Cylindrical surface near-field measurement system and method for active phased-array antenna housing

Abstract

The invention relates to a cylindrical surface near-field measurement system and method for an active phased-array antenna housing, and belongs to the technical field of antenna performance testing. The cylindrical surface near-field measurement technology for the active phased-array antenna is blank. The system comprises a transmitting link and a receiving link, wherein in the transmitting link, a control computer is sequentially connected with a receiver / transmitter, an intermediate frequency processing unit, a transmitting mixer, a power amplifier, a channel switch and a transmitting probe antenna; in the receiving link, a control computer is sequentially connected with a servo driving mechanism and a test turntable capable of rotating an azimuth angle, an active phased-array antenna is mounted on the test turntable, and an active phased-array antenna housing is mounted according to test requirements; the active phased-array antenna is sequentially connected with the receiving mixer, the intermediate frequency processing unit, the receiver / transmitter and the control computer; a scanning frame is arranged at the position right opposite to the active phased-array antenna by a certain distance, the transmitting probe antenna is installed on the scanning frame, and the transmitting probe antenna can move on the scanning frame in the Z-axis height direction. The defect of low efficiency of traditional far-field measurement of the electric performance of the antenna housing is solved, the cylindrical surface near-field measurement of the antenna housing not only improves the test efficiency, but also improves the test precision, and a three-dimensional directional diagram of the antenna housing can be obtained.

Description

Technical Field

[0001] This invention relates to a cylindrical near-field measurement system and method for active phased array radomes, belonging to the field of antenna performance testing technology. Background Technology

[0002] With the development of electronic warfare technology, modern radar technologies are increasingly focused on improving radar anti-jamming performance. New radar antenna technologies are one of the important ways to achieve this. Traditional far-field antenna test ranges are insufficient for measuring modern antennas with ultra-low sidelobes and are increasingly inadequate for the demands of new antenna technologies.

[0003] While far-field measurements can directly determine the fundamental characteristics of an antenna, they also have several limitations. Due to ground reflection, far-field measurements struggle to achieve high accuracy. Furthermore, they are highly susceptible to environmental factors such as electromagnetic interference, weather conditions, limited test distance, environmental pollution, and object scattering, making it difficult to accurately reflect the antenna's actual performance. Therefore, as the performance and testing requirements of radar antennas continue to increase, far-field measurement methods are increasingly unable to meet the testing demands of modern antennas.

[0004] To meet the measurement requirements of new radar antennas, extensive research has been conducted on near-field measurement techniques for radar antennas. Near-field measurement involves determining the far-field characteristics of an antenna within a range less than the minimum far-field distance. Near-field measurement overcomes the "finite-range effect," eliminates the need for large outdoor far-field antenna test fields, and allows for real-time acquisition of amplitude, phase, and polarization information across the entire space in a single measurement. The calculated far-field accuracy is comparable to or higher than that obtained through direct far-field measurement. Near-field measurement can accomplish the measurement tasks of modern antennas such as those with ultra-low sidelobes.

[0005] Near-field measurements include source distribution methods, near-field scanning methods, distance reduction methods, focusing methods, and extrapolation methods. Among these, the near-field scanning method measures the antenna field distribution and phase distribution at a distance of 3 to 8 wavelengths from the antenna, and then uses rigorous mode expansion theory to calculate the radiation field. This method is increasingly becoming an accurate measurement technique for antenna patterns and gain.

[0006] Near-field scanning methods include planar, cylindrical, and spherical near-field scanning. Planar near-field scanning has gained widespread application due to its strong engineering practicality, but its drawback is that it cannot consider the element radiation pattern when diagnosing the excitation current of the array antenna, resulting in a certain deviation between the reconstructed excitation current distribution and the actual current distribution. In planar near-field scanning measurements, the probe moves within two coordinate planes, making the scanning system complex, although the mathematical calculations are relatively simple. A single measurement can only determine the radiation pattern of the first half of the sphere. Spherical scanning requires the antenna to rotate around two axes, and its mathematical calculations, especially those involving the probe, are very complex. It can calculate the radiation pattern for the entire space. Cylindrical scanning has a simpler rotation mechanism compared to spherical scanning systems, requiring only rotation around one axis. Its arithmetic calculations fall between those of planar and spherical scanning, and it can calculate the radiation pattern for the entire space. Therefore, cylindrical near-field scanning technology has become an important research direction.

[0007] The cylindrical near-field method can theoretically measure antennas with large beam scanning angles on the azimuth plane, but there is very little research on cylindrical near-field measurement technology for traditional antennas, and there is even less research on cylindrical near-field measurement technology for active phased array antennas. Summary of the Invention

[0008] This invention provides a cylindrical near-field measurement system and method for active phased array radomes, applying cylindrical near-field measurement to radome measurements and solving the problem of limited angular range in traditional radome measurements. This is the first time that cylindrical near-field measurement has been applied to radome measurements, providing a novel method for testing the electrical performance of radomes and improving testing efficiency and accuracy.

[0009] In one aspect, the present invention provides a cylindrical near-field measurement system for an active phased array radome, the system comprising a transmit link and a receive link, wherein... In the transmission link, the control computer is sequentially connected to the receiver / transmitter, intermediate frequency processing unit, transmit mixer, power amplifier, channel switch, and transmit probe antenna; In the receiving link, the control computer is sequentially connected to the servo drive mechanism and the test turntable that can rotate the azimuth angle. An active phased array antenna is installed on the test turntable, and an active phased array antenna cover is installed according to the test requirements. The active phased array antenna is sequentially connected to the receiving mixer, the intermediate frequency processing unit, the receiver / transmitter, and the control computer. A scanning frame is set at a certain distance from the active phased array antenna, and the transmitting probe antenna is installed on the scanning frame. The transmitting probe antenna can move in the Z-axis height direction on the scanning frame.

[0010] Advantageously, the control computer controls the receiver / transmitter to work in coordination with the test turntable, and collects radiation pattern data of the active phased array radome for data processing, performing near-field and far-field radiation pattern transformations of the cylindrical surface.

[0011] Advantageously, the receiver / transmitter receives instructions from the control computer and sends high-frequency signals to the intermediate frequency processing unit or receives intermediate frequency signals and performs data processing and pattern calculation.

[0012] Advantageously, the intermediate frequency processing unit converts the radio frequency signals of the transmit and receive links into intermediate frequency signals that can be processed by the vector network analyzer.

[0013] Advantageously, the transmit mixer upconverts the intermediate frequency signal from the intermediate frequency processing unit into a high-frequency transmit signal and amplifies the microwave signal of the transmit link through a power amplifier.

[0014] Advantageously, the sum, variance, and dip signals of the microwave signal are controlled to enter the transmitting probe antenna in a time-division manner by the channel switch.

[0015] Advantageously, the transmitting probe antenna is directed toward the active phased array antenna and moved in the height direction to transmit wide-beam pattern electromagnetic waves.

[0016] Advantageously, the high-frequency signal of the active phased array antenna under test is down-converted to an intermediate frequency signal by the receiving mixer and then sent to the intermediate frequency processing unit.

[0017] Advantageously, the scan height dimension is determined by the formula L=D+2Z 0 tanθ m Let L be the scanning distance of the transmitting probe antenna in terms of height, and D be the aperture size of the active phased array antenna under test. Z 0 represents the distance from the active phased array antenna under test to the transmitting probe antenna. θ m It is the angle between the line connecting the edge of the aperture of the active phased array antenna under test and the scanning edge of the transmitting probe antenna in the center plane and the center line.

[0018] This invention also proposes a cylindrical near-field measurement method for active phased array radomes, employing the aforementioned cylindrical near-field measurement system. First, without installing an active phased array radome, the active phased array antenna is controlled by a test turntable to move along the height direction and scan linearly for every 1° azimuth angle movement of the active phased array antenna. After completing all cylindrical angle tests, the near-field radiation pattern data without the radome is obtained. Then, the active phased array radome is installed. The active phased array antenna and radome are controlled by the test turntable to move the transmitting probe antenna along the height direction and scan linearly after each 1° movement of the azimuth angle. After all cylindrical angle tests are completed, the near-field radiation pattern data with the radome is calculated. Finally, the performance of the radome was obtained through comparative calculations.

[0019] Beneficial effects: The application of this scheme solves the problem of low electrical efficiency of traditional far-field measurement radomes. The cylindrical near-field measurement radome not only improves the testing efficiency but also the testing accuracy, and can obtain the three-dimensional radiation pattern of the radome.

[0020] Because it uses indoor near-field measurement, it not only has a long lifespan, saves money, and is easy to maintain and manage, but it can also measure the characteristics of the antenna when it is in the erected state, and has broad application prospects.

[0021] The features, functionalities, and advantages already discussed can be implemented independently in various examples, or combined in other examples. Further details of the examples can be seen in the following description and accompanying figures. Attached Figure Description

[0022] When read in conjunction with the accompanying drawings, the embodiments, preferred modes of use, other objects, and descriptions thereof will be best understood by referring to the following detailed description of embodiments of the invention, wherein: Figure 1 This is a schematic diagram of the cylindrical near-field measurement system of the present invention; Figure 2 A top-view schematic diagram of the cylindrical test of an active phased array radome; Figure 3 This is a schematic diagram of the scan height dimensions; Figure 4 A schematic diagram of an embodiment of an active phased array radome for cylindrical near-field measurement; Figure 5 Comparison of repeatability tests for the 60° near-field pattern of the cylindrical surface; Figure 6 Comparison of near-field and far-field 30° radiation patterns (VV polarization); Figure 7 Comparison of near-field and far-field 0° difference radiation patterns (VV polarization). Detailed Implementation

[0023] The disclosed examples will be described more fully with reference to the accompanying drawings, in which some (but not all) of the disclosed examples are shown. In fact, many different examples may be described, and these examples should not be construed as limited to those set forth herein. Rather, these examples are described so that this disclosure will be thorough and complete, and will fully convey the scope of this disclosure to those skilled in the art.

[0024] The structure of the cylindrical near-field radome test system is as follows: Figure 1 As shown, it mainly includes a control computer, a servo drive mechanism, a test turntable, an active phased array antenna, a receiver mixer, an intermediate frequency processing unit, a receiver / transmitter, a transmitter probe antenna, a channel switch, a power amplifier, and a transmitter mixer.

[0025] The control computer connects to the receiver / transmitter and the servo drive mechanism. The servo drive mechanism connects to the test turntable. The control computer controls the receiver / transmitter and the test turntable to work together, and is responsible for collecting the radiation pattern data of the active phased array radome and processing the data, performing near-field and far-field radiation pattern transformations of the cylindrical surface.

[0026] The receiver / transmitter receives instructions from the control computer and sends high-frequency signals to the intermediate frequency (IF) processing unit or receives IF signals and performs data processing and pattern calculations. The IF processing unit converts the radio frequency (RF) signals from the transmit and receive links into IF signals that can be processed by the vector network analyzer.

[0027] The transmit mixer upconverts the intermediate frequency (IF) signal from the IF processing unit into a high-frequency transmit signal, and then amplifies the microwave signal from the transmit link through a power amplifier. Subsequently, the sum, variance, and dip signals of the microwave signal are controlled by a channel switch and fed into the transmit probe antenna in a time-division multiplexing manner. This transmit probe antenna faces the active phased array antenna and moves along the height direction to transmit wide-beam pattern electromagnetic waves.

[0028] The active phased array antenna under test and its radome are mounted on a test turntable. The turntable rotates the antenna and radome in the horizontal plane, causing them to move according to a designed pattern. A receiving mixer down-converts the high-frequency signal from the active phased array antenna under test to an intermediate frequency (IF) signal, which is then sent to the IF processing unit. Microwave received signals are compared with and without the radome, both on the active phased array antenna.

[0029] See Figure 2 This invention relates to the implementation of near-field measurement of a cylindrical surface. An active phased array antenna and its radome are mounted as a whole on a test turntable. A scanning frame is positioned at a certain distance directly opposite the active phased array antenna, on which the transmitting probe antenna is mounted. This transmitting probe antenna can move along the Z-axis height on the scanning frame. The active phased array antenna and its radome are located in the near-field radiation region of the transmitting probe antenna.

[0030] In this embodiment, an imported test turntable is used, capable of supporting a large antenna and radome weighing 30 tons. A 120mm high absorbing material is laid around the turntable to reduce reflection effects.

[0031] Increasing the distance between the transmitting probe antenna and the active phased array antenna under test can reduce the multiple couplings between them and achieve non-interference between the antenna and the radome.

[0032] See Figure 3 The scanning height dimension is given by the formula L=D+2Z 0 tanθ m This ensures the accuracy of the test turntable measurement results. L is the scanning distance of the transmitting probe antenna in terms of height, and D is the aperture size of the active phased array antenna under test. Z 0 represents the distance from the active phased array antenna under test to the transmitting probe antenna. θ m It is the angle between the line connecting the edge of the aperture of the active phased array antenna under test and the scanning edge of the transmitting probe antenna in the center plane, and the center line. It is generally designed... θ m ≥45°. The rotation center of the test turntable is located on the phase center axis of the transmitting probe antenna. In this embodiment, the active phased array antenna and radome under test are 6m above the ground, the azimuth angle positioning accuracy is 0.02°, and the azimuth angle scanning range is -90° to 90°.

[0033] The test is divided into two stages: one with the active phased array radome installed and the other without. The test process is the same for each stage. During the measurement, the wide beam surface of the active phased array antenna under test is set as the azimuth plane, and the transmitting probe antenna is aligned with the antenna under test.

[0034] First, without installing an active phased array radome, the active phased array antenna was controlled by a test turntable to move along the height direction and perform a linear scan for every 1° azimuth angle movement of the active phased array antenna. After completing all cylindrical angle tests, the near-field radiation pattern data without the radome was obtained.

[0035] Then, an active phased array radome was installed. Using a test turntable, the active phased array antenna and radome were controlled to move linearly along the height direction for every 1° azimuth angle movement. After completing all cylindrical angle tests, the near-field radiation pattern data with the radome was calculated. The radome performance was then determined through comparative calculations.

[0036] Temperature compensation is performed using FIMA software. Under the influence of temperature, the phase of RF cables, instruments, and active devices will experience a certain drift. The planes of the scanning frame and the radome under test will also change, causing phase drift. Both of these directly result in phase changes. FIMA software can detect phase drift at the same location and, based on the principle of electromagnetic wave position, perform real-time position determination and direct measurement of position errors during measurement, thus enabling temperature and position compensation after the test.

[0037] To prevent the low-noise amplifier in the TR component from operating in saturation, i.e., it needs to operate in a linear state, the output power of the vector network analyzer is adjusted during system setup to ensure the system operates in the linear region and achieves the desired signal-to-noise ratio.

[0038] The method for calculating the near-field radiation pattern of an active phased array antenna using a cylindrical near-field approach is based on the solution of the wave equation in a cylindrical coordinate system. The components of the electric field vector on and outside the cylindrical surface are expressed as a series of Hankel functions and trigonometric functions. Using the measured electromagnetic field distribution function as boundary conditions and considering the electrodynamic parameters of the transmitting probe antenna, the antenna radiation pattern in the far-field region can be calculated.

[0039] Example See Figure 4 The test is conducted in two phases: with and without the radome. The diagram shows the antenna under test and radome mounted on the cylindrical turntable. The test probe antenna is installed in the 8GHz-12GHz range, and the distance between the transmitting probe and the tip of the radome is 100mm. The connection of the frequency multiplier module is changed to connect the "Amp out" port to the "X2 In" port, and the "X2 Out" port to the "Cplr In" port. The measurement and control software is used to move the probe to the geometric center of the antenna array under test. Frequency parameters and scanning parameters are set. The width and height of the antenna under test are entered, and the far-field angle is set. The maximum radius of the antenna envelope is entered in the MRE, and the scanning axis Y and probe type are selected. In the dialog box, "system type" is selected as cylindrical scanning, and "Scan axis" is selected as Y-axis scanning. The far-field angle is generally set to ±90°. Click "Start Test." For every 1° rotation of the cylindrical turntable, the scanning frame scans one cycle along the Y-axis until all azimuth angles are tested. Then, the far-field radiation pattern is calculated using the near-field and far-field transformation formula of the cylindrical antenna. The calculation results are shown below. Figures 5-7 As shown.

[0040] Descriptions of various advantageous arrangements have been shown for illustrative and descriptive purposes, but such descriptions are not intended to be exclusive or limited to the disclosed forms. Many modifications and variations will be apparent to those skilled in the art. Furthermore, different advantageous examples may be described as having different advantages compared to other advantageous examples. One or more examples have been selected and described in order to best illustrate the principles and practical applications of the examples, and to enable those skilled in the art to understand that this disclosure contains various examples with various modifications suitable for the particular intended use.

Claims

1. A cylindrical near-field measurement system for an active phased array radome, characterized in that: The system includes a transmit link and a receive link, in which In the transmission link, the control computer is sequentially connected to the receiver / transmitter, intermediate frequency processing unit, transmit mixer, power amplifier, channel switch, and transmit probe antenna; In the receiving link, the control computer is sequentially connected to the servo drive mechanism and the test turntable that can rotate the azimuth angle. An active phased array antenna is installed on the test turntable, and an active phased array antenna cover is installed according to the test requirements. The active phased array antenna is sequentially connected to the receiving mixer, the intermediate frequency processing unit, the receiver / transmitter, and the control computer. A scanning frame is set at a certain distance from the active phased array antenna, and the transmitting probe antenna is installed on the scanning frame. The transmitting probe antenna can move in the Z-axis height direction on the scanning frame.

2. The cylindrical near-field measurement system according to claim 1, characterized in that: The control computer controls the receiver / transmitter to work in coordination with the test turntable, and collects radiation pattern data of the active phased array radome for data processing, performing near-field and far-field radiation pattern transformations of the cylindrical surface.

3. The cylindrical near-field measurement system according to claim 1, characterized in that: The receiver / transmitter receives instructions from the control computer and sends high-frequency signals to the intermediate frequency processing unit or receives intermediate frequency signals and performs data processing and pattern calculation.

4. The cylindrical near-field measurement system according to claim 1, characterized in that: The intermediate frequency processing unit converts the radio frequency signals of the transmit and receive links into intermediate frequency signals that can be processed by the vector network analyzer.

5. The cylindrical near-field measurement system according to claim 1, characterized in that: The transmit mixer upconverts the intermediate frequency signal from the intermediate frequency processing unit into a high-frequency transmit signal, and amplifies the microwave signal of the transmit link through a power amplifier.

6. The cylindrical near-field measurement system according to claim 1, characterized in that: The sum, variance, and dip signals of the microwave signal are controlled by the channel switch to enter the transmitting probe antenna in a time-division manner.

7. The cylindrical near-field measurement system according to claim 1, characterized in that: The transmitting probe antenna faces the active phased array antenna and moves in the height direction to transmit wide-beam pattern electromagnetic waves.

8. The cylindrical near-field measurement system according to claim 1, characterized in that: The receiving mixer down-converts the high-frequency signal of the active phased array antenna under test into an intermediate frequency signal and sends it to the intermediate frequency processing unit.

9. The cylindrical near-field measurement system according to claim 1, characterized in that: The scan height dimension is determined by the formula L=D+ 2Z 0 tanθ m Let L be the scanning distance of the transmitting probe antenna in terms of height, and D be the aperture size of the active phased array antenna under test. Z 0 represents the distance from the active phased array antenna under test to the transmitting probe antenna. θ m It is the angle between the line connecting the edge of the aperture of the active phased array antenna under test and the scanning edge of the transmitting probe antenna in the center plane and the center line.

10. A cylindrical near-field measurement method for an active phased array radome, employing the cylindrical near-field measurement system as described in any one of claims 1-9, characterized in that: First, without installing an active phased array radome, the active phased array antenna is controlled by a test turntable to move along the height direction and scan linearly for every 1° azimuth angle movement of the active phased array antenna. After completing all cylindrical angle tests, the near-field radiation pattern data without the radome is obtained. Then, the active phased array radome is installed. The active phased array antenna and radome are controlled by the test turntable to move the transmitting probe antenna along the height direction and scan linearly after each 1° movement of the azimuth angle. After all cylindrical angle tests are completed, the near-field radiation pattern data with the radome is calculated. Finally, the performance of the radome was obtained through comparative calculations.

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