A true azimuth reference calibration device and method for a non-gimbaled radar

Abstract

The application discloses a true azimuth angle reference calibration device and method for a radar without an optical axis, and belongs to the field of radar development and production.The device comprises an electronic theodolite, a radiating horn antenna, a horn support, a microwave signal source, a radar servo system, a radar antenna testing device and a gyro theodolite.The electronic theodolite is arranged on an antenna testing tower, the radiating horn antenna is arranged on the electronic theodolite through the horn support, the radiating horn antenna is electrically connected with the microwave signal source, the radar servo system and the radar antenna testing device are used for aligning the electric axis azimuth of a radar antenna to be calibrated with the radiating horn antenna, the gyro theodolite and the radar to be calibrated are arranged at the far end of the electronic theodolite, the gyro theodolite is used for transmitting the true north reference to the electronic theodolite, the center mark point of the radar antenna to be calibrated is aimed at through the electronic theodolite, and then the true azimuth angle of the electric axis of the radar antenna to be calibrated can be obtained by taking the supplement of the azimuth angle of the radar to be calibrated and the horizontal angle reading of the electronic theodolite according to a circle.

Description

Technical Field

[0001] This invention belongs to the field of radar product research and development and production, specifically relating to a true azimuth reference calibration device and method for a non-optical axis radar, which is applicable to the azimuth reference calibration of a large early warning radar without an optical axis on an antenna test tower. Background Technology

[0002] The horizontal angle between a point and the target direction line in a clockwise direction from the north reference is called the azimuth. There are three commonly used north references: magnetic north, map north, and true north. Using different north references for the same target will produce different azimuths.

[0003] Magnetic North (MN) is the North Pole determined by geomagnetic points, as the Earth has a magnetic field. The line pointing from a point to the magnetic North Pole is called the magnetic North direction line, also known as the magnetic meridian. The horizontal angle between the magnetic North direction line at a point and the target direction line in a clockwise direction is called the magnetic azimuth at that point.

[0004] Map north, also known as grid north (GN), refers to the area "above" indicated by the vertical grid lines on a map. The horizontal angle between the northward coordinate line from a point and the target direction line in a clockwise direction is called the coordinate azimuth of that point.

[0005] True North (TN) is the starting point of all meridians on Earth, also known as the geographic North Pole. The direction line pointing from a point to the North Pole is called the true north direction line. The horizontal angle between the true north direction line at a point and the direction to the target point in a clockwise direction is called the true azimuth of that point.

[0006] All three north reference systems are used in radar. Most radars using GPS, BeiDou, and inertial navigation systems employ true north as their north reference. Some search radars use magnetic north as their orientation reference, first measuring the magnetic azimuth and then converting it to true north by correcting for magnetic declination. Radar electronic maps commonly use map north as the north reference, which requires first determining true north and then correcting for meridian convergence to convert it to coordinate azimuth.

[0007] Because the GPS, Beidou system and inertial navigation equipment used in radar products inevitably have fixed installation deviations, that is, the initial north orientation of the radar deviates from the design reference, the radar target azimuth angle contains true north reference system error, which needs to be eliminated through calibration.

[0008] Radar north-pointing benchmark calibration is a crucial debugging process in radar development and production, and its accuracy directly affects the accuracy of radar target azimuth measurement. Radar azimuth benchmarks are primarily calibrated using methods such as fixed-site geodetic markers, RTK (Real-Time Kinematic) technology, and gyro-theodolites.

[0009] Using fixed-site geodetic markers for radar azimuth calibration is a method specified in GJB3153-98 "Precision Measurement Radar Calibration and Correction". However, this method has low calibration accuracy and can only be performed in fixed locations. With the widespread application of RTK calibration systems and gyrotheodolites, this method is rarely used anymore. RTK calibration systems consist of a receiver, direction-finding module, radio, power supply, etc. The calibration process is cumbersome and has stringent requirements for the electromagnetic environment of the calibration site. Radar research and production units often need to perform azimuth reference calibration at antenna test fields. Due to the complex electromagnetic environment, the accuracy of RTK calibration is significantly affected, and gyrotheodolites are generally required for calibration. Gyrotheodolites have extremely high measurement accuracy in low and mid latitudes, but conventional calibration methods require the gyrotheodolite to be aligned with the radar optical axis. For large early warning radars, since their operating range generally exceeds hundreds of kilometers, they are generally not equipped with optical telescopes or television calibration mirrors used as optical axes. Therefore, it is impossible to use the optical axis alignment method for true north reference calibration, which means that gyrotheodolite calibration cannot be used at present.

[0010] Therefore, for radar products without optical axes, such as large early warning radars, azimuth reference calibration is performed using gyro theodolites at antenna testing sites. Technical research should be conducted to explore calibration methods to meet the calibration requirements of such radars. Summary of the Invention

[0011] The technical problem to be solved:

[0012] To avoid the shortcomings of the prior art, the present invention provides a true azimuth reference calibration device and method for a non-optical axis radar, which is applicable to the true north reference calibration of non-optical axis radar products, and solves the problem that non-optical axis radar cannot use a gyro theodolite for true north reference calibration.

[0013] The technical solution of this invention is: a true azimuth reference calibration device for a non-optical axis radar, comprising an electronic theodolite, a radiating horn antenna, a horn bracket, a microwave signal source, a radar servo system, a radar antenna testing device, and a gyro theodolite; the electronic theodolite is mounted on an antenna test tower with a tripod; the radiating horn antenna is mounted on the electronic theodolite via the horn bracket, and is electrically connected to the microwave signal source, serving to transmit microwave signals to the radar to be calibrated; the radar servo system is used to drive the azimuth or pitch rotation of the radar to be calibrated; the radar antenna testing device... The device is used to measure the strength of the transmitted and received signals of the radar to be calibrated at a certain azimuth or elevation angle. The radar servo system works in conjunction with the radar antenna testing device to align the electrical axis of the radar antenna to be calibrated with the radiating horn antenna. The gyro theodolite is mounted at the far end of the electronic theodolite to transfer its true north reference to the electronic theodolite. The radar to be calibrated is mounted at the far end of the electronic theodolite. By aiming the electronic theodolite at the center marker point of the radar antenna to be calibrated, the true azimuth of the radar antenna to be calibrated can be obtained by taking the azimuth of the radar to be calibrated and the horizontal angle reading of the electronic theodolite in a circular complementary manner.

[0014] A further technical solution of the present invention is: the horn bracket includes a clamping frame and a bracket base. The clamping frame is used to fix and clamp the radiating horn antenna, and the bottom of the clamping frame is hinged to the bracket base. The bracket base is installed in the mounting hole at the center of the crossbeam of the electronic theodolite by bolts. The mounting hole at the center of the crossbeam is coaxial with the horizontal rotation axis of the electronic theodolite, so that the central axis of the radiating horn antenna and the horizontal rotation axis of the electronic theodolite are in the same plane.

[0015] A further technical solution of the present invention is: the clamping frame includes an upper clamping frame and a lower clamping frame, the upper clamping frame and the lower clamping frame cooperate with each other, and the two are connected by fasteners to fix and clamp the radiating horn antenna in the middle; the bottom of the lower clamping frame is hinged to the support base through a horizontally set rotating shaft.

[0016] A further technical solution of the present invention is that the deviation between the mounting hole at the center of the crossbeam and the horizontal axis of the electronic theodolite is no greater than 0.02mm.

[0017] A further technical solution of the present invention is: the gyro theodolite and the radar to be calibrated, both mounted at the far end of the electronic theodolite, are 300m-1000m away from the antenna test tower, ensuring that the electronic theodolite has line of sight with the radar to be calibrated and the gyro theodolite respectively.

[0018] A further technical solution of the present invention is that the radar antenna testing device includes a spectrum analyzer.

[0019] A method for calibration using a true azimuth reference calibration device for a non-optical axis radar, comprising the following steps:

[0020] Step 1: Run the radar antenna directivity control program on the radar main control computer, input the frequency point to be tested and the zero point direction, turn on the microwave signal source, and send out microwaves of the corresponding frequency through the radiating horn antenna; the operator controls the radar antenna to be calibrated to scan back and forth twice in the azimuth, read the signal strength of the corresponding frequency point output by the spectrum analyzer, find the point with the maximum signal strength, record the azimuth angle, and take the average value of the two scan measurements as the signal source azimuth angle A with the initial north direction of the radar to be calibrated as the reference.

[0021] Step 2: After leveling the gyro theodolite, power it on to complete the north-finding process. Align the gyro theodolite with the electronic theodolite. Calculate the horizontal angle C of the electronic theodolite's optical axis based on the true azimuth B of the gyro theodolite's optical axis. At this angle, zero the horizontal angle of the electronic theodolite and change the horizontal angle measurement direction to counterclockwise. Rotate the electronic theodolite counterclockwise to the horizontal angle C position, then zero the horizontal angle of the electronic theodolite again and change the horizontal angle measurement direction to clockwise.

[0022] At this time, the direction of zero degrees horizontal angle of the electronic theodolite is the true north direction, and the horizontal angle of the target measured by it is the true azimuth angle;

[0023] Step 3: Use an electronic theodolite to aim at the center marker of the radar antenna to be calibrated. Calculate the true azimuth angle E of the signal source based on the theodolite reading D. The true azimuth angle reference error calibration value δ = AE is used. In the radar main control computer software, the radar target azimuth angle is corrected according to the calibration value δ to eliminate the azimuth angle measurement system error of the radar to be calibrated, thus completing the true azimuth angle reference calibration of the radar to be calibrated.

[0024] Beneficial effects

[0025] The beneficial effects of this invention are as follows: The optical axis-less radar true azimuth reference calibration device and method of this invention directly associates the radar azimuth reference with the radar electrical axis, so that the calibration process does not depend on the radar optical axis; the radiating horn antenna is installed on the water of the electronic theodolite through the horn bracket, and the radiating horn antenna is electrically connected to the microwave signal source and placed on the antenna test tower; the radar to be calibrated and the gyro theodolite are set up at the far end of the antenna test tower, so that the electronic theodolite has a line of sight with the radar to be calibrated and the gyro theodolite; by measuring the pointing of the radar antenna to be calibrated, the azimuth of the electrical axis of the radar antenna to be calibrated is aligned with the radiating horn antenna; by transferring the true north reference of the gyro theodolite to the electronic theodolite, and by aiming the electronic theodolite at the center mark of the radar antenna to be calibrated, the true azimuth of the radar antenna to be calibrated can be obtained by taking the circumferential complement of the azimuth of the radar to be calibrated and the horizontal angle reading of the electronic theodolite.

[0026] This invention combines an electronic theodolite with a radiating horn antenna to form a fixture for radar axis measurement and true azimuth calibration. By installing the radiating horn antenna at a specific position on the electronic theodolite, the central axis of the radiating horn antenna is projected through the horizontal rotation axis center of the electronic theodolite. After completing the radar axis measurement, the electronic theodolite and the gyro theodolite are aligned to achieve the transfer of the true azimuth reference. The measurement method for completing the azimuth reference calibration of the radar axis to be calibrated is the first of its kind in this invention.

[0027] The maximum vertical deviation between the central axis of the radiating horn antenna and the optical axis of the electronic theodolite is <0.02mm, and the aiming deviation at calibration distances of 300 meters and beyond is ≤0.00007mrad, which is negligible; the alignment error between the electronic axis of the radar to be calibrated and the radiating horn antenna is ≤0.16mrad; the north-finding error of the gyro theodolite plus the aiming error is ≤0.1mrad. Therefore, the azimuth reference calibration accuracy of the radar of this invention is better than 0.26mrad.

[0028] The optical axisless radar true azimuth reference calibration device and calibration method described in this invention solves the problem that large early warning radars without optical axes cannot use gyro theodolites for high-precision azimuth reference. Moreover, this device does not require the gyro theodolite to be mounted on an antenna test tower, thus improving its north-finding accuracy. Since the gyro theodolite is extremely sensitive to the stability of its mounting position when it is working, even a slight sway of a tall building can cause its north-finding accuracy to drop sharply. Attached Figure Description

[0029] Figure 1 This is a functional block diagram of the calibration device of the present invention;

[0030] Figure 2 This is a schematic diagram of the connection structure of the radiating horn antenna, horn bracket, and electronic theodolite in the calibration device.

[0031] Figure 3 This is a schematic diagram of the speaker bracket connection;

[0032] Figure 4 This is a schematic diagram showing the connection between a radiating horn antenna and a microwave signal source.

[0033] Figure 5 This is a schematic diagram of the radar true north reference calibration method.

[0034] Explanation of reference numerals in the attached diagram: 1. Radiating horn antenna 2. Horn bracket 21. Upper clamp 22. Lower clamp 23. Rotating shaft 24. Support base 3. Electronic theodolite 31. Tripod 32. Crossbeam 4. Microwave signal source 5. Gyro theodolite 6. Radar to be calibrated. Detailed Implementation

[0035] The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0036] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0037] See Figure 1-4 The present invention provides a true azimuth reference calibration device and calibration method for a non-optical axis radar, which solves the problem that large early warning radars generally do not have calibration telescopes or television calibration mirrors installed as radar optical axes, and therefore cannot perform azimuth reference calibration by mutual aiming with true north measuring devices such as gyro theodolites.

[0038] The optical axisless radar true azimuth reference calibration device includes: an electronic theodolite 3, a radiating horn antenna 1, a horn bracket 2, a microwave signal source 4, a radar servo system, a radar antenna testing device, and a gyro theodolite 5. The electronic theodolite 3 is mounted on an antenna test tower with a tripod 31. The radiating horn antenna 1 is mounted on the electronic theodolite 3 via the horn bracket 2. Specifically, in this embodiment, the horn bracket 2 includes an upper clamping frame 21, a lower clamping frame 22, a bracket base 24, and a rotating shaft 23. The upper clamping frame 21 and the lower clamping frame 22 cooperate with each other and are connected by fasteners to fix the radiating horn antenna 1 in the middle. The bottom of the lower clamping frame 22 is connected to the support via a horizontally set rotating shaft 23. The top of the bracket base 24 is hinged, allowing the radiating horn antenna 1 to be adjusted in the elevation direction. The bracket base 24 is bolted to the center of the crossbeam 32 of the electronic theodolite 3. The center of the crossbeam 32 has a mounting hole, which is coaxial with the horizontal axis of the electronic theodolite 3. This ensures that the plumb line projection of the central axis of the radiating horn antenna 1 passes through the central axis of the horizontal axis of the electronic theodolite 3. During testing, it is not required that the radiating horn antenna 1 be aligned with the antenna of the radar 6 under test in the elevation direction. However, it is required that the deviation between the projection of the central axis of the radiating horn antenna 1 and the center of the horizontal axis of the electronic theodolite 3 in the direction perpendicular to the optical axis of the electronic theodolite 3 is not greater than 0.02 mm to ensure calibration accuracy.

[0039] The radiating horn antenna 1 is connected to the microwave signal source 4 via a cable. The microwave signal source 4 provides a suitable frequency for testing. The radiating horn antenna 1 is used to transmit microwave signals to the antenna of the radar 6 to be calibrated. The radar servo system is a component of the radar and is used to drive the radar's azimuth or elevation rotation. The radar antenna testing device is a set of test instruments specifically used for testing the electrical performance of radar antennas. It is used to measure the intensity of the transmitted and received signals of the radar to be calibrated at a certain azimuth or elevation angle. The radar servo system works in conjunction with the radar antenna testing device to measure the pointing of the electrical axis of the radar 6 to be calibrated, so that the azimuth of the electrical axis of the radar 6 to be calibrated is aligned with the radiating horn antenna 1.

[0040] The gyrotheodolite 5 is mounted at the far end of the electronic theodolite 3 to transmit its true north reference to the electronic theodolite 3. The radar 6 to be calibrated is mounted at the far end of the electronic theodolite 3. Specifically, the radar 6 and the gyrotheodolite 5 are mounted at a distance from the antenna test tower that meets the antenna far-field test conditions (the minimum far-field test distance is related to the antenna aperture and operating frequency). The distance between the two is 300m-1000m from the antenna test tower, ensuring that the electronic theodolite 3 has line of sight with both the radar 6 and the gyrotheodolite 5. By aligning the electrical axis of the radar 6 antenna to be calibrated with the radiating horn antenna 1, the electronic theodolite 3 and the gyro theodolite 5 are aligned to achieve the baseline true azimuth angle measurement. By zeroing the horizontal angle of the electronic theodolite 3 twice, the true north reference of the gyro theodolite 5 is transferred to the electronic theodolite 3. The electronic theodolite 3 is aimed at the center marker point of the radar 6 antenna to be calibrated. The true azimuth angle of the radar 6 antenna to be calibrated is obtained by taking the circumferential complement of the azimuth angle of the radar 6 antenna to be calibrated and the horizontal angle reading of the electronic theodolite 3.

[0041] See also Figure 5 The calibration test method steps of the calibration device described in this invention are as follows:

[0042] Step 1: Run the radar antenna directivity control program of the real-time control computer on the main control computer of the radar to be calibrated 6, and input the frequency point to be tested and the null direction; set the correct test frequency and turn on the microwave signal source 4 on the antenna test tower, and send out microwaves of the corresponding frequency through the radiating horn antenna 1. The operator controls the radar antenna to be calibrated to scan back and forth twice in the azimuth, and at the same time reads the signal strength of the corresponding frequency point output by the spectrum analyzer in the radar antenna test device, finds the point of maximum signal strength, records the azimuth angle, and takes the average value of the two scan measurements as the signal source azimuth angle A with the initial north direction of the radar to be calibrated 6 as the reference.

[0043] Step 2: After leveling the gyro theodolite 5 and powering it on, complete the north-finding process. Align the gyro theodolite 5 with the electronic theodolite 3. Calculate the horizontal angle C of the electronic theodolite 3 based on the true azimuth B of the optical axis of the gyro theodolite 5. At this angle, zero the horizontal angle of the electronic theodolite 3 and change the horizontal angle measurement direction to counterclockwise. Rotate the electronic theodolite 3 counterclockwise to the horizontal angle C position, then zero the horizontal angle of the electronic theodolite 3 again and change the horizontal angle measurement direction to clockwise. At this point, the zero-degree direction of the horizontal angle of the electronic theodolite 3 is the true north direction, and the measured target horizontal angle is the true azimuth.

[0044] Step 3: Use the electronic theodolite 3 to aim at the center marker point of the antenna of the radar 6 to be calibrated. Based on the reading D of the electronic theodolite 3 at this time, calculate the true azimuth angle E of the line connecting the center of the antenna of the radar 6 to be calibrated and the electronic theodolite 3 (i.e., the radiating horn antenna 1). The calibration value of the true azimuth angle reference error of the radar 6 to be calibrated is δ = AE. In the control software of the radar main control computer, the radar target azimuth angle is corrected according to the calibration value δ, which can eliminate the azimuth angle measurement system error of the radar 6 to be calibrated and complete the true azimuth angle reference calibration of the radar 6 to be calibrated.

[0045] Depending on the quadrant in which the line connecting the radar 6 to be calibrated and the electronic theodolite 3 lies in the true north coordinate system, the calculation method for the measurement data of the radar true azimuth reference calibration using the calibration device described in this invention differs slightly. True north is 0 degrees, and the true north angle increases clockwise. Therefore, in different quadrants, the method of calculating using 180° + the azimuth angle of the connecting line or the azimuth angle of the connecting line - 180° is used. The radar true azimuth reference calibration can also be completed by following steps 1-3.

[0046] Depending on the different operating frequency bands of the radar antennas to be calibrated, the azimuth reference calibration device for the non-optical axis radar can be adapted to the corresponding frequency band radiating horn antenna 1. The structural form of the calibration device remains unchanged, and the true azimuth reference calibration steps of the radar are the same.

[0047] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A method for calibration using a true azimuth reference calibration device for a non-optical axis radar, characterized in that: The optical axisless radar true azimuth reference calibration device includes: an electronic theodolite (3), a radiating horn antenna (1), a horn bracket (2), a microwave signal source (4), a radar servo system, a radar antenna testing device, and a gyro theodolite (5); the electronic theodolite (3) is mounted on an antenna test tower with a tripod (31); the radiating horn antenna (1) is mounted on the electronic theodolite (3) via the horn bracket (2), and the radiating horn antenna (1) is electrically connected to the microwave signal source (4), and the radiating horn antenna (1) is used to send microwave signals to the radar (6) to be calibrated; the radar servo system is used to drive the azimuth or pitch rotation of the radar (6) to be calibrated; the radar antenna testing device... The radar servo system is used to measure the intensity of the transmitted and received signals of the radar (6) to be calibrated at a certain azimuth or elevation angle. The radar servo system and the radar antenna test device are used to align the electric axis of the radar (6) to be calibrated with the radiating horn antenna (1). The gyro theodolite (5) is set up at the far end of the electronic theodolite (3) to transfer its true north reference to the electronic theodolite (3). The radar (6) to be calibrated is set up at the far end of the electronic theodolite (3). By aiming the electronic theodolite (3) at the center mark of the antenna of the radar (6) to be calibrated, the true azimuth of the electric axis of the radar (6) to be calibrated can be obtained by taking the azimuth of the radar (6) to be calibrated and the horizontal angle reading of the electronic theodolite (3) in a circle. The calibration method involves the following steps: Step 1: Run the radar antenna directivity control program on the radar main control computer, input the frequency point to be tested and the zero point direction, turn on the microwave signal source (4), and send out the microwave of the corresponding frequency through the radiating horn antenna (1); the operator controls the radar antenna to be calibrated to scan back and forth twice in the azimuth, read the signal strength of the corresponding frequency point output by the spectrum analyzer, find the point with the maximum signal strength, record the azimuth angle, and take the average value of the two scan measurements as the signal source azimuth angle A with the initial north direction of the radar (6) to be calibrated as the reference. Step 2: After leveling the gyro theodolite (5), power it on to complete the north search. Align the gyro theodolite (5) with the electronic theodolite (3). Calculate the horizontal angle C of the optical axis of the electronic theodolite (3) based on the true azimuth angle B of the optical axis of the gyro theodolite (5). Set the horizontal angle of the electronic theodolite (3) to zero at this angle position and change the horizontal angle measurement direction to counterclockwise. Rotate the electronic theodolite (3) counterclockwise to the horizontal angle C position, set the horizontal angle of the electronic theodolite (3) to zero again, and change the horizontal angle measurement direction to clockwise. At this time, the direction of zero degrees of horizontal angle of the electronic theodolite (3) is the true north direction, and the horizontal angle of the target measured by it is the true azimuth angle; Step 3: Use an electronic theodolite (3) to aim at the center marker of the antenna of the radar (6) to be calibrated. Calculate the true azimuth angle E of the signal source based on the reading D of the electronic theodolite (3) at this time. The true azimuth angle reference error calibration value δ=AE of the radar (6) to be calibrated is corrected in the radar main control computer control software according to the calibration value δ to eliminate the azimuth angle measurement system error of the radar (6) to be calibrated and complete the true azimuth angle reference calibration of the radar (6).

2. The method for calibration using a true azimuth reference calibration device for a non-optical axis radar according to claim 1, characterized in that: The horn bracket (2) includes a clamping frame and a bracket base (24). The clamping frame is used to fix and clamp the radiating horn antenna (1). The bottom of the clamping frame is hinged to the bracket base (24). The bracket base (24) is installed in the mounting hole at the center of the crossbeam (32) of the electronic theodolite (3) by bolts. The mounting hole at the center of the crossbeam (32) is coaxial with the horizontal rotation axis of the electronic theodolite (3), so that the central axis of the radiating horn antenna (1) and the horizontal rotation axis of the electronic theodolite (3) are in the same plane.

3. The method for calibration using a true azimuth reference calibration device for a non-optical axis radar according to claim 2, characterized in that: The clamping frame includes an upper clamping frame (21) and a lower clamping frame (22). The upper clamping frame (21) and the lower clamping frame (22) cooperate with each other and are connected by fasteners to fix the radiating horn antenna (1) in the middle. The bottom of the lower clamping frame (22) is hinged to the support base (24) through a horizontally set pivot (23).

4. The method for calibration using a true azimuth reference calibration device for a non-optical axis radar according to claim 2, characterized in that: The deviation between the mounting hole at the center of the crossbeam (32) and the horizontal axis of the electronic theodolite (3) is no greater than 0.02 mm.

5. The method for calibration using a true azimuth reference calibration device for a non-optical axis radar according to claim 1, characterized in that: The gyro theodolite (5) and the radar to be calibrated (6) mounted at the far end of the electronic theodolite (3) are both 300m-1000m away from the antenna test tower, ensuring that the electronic theodolite (3) has line of sight with the radar to be calibrated (6) and the gyro theodolite (5) respectively.

6. The method for calibration using a true azimuth reference calibration device for a non-optical axis radar according to claim 1, characterized in that: The radar antenna testing device includes a spectrum analyzer.

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