A low-frequency coaxial reflectivity test system and test method

Abstract

The application relates to the technical field of electromagnetic field shielding test, and discloses a low-frequency coaxial reflectivity test system and a test method, which comprises a horizontal main tower, a secondary tower, a shielding door and a sliding device, the sliding device is installed at the bottom of the main tower, the secondary tower and the shielding door are used to alternately open and close the main tower through the sliding device, the main tower and the secondary tower are of the same structure, the main tower comprises a tower body and a tower tip, the tower body comprises an outer conductor, an inner conductor and a supporting plate, the inner conductor is fixed in the outer conductor through the supporting plate, the outer conductor and the inner conductor are both spliced by panels and corner pieces, a jointing plate is riveted on the outer wall of the outer conductor, an outer pressing plate is riveted between two adjacent outer conductors, and an inner pressing plate is riveted between two adjacent inner conductors. The application has the beneficial effects that the tower body adopts a horizontal structure and is riveted by screws, high-altitude operation and welding construction are not needed, safety and environmental protection are achieved, the quality of the parts is controllable, the tower body has high precision and stable quality.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic field shielding testing technology, and in particular to a low-frequency coaxial reflectivity testing system and method. Background Technology

[0002] Radio frequency (RF) absorbing materials are widely used in the field of electromagnetic compatibility (EMC). Their absorption performance directly affects whether the anechoic chamber meets the EMC testing environment requirements. Therefore, accurately measuring and evaluating the absorption characteristics of absorbing materials is crucial. According to GJB 5239-2004 "Test Methods for the Absorption Performance of RF Absorbing Materials," different measurement methods are used for the reflectivity of absorbing materials in different frequency bands. The 30MHz~600MHz band uses the low-frequency coaxial reflection method. However, due to system impedance matching issues, it is difficult to improve test accuracy. Traditional low-frequency coaxial reflection method test systems often use welded tower structures, which are difficult to construct, prone to deformation, and have low test accuracy and efficiency. Summary of the Invention

[0003] The purpose of this invention is to provide a low-frequency coaxial reflectivity testing system and method to overcome the shortcomings of the prior art.

[0004] The objective of this invention is achieved through the following technical solution: a low-frequency coaxial reflectivity testing system, comprising a horizontal main tower, a secondary tower, a shielding door, and a sliding device. The sliding device is installed at the base of the main tower. The secondary tower and the shielding door are both installed on the sliding device. The sliding device causes the secondary tower and the shielding door to alternately open and close the main tower. The main tower and the secondary tower have the same structure. The main tower includes a tower body and a tower tip. The tower body is composed of several segments. The tower tip is fixed to the tower body. The tower body includes an outer conductor. The system comprises an inner conductor and a support plate. The inner conductor is fixed inside the outer conductor by the support plate. Both the outer conductor and the inner conductor are assembled from panels and corner pieces. A seam connecting plate is riveted to the outer wall of the outer conductor to seal the gap between the panel and the corner piece. An outer pressure plate is riveted between two adjacent sections of the outer conductor to seal the gap between adjacent sections of the outer conductor. An inner pressure plate is riveted between two adjacent sections of the inner conductor to seal the gap between adjacent sections of the inner conductor.

[0005] Preferably, annular positioning grooves are provided on the inner wall of the outer conductor and the outer wall of the inner conductor. A clearance hole is provided on the support plate. The support plate is U-shaped and composed of two pieces joined together. The outer side of the U-shape is engaged in the positioning groove on the outer conductor, and the inner side of the U-shape is engaged in the positioning groove on the inner conductor. The support plate is located at the connection point of two adjacent tower sections. A plate-shaped cross keel is riveted inside the inner conductor. The cross keel is located at the connection point of two adjacent inner conductor sections. The inner pressure plate is pressed tightly against the cross keel. A clamping frame is riveted at the connection point of adjacent outer conductors. The clamping frame is used to clamp the outer pressure plate. A connecting rod is fixed between adjacent clamping frames. An X-shaped reinforcing rib is riveted to the outer wall of the outer conductor, and the connecting rod is fixed to the reinforcing rib.

[0006] Preferably, the spire includes a concentric ring, an outer cone, an inner cone, and a conductive post. The outer cone has a flange integrally formed at its large end, which is fixed to the outer conductor. The inner cone is fixed inside the outer cone by the concentric ring. The conductive post connects the inner conductor and the inner cone. A low dielectric constant material is filled between the outer conductor and the inner conductor, and the low dielectric constant material is located at the connection between the inner conductor and the inner cone.

[0007] Preferably, the device further includes an adjusting plate, on which a positioning plate is fixed. The sliding device includes an A-slide rail and an I-beam. The A-slide rail is laid on the I-beam. There is a pair of I-beams, and a channel steel is fixed between the pair of I-beams. The channel steels are several in number and distributed along the extension direction of the I-beams. The two ends of the adjusting plate are respectively placed under the corresponding I-beams. Bolts that abut against the I-beams are screwed onto the positioning plate. There are two positioning plates, each close to a corresponding I-beam. Threaded holes are opened on the I-beams, and screws that abut against the ends of the adjusting plates are screwed into the threaded holes. The section plates are several and evenly distributed along the extension direction of the I-beam. A trolley is slidably mounted on the A-rail. Two A-drive modules are mounted on the mounting plate on the channel steel. The two A-drive modules are located at both ends of the A-rail, and the power ends of the two A-drive modules are close to the middle of the A-rail. The secondary tower slides through the A-drive module near the starting end of the A-rail, and the trolley slides through the A-drive module near the end of the A-rail. A B-drive module is mounted on the trolley, and the B-drive module is used to drive the shielding door to move in a direction perpendicular to the A-rail.

[0008] Preferably, the mounting plate is located between a pair of I-beams, extending along the I-beams. The A drive module includes an A motor, an A ball screw, and an A bearing housing. The shaft of the A motor is connected to the power input end of the A ball screw via a coupling. The A ball screw is mounted on the mounting plate via the A bearing housing. The nut seat of the A ball screw is an A-seat. A 7-shaped support block is fixed to the A-seat by screws. The screw holes on the support block are several oblong holes. The height of the support block is adjusted by fixing the screws into different oblong holes. The support block is used to fix the secondary tower.

[0009] Preferably, several pairs of A sliders are installed on the A slide rail, with each pair of A sliders located on two A slide rails respectively. The trolley is fixed on two pairs of A sliders. The B drive module includes a B motor, a B ball screw, and a B bearing housing. The B motor is fixed on the trolley, and the B ball screw is mounted on the trolley via the B bearing housing. The shaft of the B motor is connected to the power input end of the B ball screw via a coupling. The nut seat of the B ball screw is a B seat, and the support block is fixed to the B seat by screws. The screw holes on the support block are several oblong holes, and the height of the support block is adjusted by fixing the screws into different oblong holes. The support block is used to fix the shielding door.

[0010] Preferably, the trolley is further fixed with a pair of B slide rails, the B slide rails are laid in a direction perpendicular to the A slide rails, the B sliding module is located between the pair of B slide rails, and a plurality of pairs of B sliders are slidably installed on the B slide rails, with the B sliders of the same pair located on the two B slide rails respectively.

[0011] Preferably, the B motor is located outside the A slide rail, and a balance wheel is also installed at the bottom of the trolley, with the balance wheel located outside the A slide rail.

[0012] A testing method for a low-frequency coaxial reflectivity testing system includes the following steps:

[0013] Step 1, Low-frequency calibration: Open and remove the shielding door, close the secondary tower and the main tower, and perform open-circuit calibration, short-circuit calibration, and load calibration;

[0014] Step 2, High-frequency calibration: Close the secondary tower and the main tower, perform open-circuit calibration and short-circuit calibration, remove the secondary tower, install the load calibration component at the test position on the shielding door, close the shielding door and the main tower, and perform load calibration;

[0015] Step 3: After the above calibration is completed, install the material to be tested at the test position on the shielding door and conduct the test.

[0016] The present invention has the following advantages:

[0017] 1. The tower body adopts a horizontal structure and is assembled with screws and riveting, eliminating the need for high-altitude operations and welding, ensuring safety and environmental friendliness. Component quality is controllable, resulting in high tower precision and stable quality. 2. By innovating a segmented calibration method and designing calibration section structures and calibration components, the calibration challenges of coaxial reflectivity testing systems are solved.

[0018] 3. The innovative structural layout and motion control achieve automated calibration and testing, solving the problem of low testing efficiency.

[0019] 4. The tower body adopts a special electrical continuity structure design, which improves the system shielding effectiveness and increases the testing accuracy. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the present invention;

[0021] Figure 2 A schematic diagram of the main tower structure;

[0022] Figure 3 for Figure 2 Schematic diagram of the cross section of AA;

[0023] Figure 4 for Figure 2 Cross-sectional view of BB;

[0024] Figure 5 for Figure 3 A magnified view of a portion of point C in the middle;

[0025] Figure 6 for Figure 4 A magnified view of a portion of point D in the middle;

[0026] Figure 7 This is a schematic diagram of the sliding device.

[0027] Figure 8 This is a schematic diagram of the car's structure;

[0028] Figure 9 This is a schematic diagram of the installation structure of the A drive module;

[0029] Figure 10 This is a schematic diagram of the adjustment plate.

[0030] Figure 11 for Figure 9 A magnified view of a portion of point E in the middle;

[0031] Figure 12 for Figure 4 A magnified view of a portion of point F in the middle;

[0032] In the diagram, 1-outer conductor, 2-inner conductor, 3-support plate, 4-panel, 5-corner piece, 6-joint connecting plate, 7-outer pressure plate, 8-inner pressure plate, 9-cross keel, 10-fastening frame, 11-connecting rod, 12-concentric ring, 13-outer cone, 14-inner cone core, 15-conductive post, 16-flange, 17-clearance hole, 18-reinforcing rib, 19-low dielectric constant material, 20-copper mesh channel, 21-adjusting plate, 2 2-A slide rail, 23-I-beam, 24-channel steel, 25-positioning plate, 26-bolt, 27-trolley, 28-mounting plate, 29-A motor, 30-A bearing housing, 31-A seat, 32-A slider, 33-B motor, 34-B bearing housing, 35-B seat, 36-B slide rail, 37-B slider, 38-balance wheel, 39-main tower, 40-secondary tower, 41-shielding door, 42-support block, 43-threaded hole. Detailed Implementation

[0033] 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, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0034] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0035] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other.

[0036] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0037] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. In addition, the terms "first," "second," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0038] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0039] like Figure 1-5As shown, a low-frequency coaxial reflectivity testing system includes a horizontal main tower 39, a secondary tower 40, a shielding door 41, and a sliding device. The main tower 39 is supported on the ground by legs. The sliding device is installed at the base of the main tower 39. The secondary tower 40 and the shielding door 41 are both mounted on the sliding device. The sliding device causes the secondary tower 40 and the shielding door 41 to alternately open and close the main tower 39. Electromagnetic shielding is achieved between the main tower 39 and the secondary tower 40, and between the main tower 39 and the shielding door 41, through shielding components. The shielding components include a door frame mounted on the main tower 39 and a blade mounted on the shielding door 41. A beryllium copper spring is installed on the door frame, and the blade is a double blade. The two work together to form two single-blade single-spring shields. The main tower 39 and the secondary tower 40 have the same structure. When they are closed, they overcome the problem that traditional single towers cannot perform low-frequency calibration. 9 includes a tower body and a tower tip. The tower body is composed of several sections, and the tower tip is fixed to the tower body. The tower body includes an outer conductor 1, an inner conductor 2, and a support plate 3. The inner conductor 2 is fixed inside the outer conductor 1 by the support plate 3. Both the outer conductor 1 and the inner conductor 2 are spliced ​​together by a panel 4 and corner pieces 5. A splice connecting plate 6 is riveted to the outer wall of the outer conductor 1. The splice connecting plate 6 is used to seal the gap between the panel 4 and the corner pieces 5. An outer pressure plate 7 is riveted between two adjacent sections of the outer conductor 1. The outer pressure plate 7 is used to seal the gap between adjacent sections of the outer conductor 1. An inner pressure plate 8 is riveted between two adjacent sections of the inner conductor 2. The inner pressure plate 8 is used to seal the gap between adjacent sections of the inner conductor 2. The tower body adopts a horizontal structure and is riveted with screws. There is no high-altitude operation or welding construction. It is safe and environmentally friendly. The quality of the parts is controllable. The tower body has high precision and stable quality.

[0040] In this embodiment, as Figure 3 , 4As shown in Figure 12, the corner piece 5 on the inner conductor 2 is an outer rounded corner piece 5, and the corner piece 5 on the outer conductor 1 is an inner rounded corner piece 5. Annular positioning grooves are provided on the inner wall of the outer conductor 1 and the outer wall of the inner conductor 2. Stress-relieving clearance holes 17 are provided on the support plate 3. The fit between the rounded corners and the holes reduces the impact on electromagnetic wave transmission and improves the transmission stability of the electromagnetic wave system. The support plate 3 is U-shaped and composed of two pieces. The outer side of the U-shape is fitted into the positioning groove on the outer conductor 1, and the inner side of the U-shape is fitted into the positioning groove on the inner conductor 2. The support plate 3 is located at the connection point of two adjacent tower sections to prevent displacement of the support plate 3. As the distance between two adjacent plates increases, the inner conductor 2 between the two plates bends and deforms due to gravity. A plate-shaped cross keel 9 is riveted inside the inner conductor 2. The cross keel 9 is located at the connection between two adjacent sections of the inner conductor 2. The inner pressure plate 8 is pressed tightly on the cross keel 9 to prevent the shape of the inner conductor 2 from deforming. A clamping frame 10 is riveted at the connection between adjacent outer conductors 1. The clamping frame 10 is used to clamp the outer pressure plate 7. A connecting rod 11 is fixed between adjacent clamping frames 10. An X-shaped reinforcing rib 18 is riveted on the outer wall of the outer conductor 1. The connecting rod 11 is fixed on the reinforcing rib 18, which improves the structural rigidity and solves the problems of poor structural stability and short service life.

[0041] In this embodiment, as Figure 6 As shown, the tower tip includes a concentric ring 12, an outer cone 13, an inner cone 14, and a conductive post 15. The outer cone 13 has an integrally formed flange 16 at its large end, which is fixed to the outer conductor 1. The inner cone 14 is fixed inside the outer cone 13 by the concentric ring 12. The conductive post 15 is used to connect the inner conductor 2 and the inner cone 14. The space between the outer conductor 1 and the inner conductor 2 is filled with a low dielectric constant material 19. The low dielectric constant material 19 is located at the connection between the inner conductor 2 and the inner cone 14, ensuring the coaxiality of the inner core and the outer frame. At the same time, the inner pressure plate 8, the outer pressure plate 7, the corner piece 5, and the splice connecting plate 6 are all provided with mesh grooves 20 to place metal mesh, which improves the electrical continuity of the tower body and improves the problem of low shielding efficiency of the system.

[0042] In this embodiment, as Figure 7-11As shown, it also includes an adjusting plate 21, on which a positioning plate 25 is fixed. The sliding device includes an A-slide rail 22 and an I-beam 23. The A-slide rail 22 is laid on the I-beam 23. There is a pair of I-beams 23, and a channel steel 24 is fixed between the pair of I-beams 23. There are several channel steels 24 distributed along the extension direction of the I-beams 23. The two ends of the adjusting plate 21 are respectively placed under the corresponding I-beams 23. Bolts 26 that abut against the I-beams 23 are screwed onto the positioning plate 25. There are two positioning plates 25, which are respectively close to the corresponding I-beams 23. Threaded holes 43 are opened on the I-beams 23, and screws that abut against the ends of the adjusting plates 21 are screwed into the threaded holes 43. There are several adjusting plates 21, which are evenly distributed along the extension direction of the I-beams 23. The distance between the two I-beams 23 in each section can be adjusted by turning the bolts 26. At the same time, the I-beams 23 can be raised or lowered by turning the screws to adjust the height of the track. Adjustments are made to ensure that the left and right sides of the A-rail 22 of each section are at the same height and width, avoiding skewness during low-frequency coaxial test tower testing and ensuring the accuracy of test results. A trolley 27 is slidably mounted on the A-rail 22, and an mounting plate 28 is mounted on the channel steel 24. The mounting plate 28 has two A-drive modules, located at both ends of the A-rail 22. The power ends of the two A-drive modules are close to the middle of the A-rail 22. The secondary tower 40 slides through the A-drive module near the starting end of the A-rail 22, and the trolley 27 slides through the A-drive module near the end of the A-rail 22. A B-drive module is mounted on the trolley 27, which drives the shielding door 41 to move in a direction perpendicular to the A-rail 22. By moving the trolley 27 laterally and longitudinally, calibration and testing can be quickly switched, greatly shortening the switching time and improving testing efficiency.

[0043] In this embodiment, as Figure 7 , 9 As shown in Figure 11, the mounting plate 28 is located between a pair of I-beams 23 and extends along the I-beams 23. The A drive module includes an A motor 29, an A ball screw, and an A bearing 30 seat. The shaft of the A motor 29 is connected to the power input end of the A ball screw via a coupling. The A ball screw is mounted on the mounting plate 28 via the A bearing 30 seat. The nut seat of the A ball screw is an A seat 31. A 7-shaped support block 42 is fixed on the A seat 31 by screws. The screw holes on the support block 42 are several oblong holes. The height of the support block 42 is adjusted by fixing the screws in different oblong holes. The support block 42 is used to fix the secondary tower 40. By adjusting the height of the support block 42, the height error between the secondary tower 40 and the A seat 31 is eliminated.

[0044] In this embodiment, as Figure 1 , 7As shown in Figure 11, several pairs of A-slider 32 are installed on the A-slide rail 22. The A-slider 32 of the same pair is located on two A-slide rails 22 respectively. The trolley 27 is fixed on two pairs of A-slider 32. The B drive module includes a B motor 33, a B ball screw, and a B bearing seat 34. The B motor 33 is fixed on the trolley 27. The B ball screw is installed on the trolley 27 through the B bearing seat 34. The rotating shaft of the B motor 33 is connected to the power input end of the B ball screw through a coupling. The nut seat of the B ball screw is a B seat 35. The shielding door 41 is fixed on the B seat 35. A support block 42 is fixed on the B seat 35 by screws. The screw holes on the support block 42 are several oblong holes. The height of the support block 42 is adjusted by fixing the screws in different oblong holes. The support block 42 is used to fix the shielding door 41. By adjusting the height of the support block 42, the height error between the shielding door 41 and the B seat 35 is eliminated.

[0045] In this embodiment, as Figure 7 and 8 As shown, a pair of B slide rails 36 are also fixed on the trolley 27. The B slide rails 36 are laid in a direction perpendicular to the A slide rail 22. The B sliding module is located between the pair of B slide rails 36. Several pairs of B sliders 37 are slidably installed on the B slide rails 36. The same pair of B sliders 37 are located on the two B slide rails 36 respectively. The B sliders 37 are installed on the shielding door 41 to avoid bending of the ball screw under load and to ensure the service life of the ball screw.

[0046] In this embodiment, as Figure 8 As shown, motor B 33 is located outside slide rail A 22, and a balance wheel 38 is also installed at the bottom of the trolley 27. The balance wheel 38 is located outside slide rail A 22. When not being tested, the shielding door 41 is moved to the outside of slide rail A 22 to avoid interfering with personnel entering and exiting the test tower and to improve personnel work efficiency.

[0047] A testing method for a low-frequency coaxial reflectivity testing system includes the following steps:

[0048] Step 1, Low-frequency calibration: Open and remove the shielding door 41, close the secondary tower 40 and the main tower 39, and perform open-circuit calibration, short-circuit calibration, and load calibration;

[0049] Step 2, High-frequency calibration: Close the secondary tower 40 and the main tower 39, perform open-circuit calibration and short-circuit calibration, remove the secondary tower 40, install the load calibration component at the test position on the shielding door 41, close the shielding door 41 and the main tower 39, and perform load calibration;

[0050] Step 3: After the above calibration is completed, install the material to be tested at the test position on the shielding door 41 for testing.

[0051] By innovating the segmented calibration method and designing the calibration segment structure and calibration components, the calibration problem of the system was solved.

[0052] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A low-frequency coaxial reflectivity testing system, comprising a horizontal main tower (39), a secondary tower (40), a shielding door (41), and a sliding device, wherein the sliding device is installed at the bottom of the main tower (39), and the secondary tower (40) and the shielding door (41) are both installed on the sliding device, and the secondary tower (40) and the shielding door (41) are alternately opened and closed by the sliding device, characterized in that: The main tower (39) has the same structure as the auxiliary tower (40). The main tower (39) includes a tower body and a tower tip. The tower body consists of several segments, and the tower tip is fixed on the tower body. The tower body includes an outer conductor (1), an inner conductor (2), and a support plate (3). The inner conductor (2) is fixed inside the outer conductor (1) through the support plate (3). Both the outer conductor (1) and the inner conductor (2) are assembled by panels (4) and corner members (5). A seam connecting plate (6) is riveted on the outer wall of the outer conductor (1), and the seam connecting plate (6) is used to seal the gap between the panel (4) and the corner member (5). An outer pressing plate (7) is riveted between two adjacent segments of the outer conductor (1), and the outer pressing plate (7) is used to seal the gap between the adjacent outer conductors (1). An inner pressing plate (8) is riveted between two adjacent segments of the inner conductor (2), and the inner pressing plate (8) is used to seal the gap between the adjacent inner conductors (2); Circular positioning grooves are provided on the inner wall of the outer conductor (1) and the outer wall of the inner conductor (2). An avoidance hole (17) is provided on the support plate (3). The support plate (3) is in a square frame shape and is composed of two pieces spliced together. The outer side of the square frame is stuck in the positioning groove on the outer conductor (1), and the inner side of the square frame is stuck in the positioning groove on the inner conductor (2). The support plate (3) is located at the connection of two adjacent segments of the tower body. A plate-shaped cross keel (9) is riveted inside the inner conductor (2), and the cross keel (9) is located at the connection of two adjacent segments of the inner conductor (2). The inner pressing plate (8) presses tightly on the cross keel (9). A tightening frame (10) is riveted at the connection of adjacent outer conductors (1), and the tightening frame (10) is used to tighten the outer pressing plate (7). A connecting rod (11) is fixed between adjacent tightening frames (10). An X-shaped reinforcing rib (18) is riveted on the outer wall of the outer conductor (1), and the connecting rod (11) is fixed on the reinforcing rib (18); It also includes an adjusting plate (21), on which a positioning plate (25) is fixed. The sliding device includes an A-slide rail (22) and an I-beam (23). The A-slide rail (22) is laid on the I-beam (23). The I-beams (23) are a pair, and a channel steel (24) is fixed between the pair of I-beams (23). The channel steel (24) is several and distributed along the extension direction of the I-beams (23). The two ends of the adjusting plate (21) are respectively placed under the corresponding I-beams (23). The positioning plate (25) is screwed with bolts (26) that abut against the I-beams (23). There are two positioning plates (25) and they are respectively close to the corresponding I-beams (23). The I-beams (23) have threaded holes (43). The threaded holes (43) are screwed into the ends of the adjusting plate (21). The screws, the adjusting plate (21) is a plurality of and evenly distributed along the extension direction of the I-beam (23), the trolley (27) is slidably mounted on the A slide rail (22), the mounting plate (28) is mounted on the channel steel (24), the two A drive modules are mounted on the mounting plate (28), the two A drive modules are respectively located at both ends of the A slide rail (22), the power ends of the two A drive modules are close to the middle of the A slide rail (22), the sub-tower (40) slides through the A drive module close to the starting end of the A slide rail (22), the trolley (27) slides through the A drive module close to the end of the A slide rail (22), the trolley (27) is mounted on the trolley (27), the B drive module is used to drive the shielding door (41) to move in a direction perpendicular to the A slide rail (22); The mounting plate (28) is located between a pair of I-beams (23). The mounting plate (28) extends along the I-beams (23). The A drive module includes an A motor (29), an A ball screw, and an A bearing housing (30). The shaft of the A motor (29) is connected to the power input end of the A ball screw via a coupling. The A ball screw is mounted on the mounting plate (28) via the A bearing housing (30). The nut seat of the A ball screw is an A seat (31). A 7-shaped support block (42) is fixed on the A seat (31) by screws. The screw holes on the support block (42) are several waist-shaped holes. The height of the support block (42) is adjusted by fixing the screws in different screw waist-shaped holes. The support block (42) is used to fix the sub-tower (40).

2. The low-frequency coaxial reflectivity testing system according to claim 1, characterized in that: The corner piece (5), the seam connecting plate (6), the outer pressure plate (7) and the inner pressure plate (8) are all provided with mesh grooves (20), and metal mesh is placed in the mesh grooves (20).

3. The low-frequency coaxial reflectivity testing system according to claim 1, characterized in that: The spire includes a concentric ring (12), an outer cone (13), an inner cone (14), and a conductive post (15). The outer cone (13) has a flange (16) integrally formed at its large end. The flange (16) is fixed to the outer conductor (1). The inner cone (14) is fixed inside the outer cone (13) by the concentric ring (12). The conductive post (15) is used to connect the inner conductor (2) and the inner cone (14). The space between the outer conductor (1) and the inner conductor (2) is filled with a low dielectric constant material (19). The low dielectric constant material (19) is located at the connection between the inner conductor (2) and the inner cone (14).

4. The low-frequency coaxial reflectivity testing system according to claim 1, characterized in that: Several pairs of A sliders (32) are installed on the A slide rail (22). The A sliders (32) of the same pair are located on the two A slide rails (22). The trolley (27) is fixed on the two pairs of A sliders (32). The B drive module includes a B motor (33), a B ball screw and a B bearing seat (34). The B motor (33) is fixed on the trolley (27). The B ball screw is installed on the trolley (27) through the B bearing seat (34). The shaft of the B motor (33) is connected to the power input end of the B ball screw through a coupling. The nut seat of the B ball screw is a B seat (35). The support block (42) is fixed on the B seat (35) by screws. The screw holes on the support block (42) are several waist-shaped holes. The height of the support block (42) is adjusted by fixing the screws in different screw waist-shaped holes. The support block (42) is used to fix the shielding door (41).

5. The low-frequency coaxial reflectivity testing system according to claim 4, characterized in that: The trolley (27) is also fixed with a pair of B slide rails (36). The B slide rails (36) are laid in a direction perpendicular to the A slide rails (22). The B drive module is located between the pair of B slide rails (36). Several pairs of B sliders (37) are slidably installed on the B slide rails (36). The B sliders (37) of the same pair are respectively located on the two B slide rails (36).

6. The low-frequency coaxial reflectivity testing system according to claim 4, characterized in that: The B motor (33) is located outside the A slide rail (22), and the bottom of the trolley (27) is also equipped with a balance wheel (38), which is located outside the A slide rail (22).

7. The testing method of the low-frequency coaxial reflectivity testing system according to claim 1, characterized in that, Includes the following steps: Step 1, Low-frequency calibration: Open and remove the shielding door, close the secondary tower and the main tower, and perform open-circuit calibration, short-circuit calibration, and load calibration; Step 2, High-frequency calibration: Close the secondary tower and the main tower, perform open-circuit calibration and short-circuit calibration, remove the secondary tower, install the load calibration component at the test position on the shielding door, close the shielding door and the main tower, and perform load calibration; Step 3: After the above calibration is completed, install the material to be tested at the test position on the shielding door and conduct the test.

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