An equivalent method for compact range elevation testing

Abstract

The application relates to an equivalent method for tight-field elevation test, and relates to the technical field of electromagnetic measurement, and comprises the following steps: adjusting the elevation angle of a feed source according to the required elevation angle of a target to be measured, in combination with the focal length and the 1dB beam width of the feed source; calculating the position of the feed source in three-dimensional space according to the required elevation angle of the target to be measured, in combination with the distance difference of two end points of the target to be measured in the ideal tight field, so as to ensure that the distance difference of the two end points of the target to be measured after the reflection of the electromagnetic wave through the reflecting surface after defocusing is unchanged; fixing the elevation angle and the position of the feed source, and performing equivalent elevation test on the target to be measured; and comparing the test result with the conventional elevation test result, so as to verify the accuracy of the equivalent method. The application has the advantages of realizing the tight-field equivalent elevation test based on the foam support and avoiding the use of the knife-shaped metal support.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic measurement technology, and in particular to an equivalent method for pitch testing in a compact field. Background Technology

[0002] Since its emergence in the 1960s and 1970s, compact field measurement technology has gradually replaced traditional far-field measurement methods and become the main means of measuring the electromagnetic characteristic parameters of various scatterers and radiators due to its advantages such as being unaffected by weather and interference clutter, requiring limited test sites, and having good measurement consistency.

[0003] Common support structures for targets within a confined field quiet zone mainly include two types: foam supports and blade-shaped metal supports. Both are fixed to a one-dimensional turntable on the ground and can rotate with the turntable to complete azimuth testing. However, the blade-shaped metal support has an additional two-dimensional rotating top structure at the point where it connects to the target. This structure can rotate the target at the top to complete pitch testing, while the foam support does not have pitch testing capability.

[0004] Compared to blade-shaped metal supports, foam supports offer advantages such as low cost, high load capacity, and ease of transport, making them a common primary support structure in compaction field testing. Implementing pitch testing capabilities for foam supports can reduce or even eliminate the need for blade-shaped metal supports, thereby significantly reducing compaction field construction costs, improving testing efficiency, and lowering testing difficulty, which has important practical significance.

[0005] Therefore, an equivalent method for pitch testing in a compact field is needed. Summary of the Invention

[0006] (a) Technical problems to be solved The technical problem to be solved by the present invention is to solve how to use a foam support without pitch function to replace a blade-shaped metal support with pitch function.

[0007] (II) Technical Solution To address the aforementioned technical problems, this invention provides an equivalent method for pitch testing in a compact field, comprising the following steps: I. Adjust the elevation angle of the feed according to the required elevation angle of the target under test, combined with the focal length and the 1dB beamwidth of the feed; II. Based on the required pitch angle of the target under test, and combined with the path difference between the two endpoints of the target under test in an ideal compact field, calculate the position of the feed source in three-dimensional space to ensure that the path difference between the two endpoints of the target under test after the electromagnetic wave is defocused remains unchanged after being reflected by the reflecting surface. III. With the elevation angle and position of the fixed feed source, perform an equivalent pitch test on the target under test, and compare the test results with the results of the conventional pitch test to verify the accuracy of the equivalent method.

[0008] As a further explanation of the present invention, preferably, the defocus is the phase center of the feed source deviating from the focal point of the reflecting surface.

[0009] As a further explanation of the present invention, preferably, the path difference is the path difference between the first ray path that first contacts the target and the second ray path that last contacts the target after the electromagnetic wave is reflected by the reflecting surface.

[0010] As a further explanation of the present invention, preferably, the target to be tested is placed on a foam support that does not have a pitch adjustment function.

[0011] (III) Beneficial Effects The above-described technical solution of the present invention has the following advantages: This invention achieves an equivalent compaction field with pitch adjustment function for a knife-shaped metal support based on a foam support by adjusting the pitch angle and spatial position of the compaction field feed source. This reduces or even eliminates the use of the knife-shaped metal support, thereby reducing testing costs and improving testing efficiency. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the pitch test in the ideal compaction field of the present invention; Figure 2 This is a schematic diagram of the equivalent pitch test in a non-ideal compressed field according to the present invention.

[0013] In the diagram: 1. Feed source; 2. Reflecting surface; 3. Target under test; 4. Plane wave front; 5. Test interval; 6. Electromagnetic wave; 61. First ray path; 62. Second ray path; 7. Amplitude wave front. Detailed Implementation

[0014] 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.

[0015] An equivalent method for pitch testing in a compact field, such as Figure 1 As shown, it includes the following steps: 1. Calculate the feed elevation angle like Figure 1As shown, in an ideal compact field, in order to ensure that the main polarization amplitude of the vertical cutoff of the quiet zone is horizontal, the elevation angle α of the feed 1 usually points slightly above the center of the reflector 2. The specific angle is related to the focal length and the 1dB beamwidth of the feed 1. The shorter the focal length and the wider the 1dB beamwidth, the larger the elevation angle of the feed 1. The longer the focal length and the narrower the 1dB beamwidth, the smaller the elevation angle of the feed 1.

[0016] To achieve the equivalent pitch test state, it is necessary to consider the current focal length and the equivalent 1dB beamwidth of feed 1, such as... Figure 2 As shown, the elevation angle of the feed 1 is manually adjusted to α', so that the tilt angle of the electromagnetic wave amplitude wavefront 7 is consistent with the elevation angle of the original plane wavefront 4 and the target 3 located in the test interval 5, i.e., β.

[0017] 2. Calculate the three-dimensional spatial position of the feed source. like Figure 1 As shown, in an ideal compressed field, the elevation target 3 has a path difference of ΔL between the first ray path 61 at the top and the second ray path 62 at the bottom, and the phase deviation at the endpoints is ΔL / λ×360°, where λ represents the wavelength corresponding to the current operating frequency. The phase of the middle section follows a linear change law.

[0018] To achieve an equivalent pitch test state, feed 1 can be defocused (i.e., the phase center of feed 1 is deviated from the focal point of reflector 2). Since a small defocus will not significantly affect the amplitude, its impact on the pitch angle calculation of feed 1 is negligible. On the basis of ensuring that the path difference between the first ray path 61 and the second ray path 62 of electromagnetic wave 6 reflected by reflector 2 is ΔL, the phase fluctuation in the middle section is limited. When the fluctuation does not exceed 22.5° compared with the ideal linear change value, it can be approximately considered to meet the requirements of plane wave phase change. The position of feed 1 at this time is the final position.

[0019] 3. Actual Measurement Verification Based on the existing feed 1 support, a set of adapter fixtures that can flexibly adjust the pitch angle and spatial position of feed 1 can be fabricated. According to the existing test requirements, the required pitch angle and spatial coordinates of feed 1 are calculated. After feed 1 is locked and fixed, an equivalent pitch test is performed on the target 3 to be tested. The test results are compared with the conventional pitch test results to verify the accuracy of the method.

[0020] In summary, this invention, based on the incoherence of amplitude and phase adjustment, adjusts the amplitude and phase of the electromagnetic wave illuminating the target by addressing both the feed elevation angle and the feed spatial position. This results in obtaining an equivalent test environment for conventional elevation testing, thereby reducing or even eliminating the use of blade-shaped metal supports, thus achieving the effects of reducing test costs and improving test efficiency.

[0021] 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. An equivalent method for compact range elevation testing, characterized by: Includes the following steps: I. Based on the required pitch angle of the target (3), and in combination with the focal length and the 1dB beamwidth of the feed (1), adjust the elevation angle of the feed (1); II. Based on the required pitch angle of the target (3) to be measured, and combined with the path difference between the two endpoints of the target (3) to be measured in the ideal compact field, the fluctuation of the phase in the middle section is restricted. When the fluctuation is less than 22.5° compared with the ideal linear change value, the position of the feed source (1) in the three-dimensional space is calculated to ensure that the path difference between the two endpoints of the electromagnetic wave (6) after defocusing and reaching the target (3) after reflection by the reflector (2) remains unchanged. III. Fix the elevation angle and position of the fixed feed (1), perform an equivalent pitch test on the target (3), and compare the test results with the pitch test results of the conventional blade-shaped metal bracket to verify the accuracy of the equivalent method.

2. An equivalent method for compact range boresight testing as claimed in claim 1, characterized in that: The defocus is the phase center of the feed source (1) deviating from the focal point of the reflecting surface (2).

3. An equivalent method for compact range boresight testing as claimed in claim 2, characterized in that: The path difference is the difference between the first ray path (61) that first contacts the target (3) after the electromagnetic wave (6) is reflected by the reflecting surface (2) and the second ray path (62) that last contacts the target (3).

4. The equivalent method for pitch testing in a compact field according to claim 3, characterized in that: The target to be tested (3) is placed on a foam support that does not have pitch adjustment function.

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