A near-field calibration compensation method in a dual-antenna station layout mode

Abstract

The present application relates to a kind of near-field scaling compensation methods in dual-antenna station mode, it is related to RCS measurement field, including the following steps: by calculating the relative angle of the position of scaling body at different test distances and dual-antenna, obtain field intensity-distance distribution, determine scaling body placement position;RCS measurement system is built, the background electromagnetic data of the position of not placing scaling body and target position is measured;Scaling ball is placed in the midline position of dual-antenna, electromagnetic measurement is carried out and data is recorded;Subsequently, scaling ball is erected to target position, and electromagnetic measurement is carried out again and data is recorded;The scaling body data measured is combined with the field intensity-distance distribution data obtained by calculation, and the radiation field intensity compensation is calculated, to compensate the measurement data, the present application has the advantages that scaling body is selected suitable position and echo level compensation, improves the RCS measurement precision.

Description

Technical Field

[0001] This invention relates to the field of RCS measurement technology, and in particular to a near-field calibration compensation method in a dual-antenna deployment mode. Background Technology

[0002] As various RCS research projects continue to advance, the demand for electromagnetic scattering characteristic measurement is gradually expanding from standard far-field electromagnetic measurements in darkrooms and outdoor fields to near-field scenarios.

[0003] like Figure 1 As shown, the antenna pattern represents the gain distribution of the antenna in a fan-shaped illumination pattern towards the target. Therefore, in a near-field dual-antenna deployment scenario, as the radial distance increases, the radial illumination angle of the calibration object relative to the antenna decreases, which, combined with the antenna pattern, can increase the antenna gain. Consequently, the echo intensity varies depending on the placement of the calibration object. This significantly impacts the accuracy of conventional indoor and outdoor calibration. RCS measurement commonly uses a relative calibration method, which involves first measuring the standard object, then measuring the target object, calculating the target's RCS by comparing the measured values ​​with theoretical values, and then compensating accordingly. Therefore, accurate measurement of the standard object is crucial for target RCS measurement.

[0004] However, in near-field scenarios, the location of the standard object can affect the frequency response of the measurement system itself due to the calibration data, thus causing deviations in the processing of the target measurement data. For example... Figure 2 As shown, at different distances, after range compensation using the radar formula, the echo levels at each frequency point will first increase and then gradually level off as the relative position of the calibration object gradually moves closer to the position directly opposite the antenna. Therefore, the position of the calibration object in near-field mode will have a certain impact on calibration. Figure 3 , Figure 4 As shown, the one-dimensional image of the calibration body at different positions and its frequency response at those positions are displayed. By comparing the amplitude at the same frequency point after distance compensation, it can be calculated that the amplitude at 20m is slightly higher than that at 9m, which causes a deviation in the test results.

[0005] Therefore, to address the above shortcomings, a near-field calibration compensation method is needed in the dual-antenna deployment mode. Summary of the Invention

[0006] (a) Technical problems to be solved The technical problem to be solved by this invention is how to determine the placement area of ​​the calibration body and obtain accurate compensation in the near field of dual-antenna deployment.

[0007] (II) Technical Solution To address the aforementioned technical problems, this invention provides a near-field calibration compensation method in a dual-antenna deployment mode, comprising the following steps: I. By calculating the relative angle between the position of the calibration object and the dual antennas at different test distances, the field strength-distance distribution is obtained, and the placement position of the calibration object is determined; II. Set up an RCS measurement system to measure the background electromagnetic data at the location where no calibration body is placed and at the target location; III. Place a calibration ball at the centerline of the dual antennas, perform electromagnetic measurements and record the data; then set up the calibration ball at the target position, perform electromagnetic measurements again and record the data. VI. Combine the measured calibration data with the calculated field strength-distance distribution data to calculate radiation field strength compensation in order to compensate for the measured data.

[0008] As a further explanation of the present invention, preferably, the relative angles between the position of the calibrator at different test distances and the dual antennas are as follows: in, The relative angle between the calibration body and the two antennas, i.e., the angular domain; It is half the distance between the two antennas; This is the distance between the midpoint of the distance between the two antennas and the calibration object.

[0009] As a further explanation of the present invention, preferably, the field strength With corner domain The relationship satisfies: in as well as and All are constants.

[0010] As a further explanation of the present invention, preferably, the target echo and distance The relationship is: Combined with field strength With corner domain The relationship is used to obtain the field strength-distance distribution.

[0011] As a further explanation of the present invention, preferably, the RCS measurement system includes a vector network analyzer, a power amplifier system, an antenna feeder system, a data acquisition system, and a data processing system. The measurement system needs to be preheated after being powered on, and the measurement is performed after the preheating is completed.

[0012] As a further explanation of the present invention, preferably, after obtaining two sets of calibration body measurement data, the difference between the field strength at the current position and the maximum field strength is obtained based on the current position of the calibration body, and this difference is the compensation value.

[0013] As a further explanation of the present invention, preferably, the compensated target measurement result is as follows: in, For target RCS; The amplitude of the calibration body echo; This is the compensation value; This is the theoretical value for the calibration body; The target echo amplitude.

[0014] (III) Beneficial Effects The above-described technical solution of the present invention has the following advantages: This invention determines the appropriate placement of the calibration body through theoretical field strength calculation, avoiding echo level deviations caused by different positions in the near field; at the same time, it calculates compensation values ​​to effectively correct echo errors caused by the position of the calibration body and improve data accuracy. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the antenna direction; Figure 2 This is a schematic diagram showing the positions of the calibration body at different distances; Figure 3 It is a one-dimensional range image and frequency response curve of the calibration body at a 9m position; Figure 4 It is a one-dimensional range image and frequency response curve of the calibration body at a 20m position; Figure 5 This is a background one-dimensional distance image measured by the present invention; Figure 6 This is a diagram showing the overlap between the data points and the fitted bivariate polynomial curve of this invention. Figure 7 This is the field strength gain-distance distribution diagram of the present invention. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] A near-field calibration compensation method in a dual-antenna deployment mode includes the following steps: Ⅰ. For example Figure 1 As shown, the antenna pattern describes the field strength distribution at different circumferential angles of the current antenna. Therefore, the relative positions of the calibration object and the two antennas are offset rather than directly opposite each other. By calculating the relative angle between the position of the calibration object and the antenna at different test distances, the field strength-distance distribution is obtained. The placement position of the calibration object is determined in combination with the near-field test scenario.

[0018] Specifically, first, we use the antenna's factory test data, such as... Figure 6 As shown, the angular domain is fitted using the least squares method. With field strength of The equation of the quadratic curve is: in, angle domain This refers to the relative angle between the calibration body and the two antennas; as well as and All are constants.

[0019] The distribution of field strength with angle is obtained from the above formula. Then, the relative angle between the calibration body and the antenna is calculated. Specifically: in, It is half the distance between the two antennas; This is the distance between the midpoint of the distance between the two antennas and the calibration object.

[0020] Combining this with the radar formula, the specific details are as follows: in, For target echo; This refers to the transmission power of the electromagnetic system. Antenna gain; For testing wavelength; The target electromagnetic scattering characteristics.

[0021] Because the electromagnetic scattering characteristics of a metal sphere are isotropic, the electromagnetic scattering characteristics of the target in the formula are... Stable electromagnetic transmission power and electromagnetic wave wavelength All of these are constants, and the position directly opposite the metal sphere is chosen as the antenna gain reference point. Therefore, the above factors are normalized. That is: It can be further simplified as follows: Finally, combining the above results, the field strength gain-distance distribution was determined, as follows: Figure 7 As shown, a suitable placement position is selected for the calibration body.

[0022] II. Construct an RCS measurement system centered on a vector network analyzer. This system includes a vector network analyzer, power amplifier system, antenna feeder system, data acquisition system, and data processing system. After construction, power on the equipment and allow it to warm up until the system stabilizes, then perform relevant frequency band and polarization settings. After the measurement system warms up, use the line connecting the antenna and the center of the target area as the test direction to measure the background electromagnetic data at the location without a calibration object and at the target location; the test results are as follows: Figure 5 As shown, analysis was performed to ensure that there were no strong scattering sources in the test area, thus avoiding the influence of background levels on the calibration body.

[0023] III. Based on the background measurement in Step II, and considering the theoretical field strength location and the conditions for setting up the calibration body, select a suitable location to set up the calibration ball. For example... Figure 1 As shown, the calibration sphere should be aligned directly with the centerline of the dual antennas before performing electromagnetic measurements and recording the data. After the measurements are completed, the calibration sphere should be positioned at the target location, and electromagnetic measurements should be performed and the data recorded.

[0024] VI. After obtaining the measurement data of the calibration body in step III, observe... Figure 7 As can be seen, the curve approaches a certain value as the distance increases. Based on the current position of the calibration body, the difference between the electric field strength at this point and the maximum electric field strength can be approximated. This difference is the compensation value for the calibration body test data. .

[0025] Therefore, using the relative method, the target measurement result is: in, For target RCS; The amplitude of the calibration body echo; This is the compensation value; This is the theoretical value for the calibration body; The target echo amplitude.

[0026] In summary, this invention determines the appropriate placement of the calibration body through theoretical field strength calculations, avoiding echo level deviations caused by different positions in the near field. Background measurements ensure the absence of strong scattering sources in the test area, reducing the impact of environmental factors on calibration data. Compensation values ​​are calculated using the field strength gain-distance distribution, combined with the relative calibration method, effectively correcting echo deviations caused by the calibration body's position, improving data accuracy, and solving the core problem of the calibration body's position affecting calibration accuracy in near-field dual-antenna deployment mode. Ultimately, this improves the reliability of target RCS measurements.

[0027] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A near-field calibration compensation method under dual-antenna deployment mode, characterized in that: Includes the following steps: I. By calculating the relative angle between the position of the calibration object and the dual antennas at different test distances, the field strength-distance distribution is obtained, and the placement position of the calibration object is determined; II. Set up an RCS measurement system to measure the background electromagnetic data at the location where no calibration body is placed and at the target location; III. Place a calibration ball at the centerline of the dual antennas, perform electromagnetic measurements and record the data; then set up the calibration ball at the target position, perform electromagnetic measurements again and record the data. VI. Combine the measured calibration data with the calculated field strength gain-distance distribution data to calculate radiation field strength compensation in order to compensate for the measured data.

2. The near-field calibration compensation method in a dual-antenna deployment mode according to claim 1, characterized in that: The relative angles between the calibrator's position and the dual antennas at different test distances are as follows: in, The relative angle between the calibration body and the two antennas, i.e., the angular domain; It is half the distance between the two antennas; This is the distance between the midpoint of the distance between the two antennas and the calibration object.

3. The near-field calibration compensation method in a dual-antenna deployment mode according to claim 2, characterized in that: Field strength With corner domain The relationship satisfies: in as well as and All are constants.

4. The near-field calibration compensation method in a dual-antenna deployment mode according to claim 3, characterized in that: Target echo and distance The relationship is: Combined with field strength With corner domain The relationship is used to obtain the field strength-distance distribution.

5. The near-field calibration compensation method in a dual-antenna deployment mode according to claim 1, characterized in that: The RCS measurement system includes a vector network analyzer, a power amplifier system, an antenna feeder system, a data acquisition system, and a data processing system. The measurement system needs to be preheated after powering on before measurement can be performed.

6. The near-field calibration compensation method in a dual-antenna deployment mode according to claim 1, characterized in that: After obtaining two sets of calibration body measurement data, the difference between the current field strength and the maximum field strength is obtained based on the current position of the calibration body. This difference is the compensation value.

7. The near-field calibration compensation method in a dual-antenna deployment mode according to claim 6, characterized in that: The target measurement results after compensation are as follows: in, For target RCS; The amplitude of the calibration body echo; This is the compensation value; This is the theoretical value for the calibration body; The target echo amplitude.

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