antenna system-level rapid calibration method comprises the following steps:

[0009] S1: Construct a midfield calibration environment, place a calibration unit in front of the radar antenna array, accurately calibrate the position of the radar unit on the antenna array, and obtain the position coordinates of all radar units, where the position coordinates of the radar unit in the i-th row and j-th column in the antenna array are expressed as (x ij ,y ij , z ij ); x ij ,y ij 、z ij Respectively represent the x-axis position coordinate, y-axis position coordinate, and z-axis position coordinate of the radar unit in the i-th row and j-th column in the antenna array;

[0010] S2: The calibration unit detects the phase of all radar units on the antenna array, where the phase of the radar unit in the i-th row and j-th column in the antenna array is expressed as The phase distribution matrix is ​​composed of the phases of all radar units

[0011] S3: Yes Perform two-dimensional unwrapping to obtain the relative unwrapping phase matrix exist contains the relative unwrapped phase of all radar units in the antenna array, where the relative unwrapped phase of the radar unit in the i-th row and j-th column in the antenna array is expressed as

[0012] S4: Fit the following formula to obtain the position coordinates of the calibration unit (x b ,yb,z b ), and the offset distance d, the fitting formula is:.

[0013]

[0014] Where λ is the radar wavelength of the antenna array; x in the formula b ,yb,z b , d are the coefficients to be fitted;

[0015] in X, Y, and Z represent the relative unwrapping phase, x-axis position coordinate, y-axis position coordinate, and z-axis position coordinate of the radar unit, respectively;

[0016] S5: According to the position coordinates (x b ,yb,z b ), calculate the phase to be corrected of each radar unit, and correct the phase of the corresponding radar unit.

[0017] Preferably, the method further comprises the steps of:

[0018] S6: Repeat steps S1-S5 one more time to complete the calibration.

[0019] Preferably, in step S5, according to the position coordinates (x b ,yb,z b ), calculate the phase to be corrected of each radar unit, and the specific method for correcting the phase of the corresponding radar unit is:

[0020] Calculate the expected relative unwrapped phase of the radar element in the i-th row and j-th column of the antenna array:

[0021]

[0022] in, represents the expected relative unwrapped phase of the radar unit in the i-th row and j-th column in the linear array;

[0023] According to the calculated Phase compensation is performed on the corresponding radar unit of the antenna array unit.

[0024] Preferably, in step S5, according to the position coordinates (x b ,yb,z b ), calculate the phase to be corrected of each radar unit, and the specific method for correcting the phase of the corresponding radar unit is:

[0025] The expected actual unwrapped phase of the radar unit in the i-th row and j-th column of the antenna array is calculated as:

[0026]

[0027] in, represents the expected actual unwrapped phase of the radar unit in the i-th row and j-th column of the antenna array;

[0028] According to the calculated Phase compensation is performed on the corresponding radar unit of the antenna array unit.

[0029] Preferably, the fitting process in step S4 uses the least squares method or the Lagrange interpolation method for fitting.

[0030] Beneficial effects:

[0031] The present invention proposes an adaptive calibration method based on midfield calibration data. When performing midfield calibration, it is not necessary to perform precise position calibration of the calibration unit. The phase error estimation of the array surface is achieved by performing two-dimensional phase unwrapping by using the measured data and fitting according to the model. Since the method makes full use of the information of the midfield calibration data and the calibration model to perform adaptive estimation of the calibration unit position, it is not necessary to perform high-precision and complex calibration of the calibration unit position, thus solving the problems of high dependence on midfield calibration of phased array radar and high difficulty in operation, and greatly improving the calibration efficiency of phased array antennas. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A typical scene diagram when the present invention is implemented;

[0033] Figure 2 is a phase diagram in an embodiment of the present invention;

[0034] Figure 3 is a relative unwrapped phase diagram obtained after the phase diagram is unwrapped in an embodiment of the present invention;

[0035] Figure 4 is a typical antenna unit distribution diagram of a phased array antenna simulated in an embodiment;

[0036] Figure 5 is a phase distribution diagram of mid-field focusing folding obtained when a fault channel exists in the antenna unit in the embodiment;

[0037] Figure 6 It is a phase distribution diagram of secondary phase unfolding when there is a fault channel in the antenna unit in the embodiment;

[0038] Figure 7 In the embodiment, the fitting results are used to perform the theoretical expected unwrapping phase diagram of the front face;

[0039] Figure 8 1 is a lobe parameter diagram before calibration and after calibration using the method in the embodiment. DETAILED DESCRIPTION

[0040] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] A phased array antenna system-level rapid calibration method comprises the following steps:

[0042] S1: Construct a midfield calibration environment, place a calibration unit in front of the radar antenna array, accurately calibrate the position of the radar unit on the antenna array, and obtain the position coordinates of all radar units, where the position coordinates of the radar unit in the i-th row and j-th column in the antenna array are expressed as (x ij ,y ij , z ij ), x ij ,y ij 、z ij They represent the x-axis position coordinate, y-axis position coordinate, and z-axis position coordinate of the radar unit in the i-th row and j-th column in the antenna array respectively; Figure 1 The figure shows a typical mid-field calibration environment; in this embodiment, the antenna array is rectangular;

[0043] S2: The calibration unit detects the phase of all radar units on the antenna array, where the phase of the radar unit in the i-th row and j-th column in the antenna array is expressed as The phase distribution matrix is ​​composed of the phases of all radar units like Figure 2 Shown is a phase distribution diagram. Different colors are used in the figure to represent different phases;

[0044] S3: Yes Perform two-dimensional unwrapping to obtain the relative unwrapping phase matrix Contains the relative unwrapped phase of all radar units in the antenna array, where the relative unwrapped phase of the radar unit in the i-th row and j-th column in the antenna array is expressed as like Figure 3 As shown, it is expressed in the form of a phase distribution diagram Different colors are used in the figure to represent different phases;

[0045] S4: Fit the following formula to obtain the position coordinates of the calibration unit (x b ,y b , z b ), and the offset distance d, the fitting formula is:.

[0046]

[0047] Where λ is the radar wavelength of the antenna array; x in the formula b ,y b 、z b , d are the coefficients to be fitted;

[0048] in X, Y, and Z represent the relative unwrapping phase, x-axis position coordinate, y-axis position coordinate, and z-axis position coordinate of the radar unit, respectively.

[0049] The principle of the formula:

[0050] represents the actual distance between the radar unit in the i-th row and j-th column of the antenna array and the calibration unit, and the relative unwrapped phase The calculated distance There is an offset from the actual distance, and the offset distance d of all radar units is equal, so the offset distance d is added to the fitting formula.

[0051] S5: Calculate the expected relative unwrapped phase of the radar unit in the i-th row and j-th column of the antenna array:

[0052]

[0053] in, represents the expected relative unwrapped phase of the radar unit in the i-th row and j-th column in the linear array;

[0054] According to the calculated Phase compensation is performed on the corresponding radar unit of the antenna array unit.

[0055] After obtaining the position coordinates (x b ,yb,z b ), the phase compensation of the corresponding radar unit of the antenna array unit can be performed by calculating the expected actual unwrapping phase of the radar unit in the i-th row and j-th column in the antenna array. The calculation method is:

[0056]

[0057] in, represents the expected actual unwrapped phase of the radar unit in the i-th row and j-th column in the antenna array.

[0058] S6: Repeat steps S1-S5 one more time to complete the calibration; repeating steps S1-S5 multiple times can reduce the impact of test errors on the calibration results.

[0059] In some embodiments, the fitting process in step S4 uses the least squares method, Lagrange interpolation method, etc. to fit.

[0060] The present invention mainly includes two typical application scenarios. One is when some channels of the array fail and need to be replaced with spare parts. The method can be used to obtain the phase value required to compensate for the corresponding failed channel. The other is when the entire array phase calibration is required. Generally, there are certain requirements for the phase consistency of the components when they leave the factory. Calibration can be achieved through multiple iterations of this method.

[0061] A more specific embodiment is described below by taking the failure of some channels on the array as an example:

[0062] The antenna array in this embodiment is as follows Figure 4 As shown, its electrical aperture is about 6m×5m, λ is 0.1m, the azimuth aperture of the array is 6m, the elevation aperture is 5m, and the calibration unit is placed about 20m in front of the array and at a height that is basically flush with the center of the array.

[0063] Steps S1-S5 are performed sequentially, wherein the In the form of a phase distribution diagram Figure 5 As shown, the white color in the figure indicates that there is no data, that is, the radar unit at the corresponding position is a faulty radar unit.

[0064] In step S3, the obtained In the form of a phase distribution diagram Figure 6 As shown, the white color in the figure indicates that there is no data, that is, the radar unit at the corresponding position is a faulty radar unit.

[0065] In step S4, the fitting result is: b ,yb,z b , d are -0.4999, 0.2001, 18, and -18.4 respectively, in meters.

[0066] In step S5, the obtained In the form of phase distribution area diagram Figure 7 As shown, according to Replace the faulty radar unit at the corresponding position and correct the corresponding phase.

[0067] After phase correction, repeat steps S1-S5 several times to complete the calibration. The antenna beam performance before and after calibration is as follows: Figure 8 shown.

[0068] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A phased array antenna system-level rapid calibration method, characterized in that The following steps are involved: S1: Construct a midfield calibration environment, place a calibration unit in front of the radar antenna array, accurately calibrate the position of the radar unit on the antenna array, and obtain the position coordinates of all radar units, where the position coordinates of the radar unit in the i-th row and j-th column in the antenna array are expressed as (x ij ,y ij , z ij ); x ij ,y ij 、z ij Respectively represent the x-axis position coordinate, y-axis position coordinate, and z-axis position coordinate of the radar unit in the i-th row and j-th column in the antenna array; S2: The calibration unit detects the phase of all radar units on the antenna array, where the phase of the radar unit in the i-th row and j-th column in the antenna array is expressed as The phase distribution matrix is ​​composed of the phases of all radar units S3: Yes Perform two-dimensional unwrapping to obtain the relative unwrapping phase matrix exist contains the relative unwrapped phase of all radar units in the antenna array, where the relative unwrapped phase of the radar unit in the i-th row and j-th column in the antenna array is expressed as S4: Fit the following formula to obtain the position coordinates of the calibration unit (x b ,y b , z b ), and the offset distance d, the fitting formula is: Where λ is the radar wavelength of the antenna array; x in the formula b ,y b 、z b , d are the coefficients to be fitted; in X, Y, and Z represent the relative unwrapping phase, x-axis position coordinate, y-axis position coordinate, and z-axis position coordinate of the radar unit, respectively; S5: According to the position coordinates (x b ,y b , z b ), calculate the phase to be corrected of each radar unit, and correct the phase of the corresponding radar unit.

2. A phased array antenna system-level rapid calibration method according to claim 1, characterized in that Also includes the steps: S6: Repeat steps S1-S5 one more time to complete the calibration.

3. The phased array antenna system-level rapid calibration method according to claim 1, characterized in that: In step S5, according to the position coordinates (x b ,y b , z b ), calculate the phase to be corrected of each radar unit, and the specific method for correcting the phase of the corresponding radar unit is: Calculate the expected relative unwrapped phase of the radar element in the i-th row and j-th column of the antenna array: in, represents the expected relative unwrapped phase of the radar unit in the i-th row and j-th column in the linear array; According to the calculated Phase compensation is performed on the corresponding radar unit of the antenna array unit.

4. The phased array antenna system-level rapid calibration method according to claim 1, characterized in that: In step S5, according to the position coordinates (x b ,y b , z b ), calculate the phase to be corrected of each radar unit, and the specific method for correcting the phase of the corresponding radar unit is: The expected actual unwrapped phase of the radar unit in the i-th row and j-th column of the antenna array is calculated as: in, represents the expected actual unwrapped phase of the radar unit in the i-th row and j-th column of the antenna array; According to the calculated Phase compensation is performed on the corresponding radar unit of the antenna array unit.

5. The phased array antenna system-level rapid calibration method according to claim 1, characterized in that: The fitting process in step S4 uses the least square method or the Lagrange interpolation method for fitting.

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