A method for correcting test grating lobes of a large compact field terahertz antenna

Abstract

This invention discloses a method for correcting the grating lobe of a large-scale compact field terahertz antenna test, comprising the following steps: performing a first installation and site calibration to establish a terahertz compact field test environment; obtaining the far-field radiation pattern of the antenna in the first state; performing a second installation and site calibration to obtain the far-field radiation pattern of the antenna in the second state; performing coordinate transformation to obtain the second-state radiation pattern in the first-state coordinate system; and obtaining a radiation pattern free from the site coupling of the compact field itself. This invention reduces the influence of the grating effect formed by the processing of the compact field reflector in the terahertz band on the radiation pattern results of the antenna under test, thereby improving the accuracy of the terahertz compact field test antenna.

Description

Technical Field

[0001] This invention relates to a method for correcting test grating lobes in a compact field test, and more particularly to a method for correcting test grating lobes in a large compact field terahertz antenna, belonging to the field of antenna measurement technology. Background Technology

[0002] Compact fields, as an important part of the antenna testing family, also have a place in the terahertz field. Similar to the mechanical accuracy requirements of the near-field terahertz band (500GHz, 0.012mm for planar near-field), the mechanical accuracy of compact fields mainly depends on the accuracy of the reflecting surface that forms the plane wave. Generally, the reflecting surface is made of metal, which is milled in large blocks during processing and then calibrated by splicing.

[0003] The vertical lines visible to the naked eye on the mirror-like reflective surface are primarily caused by the milling cutter scanning along this direction and stepping vertically during machining. This creates undulating patterns on the order of micrometers (µm). At lower frequencies (300 GHz), these patterns do not significantly affect quiet zone performance. However, at higher terahertz frequencies, the unique periodic structure creates a grid effect, impacting radiation pattern testing. Summary of the Invention

[0004] The technical problem solved by this invention is to provide a method for correcting the grating lobe of a large compact field terahertz antenna test. This method uses existing test equipment to perform multiple tests on the antenna under test, and calculates the radiation pattern to remove the coupling of the compact field itself through mathematical algorithms, thereby achieving the suppression effect of the grating effect caused by the terahertz compact field.

[0005] The technical solution of this invention is:

[0006] A method for correcting the test grating lobe of a large compact field terahertz antenna includes the following steps:

[0007] 1) Establish the antenna coordinate system O'-X'Y'Z' and the site coordinate system O-XYZ; wherein, the antenna coordinate system is fixedly connected to the reflecting surface of the antenna under test;

[0008] 2) Establish the first state by setting the positional relationship between the antenna coordinate system and the site coordinate system; establish a terahertz compact field test environment; in the first state, the three axes in the antenna coordinate system and the site coordinate system coincide;

[0009] 3) Use the antenna under test to transmit and receive electromagnetic wave signals and perform data sampling; complete the radiation pattern test of the antenna under test in the first state point by point to obtain the radiation pattern data of the first state.

[0010] 4) Rotate the antenna under test 90° around the antenna Z-axis to form a second state in the positional relationship between the antenna coordinate system and the field coordinate system; establish a terahertz compact field test environment; the antenna Z-axis and the reflector surface of the antenna under test point in the same direction and pass through the geometric midpoint of the reflector surface of the antenna under test;

[0011] 5) Use the antenna under test to transmit and receive electromagnetic wave signals and perform data sampling; complete the radiation pattern test of the antenna under test in the second state point by point to obtain the radiation pattern data of the second state.

[0012] 6) Obtain the second state radiation pattern data obtained in step 5). Transform from the antenna coordinate system to the site coordinate system; obtain the second-state radiation pattern data with the same coordinates as the first state.

[0013] 7) Based on the first state radiation pattern data obtained in step 3), And the second-state pattern data obtained in step 6) that has the same coordinates as the first state. Determine the interference spectral function B(k) x ,k y );

[0014] 8) Based on the interference spectrum function B(k) determined in step 7), x ,k y Add a compacted field ideal beam function δ(k) x ,k y The deconvolution formula is used to obtain the radiation pattern after removing the coupling of the compacted field.

[0015] Preferably, a site coordinate system O'-X'Y'Z' is established, specifically as follows:

[0016] The origin O' of the site coordinate system is located at the geometric center of the reflector surface of the antenna under test;

[0017] The Z' axis of the field is parallel to the azimuth axis of the turntable of the antenna under test, and the positive direction of the Z' axis of the field points in the direction of the incoming wave.

[0018] The Y' axis of the site is parallel to the elevation axis of the turntable of the antenna under test, and the positive direction of the Y' axis of the site points in the opposite direction of the Earth's center.

[0019] Establish the coordinate system O-XYZ for the antenna under test, specifically as follows:

[0020] The XOY plane is located within the reflector surface of the antenna under test.

[0021] Preferably, the first state corresponds to the antenna X-axis being parallel to the field X' axis, the antenna Y-axis being parallel to the field Y' axis, and the antenna Z-axis being parallel to the field Z' axis.

[0022] Preferably, the second state corresponds to the antenna X-axis being parallel to the field Y' axis, the positive direction of the antenna Y-axis pointing towards the negative direction of the field X' axis, and the antenna Z-axis being parallel to the field Z' axis.

[0023] Preferably, the interference spectrum function B(k) is determined. x ,k y The method is as follows:

[0024]

[0025]

[0026] Where, k aut-sll k represents the spectral width corresponding to the main lobe width of the antenna under test. x k represents the spectral value along the X-axis of the antenna. y B′(k) represents the spectral value along the Y-axis of the antenna. x ,k y ) is the spectral function containing grating lobe interference; N is the level threshold of the spurious spectrum caused by ignoring the test noise floor; N is determined according to the dynamic range of the terahertz compact field system radiation pattern test; θ is the angle between the antenna Z-axis and the field Z' axis; The angle between the projection of the antenna's Z-axis onto the X'O'Y' plane of the site coordinate system and the X' axis of the site.

[0027] Preferably, N is 30 dB smaller than the dynamic range of the terahertz compact field system radiation pattern test.

[0028] Preferably, a radiation pattern is obtained by removing the coupling of the compression field. The method is as follows:

[0029]

[0030] Here, deco is used for deconvolution calculation.

[0031] Preferably, the radiation pattern test of the antenna under test in the first state corresponds to: θ ranging from -50° to +50°, with a step size of 0.1°, and the step size ranging from 0.01° to 2°; and Keep the temperature at zero degrees.

[0032] Preferably, the radiation pattern test of the second state of the antenna under test corresponds to: θ ranging from -50° to +50°, with a step size of 0.1°, and the step size ranging from 0.01° to 2°; and Keep it at 90°.

[0033] Preferably, in steps 3) and 5), the data sampling interval for the radiation pattern test should be less than Δ. max ;

[0034] Δ maxDetermined by the following formula:

[0035]

[0036] Where, θ 3dB It is equal to the 3dB beamwidth of the antenna under test.

[0037] The advantages of this invention compared to the prior art are:

[0038] (1) This invention utilizes ordinary compact field testing equipment, without the need for additional hardware equipment, and obtains radiation pattern data that removes the influence of the terahertz compact field reflector grid effect through data processing calculation, thereby improving the antenna testing accuracy;

[0039] (2) The algorithm in this invention has no frequency requirement. It can be used not only in terahertz compressed fields, but also extended to ordinary compressed fields to improve test accuracy.

[0040] (3) The algorithm in this invention implies multiple averaging effects, which can improve the dynamic range of the system to a certain extent and further improve the accuracy. Attached Figure Description

[0041] Figure 1 This is a flowchart of the method steps of the present invention;

[0042] Figure 2(a) is a schematic diagram of the first state coordinate system of the antenna under test.

[0043] Figure 2(b) is a schematic diagram of the second state coordinate system of the antenna under test.

[0044] Figure 3 The graph shows a comparison of algorithm simulation verification.

[0045] Figure 4 Comparison chart of real-world testing without algorithm validation. Detailed Implementation

[0046] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments, as follows:

[0047] 1. Terahertz Compact Field Test Environment

[0048] The terahertz compressed field consists of a plane wave generator, a mechanical subsystem, a radio frequency subsystem, and a control subsystem.

[0049] The plane wave generator includes a reflecting surface and a compacted field feed. It is used to convert spherical electromagnetic waves into quasi-plane electromagnetic waves, with the future wave direction defined as the Z-axis. Through the special shape of the reflecting surface, the spherical electromagnetic waves emitted by the compacted field feed are converted into quasi-plane waves, and the region containing the plane wave is a quiet zone.

[0050] The mechanical subsystem includes a feed turntable and an antenna under test (AUT) turntable. The compact field feed is mounted on the feed turntable and is used for rotation of the feed during antenna testing, which can be used to change the polarization of the reflected electromagnetic wave. The AUT turntable is mainly used to support the AUT and to change the AUT's attitude during testing. The AUT turntable consists of an azimuth rotation axis parallel to the horizontal plane, an elevation rotation axis perpendicular to the horizontal plane, and polarization rotation axes orthogonal to the azimuth and elevation rotation axes, respectively.

[0051] Select a compact field feed corresponding to the transmit / receive frequency band of the antenna under test to form a plane wave generating device, and install it on the compact field feed turntable of the mechanical subsystem.

[0052] The radio frequency subsystem generates, transmits, and acquires electromagnetic wave signals in the required test frequency band, while the control subsystem is responsible for coordinating various hardware components to perform automated work and storing and analyzing the acquired data.

[0053] A typical antenna turntable consists of an azimuth axis parallel to the horizontal plane, an elevation axis perpendicular to the horizontal plane, and polarization axes orthogonal to the azimuth and elevation axes, respectively.

[0054] Coordinate system of the antenna under test: O-XYZ; Coordinate system of the turntable for the antenna under test: O1-X1 Y1 Z1;

[0055] In the initial state, the Z1 axis coincides with the polarization axis, the Y1 axis coincides with the azimuth axis, and the X1 axis coincides with the pitch axis.

[0056] Through calibration, the three axes of the two coordinate systems, namely the antenna under test coordinate system and the antenna turntable coordinate system, can be made to correspond and parallel. Therefore, the two coordinate systems can be merged, and the antenna under test coordinate system can be used to represent the antenna turntable coordinate system.

[0057] Establish the site coordinate system O'-X'Y'Z':

[0058] The origin O' of the site coordinate system is located at the geometric center of the reflecting surface in the plane wave generating device;

[0059] The Z' axis of the field is parallel to the azimuth axis of the turntable of the antenna under test, and the positive direction of the Z' axis of the field points in the direction of the incoming wave.

[0060] The Y' axis of the site is parallel to the elevation axis of the turntable of the antenna under test, and the positive direction of the Y' axis of the site points in the opposite direction of the Earth's center.

[0061] Establish the coordinate system O-XYZ for the antenna under test:

[0062] The antenna's Z-axis points in the same direction as the antenna and passes through the geometric midpoint of the reflecting surface in the plane wave generator.

[0063] The XOY plane is located within the reflector surface of the antenna under test.

[0064] During testing, the positional relationship between the antenna's coordinate system and the site coordinate system is changed by rotating the turntable of the antenna under test, forming an angle, and thus obtaining radiation pattern test data at different angles.

[0065] Most tests require site calibration, which involves establishing a definite relationship between the coordinate system of the antenna under test and the site coordinate system, or adjusting it to ensure that the three axes are parallel, as shown in Figure 2(a). The adjustment process can be aided by mechanical measuring equipment such as a theodolite or laser tracker.

[0066] 2. The specific steps for constructing a compact field antenna are as follows:

[0067] (1) Install the antenna under test and calibrate the site according to the compact field test method to establish a compact field test environment;

[0068] (2) Set the scanning range, sampling interval, and test frequency. The scanning range is the range that needs to be examined for the corresponding antenna pattern. The sampling interval is the position density of the antenna pattern acquisition, which is generally required to be no more than one-tenth of the beamwidth. For example, if the antenna pattern beamwidth is 0.1 degrees, the sampling interval should not be greater than 0.01 degrees. The test frequency is the typical frequency value within the nominal operating range of the antenna. These frequencies can be equally spaced or non-equally spaced. For example, when the antenna frequency range is 325GHz to 500GHz, it is a list of the frequencies to be tested for the antenna, such as 325GHz, 412.5GHz, 500GHz, etc.

[0069] (3) The operation control subsystem performs pattern testing on the antenna under test.

[0070] (4) Process the required test results and output the results.

[0071] 3. Compact Field Pattern Test Raster Lobe Correction Algorithm

[0072] According to the principle of compact field testing, the compact field is actually an antenna, and the compact field test uses the near-field region of the compact field antenna. Therefore, the antenna test response is the integral of the near-field spectrum of the compact field and the radiation pattern of the antenna under test.

[0073]

[0074]

[0075] In the formula

[0076] —The orientation diagram of the contraction field itself;

[0077] B(k x ,k y — Compact field spectral function;

[0078] — Spectral function coefficients;

[0079] —Panoramic view of the test results for the compression field;

[0080] —The actual radiation pattern of the antenna under test;

[0081] Ideally, since the amplitude and phase of the compressed field in the static region on the same Z-coordinate are constants (plane wave), and the coefficient is negligible, it is 1, i.e. Therefore, the spectral function is the impulse function B(k) x ,k y )=δ(k x ,k y ).

[0082] Therefore, the response of the compressed field to the antenna under test is the antenna's own radiation pattern.

[0083]

[0084] If the spectrum of the compacted field contains not only the spectrum of the ideal compacted field but also the spectrum caused by the grid structure and other factors, then the obtained antenna pattern under test will include the coupling response of the compacted field itself.

[0085]

[0086] If the interference spectrum B1(k) of the grid can be obtained x ,k y The ideal radiation pattern of the antenna under test can be obtained by performing the inverse operation of the above formula.

[0087] The characteristic that the energy of the spectral function is positive can be used to solve the interference spectrum without considering the phase. The effect on the phase can be regarded as the overall effect of the vector superposition of the amplitude spectrum, so there is no need to consider the phase.

[0088] Assume the antenna's first-state test response:

[0089]

[0090] The antenna's second-state test response, along with coordinate transformation, shows that for the same antenna under test, its radiation pattern does not change with the number of tests in the same coordinate system. Therefore:

[0091]

[0092] The first state corresponds to: θ ranging from -50° to +50°, with a step size of 0.1°, and the step size ranging from 0.01° to 2°; and Keep 0° unchanged;

[0093] Drive the turntable of the antenna under test to rotate the antenna under test 90° around the Z-axis of the antenna under test coordinate system;

[0094] The second state corresponds to: θ ranging from -50° to +50°, with a step size of 0.1°, and the step size ranging from 0.01° to 2°; and Keep it at 90°.

[0095] By subtracting (Equation 8) and (Equation 9) and taking the absolute value, since the amplitude spectrum is positive and the probability of the interference spectrum falling at the same position is extremely low, it can be assumed that the interference spectrum of the two states has no overlapping part, thus obtaining (Equation 10).

[0096]

[0097] By summing (Equation 8) and (Equation 9), we obtain the radiation pattern results for the two states (Equation 11).

[0098]

[0099] Observation of (Equation 11) shows that it only adds an impulse function compared to (Equation 10). Therefore, by adding an impulse function to the discrete spectrum obtained from (Equation 10) and then performing deconvolution on it, the corrected radiation pattern of the antenna under test can be obtained.

[0100] Based on the above principle analysis, this invention proposes a method for correcting the test grating lobe of a large compact field terahertz antenna, combined with... Figure 1 The specific process is as follows:

[0101] (1) Install and calibrate the antenna under test in its first state to establish a terahertz compact field test environment. The terahertz compact field consists of a plane wave generator, a mechanical subsystem, a radio frequency subsystem, and a control subsystem. The plane wave generator converts spherical electromagnetic waves into quasi-plane electromagnetic waves, and the direction of arrival is generally defined as the Z-axis. The mechanical subsystem mainly includes a feed turntable and an antenna under test turntable. Generally, the antenna under test turntable consists of four axes: azimuth, elevation, polarization, and translation at the bottom. The antenna under test is installed on the antenna under test turntable. The site calibration establishes a definite relationship between the coordinate system of the antenna under test and the coordinate system of the site or adjusts it to be parallel to the site coordinate system, i.e., the X-axis of the antenna under test is parallel to the X' axis of the site, the Y-axis of the antenna under test is parallel to the Y' axis of the site, and the Z-axis of the antenna under test is parallel to the Z' axis of the site, as shown in Figure 2(a). Select a compact field feed of the corresponding frequency and install it on the compact field feed turntable.

[0102] (2) The compact field control subsystem is used to automatically rotate the turntable and control the radio frequency transmission signal, while simultaneously collecting and recording data. The radiation pattern test of the antenna under test in the first state is completed point by point to obtain the radiation pattern data of the first state. is the angle between the antenna Z-axis and the field Z'-axis; is the angle between the projection of the antenna Z-axis onto the X'O'Y' plane of the field coordinate system and the field X'-axis.

[0103] (3) Referring to step (1), perform the second-state installation and site calibration of the antenna under test. You can directly rotate the polarization axis of the antenna under test by 90 degrees and then perform site calibration, so that you do not need to reinstall the antenna under test. Site calibration establishes a definite relationship between the coordinate system of the antenna under test and the coordinate system of the site or adjusts it to be parallel to the site coordinate system, that is, the X-axis of the antenna under test is parallel to the Y-axis of the site, the positive direction of the Y-axis of the antenna under test points to the negative direction of the X-axis of the site, and the Z-axis of the antenna under test is parallel to the Z-axis of the site, as shown in Figure 2(b). Use the translation axis of the antenna under test turntable to place the antenna in a quiet zone position that is as similar as possible to the first state (that is, ensure that the three axes of the two coordinate systems are parallel and the origins coincide). If the positions are basically the same, translation operation is not required.

[0104] (4) Referring to step (2), perform a second-state radiation pattern test on the antenna under test to obtain the second-state radiation pattern data.

[0105] (5) Perform calculations on the results obtained in step (4) using coordinate transformation to obtain the direction pattern data with the same coordinate state as the first state.

[0106]

[0107] (6) Using the radiation pattern data obtained in steps (2) and (5) The interference spectrum function B(k) is obtained by calculation using the following formula. x ,k y Because there are background noise and environmental interferences during actual testing, the small signal spectrum needs to be filtered out during calculation.

[0108]

[0109]

[0110] In the formula k aut-sllHere, N represents the spectral width corresponding to the main lobe width of the antenna under test, and N is the level threshold for spurious spectra caused by neglecting the test noise floor. The value of N is typically 40 dB. This mainly depends on the dynamic range of the terahertz compact field system pattern test. If the dynamic range is poor, this value can be appropriately reduced; if the dynamic range is good, this value can be appropriately increased. The general principle is that N should be 30 dB smaller than the dynamic range. Choosing this rule covers most engineering requirements. That is, when the dynamic range is 70 dB, N is 40 dB. x ,k y ) is the spectral function containing grating lobe interference.

[0111] k x Let k be the spectral value along the X-axis of the antenna coordinate system. y This represents the spectral value along the Y-axis of the antenna coordinate system.

[0112] (7) Add a compacted field ideal beam function δ(k x ,k y The orientation pattern obtained by removing the coupling of the compacted field is obtained using the deconvolution formula.

[0113]

[0114] In the formula, deco represents the deconvolution calculation.

[0115] The sampling interval of the radiation pattern tested in steps (2) and (4) should be less than Δ. max ;

[0116] Where, Δ max Determined by the following formula:

[0117]

[0118] In the formula θ 3dB It is equal to the 3dB beamwidth of the antenna under test.

[0119] In step (3), the polarization axis of the antenna under test is rotated 90 degrees because pattern testing is generally performed... and Most tests involve two cross-sections; the second state corresponds to a 90-degree rotation. and It corresponds exactly to the first state coordinate system and For ease of calculation. If the rotation angle is not 90 degrees, the corresponding angle transformation is required, and the tangent positions of the test also need to be matched one by one.

[0120] Figure 2(a) shows the antenna under test (UTD) fixed to the UTD turntable, with the UTD coordinate system and the field coordinate system having parallel axes. Assume that in this state, the radiation pattern data obtained by rotating the azimuth axis corresponds to Theta values ​​from -50 to 50 degrees, with a 1-degree interval, resulting in 101 radiation pattern data points. At this time, Phi is 0 degrees.

[0121] Figure 2(b) shows the antenna under test being rotated using the polarization axis of the turntable. A 90-degree clockwise rotation changes the relationship between the antenna's coordinate system and the site coordinate system, resulting in the Z-axis corresponding to the Z'-axis, the X-axis to the Y'-axis, and the Y-axis to the X'-axis. In this state, the elevation axis needs to be rotated to achieve the same correspondence as the data in the first state. At this point, the radiation pattern corresponds to a Phi of 90 degrees.

[0122] Figure 3 To verify the simulation results, the dotted line represents the radiation pattern test result in the first state, and the horizontal dotted line represents the radiation pattern test result in state 2 after coordinate changes. It can be seen that inconsistencies occur between the two results within ±1 degree and ±3 degree, which is caused by the grid structure. The solid line with dots represents the corrected result, and the solid line with triangles represents the radiation pattern result without the influence of the grid structure. The overlap of the corrected results verifies the effectiveness of the method.

[0123] Figure 4 The results are from actual measurements. The dashed line represents the test results of the first-state radiation pattern, and the solid line represents the test results of the second-state radiation pattern after coordinate changes. It can be seen that there are inconsistencies in many places. The dotted line represents the correction results.

[0124] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make possible variations and modifications to the technical solutions of the present invention using the disclosed methods and techniques without departing from the spirit and scope of the invention. Therefore, any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention, without departing from the content of the technical solutions of the present invention, shall fall within the protection scope of the present invention. Where there is no conflict, the embodiments of this application and the technical features thereof can be combined with each other.

[0125] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A method for correcting the test grating lobe of a large compact field terahertz antenna, characterized in that, Includes the following steps: 1) Establish the antenna coordinate system O'-X'Y'Z' and the site coordinate system O-XYZ; wherein, the antenna coordinate system is fixedly connected to the reflecting surface of the antenna under test; 2) Establish the first state by setting the positional relationship between the antenna coordinate system and the site coordinate system; establish a terahertz compact field test environment; in the first state, the three axes of the antenna coordinate system and the site coordinate system coincide; 3) Use the antenna under test to transmit and receive electromagnetic wave signals and perform data sampling; complete the radiation pattern test of the antenna under test in the first state point by point to obtain the radiation pattern data of the first state. ; 4) Rotate the antenna under test 90° around the antenna Z-axis to form a second state in the positional relationship between the antenna coordinate system and the field coordinate system; establish a terahertz compact field test environment; the antenna Z-axis and the reflector surface of the antenna under test point in the same direction and pass through the geometric midpoint of the reflector surface of the antenna under test; 5) Use the antenna under test to transmit and receive electromagnetic wave signals and perform data sampling; complete the radiation pattern test of the antenna under test in the second state point by point to obtain the radiation pattern data of the second state. ; 6) Obtain the second-state radiation pattern data obtained in step 5). Transform from the antenna coordinate system to the site coordinate system; obtain the second-state radiation pattern data with the same coordinates as the first state. ; 7) Based on the first state radiation pattern data obtained in step 3), And the second-state pattern data obtained in step 6) that has the same coordinates as the first state. Determine the interference spectral function ; 8) Based on the interference spectrum function determined in step 7). Add a compacted field ideal beam function The deconvolution formula is used to obtain the radiation pattern after removing the coupling of the compacted field. ; Determine the interference spectral function The method is as follows: in, The spectral width is the width of the main lobe of the antenna under test. This represents the spectral value along the X-axis of the antenna. This represents the spectral value along the Y-axis of the antenna; is the spectral function containing grating lobe interference; N is the level threshold of the spurious spectrum caused by ignoring the test noise floor; N is determined according to the dynamic range of the terahertz compact field system pattern test; The angle between the antenna's Z-axis and the field's Z'-axis; The angle between the projection of the antenna's Z-axis onto the X'O'Y' plane of the site coordinate system and the X' axis of the site; Obtain the radiation pattern after removing the compression field coupling The method is as follows: in, This is for deconvolution calculation.

2. The method for correcting the test grating lobe of a large compact field terahertz antenna according to claim 1, characterized in that, Establish the site coordinate system O'-X'Y'Z', specifically as follows: The origin O' of the site coordinate system is located at the geometric center of the reflector surface of the antenna under test; The Z' axis of the field is parallel to the azimuth axis of the turntable of the antenna under test, and the positive direction of the Z' axis of the field points in the direction of the incoming wave. The Y' axis of the site is parallel to the elevation axis of the turntable of the antenna under test, and the positive direction of the Y' axis of the site points in the opposite direction of the Earth's center. Establish the coordinate system O-XYZ for the antenna under test, specifically as follows: The XOY plane is located within the reflector surface of the antenna under test.

3. The method for correcting the test grating lobe of a large compact field terahertz antenna according to claim 2, characterized in that, The first state corresponds to the antenna X-axis being parallel to the field X' axis, the antenna Y-axis being parallel to the field Y' axis, and the antenna Z-axis being parallel to the field Z' axis.

4. The method for correcting the test grating lobe of a large compact field terahertz antenna according to claim 3, characterized in that, The second state corresponds to the antenna X-axis being parallel to the field Y' axis, the positive direction of the antenna Y-axis pointing towards the negative direction of the field X' axis, and the antenna Z-axis being parallel to the field Z' axis.

5. The method for correcting the test grating lobe of a large compact field terahertz antenna according to claim 4, characterized in that, The dynamic range of the N-type terahertz compact field system pattern test is 30 dB smaller.

6. A method for correcting the test grating lobe of a large compact field terahertz antenna according to claim 4 or 5, characterized in that, Corresponding radiation pattern test for the first state of the antenna under test: The value range is -50° to +50°, with a step size of 0.1°, and the step size ranges from 0.01° to 2°; and Keep the temperature at zero degrees.

7. The method for correcting the test grating lobe of a large compact field terahertz antenna according to claim 6, characterized in that, Corresponding radiation pattern test for the second state of the antenna under test: The value range is -50° to +50°, with a step size of 0.1°, and the step size ranges from 0.01° to 2°; and Keep it at 90°.

8. The method for correcting the test grating lobe of a large compact field terahertz antenna according to claim 7, characterized in that, In steps 3) and 5), the data sampling interval for the radiation pattern test should be less than [a certain value]. ; Determined by the following formula: in, It is equal to the 3dB beamwidth of the antenna under test.

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