Uncertainty evaluation method introduced by near-field-to-far-field transformation algorithm in near-field directivity pattern measurement

Abstract

The present invention relates to the field of antenna measurement technology, and discloses a method for evaluating the uncertainty introduced by a near-field-far-field transformation algorithm in the measurement of a near-field method directivity pattern. The method comprises the following steps: step S1. verification of a simulation method; step S2. an evaluation method for the uncertainty introduced by a near-field-far-field transformation algorithm under an ideal near-field probe; and step S3. an evaluation method for the uncertainty introduced by a near-field-far-field transformation algorithm under an actual near-field probe. The present invention proposes a complete process, which can accurately and quantitatively evaluate the uncertainty introduced by a near-field-far-field transformation algorithm in the measurement of an antenna directivity pattern, and has strong operability and is easy to implement.

Description

Technical Field

[0001] The present invention relates to the field of antenna measurement technology, and in particular to an uncertainty evaluation method introduced by a near-field-far-field transformation algorithm in near-field directivity pattern measurement. Background Art

[0002] Antenna is a key component in the field of radio. It can radiate the signal (guided wave) in the instrument into space (free space wave), and can also receive electromagnetic waves in space, converting invisible electromagnetic waves into guided waves and using measurement receivers to complete the measurement. It is with the help of antenna, a key converter, that people can manipulate electromagnetic waves for wireless communication, long-distance detection, remote sensing imaging and many other applications. Today, the structure and appearance of antennas have become increasingly complex, becoming a complex system, so it is called an antenna system.

[0003] In order to use the antenna system to more accurately control electromagnetic waves, it is necessary to obtain the conversion characteristics of the antenna between the guided wave signal and the electromagnetic wave in space through actual measurement - the antenna radiation characteristics. The parameter that comprehensively describes the radiation characteristics of the antenna system is the three-dimensional antenna radiation directivity diagram (hereinafter referred to as the directivity diagram). The more accurate the directivity diagram is measured, the more conducive it is to accurately control the electromagnetic waves to achieve the desired purpose (such as forming a phased array radar to detect enemy aircraft, etc.).

[0004] The directivity diagram of the antenna system usually needs to be measured to get accurate results, and the directivity diagram measurement technology has undergone a long evolution process. Except for a few particularly simple antennas that can get their accurate directivity diagrams through simulation calculation methods, most antennas can only get their accurate directivity diagrams through measurement. In order to carry out the measurement of the directivity diagram, the basic principle is to use a transmitting antenna to irradiate the known electromagnetic wave onto the antenna system to be tested, and then record its response under different postures. This response relationship with the change of posture is the directivity diagram. In order to obtain an accurate directivity diagram, the transmitting antenna needs to be far enough away from the antenna under test (Antenna under test-AUT), hence the name far-field method. The required far-field distance is proportional to the square of the aperture of the antenna to be tested and inversely proportional to the wavelength. Therefore, when the size of the antenna system becomes larger and the wavelength becomes shorter (that is, the frequency becomes higher), this distance requirement will be very demanding, reaching hundreds or even thousands of kilometers. In order to circumvent this demanding requirement, the near-field scanning method has emerged. At present, there are three basic near-field scanning methods: planar near-field (PNF), cylindrical near-field (CNF) and spherical near-field (SNF). Figure 5-7 shown.

[0005] Depend on Figure 5-Figure 7 It can be seen that the three near-field scanning methods mentioned above have different scanning surfaces, resulting in great differences in their measurement devices. For example, for PNF, the AUT is fixed, while the near-field scanning probe needs to move in a plane; for CNF, the AUT needs to rotate along the azimuth axis; and the near-field probe needs to move up and down; for SNF, the probe does not need to be scanned, but the AUT needs to rotate around two orthogonal axes. This difference brings difficulties to system design and also to the accurate evaluation of the uncertainties introduced by different systems, not only because the actual antenna measurement device is very complex, but also because many uncertainty components are easily entangled.

[0006] How to find a simple way to overcome the above problems so as to:

[0007] 1) It can quickly and quantitatively evaluate the uncertainty introduced by the near-field-to-far-field transformation method so as to select the appropriate method for the specific AUT and carry out detailed design;

[0008] 2) For an existing measurement system, the uncertainty component introduced by the accurate near-field-to-far-field transformation algorithm can be easily evaluated and ensured to be uncorrelated with other uncertainty components.

[0009] In 2010, the National Institute of Standards and Technology (NIST) conducted an experimental study of three near-field scanning methods, PNF, CNF and SNF, based on a Ku-band dual-port linearly polarized Cassegrain reflector antenna, and compared their directivity diagrams. Although this experimental method is very reliable, it is expensive and requires three sets of scanning devices, or at least three scanning modes. The conclusions obtained are only applicable to this high-gain antenna.

[0010] In 2013, Allen Newel, an expert from NIST, conducted a study on 18 uncertainty assessments based on six PNF measurement devices. This study is very useful for PNF, but it is also very expensive and involves six devices, so it is not a universal and simple method.

[0011] In 2022, the 38th Institute of China Electronics Group analyzed the uncertainty introduced by truncation error when the 43 x 41 array antenna adopted the PNF near-field-far-field transformation algorithm. However, this method lacked metrological support and verification, and did not include the impact of probe correction effects. It was only a simple verification under ideal conditions.

[0012] In summary, the existing literature and technology do not meet the above two requirements. They cannot quickly and quantitatively evaluate the uncertainty introduced by the near-field-to-far-field transformation method so as to select a suitable method for a specific AUT to carry out detailed design. They also cannot easily evaluate the uncertainty component introduced by the near-field-to-far-field transformation algorithm for an existing measurement system and ensure that it is uncorrelated with other uncertainty components. Summary of the invention

[0013] In order to solve the above-mentioned problems and shortcomings in the prior art, the present invention proposes a complete process, which can accurately and quantitatively evaluate the uncertainty introduced by the near-field-to-far-field transformation algorithm in the measurement of antenna directivity patterns, and has strong operability and is easy to implement.

[0014] In order to achieve the above-mentioned object of the invention, the technical solution of the present invention is as follows:

[0015] A method for evaluating uncertainty introduced by a near-field-to-far-field transformation algorithm in near-field directivity pattern measurement comprises the following steps:

[0016] Step S1. Verification of the simulation method;

[0017] Step S2. Uncertainty evaluation method introduced by near-field-to-far-field transformation algorithm under ideal near-field probe;

[0018] Step S3. Uncertainty evaluation method introduced by the near-field-to-far-field transformation algorithm under an actual near-field probe.

[0019] Preferably, the step S1 specifically includes the following steps:

[0020] Step S1.1. Model and simulate the antenna model in the software to obtain its far-field directivity diagram;

[0021] Step S1.2. Use the precision spherical near-field antenna pattern measurement method to measure the far-field directivity pattern of the antenna model;

[0022] Step S1.3. Compare the far-field directivity diagram obtained from the modeling simulation results with the far-field directivity diagram measured by the precision spherical near-field antenna directivity measurement method to verify whether the simulation method is correct.

[0023] Preferably, the step S2 specifically includes the following steps:

[0024] Step S2.1. Use the verified simulation method to model and simulate the antenna to be tested, and set the corresponding spherical coordinate system as ;

[0025] Step S2.2. Set the probe near-field data acquisition parameters to obtain the far-field directivity diagram of the antenna to be tested and near-field scan data;

[0026] Step S2.3. Set the scanning probe correction parameters to the ideal electric field probe, and then use the above near-field scanning data to perform near-field-to-far-field transformation to obtain the far-field directivity diagram ;

[0027] Step S2.4. Comparison and The difference between the near-field and far-field transformations is evaluated.

[0028] Preferably, step S3 specifically includes the following steps:

[0029] Step S3.1. Model the near-field scanning probe used separately to obtain its directivity diagram, set as ;

[0030] Step S3.2. Simulate and model the antenna to be tested and the near-field scanning probe together according to the above-mentioned verified method, wherein the near-field data acquisition parameters of the probe are set with reference to the ideal near-field probe;

[0031] Step S3.3. Simulate and solve to obtain the spatial position between the antenna to be tested and the near-field scanning probe. The transmission coefficient on ;

[0032] Step S3.4. Repeat steps S3.2 to S3.3 to obtain the transmission coefficients of several near-field scanning probes at the near-field scanning positions used by the antenna to be tested;

[0033] Step S3.5. Set the probe correction parameters to , and then use the above transmission coefficient to carry out near-field-far-field transformation to obtain the far-field directivity diagram ;

[0034] Step S3.5. Comparison and The difference between the near-field and far-field results is evaluated by using the actual near-field scanning probe.

[0035] Preferably, the near-field data acquisition parameters include a scanning range and a scanning interval.

[0036] In the present invention, for the planar near-field scanning method, the scanning range and the scanning interval are calculated by formula (1) and formula (2):

[0037] (1);

[0038] (2);

[0039] in, L is the scanning range; Δ x and Δ y is the scanning interval; D is the aperture of the antenna to be tested; R The distance from the antenna to be tested to the near-field scanning probe must be more than 3 times the longest wavelength; θ 0 is the cutoff angle of PNF scanning, θ 0≤20°; λ is the wavelength.

[0040] In the present invention, for the spherical near-field scanning method, the spherical scanning radius is determined R When the minimum sphere of the antenna to be tested is 3 times greater than the minimum sphere of the probe, the interval between the minimum sphere of the antenna to be tested and the maximum wavelength in the measurement frequency band should be at least 3 times greater than the minimum sphere of the probe. The polarization angle scanning interval of data sampling is Δ θ Calculated by formula (3)

[0041] (3);

[0042] Azimuth scanning interval The requirements and Δ θ same.

[0043] In the present invention, when the antenna to be tested is included and z Radius of the cylinder with the axis parallel to it r c Satisfy the conditions r c < r 0 When , the azimuth scanning interval is calculated by formula (4): :

[0044] (4).

[0045] In the present invention, for the cylindrical near-field scanning method, the cylindrical longitudinal scanning distance can refer to the planar near-field scanning method, and the longitudinal scanning interval , λ is the wavelength, and the scanning interval can be calculated by referring to formula (3) of the spherical near-field scanning method.

[0046] Beneficial effects of the present invention:

[0047] 1. The present invention proposes a systematic and complete method for quantitatively analyzing the uncertainty introduced by different near-field-to-far-field transformation algorithms, which is very easy to operate and implement. A practical method is proposed for the design of near-field scanning systems and for the evaluation of the near-field-to-far-field transformation uncertainty components of a practical near-field scanning system.

[0048] 2. The different near-field-to-far-field transformation algorithms proposed in the present invention can accurately evaluate the near-field uncertainty component, and this component is completely independent of other components.

[0049] 3. The present invention can conveniently and accurately evaluate the uncertainty introduced by truncation error, near-field scanning radius, data sampling interval, etc., and can be used to guide system design and carry out practical measurement applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The foregoing and following detailed description of the present invention will become more apparent when read in conjunction with the following drawings, in which:

[0051] Figure 1 is a flow chart of the method of the present invention;

[0052] Figure 2 It is a schematic diagram of the coordinate system of AUT;

[0053] Figure 3 This is a schematic diagram of the near-field data acquisition parameter settings for the planar near-field method;

[0054] Figure 4 Schematic diagram of the method for determining the scanning radius R of the cylindrical and spherical near-field method;

[0055] Figure 5 It is a schematic diagram of the planar near-field scanning method;

[0056] Figure 6 Schematic diagram of cylindrical near-field scanning method;

[0057] Figure 7 Schematic diagram of the spherical near-field scanning method. DETAILED DESCRIPTION

[0058] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions for achieving the purpose of the present invention will be further described below through several specific embodiments. It should be noted that the technical solutions claimed for protection in the present invention include but are not limited to the following embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those skilled in the art without creative work shall fall within the scope of protection of the present invention.

[0059] At present, there are three basic near-field scanning methods: planar near-field (PNF), cylindrical near-field (CNF) and spherical near-field (SNF). Figure 5-7As shown. The three near-field scanning methods mentioned above have different scanning surfaces, resulting in very different measurement devices. For example, for PNF, the AUT is fixed, while the near-field scanning probe needs to move in a plane; for CNF, the AUT needs to rotate along the azimuth axis; and the near-field probe needs to move up and down; for SNF, the probe does not need to be scanned, but the AUT needs to rotate around two orthogonal axes. This difference brings difficulties to system design and also to the accurate evaluation of the uncertainties introduced by different systems, not only because the actual antenna measurement device is very complex, but also because many uncertainty components are easily entangled.

[0060] How to find a simple way to overcome the above problems so as to:

[0061] 1) It can quickly and quantitatively evaluate the uncertainty introduced by the near-field-to-far-field transformation method so as to select the appropriate method for the specific AUT and carry out detailed design;

[0062] 2) For an existing measurement system, the uncertainty component introduced by the accurate near-field-to-far-field transformation algorithm can be easily evaluated and ensured to be uncorrelated with other uncertainty components.

[0063] However, the existing literature and technology do not meet the above two requirements. They cannot quickly and quantitatively evaluate the uncertainty introduced by the near-field-to-far-field transformation method so as to select a suitable method for a specific AUT to carry out detailed design. In addition, they cannot easily evaluate the uncertainty component introduced by the near-field-to-far-field transformation algorithm for an existing measurement system and ensure that it is uncorrelated with other uncertainty components.

[0064] Based on this, an embodiment of the present invention proposes a method for evaluating the uncertainty introduced by the near-field-to-far-field transformation algorithm in the near-field directional pattern measurement. The present invention can conveniently and accurately evaluate the uncertainty introduced by truncation error, near-field scanning radius, data sampling interval, etc., and can be used to guide system design and carry out actual measurement applications.

[0065] This embodiment discloses a method for evaluating the uncertainty introduced by the near-field-to-far-field transformation algorithm in the near-field directivity pattern measurement. Figure 1 , the method is specifically as follows:

[0066] Step S1. Verification of the simulation method.

[0067] Step S1.1. For the antenna model, use methods such as the method of moments (MoM) to model and simulate the solution in the software to obtain its far-field directivity diagram.

[0068] In this embodiment, as long as the passive antenna has a simple structure and is made of metal material, and its electrical size is not electrically large (i.e., its volume is less than 1000λ³, where λ is the wavelength), the electromagnetic moment method MoM can be used for simulation calculation to obtain its accurate far-field directivity diagram. In addition to the moment method, there are many other methods, such as the finite element method FEM, the finite difference time domain method FDTD, etc., but in terms of the simulation accuracy of the antenna radiation directivity diagram, MoM is the most accurate.

[0069] Step S1.2. Use the precision spherical near-field antenna pattern measurement method to measure the far-field directivity pattern of the antenna model.

[0070] In this embodiment, it should be noted that the spherical near-field method has the widest application range and theoretically has no truncation error. The planar near-field method is only applicable to high-gain antennas and not to omnidirectional antennas; the cylindrical near-field method is only applicable to fan-beam antennas. Both the planar near-field method and the cylindrical near-field method have certain truncation errors. Therefore, the choice of the near-field method mainly depends on the strength of the antenna radiation directivity. In addition, it is also necessary to combine the frequency range, device availability, type of antenna to be tested, and whether it is easy to install.

[0071] Step S1.3. Compare the far-field directivity diagram obtained from the modeling simulation results with the far-field directivity diagram measured by the precision spherical near-field antenna directivity measurement method to verify whether the simulation method is correct.

[0072] Step S2. Uncertainty evaluation introduced by the near-field-to-far-field transformation algorithm under an ideal near-field probe.

[0073] Step S2.1. Use the verified simulation method to model and simulate the antenna under test. Details or components that do not affect the radiation characteristics can be ignored, such as removing the active part or the part that cannot be modeled. The part that has a greater impact on radiation needs to be retained intact. For ease of explanation, the coordinate system of the AUT is usually as follows Figure 2 As shown, the corresponding spherical coordinate system is .

[0074] In this embodiment, it should be noted that the coordinate system of the AUT is usually selected with the origin of the coordinate system being the center of the antenna radiation aperture, or other conveniently determined geometric position, and the z-axis is pointed in the direction of the antenna visual axis. Usually, industry practices can be referred to.

[0075] Step S2.2. Set the probe near-field data acquisition parameters to obtain the far-field directivity diagram of the antenna to be tested And near-field scanning data. Usually, near-field data acquisition parameters include near-field scanning radius, scanning interval, etc.

[0076] In this embodiment, it should be noted that the far-field directivity diagram obtained in this step is As a standard quantity, it is used for subsequent uncertainty assessment.

[0077] Step S2.3. Set the scanning probe correction parameters to an ideal electric field probe, that is, its directivity is omnidirectional and the cross-polarization ratio is 0. Then use the above near-field scanning data to perform near-field-to-far-field transformation to obtain the far-field directivity diagram, which is set as ;

[0078] Step S2.4. Comparison and The difference between the near-field and far-field transformations can be used to evaluate the error in the near-field-far-field transformation, which can be considered as the standard uncertainty component.

[0079] Step S3. Evaluating the uncertainty introduced by the near-field-to-far-field transformation algorithm under an actual near-field probe.

[0080] Step S3.1. Model the near-field scanning probe used separately to obtain its directivity diagram, set as .

[0081] Step S3.2. Perform simulation modeling on the antenna to be tested and the near-field scanning probe together according to the method verified in step S1, wherein the near-field data acquisition parameters of the probe are set with reference to the ideal near-field probe.

[0082] Step S3.3. Simulate and solve to obtain the spatial position between the antenna to be tested and the near-field scanning probe. The transmission coefficient on .

[0083] In this embodiment, the position of the probe refers to the position of the probe in step S2 and needs to be located at one of its spatial positions.

[0084] Step S3.4. Repeat steps S3.2-S3.3 to obtain several transmission coefficients of the near-field scanning probe at the near-field scanning position used by the antenna to be tested. .

[0085] Step S3.5. Set the probe correction parameters to , and then use the above transmission coefficients to carry out near-field-far-field transformation to obtain the far-field directivity diagram, which is set as ;

[0086] Step S3.5. Comparison and The difference between the near-field and far-field results is evaluated by using the actual near-field scanning probe.

[0087] Preferably, in the present invention, the near-field scanning radius, scanning interval and scanning range are calculated in different ways for different near-field methods, as described below.

[0088] For PNF (planar near field scanning method), refer to the manual Figure 3 , calculate the scanning range using formula (1) L :

[0089] (1);

[0090] Where: L is the scanning range; Δ x and Δ y is the scanning interval; D is the aperture of the antenna to be tested; R The distance from the antenna to be tested to the near-field scanning probe must be more than 3 times the longest wavelength; θ 0 is the cutoff angle of PNF scanning. Generally, θ 0≤20°; λ is the wavelength of the AUT.

[0091] Furthermore, the scanning interval Δ x and Δ y All are required to be less than half the wavelength, as shown in formula (2):

[0092] (2);

[0093] For SNF (Spherical Near Field Scanning), refer to the manual. Figure 4 , determine the spherical scanning radius R When the minimum sphere of AUT (assuming the radius is r 0 ) and the probe's smallest sphere (assuming the radius is More than three times the maximum wavelength in the frequency band;

[0094] The polarization angle scanning interval of data sampling Δ θ Calculated by formula (3):

[0095] (3);

[0096] The integer N is calculated by formula (4):

[0097] (4);

[0098] Express kr 0 Rounding, wave number , λ is the wavelength, in m;

[0099] n 2 is calculated by formula (5):

[0100] (5);

[0102] Azimuth scanning interval The requirements and Δ θ Same as; but when including AUT and z Radius of the cylinder with the axis parallel to it r c Satisfy the conditions r c < r 0 The sampling interval can be calculated by the following formula:

[0103] (6);

[0104] Where:

[0105] ;

[0106] Usually, the azimuth φ : 0 ~ 360°, polarization angle θ: 0 ~ 180°.

[0107] For CNF (cylindrical near field scanning method), the distance from the near field scanning probe to the AUT can be referred to Figure 4 , cylindrical longitudinal scanning distance L Refer to formula (1) for calculation; longitudinal scanning interval ; Azimuth scanning angle interval It can be calculated by referring to formula (3).

[0108] In the present invention, when different scanning intervals are set, the uncertainty introduced by the sampling rate can be analyzed.

[0109] Furthermore, when setting different scanning areas, the uncertainty introduced by the truncation error can be analyzed.

[0110] By using different scanning methods for the same AUT and transforming it to the far field, the uncertainty of different near-field methods obtained by the near-field-to-far-field transformation when measuring the AUT can be quantitatively evaluated. Based on this, the system design can be carried out and the corresponding uncertainty components can be evaluated for the actual near-field scanning device.

[0111] The uncertainty evaluation method introduced by the near-field-to-far-field transformation algorithm under an ideal near-field probe can quickly verify the accuracy of the algorithm; if the result after verification is yes or no, it is necessary to check whether the near-field-to-far-field algorithm is correct; this step can quickly verify whether it is correct.

[0112] The uncertainty evaluation method introduced by the near-field-far-field transformation algorithm under the actual near-field probe is very time-consuming and labor-intensive, and the time allocated is several orders of magnitude longer than the above steps. Therefore, the uncertainty evaluation introduced by the near-field-far-field transformation algorithm under the actual near-field probe is usually carried out only after the uncertainty evaluation method introduced by the near-field-far-field transformation algorithm under the ideal near-field probe is passed.

[0113] The above description is only a preferred embodiment of the present invention and does not constitute any form of hindrance to the present invention. Any simple modification or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for evaluating uncertainty introduced by a near-field-to-far-field transformation algorithm in near-field directivity pattern measurement, characterized in that: The following steps are involved: Step S1. Verification of the simulation method; Step S2. uncertainty assessment introduced by the near-field-to-far-field transformation algorithm under an ideal near-field probe; Step S3. After the uncertainty evaluation method introduced by the near-field-to-far-field transformation algorithm under the ideal near-field probe is passed, the uncertainty evaluation introduced by the near-field-to-far-field transformation algorithm under the actual near-field probe is performed; The step S2 comprises: Step S2.

1. Use the verified simulation method to model and simulate the antenna to be tested, and set the corresponding spherical coordinate system as ; Step S2.

2. Set the probe near-field data acquisition parameters to obtain the far-field directivity diagram of the antenna to be tested and near-field scan data; Step S2.

3. Set the scanning probe correction parameters to the ideal electric field probe, and then use the above near-field scanning data to perform near-field-to-far-field transformation to obtain the far-field directivity diagram ; Step S2.

4. Comparison and The difference between the near field and the far field is used to evaluate the error of the corresponding near field-far field transformation result; The step S3 comprises: Step S3.

1. Perform separate modeling and calculation on the near-field scanning probe used to obtain its directivity diagram ; Step S3.

2. Use a verified simulation method to simulate and model the antenna to be tested and the near-field scanning probe together, wherein the near-field data acquisition parameters of the probe refer to the ideal near-field probe settings; Step S3.

3. Simulate and solve to obtain the spatial position between the antenna to be tested and the near-field scanning probe. The transmission coefficient on ; Step S3.

4. Repeat steps S3.2 to S3.3 to obtain the transmission coefficients of several near-field scanning probes at the near-field scanning positions used by the antenna to be tested; Step S3.

5. Set the probe correction parameters to , and then use the above transmission coefficient to carry out near-field-far-field transformation to obtain the far-field directivity diagram ; Step S3.

5. Comparison and The difference between the near-field and far-field results is evaluated by using the actual near-field scanning probe.

2. The uncertainty evaluation method introduced by the near-field-to-far-field transformation algorithm in the near-field directivity pattern measurement according to claim 1 is characterized in that: The step S1 comprises: Step S1.

1. Model and simulate the antenna model in the software to obtain its far-field directivity diagram; Step S1.

2. Use the precision spherical near-field antenna pattern measurement method to measure the far-field directivity pattern of the antenna model; Step S1.

3. Compare the far-field directivity diagram obtained from the modeling simulation results with the far-field directivity diagram measured by the precision spherical near-field antenna directivity measurement method to verify whether the simulation method is correct.

3. The uncertainty evaluation method introduced by the near-field-to-far-field transformation algorithm in the near-field directivity pattern measurement according to claim 1 is characterized in that: The near-field data acquisition parameters include a scanning range and a scanning interval.

4. The uncertainty evaluation method introduced by the near-field-to-far-field transformation algorithm in the near-field directivity pattern measurement according to claim 3 is characterized in that: For the planar near-field scanning method, the scanning range and scanning interval are calculated using formula (1) and formula (2): （1）； （2）； in, L is the scanning range; Δ x and Δ y is the scanning interval; D is the aperture of the antenna to be tested; R The distance from the antenna to be tested to the near-field scanning probe must be more than 3 times the longest wavelength; θ 0 is the cutoff angle of PNF scanning, θ 0≤20°; λ is the wavelength.

5. The uncertainty evaluation method introduced by the near-field-to-far-field transformation algorithm in the near-field directivity pattern measurement according to claim 4 is characterized in that: For the spherical near-field scanning method, when determining the spherical scanning radius, it should be ensured that the minimum sphere of the antenna to be tested and the minimum sphere of the probe are separated by more than three times the maximum wavelength in the measurement frequency band; the polarization angle scanning interval of data sampling Δ θ Calculated by formula (3): （3）； in, N is an integer; Furthermore, the azimuth scanning interval The requirements and Δ θ same.

6. The uncertainty evaluation method introduced by the near-field-to-far-field transformation algorithm in the near-field directivity pattern measurement according to claim 5 is characterized in that: For the spherical near-field scanning method, when the antenna to be tested is included and z Radius of the cylinder with the axis parallel to it r c Satisfy the conditions r c < r When 0, the azimuth scanning interval is calculated by formula (4): : （4）； Further, M The calculation expression is as follows: ； Among them, the wave number , λ is the wavelength; Further, n 2 is obtained by the following calculation expression: ； in, r 0 is the minimum spherical radius of the AUT.

7. The uncertainty evaluation method introduced by the near-field-to-far-field transformation algorithm in the near-field directivity pattern measurement according to claim 5 is characterized in that: For the cylindrical near-field scanning method, the cylindrical longitudinal scanning distance is calculated by referring to the formula (1) in the plane near-field scanning method, and the longitudinal scanning interval is , λ is the wavelength, and the azimuth scanning interval is calculated according to formula (3) in the spherical near-field scanning method.

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