Inner loop matching clamp suitable for cable transfer impedance test of three-coaxial method

Abstract

The utility model discloses an inner loop matching clamp suitable for a cable transfer impedance test of a three-coaxial method, and belongs to the field of electromagnetic compatibility test. The device is characterized by comprising a main body (6), a through inner cavity is formed in the main body (6), the inner cavity comprises a clamping cavity (8), a clamping block mechanism (3) is arranged in the clamping cavity (8) in a tightly attached mode, a cable (1) to be tested is located in the clamping block mechanism (3), a shielding layer (103) of the cable (1) to be tested is attached to the inner wall of the clamping block mechanism (3), and a resistor containing cavity (9) communicated with the clamping cavity (8) is further formed in the main body (6). And a matched resistor (4) is placed in the resistor accommodating cavity (9) and is connected with an inner core (102) of the to-be-tested cable (1). According to the inner loop matching clamp suitable for the cable transfer impedance test of the three-coaxial method, an inner loop in the test of the three-coaxial method is formed, the coaxiality of a cable to be tested and a shielding layer is met, and the arrangement of a matching resistor is facilitated.

Description

Technical Field

[0001] The invention relates to an inner loop matching fixture suitable for a cable transfer impedance test using a triaxial method, belonging to the field of electromagnetic compatibility testing. Background Art

[0002] The triaxial method is a test method for measuring cable shielding effectiveness and is widely used in electromagnetic compatibility (EMC) testing. This method primarily measures the surface transfer impedance and shield attenuation of cables. "IEC 62153-4-3:2002 Electromagnetic Compatibility (EMC) -- Surface Transfer Impedance (Triaxial Measurement Method)" further discloses two test methods: Method A and Method B. In Method A, the shield and inner conductor (core) of the cable under test form an inner loop. An outer sleeve made of a non-ferromagnetic metal (such as brass or pure copper) is placed over the cable under test. The outer sleeve and the shield of the cable under test form the outer loop. The axes of the inner conductor, shield, and outer sleeve of the cable under test are aligned.

[0003] In the inner loop, a matching resistor is also set in the inner loop. The resistance of the matching resistor is equal to the characteristic impedance of the cable to be tested. The matching resistor is connected between the core and the shielding layer of the cable to be tested. In order to complete the above inner loop while ensuring the coaxial structure, a connector is generally set at one end of the cable to be tested (denoted as the extreme end). The connector can be connected to the shielding layer of the cable to be tested while coaxially clamping the cable to be tested. At the same time, the core of the cable to be tested needs to be connected to the matching resistor.

[0004] After completing the proximal connection, the outer sleeve is connected to the shield of the cable under test at the distal end. A signal generator is also installed at the distal end, and its output is connected to the core of the cable under test. During testing, the signal generator injects a signal into the inner loop, and a signal receiver is installed in the outer loop to further determine the transfer impedance of the cable under test.

[0005] The technical solutions for realizing the above-mentioned three-coaxial method recorded in the prior art (such as: the Chinese invention patent with application number 201711074763.0, application date November 6, 2017, and patent name “A three-coaxial test system for RF coaxial connectors”; the Chinese invention patent with application number 202110871303.0, application date July 30, 2021, and patent name “A high-frequency enhanced three-coaxial method shielding effectiveness test system and test method thereof”; and the Chinese invention patent with application number 202220049501.9, application date January 1, 2022 On the 0th, a Chinese invention patent entitled "High-frequency 3M circular test fixture for a three-coaxial method cable shielding effectiveness test system" was published, disclosing corresponding specific solutions based on the basic principle of the three-coaxial method. However, in the above-mentioned prior art, there is no record of the specific structure of the connector that forms the inner loop. As can be seen from the above, when forming the inner loop, a matching resistor needs to be set. Since the matching resistors of different cables to be tested are different, designing a connector technical solution that is suitable for forming a corresponding inner loop when performing three-coaxial method testing and is convenient for arranging matching resistors has become an urgent problem to be solved in this field. Utility Model Content

[0006] The technical problem to be solved by the utility model is: to overcome the shortcomings of the existing technology and provide an inner loop matching fixture suitable for the cable transfer impedance test of the triaxial method, which satisfies the coaxiality of the cable to be tested and the shielding layer while forming an inner loop in the triaxial method test and is convenient for arranging matching resistors.

[0007] The technical solution adopted by the utility model to solve its technical problems is: the inner loop matching fixture suitable for cable transfer impedance testing using a triaxial method is characterized in that it includes a main body, a penetrating inner cavity is provided in the main body, the inner cavity includes a clamping cavity, a clamping block mechanism is tightly provided in the clamping cavity, the cable to be tested is located inside the clamping block mechanism, and the shielding layer of the cable to be tested is in contact with the inner wall of the clamping block mechanism, a resistor accommodating cavity connected to the clamping cavity is further provided in the main body, a matching resistor is placed in the resistor accommodating cavity, and the matching resistor is connected to the inner core of the cable to be tested.

[0008] Preferably, the inner cavity of the main body further includes a locking cavity, the clamping cavity, the resistor accommodating cavity and the locking cavity are arranged in sequence and connected end to end, and a screw for axially clamping the matching resistor is provided in the locking cavity.

[0009] Preferably, an internal thread cooperating with the screw is provided in the locking cavity.

[0010] Preferably, a threaded section is provided on the outer wall of the main body, an external thread is opened on the surface of the threaded section, the threaded section is located outside the clamping cavity, and a locking nut for driving the clamping block mechanism to move axially is threadedly connected to the threaded section.

[0011] Preferably, the clamping block mechanism is in the shape of a truncated cone and is formed by a plurality of clamping block units that are surrounded and connected together.

[0012] Preferably, a groove is provided at the axis of the clamping block unit, and the grooves of all the clamping block units surround and form a threading hole for accommodating the cable to be tested.

[0013] Preferably, the clamping block mechanism is in the shape of a truncated cone, and the inner diameter of the clamping cavity decreases gradually from the end of the main body toward the inside.

[0014] Preferably, a shielding layer is further provided on the inner wall of the resistor accommodating cavity, and the matching resistor is located on the inner side of the shielding layer.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] By using the inner loop matching fixture for the cable transfer impedance test of the triaxial method, the inner loop in the triaxial method test is formed while meeting the coaxiality of the cable to be tested and the shielding layer, and facilitating the arrangement of the matching resistor.

[0017] In the inner loop matching fixture for the cable transfer impedance test using the triaxial method, a screw is provided. When the screw is screwed into the end of the main body, the matching resistor is pressed tightly, thereby achieving reliable contact between the cable to be tested, the matching resistor and the main body.

[0018] A shielding layer is provided on the inner wall of the resistor accommodating cavity, which prevents the matching resistor from contacting the main body and has a shielding effect on the matching resistor.

[0019] During use, the clamping mechanism compresses and positions the shielded wire. Adjusting the position of the clamping nut allows the diameter of the wire hole within the clamping mechanism to be adjusted, thus accommodating the testing of shielded wires of varying diameters. This eliminates the existing drawback of customizing the matching fixture required to replace shielded wires, reducing workload. It also eliminates the high-frequency inductance introduced by pin matching resistors, offering improved operability and repeatability. This significantly improves the efficiency of matching during cable testing while reducing the labor intensity of testers. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A cross-sectional view of the inner-loop matching fixture for triaxial cable transfer impedance testing.

[0021] Figure 2 A cross-sectional view of the inner-loop matching fixture body for triaxial cable transfer impedance testing.

[0022] Figure 3 A top view of the wedge-shaped clamp mechanism of the inner loop matching fixture suitable for cable transfer impedance testing using the triaxial method.

[0023] Figure 4 for Figure 3 Middle AA section view.

[0024] Figure 5 A cross-sectional view of Example 2 of an inner loop matching fixture suitable for cable transfer impedance testing using the triaxial method.

[0025] Wherein: 1. Cable to be tested 101, insulation layer 102, inner core 103, shielding layer 2, locking nut 3, clamping block mechanism 4, matching resistor 5, screw 6, main body 7, shielding sleeve 8, clamping cavity 9, resistor accommodating cavity 10, locking cavity 11, threading hole 12, clamping block unit. DETAILED DESCRIPTION

[0026] Figures 1 to 4 This is the best embodiment of the present invention, Figures 1 to 5 The utility model is further described.

[0027] Example 1:

[0028] like Figure 1 As shown, the inner loop matching fixture for triaxial cable transfer impedance testing includes a main body 6. The cable 1 to be tested is loaded from the rear end of the main body 6. A clamping block mechanism 3 is provided at the rear end of the main body 6. The clamping block mechanism 3 is arranged on the outer ring of the cable 1 to be tested and enters the rear end of the main body 6 along with the cable 1 to be tested. A locking nut 2 is also mounted on the rear end of the main body 6. The locking nut 2 is fixed to the rear end of the main body 6 while squeezing the clamping block mechanism 3 and the cable 1 to be tested into the interior of the main body 6, thereby securing the cable to be tested.

[0029] A matching resistor 4, designed to match the cable 1 under test, is placed within the main body 6. The cable 1 under test is inserted and secured at the rear of the main body 6, butting against one end of the matching resistor 4. A screw 5 is screwed in from the front of the main body 6. During the screwing process, the screw 5 contacts the other end of the matching resistor 4. As the screw 5 is screwed in, it squeezes the matching resistor 4, ensuring reliable contact between the matching resistor 4 and the core of the cable 1 under test.

[0030] like Figure 2 As shown, the cross section of the main body 6 is circular, and the outer portion of the main body 6 gradually becomes smaller from the middle to the front end and becomes conical. The rear end of the main body 6 is provided with a thread that cooperates with the lock nut 2. The interior of the main body 6 is provided with an axially penetrating inner cavity.

[0031] The interior of the main body 6 is divided, from front to back, into a locking chamber 10, a resistor accommodating chamber 9, and a clamping chamber 8. These chambers are butted end-to-end and axially interlinked. The inner wall of the locking chamber 10 is threaded, mateable with the screw 5. A shielding sleeve 7 is fitted over the inner wall of the resistor accommodating chamber 9, with the matching resistor 4 positioned within it. The clamping chamber 8 is located at the end of the resistor accommodating chamber 9, and its diameter gradually increases from the inside out, forming a flared shape.

[0032] like Figures 3 and 4 As shown, the clamping mechanism 3 is truncated cone-shaped with a successively varying diameter, and the inclination angle of the clamping mechanism 3 surface is the same as the inclination angle of the inner wall of the clamping cavity 8. The clamping mechanism 3 is composed of a plurality of clamping block units 12, each of which has a fan-shaped cross-section. The clamping mechanism 3 preferably comprises 3 to 4 clamping block units 12. Each clamping block unit 12 has a cylindrical groove with a fan-shaped cross-section. Therefore, after the clamping block units 12 form the clamping mechanism 3, they are butted together at the axis of the clamping mechanism 3 to form a threading hole 11, through which the cable 1 to be tested passes.

[0033] The specific assembly process is as follows:

[0034] First, install the matching resistor 4 from the rear end of the main body 6 and ensure that the matching resistor 4 falls into the resistor accommodation cavity 9. Then, fit the locking nut 2 over the cable 1 under test. As in the prior art, the cable 1 under test comprises an inner core 102, an insulating layer 101 disposed outside the inner core 102, and a shielding layer 103 disposed outside the insulating layer 101. A sheath (not shown) is also disposed outside the shielding layer 103. Beforehand, remove the outer sheath of the cable 1 under test, and also remove a length of the insulating layer 101 and shielding layer 103, leaving the inner core 102 protruding from the end of the cable 1 under test.

[0035] The multiple clamping blocks 12 that make up the clamping mechanism 3 are then arranged outside the shielding layer 103. The cable 1 to be tested is then inserted into the rear end of the main body 6 along with the clamping block 3. During the insertion process, the exterior of the clamping block 3 gradually mates with the inner wall of the clamping cavity 8. After this mates, the locking nut 2 is mated with the threads at the rear end of the main body 6 and gradually tightened. As the locking nut 2 is tightened, the clamping block 3 and the cable 1 to be tested are squeezed into the interior of the main body 6. The clamping blocks 12 that make up the clamping mechanism 3, acting on the inclined surface of the inner wall of the clamping cavity 8, continuously move toward the axis and clamp the cable 1 to be tested.

[0036] Then, screw 5 is screwed in from the front end of main body 6. During the screwing process, screw 5 contacts the other end of matching resistor 4. As screw 5 is screwed in, it squeezes matching resistor 4, ensuring that matching resistor 4 is in reliable contact with the inner core 102 of the cable under test 1. This ensures that the inner core 102 of the cable under test 1, matching resistor 4, main body 6, clamping block mechanism 3, and shielding layer 103 are connected, forming the inner loop of the triaxial method test.

[0037] Example 2:

[0038] The difference between this embodiment and embodiment 1 is that: Figure 5 As shown, the length of the screw 5 can be lengthened so that the screw 5 still extends to the outside of the main body 6 after clamping the matching resistor 4 , so that an external loop impedance is arranged at the end of the screw 5 .

[0039] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation thereto. Any person skilled in the art may utilize the above disclosure to modify or remodel the present invention into equivalent embodiments. However, any simple modification, equivalent variation, or modification of the above embodiment that does not depart from the technical content of the present invention and is based on the technical essence of the present invention shall still fall within the scope of protection of the present invention.

Claims

1. This inner loop matching fixture is suitable for the cable transfer impedance test using the triaxial method, and is characterized by: The invention comprises a main body (6), a through inner cavity is provided in the main body (6), the inner cavity comprises a clamping cavity (8), a clamping block mechanism (3) is closely provided in the clamping cavity (8), the cable to be tested (1) is located inside the clamping block mechanism (3), and the shielding layer (103) of the cable to be tested (1) is in contact with the inner wall of the clamping block mechanism (3), a resistor accommodating cavity (9) connected to the clamping cavity (8) is further provided in the main body (6), a matching resistor (4) is placed in the resistor accommodating cavity (9), and the matching resistor (4) is connected to the inner core (102) of the cable to be tested (1).

2. The inner loop matching fixture for cable transfer impedance testing using the triaxial method according to claim 1, characterized in that: The inner cavity of the main body (6) further includes a locking cavity (10). The clamping cavity (8), the resistor accommodating cavity (9) and the locking cavity (10) are arranged in sequence and connected end to end. A screw (5) for axially clamping the matching resistor (4) is provided in the locking cavity (10).

3. The inner loop matching fixture for cable transfer impedance testing using a triaxial method according to claim 2, characterized in that: An internal thread that cooperates with the screw (5) is provided in the locking cavity (10).

4. The inner loop matching fixture for cable transfer impedance testing using a triaxial method according to claim 1, characterized in that: A threaded section is provided on the outer wall of the main body (6), an external thread is provided on the surface of the threaded section, the threaded section is located outside the clamping cavity (8), and a locking nut (2) for driving the clamping block mechanism (3) to move axially is threadedly connected to the threaded section.

5. The inner loop matching fixture for cable transfer impedance testing using a triaxial method according to claim 1 or 4, characterized in that: The clamping block mechanism (3) is truncated and formed by a plurality of clamping block monomers (12) that are surrounded and connected.

6. The inner loop matching fixture for cable transfer impedance testing using a triaxial method according to claim 5, characterized in that: A groove is provided at the axis of the clamping block monomer (12), and the grooves of all the clamping block monomers (12) surround and form a threading hole (11) for accommodating the cable (1) to be tested.

7. The inner loop matching fixture for cable transfer impedance testing using a triaxial method according to claim 1, characterized in that: The clamping block mechanism (3) is truncated cone-shaped, and the inner diameter of the clamping cavity (8) decreases in sequence from the end of the main body (6) inward.

8. The inner loop matching fixture for cable transfer impedance testing using a triaxial method according to claim 1, characterized in that: A shielding sleeve (7) is also provided on the inner wall of the resistor accommodating cavity (9), and the matching resistor (4) is located on the inner side of the shielding sleeve (7).

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