A mid-field calibration method for phased array radar antenna

Abstract

The present invention relates to a mid-field calibration method for a phased array radar antenna, and belongs to the field of radar. The present invention selects three characteristic points A, B, and C on the array plane of the phased array radar antenna at random, selects a horn antenna of the same frequency band as the phased array radar antenna, and places the horn antenna aperture directly opposite the phased array radar antenna, so that the main lobe of the horn can cover the entire array plane of the phased array radar antenna, and uses a total station to measure the distances PA, PB, and PC from the center point P of the horn antenna aperture to the marking points A, B, and C on the phased array radar antenna array plane, and then obtains the distances P1, P2...PN from the center of each channel to the center of the horn antenna aperture, and obtains the phase change of each channel according to the distances P1, P2...PN, and obtains the phase correction coefficient of each channel in combination with the phase test values ​​of each channel. The present invention can complete the test in a field with a depth of 30m, greatly reducing the test distance, simplifying the test process, improving the test efficiency, and saving test expenses.

Description

Technical Field

[0001] The invention belongs to the field of radars, and in particular relates to a mid-field calibration method for a phased array radar antenna. Background Art

[0002] Phased array radar is a new type of multifunctional electronically scanned radar that uses phased array antennas. Since its introduction in the 1960s, it has achieved tremendous development and application. Phased array radar has unique advantages in observing high-speed moving targets, realizing radar multi-functions, multi-target tracking, and extending the radar's range, and has become the mainstream of today's era. Phased array antennas are a key component of phased array radars and often determine the radar's system solution.

[0003] For active phased array antennas, accurate beam pointing can only be achieved by accurately measuring the amplitude and phase differences between channels and making corresponding compensation. Nowadays, the amplitude consistency of each channel of the component is high and the difference is small, so the calibration of the channel phase is the key to ensuring the performance of the phased array antenna. Accurately measuring the phase difference between each channel is the basis for ensuring the accurate beam pointing of the phased array radar.

[0004] Generally, the calibration of phased array radar antennas is often carried out under far-field conditions. Under far-field conditions, the distance from the test signal source to the center of each channel of the radar array is approximately equal. The measured phase differences between the channels are mainly caused by the differences in the internal components of the phased array antenna. The phase far-field calibration of phased array radar antennas has high requirements for test conditions and is easily limited by time, venue, funds and other reasons, making it difficult to achieve ideal test results. How to quickly, conveniently and accurately calibrate radar phased array antennas under mid-field conditions (test distance is less than far-field) is an urgent problem to be solved. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] The technical problem to be solved by the present invention is how to provide a mid-field calibration method for a phased array radar antenna to solve the channel calibration problem of the phased array radar.

[0007] (II) Technical solution

[0008] In order to solve the above technical problems, the present invention proposes a mid-field calibration method for a phased array radar antenna, the method comprising the following steps:

[0009] S1. Power on and preheat each system of the phased array radar to ensure that each part of the radar is in a stable working state and that each channel of the phased array radar antenna is in a stable state;

[0010] S2. Arbitrarily select three characteristic points A, B, and C on the antenna array of the phased array radar. The center positions of each channel of the phased array radar antenna and the points A, B, and C marked on the antenna array are in the same plane. Set this plane as the XOY plane and establish a spatial coordinate system.

[0011] S3, specify the coordinates of point A as (x a ,y a ,0), the coordinates of point B are (x b ,y b ,0), the coordinates of point C are (x c ,y c ,0), the coordinates of each channel on the array are (x1,y1,0), (x2,y2,0),…, (x n ,y n ,0);

[0012] S4. Select a horn antenna with the same frequency band as the phased array radar antenna, and place the horn antenna mouth directly opposite the phased array radar antenna so that the main lobe of the horn can cover the entire phased array radar antenna array surface;

[0013] S5. Mark the center of the horn antenna aperture as point P, and measure the distances PA, PB, and PC from point P to the marking points A, B, and C on the phased array radar antenna surface;

[0014] S6. Calculate the coordinates of point P (x p ,y p ,z p );

[0015] S7, calculate the distances P1, P2, ... PN from the center of each channel of the phased array radar antenna to the center of the horn antenna aperture;

[0016] S8. The phase changes of each channel caused by the distance difference from the center of the horn antenna aperture to the center of each channel of the phased array radar antenna are:

[0017]

[0018] S9. Set the radar frequency synthesis to transmit the calibration test signal with a frequency of F. Set each channel of the phased array radar antenna to the receiving state. Record the received phase test value of each channel as

[0019] S10. Use θ'1, θ'2,..., θ' n Test results Make corrections, θ1, θ2, …, θ n is the phase of the test signal received by each channel of the antenna after the radar phased array error correction, Therefore, the phase correction coefficients of the phased array radar channel [J1, J2, …, J n ]:

[0020]

[0021]

[0022] …

[0023]

[0024] Furthermore, in step S1, each system of the phased array radar is powered on and preheated for 30 minutes.

[0025] Furthermore, in step S4, the horn antenna aperture is fixedly placed 20 m away from the phased array radar antenna surface.

[0026] Furthermore, the step S4 also includes: connecting the test speaker and the radar frequency synthesizer using a phase-stable cable.

[0027] Furthermore, in step S5, a total station is used to measure the distances PA, PB, and PC from point P to the marking points A, B, and C on the antenna plane of the phased array radar.

[0028] Further, the step S6 specifically includes: according to the spatial coordinate relationship, there is the following relationship:

[0029]

[0030]

[0031]

[0032] The coordinates of point P (x p ,y p ,z p ).

[0033] Further, the step S7 specifically includes: the distances P1, P2, ... PN from the center of each channel of the phased array radar antenna to the center of the horn antenna aperture are calculated by the following formula:

[0034]

[0035] . . . . . . .

[0036]

[0037] Furthermore, after step S10, the method further includes: S11, modifying the frequency F in step S9, and repeating steps S9 and S10 to obtain correction coefficients at different frequency points.

[0038] (III) Beneficial effects

[0039] The present invention proposes a mid-field calibration method for phased array radar antennas. The advantages of the present invention are that the antenna calibration test distance is reduced, the test efficiency is improved, and the test cost is saved. Taking the S-band two-dimensional phased array radar antenna as an example, the diagonal size D of the phased array antenna is about 5m, the wavelength λ is about 0.1m, and the minimum far-field test distance is The test distance under the condition of mid-field can be solved by connecting the radar frequency synthesizer with SMA cable, which simplifies the test process, improves the test efficiency and saves the test cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 A schematic diagram of the relationship between the radar phased array antenna channel center and the marker point coordinates in the present invention;

[0041] Figure 2 Schematic diagram of the spatial coordinate relationship between the center of the horn antenna aperture and the center of the antenna channel. DETAILED DESCRIPTION

[0042] In order to make the purpose, content and advantages of the present invention more clear, the specific implementation methods of the present invention are further described in detail below in conjunction with the drawings and examples.

[0043] The present invention provides a mid-field calibration method for a radar phased array antenna. By establishing a spatial relationship to compensate for mid-field test data, an antenna correction coefficient is obtained to solve the channel calibration problem of the phased array radar.

[0044] This embodiment proposes a method for calibrating the mid-field phase of a phased array radar antenna. Taking the actual test of a radar antenna as an example, the specific implementation method is as follows:

[0045] S1. Power on each system of the phased array radar and preheat it for 30 minutes to ensure that each part of the radar is in a stable working state and that each channel of the phased array radar antenna is in a stable state.

[0046] S2. Reference Figure 1 As shown, three feature points A, B, and C are randomly selected on the phased array radar antenna plane (such as Figure 1 The center position of each channel of the phased array radar antenna (as shown in the black cross in the middle) Figure 1 The black dots in the figure and the points A, B, and C marked on the antenna array are in the same plane. Set this plane as the XOY plane and establish a spatial coordinate system.

[0047] S3, specify the coordinates of point A as (x a ,y a ,0), the coordinates of point B are (x b ,y b ,0), the coordinates of point C are (x c ,y c ,0), the coordinates of each channel on the array are (x1,y1,0), (x2,y2,0),…, (x n ,y n ,0).

[0048] S4. Select a horn antenna with the same frequency band as the phased array radar antenna, and place the horn antenna mouth directly opposite the phased array radar antenna so that the main lobe of the horn can cover the entire phased array radar antenna array surface (the distance here is sufficient to meet the requirement that the main lobe of the horn antenna can cover the radar antenna array surface, in this case 20m is sufficient, and it is fixed about 20m away from the phased array radar antenna array surface). Use a phase-stable cable to connect the test horn and the radar frequency synthesizer to ensure that the test signal is synchronized and the phase will not change due to cable jitter.

[0049] S5, such as Figure 2 As shown, the center of the horn antenna aperture is marked as point P, and a total station (a surveying and mapping instrument system that integrates distance, angle, and height difference measurement functions) is used to measure the distances PA, PB, and PC from point P to the marking points A, B, and C on the phased array radar antenna surface.

[0050] S6. According to the spatial coordinate relationship, the following relationship can be obtained:

[0051]

[0052]

[0053]

[0054] The coordinates of point P (x p ,y p ,z p ).

[0055] S7. The distances P1, P2…PN from the center of each channel of the phased array radar antenna to the center of the horn antenna aperture can be calculated using the following formula:

[0056]

[0057] .......

[0058]

[0059] S8. The phase changes of each channel caused by the distance difference from the center of the horn antenna aperture to the center of each channel of the phased array radar antenna are:

[0060]

[0061] S9. Set the radar frequency synthesis to transmit the calibration test signal with a frequency of F. Set each channel of the phased array radar antenna to the receiving state. Record the received phase test value of each channel as

[0062] S10, consider the phase change caused by the distance difference, use θ'1, θ'2, ..., θ' n Midfield test results Make corrections, θ1, θ2, …, θ n is the phase of the test signal received by each channel of the antenna after the radar phased array error correction, and it can be obtained Therefore, the phase correction coefficients [J1, J2, …, J n ]:

[0063]

[0064]

[0065] …

[0066]

[0067] S11. Modify the frequency F in step S9, and repeat steps S9 and S10 to obtain correction coefficients at different frequency points.

[0068] At this point, the mid-field phase calibration process of the phased array radar antenna is completed.

[0069] The advantages of the present invention are that the antenna calibration test distance is reduced, the test efficiency is improved, and the test cost is saved. Taking the S-band two-dimensional phased array radar antenna as an example, the diagonal size D of the phased array radar antenna is about 5m, the wavelength λ is about 0.1m, and the minimum far-field test distance is The test distance under the condition of mid-field can be solved by connecting the radar frequency synthesizer with SMA cable, which simplifies the test process, improves the test efficiency and saves the test cost.

[0070] 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 technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A mid-field calibration method for a phased array radar antenna, characterized in that: The method comprises the following steps: S1. Power on and preheat each system of the phased array radar to ensure that each part of the radar is in a stable working state and that each channel of the phased array radar antenna is in a stable state; S2. Arbitrarily select three characteristic points A, B, and C on the antenna array of the phased array radar. The center positions of each channel of the phased array radar antenna and the points A, B, and C marked on the antenna array are in the same plane. Set this plane as the XOY plane and establish a spatial coordinate system. S3, specify the coordinates of point A as (x a ,y a ,0), the coordinates of point B are (x b ,y b ,0), the coordinates of point C are (x c ,y c ,0), the coordinates of each channel on the array are (x1,y1,0), (x2,y2,0),…, (x n ,y n ,0); S4. Select a horn antenna with the same frequency band as the phased array radar antenna, and place the horn antenna mouth directly opposite the phased array radar antenna so that the main lobe of the horn can cover the entire phased array radar antenna array surface; S5. Mark the center of the horn antenna aperture as point P, and measure the distances PA, PB, and PC from point P to the marking points A, B, and C on the phased array radar antenna surface; S6. Calculate the coordinates of point P (x p ,y p ,z p ); S7, calculate the distances P1, P2, ... PN from the center of each channel of the phased array radar antenna to the center of the horn antenna aperture; S8. The phase changes of each channel caused by the distance difference from the center of the horn antenna aperture to the center of each channel of the phased array radar antenna are: S9. Set the radar frequency synthesis to transmit the calibration test signal with a frequency of F. Set each channel of the phased array radar antenna to the receiving state. Record the received phase test value of each channel as S10. Use θ'1, θ'2,..., θ' n Test results Make corrections, θ1, θ2, …, θ n is the phase of the test signal received by each channel of the antenna after the radar phased array error correction, Therefore, the phase correction coefficients of the phased array radar channel [J1, J2, …, J n ]: …… 2. The mid-field calibration method for a phased array radar antenna as claimed in claim 1, characterized in that: In step S1, each system of the phased array radar is powered on and preheated for 30 minutes.

3. The mid-field calibration method for a phased array radar antenna as claimed in claim 1, characterized in that: In step S4, the horn antenna aperture is fixedly placed 20 meters away from the phased array radar antenna array.

4. The mid-field calibration method for a phased array radar antenna as claimed in claim 1, characterized in that: The step S4 also includes: connecting the test speaker and the radar frequency synthesizer using a phase-stable cable.

5. The mid-field calibration method for a phased array radar antenna as claimed in claim 1, characterized in that: In step S5, a total station is used to measure the distances PA, PB, and PC from point P to the marking points A, B, and C on the antenna plane of the phased array radar.

6. The mid-field calibration method for a phased array radar antenna as claimed in claim 1, characterized in that: The step S6 specifically includes: according to the spatial coordinate relationship, there is the following relationship: The coordinates of point P (x p ,y p ,z p ).

7. The mid-field calibration method of a phased array radar antenna as claimed in claim 6, characterized in that: The step S7 specifically includes: the distances P1, P2, ... PN from the center of each channel of the phased array radar antenna to the center of the horn antenna aperture are calculated by the following formula: …… 8. The mid-field calibration method for a phased array radar antenna according to any one of claims 1 to 7, characterized in that: After step S10, the method further includes: S11, modifying the frequency F in step S9, repeating steps S9 and S10, and obtaining correction coefficients at different frequency points.

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