Cable radiation emission standard exceeding detection method and system

Abstract

The invention discloses a cable radiation emission standard exceeding detection method and system, and the method comprises the steps: calculating a common-mode current limit value of a type of test cable in a broadband below 1GHz according to a current test value along the test cable by setting a current initial value of a head end of the test cable, and carrying out the calculation of a common-mode current limit value of the type of test cable in the later stage of radiation exceeding detection of the same type of cable. The common-mode current of the head end of the test cable is obtained through an experiment, if the common-mode current of the head end of the test cable is larger than the common-mode current limit value of the test cable, the radiation emission of the tested cable exceeds the standard, and if the common-mode current of the head end of the test cable is smaller than or equal to the common-mode current limit value of the test cable, the radiation emission of the test cable meets the requirement. Whether the radiation emission exceeds the standard or not is judged according to the size of the single-point common-mode current at the head end, the common-mode current limit value of any cable can be given, the test result is equivalent to that of a standard anechoic chamber test method, the method is simpler and more reliable, the measurement consistency is higher, and the method provided by the invention is suitable for RE standard-exceeding rapid screening of large-batch cables in production.

Description

Technical Field

[0001] The present invention belongs to the technical field of electromagnetic compatibility, and in particular relates to a method and system for detecting excessive radiation emission of cables. Background Art

[0002] Radiated emission (RE) refers to the electromagnetic interference radiated to the external environment by electrical and electronic equipment under normal working conditions. Exceeding the standard may cause radiation vulnerability problems of other surrounding electronic equipment, leading to bit errors, downtime, or even damage. It is one of the important contents of electromagnetic compatibility testing.

[0003] The detection of traditional cable radiation emission is carried out in a microwave darkroom (referred to as the darkroom method). According to the national standard GB9254.1:2021, the equipment to be tested should be placed horizontally on the electrostatic table, and the distance between the ends of the cables should be controlled to be 10 cm, and they should be allowed to droop freely. In the far field, the receiving antenna is used to measure the radiation electric field size of the equipment to be tested in different rotation directions and polarization directions, and compared with the limit values ​​specified in the standard, it is determined whether the radiation emission exceeds the standard. The darkroom method has high requirements for the test environment, and the test is expensive and time-consuming. It is not convenient for consistency screening of a large number of cables to be tested in industrial sites, and the calibration efficiency is low. Summary of the invention

[0004] The purpose of the present invention is to provide a method and system for detecting excessive radiation emission of cables to overcome the shortcomings of the prior art. The present invention measures the current at the head end of the cable and compares it with the calculated current limit to screen cables with excessive RE. The method is simple and can greatly improve the detection efficiency and accuracy.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A method for detecting excessive cable radiation emission, comprising the following steps:

[0007] S1, setting the initial value of the current at the first end of the test cable, and obtaining the common mode current limit of the test cable according to the initial value of the current at the first end of the test cable;

[0008] S2, use the experimental method to obtain the common-mode current at the head end of the test cable. If the common-mode current at the head end of the test cable is greater than the common-mode current limit of the test cable, it means that the radiated emission of the test cable exceeds the standard. If the common-mode current at the head end of the test cable is less than or equal to the common-mode current limit of the test cable, it means that the radiated emission of the test cable meets the requirements.

[0009] Preferably, an experimental method is used to test and obtain the common-mode current at the head end of the test cable: the two ends of the test cable are respectively connected to the disturbed measurement device and the auxiliary measurement device, a broadband current measuring clamp is set on the test cable, and the common-mode current at the head end of the test cable is measured using the broadband current measuring clamp.

[0010] Preferably, the initial value of the current at the first end of the test cable is set, and based on the iterative optimization method, the specific process of obtaining the common mode current limit of the test cable according to the initial value of the current at the first end of the test cable is:

[0011] Given an initial guess value I0 of the current at the head end of the test cable, calculate the current distribution along the test cable according to the initial value I0 of the current at the head end of the test cable, and calculate the radiation emission size E0 of the test cable under the initial value I0 of the current at the head end of the test cable based on the current distribution along the test cable. If the radiation emission size E0 of the test cable is greater than the set radiation emission limit E lim If the relative error is less than 5%, the common mode current limit I 0lim =I0, if the radiated emission size E0 of the tested cable is equal to the set radiated emission limit E lim If the relative error is greater than or equal to 5%, the initial value of the current at the head end of the test cable is updated to I0+△I0, where △I0 is the optimized adjustment current, and the radiation emission size E0 of the test cable is recalculated with the set radiation emission limit E lim The relative error is until the radiation emission size E0 of the test cable is equal to the set radiation emission limit E lim The relative error is less than 5%.

[0012] Preferably, the common mode current distribution along the cable is obtained, and the cable is divided into N sections. Each section is regarded as a dipole. The radiation emission value of any section of the cable can be calculated by the dipole radiation emission formula. The total radiation emission value is the superposition of N sections:

[0013]

[0014] Where: j is the imaginary number symbol, η is the free space wave impedance; θ is the azimuth angle; r i Represents the distance between the observation point and the i-th source point; I i is the current of the i-th cable section; l i is the length of the i-th cable segment, is the azimuth direction vector, For r i direction vector, k is the electromagnetic wave number.

[0015] Preferably, the current ratio K between the beginning and the end of the cable should comply with:

[0016]

[0017] Where: I0 is the current at the beginning of the cable, I L is the current at the end of the cable, Γ L is the end reflection coefficient; β is the propagation constant.

[0018] Preferably, N points are taken on the cable (usually the number of points is ensured to be less than 0.1 times the wavelength), and then the ratio of the amplitude of the current at any point along the line to the amplitude of the terminal current is calculated:

[0019]

[0020] From this, N sets of equations can be written out, and the residual value between measurement and calculation can be minimized through optimization algorithm to obtain the reflection coefficient Γ L and an estimate of the propagation constant β.

[0021] Preferably, the angles of the test points in the spherical coordinate system are Therefore, the calculation formula for each component in the rectangular coordinate system is:

[0022]

[0023] Therefore, the vertically polarized radiated electric field E VP and the horizontally polarized radiated electric field E HP They are:

[0024]

[0025] A cable radiation emission exceeding standard detection system, comprising a test module and a detection module;

[0026] The test module obtains the common mode current limit of the test cable according to the initial value of the current at the first end of the test cable according to the initial value of the current at the first end of the test cable;

[0027] The detection module obtains the common-mode current at the head end of the test cable according to the experimental method. If the common-mode current at the head end of the test cable is greater than the common-mode current limit of the test cable, it means that the radiation emission of the test cable exceeds the standard; if the common-mode current at the head end of the test cable is less than or equal to the common-mode current limit of the test cable, it means that the radiation emission of the test cable meets the requirements.

[0028] Preferably, the two ends of the test cable are respectively connected to the disturbed measurement device and the auxiliary measurement device, a broadband current measuring clamp is set on the test cable, and the broadband current measuring clamp is used to measure the common mode current at the beginning and end of the test cable respectively.

[0029] Preferably, the specific process of setting the initial value of the current at the first end of the test cable and obtaining the common mode current limit of the test cable according to the initial value of the current at the first end of the test cable is:

[0030] Given the initial current value I0 at the head end of the test cable, calculate the current distribution along the test cable according to the initial current value I0 at the head end of the test cable, and calculate the radiation emission size E0 of the test cable under the initial current value I0 at the head end of the test cable based on the current distribution along the test cable. If the radiation emission size E0 of the test cable is greater than the set radiation emission limit E0,lim If the relative error is less than 5%, the common mode current limit I 0lim =I0, if the radiated emission size E0 of the tested cable is equal to the set radiated emission limit E lim If the relative error is greater than or equal to 5%, the initial value of the current at the head end of the test cable is updated to I0+ΔI0, where ΔI0 is the optimized adjustment current, and the radiation emission size E0 of the test cable is recalculated with the set radiation emission limit E lim The relative error is until the radiation emission size E0 of the test cable is equal to the set radiation emission limit E lim The relative error is less than 5%.

[0031] Compared with the prior art, the present invention has the following beneficial technical effects:

[0032] The present invention provides a method for detecting excessive radiation emission of a cable. The method uses a set initial value of the current at the head end of a test cable, obtains a common-mode current limit of the test cable according to the initial value of the current at the head end of the test cable, and obtains the common-mode current at the head end of the test cable by an experimental method. If the common-mode current at the head end of the test cable is greater than the common-mode current limit of the test cable, it indicates that the radiation emission of the test cable exceeds the standard. If the common-mode current at the head end of the test cable is less than or equal to the common-mode current limit of the test cable, it indicates that the radiation emission of the test cable meets the requirement. The present invention determines whether the radiation emission exceeds the standard by the size of the common-mode current at a single point at the head end. The method of the present invention is simple, not affected by the environment, and the common-mode current has better measurement consistency than the radiation electric field. The method can be simply and reliably used as a new standard for RE excessive screening. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The present invention is a schematic diagram of a method for detecting excessive radiated emissions from cables according to an embodiment of the present invention.

[0034] Figure 2 The figure is a schematic diagram of the process of obtaining the common mode current limit value of a cable in an embodiment of the present invention.

[0035] Figure 3 Schematic diagram of measuring the current at the head end of a cable in an embodiment of the present invention.

[0036] Figure 4 Schematic diagram of measuring the current at the end of a cable in an embodiment of the present invention.

[0037] Figure 5 Graph showing the relationship between the first and last current ratio K and frequency in an embodiment of the present invention.

[0038] Figure 6 4 is a current limit diagram under vertical polarization when the head-end current limit varies with frequency in an embodiment of the present invention.

[0039] Figure 74 is a current limit diagram of the first-end current limit under horizontal polarization with frequency variation in an embodiment of the present invention. DETAILED DESCRIPTION

[0040] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0041] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0042] like Figure 1 As shown, the present invention provides a method for detecting excessive radiated emission of cables, which uses a broadband current measurement system composed of a broadband current measuring clamp, a low-noise power amplifier, and a spectrum analyzer to measure the current at the head end of the cable and compare it with the calculated current limit to screen cables with excessive RE; specifically, the following steps are included:

[0043] S1, setting the initial value of the current at the first end of the test cable, and obtaining the common mode current limit of the test cable according to the initial value of the current at the first end of the test cable;

[0044] S2, use the experimental method to obtain the common-mode current at the head end of the test cable. If the common-mode current at the head end of the test cable is greater than the common-mode current limit of the test cable, it means that the radiated emission of the test cable exceeds the standard. If the common-mode current at the head end of the test cable is less than or equal to the common-mode current limit of the test cable, it means that the radiated emission of the test cable meets the requirements.

[0045] In a specific implementation of the present application, an experimental method is used to test and obtain the common-mode current at the head end of the test cable. Specifically, the two ends of the test cable are respectively connected to a disturbed measurement device (EUT) and an auxiliary measurement device (AE), and a broadband current measuring clamp is placed on the test cable. The broadband current measuring clamp is used to measure the common-mode current at the head end and the end of the test cable, respectively.

[0046] Specifically, place the disturbed measurement equipment (EUT) and the auxiliary measurement equipment (AE) on the electrostatic table, with a distance of 10 cm between the disturbed measurement equipment (EUT) and the auxiliary measurement equipment (AE). The disturbed measurement equipment (EUT) and the auxiliary measurement equipment (AE) are respectively connected to the test cable, and the test cable hangs freely. Obtain the common-mode current at the head end of the test cable, and the broadband current measuring clamp is close to the port of the disturbed measurement equipment. The output port of the broadband current measuring clamp is connected to the low-noise amplifier (LNA), and the output of the low-noise amplifier is connected to the spectrum analyzer. The measurement frequency band of the broadband current measuring clamp, the low-noise amplifier and the spectrum analyzer should cover 30MHz~1GHz. When the disturbed measurement equipment and the auxiliary measurement equipment are turned on and working normally, use the common-mode current I at the head end of the cable within the measurement bandwidth. m .

[0047] Move the broadband current measurement clamp to close to the port of the auxiliary measurement device, repeat the above steps, and measure the common-mode current at the end of the test cable.

[0048] Based on the common mode current at the beginning and end of the test cable, calculate the ratio of the current amplitude at the beginning and end of the cable within 30MHz to 1GHz:

[0049]

[0050] Serves as input for the calculation of common-mode current limit.

[0051] The specific process of setting the initial value of the current at the first end of the test cable and obtaining the common mode current limit of the test cable according to the initial value of the current at the first end of the test cable is as follows:

[0052] like Figure 2 As shown, given the initial value I0 of the current at the head end of the test cable, the current distribution along the test cable is calculated according to the initial value I0 of the current at the head end of the test cable, and the radiation emission size E0 of the test cable under the initial value I0 of the current at the head end of the test cable is calculated based on the current distribution along the test cable. If the radiation emission size E0 of the test cable is greater than the set radiation emission limit E lim If the relative error is less than 5%, the common mode current limit I 0lim =I0, if the radiated emission size E0 of the tested cable is equal to the set radiated emission limit E lim If the relative error is greater than or equal to 5%, the initial value of the current at the head end of the test cable is updated to I0+ΔI0, where ΔI0 is the optimized adjustment current, and the radiation emission size E0 of the test cable is recalculated with the set radiation emission limit E lim The relative error is until the radiation emission size E0 of the test cable is equal to the set radiation emission limit E lim The relative error is less than 5%.

[0053] Calculation of the common mode current amplitude along the test cable during use:

[0054] According to transmission line theory, the common mode current amplitude along the cable is approximately cosine distributed:

[0055]

[0056] Where: λ is the wavelength; z is the distance along the line; A and B are unknown parameters.

[0057] According to the transmission line theory, the current ratio between the beginning and the end of the cable should obey:

[0058]

[0059] Where: I0 is the current at the beginning of the cable, I L is the current at the end of the cable, Γ L is the end reflection coefficient; β is the propagation constant, and L is the cable length, i.e., 1m. The effect of the propagation constant β on K can be ignored, and it is assumed that K is only related to Γ L Under the condition that the disturbed measuring equipment and the auxiliary measuring equipment remain unchanged, the current ratio K of the cable head and end is fixed and unchanged. The current at the end of the cable can be measured by I L =I0 / K calculation.

[0060] Under the condition of measuring the current I0 at the beginning of the cable, the current I at the end of the cable can be calculated using formula (1): L , the unknown coefficients A and B in (2) are calculated according to the following formula:

[0061]

[0062] Under the premise that the disturbed measuring equipment and auxiliary measuring equipment remain unchanged and only the cable is replaced, the K value does not change. The common mode current amplitude and ratio K at the head and end are obtained by experimental test, and then the current amplitude along the cable is inverted using formula (4).

[0063] Test the common mode current phase along the cable during use:

[0064] According to the transmission line model, the current along the cable should satisfy the following rules:

[0065]

[0066] Where: I z is the current at any point in the cable; I L is the current at the end of the cable, and z is any point in the cable.

[0067] According to the law of current along the cable, the reflection coefficient Γ at the end of the cable LSince the propagation constant β is an unknown number, N points are taken on the cable (usually the number of points is ensured to be less than 0.1 times the wavelength), and then the ratio of the amplitude of the current at any point along the line to the amplitude of the terminal current is calculated:

[0068]

[0069] From this, N sets of equations can be written out, and the residual value between measurement and calculation can be minimized through optimization algorithm to obtain the reflection coefficient Γ L This application only focuses on the amplitude of the electric field radiated by the cable, that is, the absolute value of the current phase along the line does not affect the current limit calculation, and the current phase at the head end of the cable is assumed to be 0°. Then calculate the current phase value along the cable according to formula (7):

[0070]

[0071] Calculate the radiated emission based on the inversion results of the common mode current along the line:

[0072] Considering the radiation emission of a freely drooping cable, the cable is divided into N segments based on the common-mode current distribution along the cable. Each segment is regarded as a dipole. The radiation emission value of any segment of the cable can be calculated using the dipole radiation emission formula. The total radiation emission value is the superposition of the N segments:

[0073]

[0074] Where: spherical coordinate system is used; j is the imaginary number symbol, η is the free space wave impedance; θ is the azimuth angle; r i Represents the distance between the observation point and the i-th source point; I i is the current of the i-th cable section; l i is the length of the i-th cable segment, is the azimuth direction vector, For r i direction vector, k is the electromagnetic wave number.

[0075] The spherical coordinate system of formula (8) is converted into a rectangular coordinate system to more conveniently derive the horizontal polarization and vertical polarization formulas. Specifically, let the angles of the test points in the spherical coordinate system be Therefore, the calculation formula for each component in the rectangular coordinate system is:

[0076]

[0077] Therefore, the vertically polarized radiated electric field E VP and the horizontally polarized radiated electric field E HP They are:

[0078]

[0079] In another embodiment of the present invention, a cable radiated emission exceeding standard detection system is provided, comprising a test module and a detection module;

[0080] The test module obtains the common mode current limit of the test cable according to the initial value of the current at the first end of the test cable according to the initial value of the current at the first end of the test cable;

[0081] The detection module obtains the common-mode current at the head end of the test cable according to the experimental method. If the common-mode current at the head end of the test cable is greater than the common-mode current limit of the test cable, it means that the radiation emission of the test cable exceeds the standard; if the common-mode current at the head end of the test cable is less than or equal to the common-mode current limit of the test cable, it means that the radiation emission of the test cable meets the requirements.

[0082] Preferably, the two ends of the test cable are respectively connected to the disturbed measurement device and the auxiliary measurement device, a broadband current measuring clamp is set on the test cable, and the broadband current measuring clamp is used to measure the common mode current at the beginning and end of the test cable respectively.

[0083] Preferably, the specific process of setting the initial value of the current at the first end of the test cable and obtaining the common mode current limit of the test cable according to the initial value of the current at the first end of the test cable is:

[0084] Given the initial current value I0 at the head end of the test cable, calculate the current distribution along the test cable according to the initial current value I0 at the head end of the test cable, and calculate the radiation emission size E0 of the test cable under the initial current value I0 at the head end of the test cable based on the current distribution along the test cable. If the radiation emission size E0 of the test cable is greater than the set radiation emission limit E0, lim If the relative error is less than 5%, the common mode current limit I 0lim =I0, if the radiated emission size E0 of the tested cable is equal to the set radiated emission limit E lim If the relative error is greater than or equal to 5%, the initial value of the current at the head end of the test cable is updated to I0+ΔI0, where ΔI0 is the optimized adjustment current, and the radiation emission size E0 of the test cable is recalculated with the set radiation emission limit E lim The relative error is until the radiation emission size E0 of the test cable is equal to the set radiation emission limit E lim The relative error is less than 5%.

[0085] Example

[0086] The present invention tests the existing cables, first measuring the current at the beginning and end of the cable as an example (such as Figure 3 , Figure 4 As shown), the relationship between the head-to-end current ratio K and the frequency is calculated as follows Figure 5As shown, by setting the initial current I0 to 0.1μA, and increasing ΔI0 to 0.1μA each time in the cycle, according to the above method, the cable current limit is obtained as follows Figure 6 , Figure 7 As shown in the figure, the overall cable current limit shows a trend of first decreasing, then increasing, and then decreasing. Compared with the RE limit, it can be seen that the decrease in the common-mode current limit in the low-frequency band is caused by the increase of the radiated electric field with the increase of frequency.

[0087] Those skilled in the art will readily appreciate other embodiments of the present invention after considering the specification and disclosure of the invention. This application is intended to cover any variations, uses or adaptations of the present invention that follow the general principles of the present invention and include common knowledge or customary techniques in the art that are not disclosed by the present invention. The specification and examples are to be considered exemplary only, and the true scope and spirit of the present invention is indicated by the following claims.

[0088] It should be understood that the present invention is not limited to the exact construction that has been described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

[0089] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural change made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for detecting excessive cable radiation emission, characterized in that: The following steps are involved: S1, setting the initial value of the current at the first end of the test cable, and obtaining the common mode current limit of the test cable according to the initial value of the current at the first end of the test cable; S2, use the experimental method to obtain the common-mode current at the head end of the test cable. If the common-mode current at the head end of the test cable is greater than the common-mode current limit of the test cable, it means that the radiated emission of the test cable exceeds the standard. If the common-mode current at the head end of the test cable is less than or equal to the common-mode current limit of the test cable, it means that the radiated emission of the test cable meets the requirements.

2. A cable radiation emission exceeding standard detection method according to claim 1, characterized in that: The common-mode current at the beginning of the test cable is obtained by the experimental method: the two ends of the test cable are connected to the disturbed measurement equipment and the auxiliary measurement equipment respectively, a broadband current measurement clamp is set on the test cable, and the common-mode current at the beginning and end of the test cable is measured respectively by the broadband current measurement clamp.

3. A cable radiation emission exceeding standard detection method according to claim 1, characterized in that: The specific process of setting the initial value of the current at the first end of the test cable and calculating the common mode current limit of the test cable according to the initial value of the current at the first end of the test cable is as follows: Given the initial current value I0 at the head end of the test cable, calculate the current distribution along the test cable according to the initial current value I0 at the head end of the test cable, and calculate the radiation emission size E0 of the test cable under the initial current value I0 at the head end of the test cable based on the current distribution along the test cable. If the radiation emission size E0 of the test cable is greater than the set radiation emission limit E0, lim If the relative error is less than 5%, the common mode current limit I 0lim =I0, if the radiated emission size E0 of the tested cable is equal to the set radiated emission limit E lim If the relative error is greater than or equal to 5%, the initial value of the current at the head end of the test cable is updated to I0+ΔI0, where ΔI0 is the optimized adjustment current, and the radiation emission size E0 of the test cable is recalculated with the set radiation emission limit E lim The relative error is until the radiation emission size E0 of the test cable is equal to the set radiation emission limit E lim The relative error is less than 5%.

4. A cable radiation emission exceeding standard detection method according to claim 3, characterized in that: Get the common mode current distribution along the cable, divide the cable into N segments, and regard each segment as a dipole. The radiation emission value of any segment of the cable can be calculated by the dipole radiation emission formula. The total radiation emission value is the superposition of N segments: Where: j is the imaginary number symbol, η is the free space wave impedance; θ is the azimuth angle; r i Represents the distance between the observation point and the i-th source point; I i is the current of the i-th cable section; l i is the length of the i-th cable segment, is the azimuth direction vector, For r i direction vector, k is the electromagnetic wave number.

5. A cable radiation emission exceeding standard detection method according to claim 4, characterized in that: The current ratio K between the beginning and the end of the cable should comply with: Where: I0 is the current at the beginning of the cable, I L is the current at the end of the cable, Γ L is the end reflection coefficient; β is the propagation constant.

6. A cable radiation emission exceeding standard detection method according to claim 5, characterized in that: Take N points on the cable (usually ensure that the number of points is less than 0.1 times the wavelength), and then according to the ratio of the amplitude of the current at any point along the line to the amplitude of the terminal current: From this, N sets of equations can be written out, and the residual value between measurement and calculation can be minimized through optimization algorithm to obtain the reflection coefficient Γ L and an estimate of the propagation constant β.

7. A cable radiation emission exceeding standard detection method according to claim 5, characterized in that: Let the angles of the test points in the spherical coordinate system be Therefore, the calculation formula for each component in the rectangular coordinate system is: Therefore, the vertically polarized radiated electric field E VP and the horizontally polarized radiated electric field E HP They are:

8. A cable radiation emission exceeding standard detection system, characterized in that: Including test module and detection module; The test module obtains the common mode current limit of the test cable according to the initial value of the current at the first end of the test cable according to the initial value of the current at the first end of the test cable; The detection module obtains the common-mode current at the head end of the test cable according to the experimental method. If the common-mode current at the head end of the test cable is greater than the common-mode current limit of the test cable, it means that the radiation emission of the test cable exceeds the standard; if the common-mode current at the head end of the test cable is less than or equal to the common-mode current limit of the test cable, it means that the radiation emission of the test cable meets the requirements.

9. A cable radiation emission exceeding standard detection system according to claim 8, characterized in that: Connect the two ends of the test cable to the disturbed measurement device and the auxiliary measurement device respectively, use a broadband current measurement clamp to cover the test cable, and use the broadband current measurement clamp to measure the common mode current at the beginning and end of the test cable respectively.

10. A cable radiation emission exceeding standard detection system according to claim 8, characterized in that: The specific process of setting the initial value of the current at the first end of the test cable and obtaining the common mode current limit of the test cable according to the initial value of the current at the first end of the test cable is as follows: Given the initial current value I0 at the head end of the test cable, calculate the current distribution along the test cable according to the initial current value I0 at the head end of the test cable, and calculate the radiation emission size E0 of the test cable under the initial current value I0 at the head end of the test cable based on the current distribution along the test cable. If the radiation emission size E0 of the test cable is greater than the set radiation emission limit E0, lim If the relative error is less than 5%, set the common mode current limit I 0lim This is the iterative current value I0. If the radiated emission size E0 of the test cable is consistent with the set radiated emission limit E lim If the relative error is greater than or equal to 5%, the initial value of the current at the head end of the test cable is updated to I0+△I0, where △I0 is the optimized adjustment current, and the radiation emission size E0 of the test cable is recalculated with the set radiation emission limit E lim The relative error is until the radiation emission size E0 of the test cable is equal to the set radiation emission limit E lim The relative error is less than 5%.

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