Radar radome equivalent flat plate reflectivity measuring method and device

Abstract

The invention belongs to the technical field of radar radome testing, and discloses a radar radome equivalent panel reflectivity measuring method and device, and the method comprises the steps: installing a transmitting antenna and a receiving antenna on a straight line parallel to an equivalent panel, enabling the equivalent panel to rotate an angle towards the direction of the straight line where the transmitting antenna and the receiving antenna are located, and measuring the reflectivity of the equivalent panel. Then the angles of the transmitting antenna and the receiving antenna are rotated, so that the incident angle and the reflection angle of the transmitting antenna and the receiving antenna relative to the rotated equivalent flat plate are equal, a rectangular coordinate system is established by taking the rotating point of the equivalent flat plate as an original point, and according to the coordinates of the transmitting antenna and the receiving antenna in the rectangular coordinate system, a rectangular coordinate is established; calculating whether the incident angle is within the measurable range of the equivalent plate reflectivity; and finally measuring the reflectivity of the equivalent flat plate by using the transmitting antenna and the receiving antenna. According to the invention, the reflectivity test of the equivalent flat plate at different angles can be completed within the incident angle range, the dragging of the microwave cable is reduced, the interference to the microwave signal is avoided, the measurement frequency range is wide, the measurement speed is high, and the reproducibility is good.

Description

Technical Field

[0001] The invention belongs to the technical field of radar antenna cover testing, relates to a measurement method of a radar antenna cover and a device used therein, and specifically relates to a method and a device for measuring the equivalent flat plate reflectivity of a radar antenna cover. Background Art

[0002] Under the conditions of given wavelength and polarization, electromagnetic waves are incident on the radar absorbing material plane and the good conductor plane from the same direction and with the same power density. The ratio of the mirror reflection power of the radar absorbing material plane and the good conductor plane of the same size is the reflectivity of the radar absorbing material. The radar antenna cover equivalent plate is also a radar absorbing material, and the reflectivity of the equivalent plate also follows the above law.

[0003] There are a series of measurement standards for reference in China and abroad for the measurement of equivalent flat plate reflectivity of radar antenna covers. These standards provide a number of measurement methods, such as sample space translation measurement method, closed waveguide measurement method, arch frame measurement method, etc. The arch frame measurement method was first designed and proposed by the U.S. Naval Research and Testing Institute and is the most widely used absorbing material measurement method in China and abroad. Figure 1 The transmitting and receiving antennas are respectively installed on the arch frame above the sample of the absorbing material to be measured, and the sample is placed at the center of the arch frame. During measurement, the reflectivity of the absorbing material at different incident angles can be measured by changing the position of the transmitting and receiving antennas on the arch frame.

[0004] Compared with other methods, the arch frame method has the advantages of a wider measurement frequency range, fast measurement speed, good reproducibility, and is a non-destructive measurement method. However, it also has disadvantages such as the microwave cable needs to move with the transmitting and receiving antennas, the frame body interferes with the microwave signal, the stabilization time after vibration is long, the hardware occupies a large space, and the track laying is cumbersome.

[0005] In order to solve the problems of measuring the reflectivity of flat plates using the arch frame method, such as the microwave cables needing to move with the transmitting and receiving antennas, the frame body interfering with the microwave signals, occupying a large space, and complicated track laying, domestic research institutes have proposed improvements such as the "7"-shaped arch frame. However, there are still problems such as poor balancing of the front and rear ends, sagging of the antenna, and inaccurate adjustment of the incident angle and reflection angle. Summary of the invention

[0006] The present invention provides a method and device for measuring the equivalent flat-plate reflectivity of a radar antenna cover, which does not use a testing method using an arch frame model, so that a transmitting antenna and a receiving antenna are in a state of only rotating angles but not moving positions when working, thereby reducing the dragging of microwave cables and eliminating the interference of the frame body with microwave signals.

[0007] The technical solution of the present invention is as follows:

[0008] A method for measuring the reflectivity of a radar antenna cover equivalent flat plate comprises the following steps:

[0009] S1: Install the transmitting antenna and the receiving antenna on a straight line parallel to the equivalent flat plate, and the directions of the transmitting antenna and the receiving antenna are the same as one side of the straight line;

[0010] S2: Rotate the equivalent plate by an angle θ toward the straight line where the transmitting antenna and the receiving antenna are located, and then rotate the transmitting antenna and the receiving antenna so that the incident angle and reflection angle of the transmitting antenna and the receiving antenna to the rotated equivalent plate are equal;

[0011] S3: Establish a rectangular coordinate system with the equivalent plate rotation point as the origin, and calculate whether the incident angle α is within the measurable range of the equivalent plate reflectivity according to the coordinates of the transmitting antenna and the receiving antenna in the rectangular coordinate system; if so, enter S4; otherwise, change the positions of the transmitting antenna and the receiving antenna and enter S2;

[0012] S4, using the transmitting antenna and the receiving antenna to measure the reflectivity of the equivalent flat plate.

[0013] Furthermore, in S1, the transmitting antenna and the receiving antenna are placed in the far field region of the equivalent flat plate.

[0014] Furthermore, in S1, the minimum distance from the aperture of the transmitting antenna and the receiving antenna to the equivalent flat plate reflection point is r min，

[0015]

[0016] Where D is the aperture of the transmitting antenna and λ is the wavelength of the incident wave.

[0017] Further, in S3, after the rectangular coordinate system is established, the coordinate point of the transmitting antenna is A (a, b), and the coordinate point of the receiving antenna is B (a+d, b);

[0018] The measurable range of the equivalent flat plate reflectivity is:

[0019]

[0020] Furthermore, the transmitting antenna coordinate point is A(a, b) and the receiving antenna coordinate point is B(a+d, b), where a<0, b<0, d>0.

[0021] Furthermore, a, b and d are obtained by measuring the rotation angle β of the transmitting antenna. 1 , the rotation angle of the receiving antenna β 2 , the equivalent plate rotation angle θ and the incident angle α, and then calculated.

[0022] Furthermore, the calculation method is:

[0023]

[0024] A device for measuring the reflectivity of an equivalent flat plate of a radar antenna cover is used in the method for measuring the reflectivity of an equivalent flat plate of a radar antenna cover, and comprises a turntable A, a turntable B and a turntable C. Turntable A and turntable B are arranged on the same straight line. Turntable A and turntable B are respectively provided with mounting interfaces for installing a transmitting antenna and a receiving antenna. Turntable C is provided with an interface for installing an equivalent flat plate. After the equivalent flat plate is installed on turntable C, the reflecting surface of the equivalent flat plate faces turntable A and turntable B.

[0025] Furthermore, the rotation surfaces of turntable A, turntable B and turntable C are all on the same plane.

[0026] Furthermore, turntable A, turntable B and turntable C are all provided with a rotation angle reading structure and a rotation angle zeroing structure.

[0027] The beneficial effects of the present invention are as follows:

[0028] 1. The present invention adopts a three-turntable mechanism to complete the reflectivity test of the equivalent flat plate at different angles by rotating the angles of turntables A, B, and C. In the present invention, the transmitting antenna and the receiving antenna only rotate the angle when working, and do not move the position, thereby reducing the drag on the microwave cable and eliminating the interference of the frame body on the microwave signal in the arch frame method.

[0029] 2. The measurement frequency range of the present invention is wide, the measurement speed is fast, the reproducibility is good, and it is also a non-destructive measurement method. The turntable will not interfere with the microwave signal. At the same time, the turntable hardware occupies a flexible space and the track laying is simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solution of the implementation method of the patent of the present invention, the following is a brief introduction to the drawings required for use in the implementation method. It should be understood that the following drawings only show certain embodiments of the patent of the present invention and should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying creative work.

[0031] Figure 1 A schematic diagram of an arch frame measurement method of the background technology of the present invention;

[0032] Figure 2 It is a schematic diagram of the three-turntable mechanism measurement method of the present invention;

[0033] Figure 3 It is a schematic diagram of the angle relationship of the equivalent flat plate rotating θ of the present invention;

[0034] Figure 4This is a schematic diagram of measuring the equivalent flat plate reflectivity using the three-turntable method of the present invention. DETAILED DESCRIPTION

[0035] This section is an embodiment of the present invention, which is used to explain and illustrate the technical solution of the present invention. In the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0036] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate directions or positional relationships as given in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or case referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", etc. are used only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implying the number of technical features indicated. Thus, features defined as "first", "second", etc. may explicitly or implicitly include more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0037] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be interpreted in a broad sense, for example, it can be a fixed connection, a detachable connection or an integrated connection; it can be a mechanical connection or a point connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0038] Embodiment 1:

[0039] A method for measuring the reflectivity of a radar antenna cover equivalent flat plate comprises the following steps:

[0040] S1: Install the transmitting antenna and the receiving antenna on a straight line parallel to the equivalent flat plate, and the directions of the transmitting antenna and the receiving antenna are the same as one side of the straight line;

[0041] S2: Rotate the equivalent plate by an angle θ toward the straight line where the transmitting antenna and the receiving antenna are located, and then rotate the transmitting antenna and the receiving antenna so that the incident angle and reflection angle of the transmitting antenna and the receiving antenna to the rotated equivalent plate are equal;

[0042] S3: Establish a rectangular coordinate system with the equivalent plate rotation point as the origin, and calculate whether the incident angle α is within the measurable range of the equivalent plate reflectivity according to the coordinates of the transmitting antenna and the receiving antenna in the rectangular coordinate system; if so, enter S4; otherwise, change the positions of the transmitting antenna and the receiving antenna and enter S2;

[0043] S4, using the transmitting antenna and the receiving antenna to measure the reflectivity of the equivalent flat plate.

[0044] In S1, the transmitting antenna and the receiving antenna are placed in the far field region of the equivalent flat plate.

[0045] In S1, the minimum distance from the transmitting antenna and the receiving antenna to the equivalent flat plate reflection point is r min，

[0046]

[0047] Where D is the aperture of the transmitting antenna and λ is the wavelength of the incident wave.

[0048] In S3, after the rectangular coordinate system is established, the coordinate point of the transmitting antenna is A (a, b), and the coordinate point of the receiving antenna is B (a+d, b);

[0049] The measurable range of the equivalent flat plate reflectivity is:

[0050]

[0051] The transmitting antenna coordinate point is A(a, b) and the receiving antenna coordinate point is B(a+d, b), where a<0, b<0, d>0.

[0052] a, b and d are obtained by measuring the rotation angle β of the transmitting antenna. 1 , the rotation angle of the receiving antenna β 2 , the equivalent plate rotation angle θ and the incident angle α, and then calculated.

[0053] The calculation method is:

[0054]

[0055] A device for measuring the reflectivity of an equivalent flat plate of a radar antenna cover is used in the method for measuring the reflectivity of an equivalent flat plate of a radar antenna cover, and comprises a turntable A, a turntable B and a turntable C. Turntable A and turntable B are arranged on the same straight line. Turntable A and turntable B are respectively provided with mounting interfaces for installing a transmitting antenna and a receiving antenna. Turntable C is provided with an interface for installing an equivalent flat plate. After the equivalent flat plate is installed on turntable C, the reflecting surface of the equivalent flat plate faces turntable A and turntable B.

[0056] The rotating surfaces of turntable A, turntable B and turntable C are all on the same plane.

[0057] Turntable A, turntable B and turntable C are all provided with a rotation angle reading structure and a rotation angle zeroing structure.

[0058] Embodiment 2:

[0059] like Figure 2 In a microwave darkroom, a three-turntable mechanism is used, and the transmitting antenna and the receiving antenna are installed on turntables A and B respectively, and the equivalent plate to be measured is clamped on turntable C. Turntable C is rotated, and the incident angle and reflection angle are adjusted by rotating turntables A and B to achieve the reflectivity measurement of the equivalent plate under different incident angles.

[0060] a) This method requires that the measurement be carried out in a microwave darkroom, with the ambient temperature maintained at 20±5℃ and the relative humidity maintained below 80%;

[0061] b) This method requires the antenna to be placed in the far field of the panel to be tested. If the transmitting antenna and the receiving antenna can be considered as point sources, and the phase error caused by the lateral size of the panel to be tested is π / 8, then the minimum test distance is:

[0062]

[0063] Where rmin is the minimum distance from the antenna aperture to the reflection point of the plate to be measured.

[0064] Where D is the aperture of the transmitting antenna and λ is the wavelength of the incident wave.

[0065] The principle of the present invention is discussed:

[0066] After turning the turntable C by angle θ, that is, the equivalent flat plate is turned by angle θ, the angle of the transmitting antenna is adjusted to β1 by turning the turntable A, so that the incident angle is α, and the incident angle is equal to the reflection angle. After the beam is reflected, it passes through point B, and the angle of the receiving antenna is adjusted to β2, that is, the beam is incident on the receiving antenna.

[0067] A rectangular coordinate system is established at the turntable C, and the coordinates of point A are set to A(a, b), and the coordinates of point B are set to B(a+d, b), where a<0, b<0, d>0. After rotating by θ, the formula of the straight line is:

[0068] y=kX

[0069] Where k = tanθ.

[0070] The coordinates of the intersection point D of the straight line CD and AB are

[0071] Draw a perpendicular line through points A and B to line CD at A' and B', and the perpendicular line segments are L1 and L2.

[0072]

[0073] The distance between A'B' is

[0074] A'B'=d cosθ

[0075] And since the angle of incidence and the angle of reflection are the same, we have

[0076]

[0077] It can be seen that

[0078]

[0079] Due to β 1 It has been determined, and it can be guaranteed that the reflected wave passes through point B, so β 2 The angle can also be obtained by rotating the turntable to scan the direction diagram. In the present invention, the incident angle α can be achieved at Reflectivity measurement within the range.

[0080] After determining that the incident angle meets the requirements, the transmitting antenna A transmits electromagnetic waves, and the receiving antenna B receives the electromagnetic waves generated by the transmitting antenna A, and then the reflectivity of the equivalent flat plate is obtained after comparison.

[0081] Embodiment 3:

[0082] See also Figure 3 , Figure 4 In the example, three turntables A, B, and C are set up. Turntable A is placed 1m in front of C and 1m to the left, and turntable B is placed 1m in front of C and in the middle of the left and right. The three turntables are set up at the same height. Clamp the equivalent plate to be measured on turntable C, and make the plate parallel to the line connecting turntables A and B. Turn turntable C to measure the reflectivity of the plate within the incident angle range of 45° to 70°.

[0083] Follow these steps to take the measurement:

[0084] Turntable C rotates leftward θ;

[0085] Adjust the angle of turntable A to:

[0086] θ+tan -1 (3tanθ-2)

[0087] The signal source transmits a frequency signal, rotates turntable B, and scans the directional pattern of the receiving antenna;

[0088] Calculate the incident angle as |tan -1 (3tanθ-2)|, the reflectivity at this frequency.

[0089] The above is only a specific embodiment of the present invention, and the present invention is described in detail. The unexplained part is a conventional technology. However, the protection scope of the present invention is not limited to this. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. The protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A method for measuring the reflectivity of a radar antenna cover equivalent flat plate, characterized in that: The following steps are involved: S1: Install the transmitting antenna and the receiving antenna on a straight line parallel to the equivalent flat plate, and the directions of the transmitting antenna and the receiving antenna are the same as one side of the straight line; S2: Rotate the equivalent plate by an angle θ toward the straight line where the transmitting antenna and the receiving antenna are located, and then rotate the transmitting antenna and the receiving antenna so that the incident angle and reflection angle of the transmitting antenna and the receiving antenna to the rotated equivalent plate are equal; S3: Establish a rectangular coordinate system with the equivalent plate rotation point as the origin, and calculate whether the incident angle α is within the measurable range of the equivalent plate reflectivity according to the coordinates of the transmitting antenna and the receiving antenna in the rectangular coordinate system; if so, enter S4; otherwise, change the positions of the transmitting antenna and the receiving antenna and enter S2; S4, using the transmitting antenna and the receiving antenna to measure the reflectivity of the equivalent flat plate.

2. The method for measuring the equivalent flat plate reflectivity of a radar antenna cover according to claim 1, characterized in that: In the above S1, the transmitting antenna and the receiving antenna are placed in the far field area of ​​the equivalent flat plate.

3. The method for measuring the equivalent flat plate reflectivity of a radar antenna cover according to claim 2, characterized in that: In S1, the minimum distance from the transmitting antenna and the receiving antenna to the equivalent flat plate reflection point is r min， Where D is the aperture of the transmitting antenna and λ is the wavelength of the incident wave.

4. The method for measuring the equivalent flat plate reflectivity of a radar antenna cover according to claim 1, characterized in that: In the above S3, after the rectangular coordinate system is established, the coordinate point of the transmitting antenna is A (a, b), and the coordinate point of the receiving antenna is B (a+d, b); The measurable range of equivalent flat plate reflectivity is:

5. The method for measuring the equivalent flat plate reflectivity of a radar antenna cover according to claim 4, characterized in that: The transmitting antenna coordinate point is A(a, b) and the receiving antenna coordinate point is B(a+d, b), where a<0, b<0, d>0.

6. The method for measuring the equivalent flat plate reflectivity of a radar antenna cover according to claim 5, characterized in that: The rotation angle β1 of the transmitting antenna, the rotation angle β2 of the receiving antenna, the equivalent plate rotation angle θ and the incident angle α are measured, and then a, b and d are calculated.

7. The method for measuring the equivalent flat plate reflectivity of a radar antenna cover according to claim 6, characterized in that: The calculation method is:

8. A device for measuring the equivalent flat plate reflectivity of a radar antenna cover, characterized in that: Used in a radar antenna cover equivalent flat plate reflectivity measurement method as described in any one of claims 1 to 7, comprising a turntable A, a turntable B and a turntable C, wherein turntable A and turntable B are arranged on the same straight line, turntable A and turntable B are respectively provided with installation interfaces for installing a transmitting antenna and a receiving antenna, and turntable C is provided with an interface for installing an equivalent flat plate; after the equivalent flat plate is installed on turntable C, the reflecting surface of the equivalent flat plate is facing turntable A and turntable B.

9. The device used in the method for measuring the equivalent flat plate reflectivity of a radar antenna cover according to claim 8, characterized in that: The rotating surfaces of turntable A, turntable B and turntable C are all on the same plane.

10. The device used in the method for measuring the equivalent flat plate reflectivity of a radar antenna cover according to claim 8, characterized in that: Turntable A, turntable B and turntable C are all provided with a rotation angle reading structure and a rotation angle zeroing structure.

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