An engineering grade assessment method for power line conduction emission test results

Abstract

The application provides an engineering grade evaluation method for power line conducted emission test results. First, based on all equipment CE101 test data of an existing engineering, the data is normalized according to the electrical system and current, and is divided into corresponding grade intervals. In combination with electromagnetic characteristics of the engineering, a risk frequency band is divided. After comparing the CE101 data of the equipment to be evaluated with the grade intervals and the risk frequency band, the corresponding engineering evaluation grade is given. Therefore, the application is easy to understand, can objectively reflect the overall level of the evaluated object based on the actual engineering data results, has strong operability, high evaluation efficiency, and can be used to develop a software system for batch processing, and has strong practicality and engineering practicability.

Description

Technical Field

[0001] The present invention belongs to the technical field of electronic testing and electromagnetic compatibility, and in particular relates to an engineering grade evaluation method for power line conducted emission test results. Background Art

[0002] With the increasing number of electronic devices installed on various weapon platforms, electromagnetic interference (EMI) issues are becoming increasingly prominent. To reduce the risk of EMI on these platforms, model engineering generally adopts a three-level EMC control model: overall, system, and equipment. Each level requires various electromagnetic emission and sensitivity tests to verify compliance with predetermined EMC performance requirements. Among these numerous projects, power line conducted emissions (CE101) are among those that must be tested and evaluated.

[0003] Due to the limitations of electromagnetic compatibility standards, it's difficult to standardize electromagnetic compatibility testing requirements across platforms. This is especially true for electromagnetic emission testing. If strictly adhered to the standards, there's a chance of over-design or over-assessment. Currently, some model projects, including CE101, include electromagnetic emission as an evaluation item rather than an assessment item. Therefore, platform management units must conduct an assessment of electromagnetic emission.

[0004] In the past, when conducting EMC assessments, the overall unit first checked whether the system met the standard limits. If so, the assessment was passed directly, and the electromagnetic emission data was used as the stimulus for the platform's electromagnetic environment. If the standard limits were not met, the overall unit would evaluate the electromagnetic compatibility risks under the platform based on experience, simulation, or testing, and ultimately determine whether the risks were controllable. If the controllable requirements were met, the assessment was passed. Otherwise, rectification, retesting, and reassessment were required until the risks were controllable. The traditional evaluation method based on experience, simulation, or testing has problems such as difficulty in standardizing experience, large simulation uncertainties, and long test evaluation cycles. Therefore, engineering EMC assessments urgently need an objective, reasonable, highly operational, and efficient evaluation method. Summary of the Invention

[0005] To solve the above problems, the present invention provides an engineering grade assessment method for power line conducted emission test results. The basic data for the grade assessment is based on the electromagnetic compatibility test results of engineering equipment, which can objectively reflect the true level of the assessed equipment in the industry, and has strong operability and high assessment efficiency.

[0006] A method for evaluating the engineering grade of a power line conducted emission test result includes the following steps:

[0007] S1: Select the corresponding amplitude normalization method according to the power system used by the device to be evaluated;

[0008] S2: Normalize the amplitude sequence of the device to be evaluated at different frequencies using the selected amplitude normalization method;

[0009] S3: Extract the maximum amplitude from the amplitude sequence at different frequency points to obtain the maximum amplitude of the device to be evaluated at different frequency points;

[0010] S4: Select the corresponding risk margin based on whether the device to be evaluated operates in the risk frequency band, and use the difference between the maximum value of each amplitude and the risk margin as the evaluation data of the device to be evaluated at different frequency points;

[0011] S5: Determine the engineering level of the power cord conducted emission test results of the device under evaluation based on the level of the data under evaluation at each frequency point.

[0012] Furthermore, in step S1, the corresponding amplitude normalization method is selected according to the power system used by the device to be evaluated:

[0013] If the power system used by the device to be evaluated is 50Hz, the amplitude normalization method is as follows:

[0014] AMP norm =AMP-20log(I)

[0015] Among them, AMP is the amplitude sequence of the device to be evaluated at different frequencies. norm is the normalized amplitude sequence, I is the current of the device to be evaluated;

[0016] If the power system used by the device to be evaluated is DC, the amplitude normalization method is as follows:

[0017] AMP norm =AMP I≤3A

[0018] AMP norm =AMP-20log(I / 3) 3<I≤185A

[0019] AMP norm =AMP-35 I>185A

[0020] Here, A represents ampere.

[0021] Furthermore, the data to be evaluated is divided into levels one, two, three, and four from high to low. The level division method corresponding to any frequency point is:

[0022] Sort all amplitudes in the amplitude sequence at the current frequency point from low to high, and use the amplitude at the 10% position as the dividing point AMP between the first and second levels 12, the amplitude at the 20% position is used as the dividing point AMP between the second and third levels 23 , the amplitude at the 30% position is used as the dividing point AMP between level 3 and level 4 34 , the amplitude at the 40% position is used as the dividing point AMP4 of the fourth level;

[0023] Then, the amplitude range [0,AMP 12 ) corresponds to the first level, the amplitude range [AMP 12 ,AMP 23 ) corresponds to the second level, the amplitude range [AMP 23 ,AMP 34 ) corresponds to level three, amplitude range [AMP 34 , Spec max ) corresponds to level 4, among which Spec max Indicates the maximum amplitude in the amplitude sequence at the current frequency point.

[0024] Furthermore, the engineering grades of the power cord conducted emission test results of the equipment to be evaluated are divided into Grade A, Grade B, Grade C, and Grade D from best to worst, and Grade A is further divided into Grade A+ and Grade A- according to the excellent grade, Grade B is further divided into Grade B+ and Grade B- according to the excellent grade, Grade C is further divided into Grade C+ and Grade C- according to the excellent grade, and Grade D is further divided into Grade D+ and Grade D- according to the excellent grade; among them, Grade A, Grade B, Grade C, and Grade D are all Grade I, and Grade A+, Grade A-, Grade B+, Grade B-, Grade C+, Grade C-, Grade D+, and Grade D- are all Grade II.

[0025] The method for determining the engineering grade of the power line conducted emission test result of the device to be evaluated in step S5 is as follows:

[0026] Determine whether the device to be evaluated is operating in a risky frequency band. If the device to be evaluated is operating in a non-risky frequency band, perform operation 1. If the device to be evaluated is operating in a risky frequency band, perform operation 2.

[0027] The first operation is to obtain the number of data to be evaluated at each frequency point that belongs to level 1, level 2, level 3, and level 4, respectively. If any data to be evaluated at any frequency point belongs to level 4, the engineering grade of the power line conducted emission test result of the device to be evaluated is D+. If no data to be evaluated at any frequency point belongs to level 4, the first level with the largest number of data to be evaluated is used as the alternative level, and the second level with a good attribute in the first level one level above the alternative level is used as the engineering grade of the power line conducted emission test result of the device to be evaluated. If the first level with the largest number of data to be evaluated is level A, level A+ is used as the engineering grade of the power line conducted emission test result of the device to be evaluated.

[0028] The second operation is: obtaining the number of data to be evaluated at each frequency point that belongs to level 1, level 2, level 3, and level 4, respectively; wherein, if the data to be evaluated at any frequency point belongs to level 4, the engineering grade of the power line conducted emission test result of the device to be evaluated is D-; if no data to be evaluated at any frequency point belongs to level 4, the first level with the largest number of data to be evaluated is used as an alternative level, and the second level with an excellent attribute in the first level ranked one level below the alternative level is used as the engineering grade of the power line conducted emission test result of the device to be evaluated; wherein, if the first level with the largest number of data to be evaluated is level A, level A- is used as the engineering grade of the power line conducted emission test result of the device to be evaluated.

[0029] Furthermore, the risk frequency band of the equipment to be evaluated is determined based on the engineering electromagnetic characteristics, wherein the electromagnetic interference risk of the risk frequency band is greater than the electromagnetic interference risk of the non-risk frequency band.

[0030] Furthermore, 1k-10kHz is the risk band, and 25Hz-1kHz is the non-risk band.

[0031] Furthermore, in step S4, the risk margin corresponding to the risk band is in the range of 0-6 dB, and the risk margin corresponding to the non-risk band is in the range of 0-10 dB.

[0032] Beneficial effects:

[0033] 1. The present invention provides an engineering grade assessment method for power line conducted emission test results. First, based on the CE101 test data of all equipment in an existing project, the data is normalized according to the electrical system and current, and then divided into corresponding grade intervals. In combination with the electromagnetic characteristics of the project, risk frequency bands are divided. The CE101 data of the equipment to be assessed is compared with the grade intervals and risk frequency bands to assign a corresponding engineering assessment grade. Therefore, the present invention is easy to understand, based on actual engineering data results, can objectively reflect the overall level of the assessed object, and has strong operability and high assessment efficiency. The present invention can be used to develop a software system for batch processing, and has strong practicality and engineering applicability.

[0034] 2. The present invention provides an engineering grade assessment method for power line conducted emission test results. Since the basic engineering data has been statistically processed in advance, after setting some basic data, software or other tools can be used to quickly carry out the assessment, and the grade assessment time generally does not exceed 1 hour. In addition, the present invention can also use the software batch processing function to realize batch assessment, which can greatly improve the efficiency of electromagnetic compatibility assessment of engineering equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a flow chart of the engineering grade assessment method for power line conducted emission test results provided by the present invention. DETAILED DESCRIPTION

[0036] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application.

[0037] To meet the needs of evaluating engineering CE101 assessment items, the present invention provides an engineering grade assessment method based on power line conducted emission (CE101) test results. Based on the CE101 test data of all equipment in existing projects, the data is normalized according to the power system and current, and then divided into corresponding grade intervals. Combined with the electromagnetic characteristics of the project, the risk frequency bands are divided. The CE101 data of the equipment to be evaluated is compared with the grade intervals and risk frequency bands to give the corresponding engineering assessment grade.

[0038] Specifically, such as Figure 1 As shown, a method for evaluating the engineering grade of power line conducted emission test results includes the following steps:

[0039] S1: Select the corresponding amplitude normalization method according to the power system used by the device to be evaluated;

[0040] It should be noted that the code for power line conducted emissions is CE101. The basic data of CE101 includes: spectrum data Spec (including a two-dimensional array of frequencies f (for example, a total of 376 frequency points, including 196 frequency points at 5Hz intervals from 25Hz to 1kHz and 180 frequency points at 50Hz intervals from 1kHz to 10kHz) and amplitude A), power system ES (generally including DC and 50Hz), voltage (220V, 380V, 900V, etc.), and current I (in amperes). Voltage is not considered during processing; only the power system is processed separately. Amplitude data is normalized according to different power systems using the following formula to obtain AMPnorm. If a device has multiple CE101 data points, the maximum amplitude corresponding to the frequency under that power system is retained.

[0041] Based on this, if the power system used by the device to be evaluated is 50Hz, the amplitude normalization method selected is as follows:

[0042] AMP norm =AMP-20log(I)

[0043] Among them, AMP is the amplitude sequence of the device to be evaluated at different frequencies. norm is the normalized amplitude sequence, I is the current of the device to be evaluated;

[0044] If the power system used by the device to be evaluated is DC, the amplitude normalization method is as follows:

[0045] AMPnorm =AMP I≤3A

[0046] AMP norm =AMP-20log(I / 3) 3<I≤185A

[0047] AMP norm =AMP-35 I>185A

[0048] Here, A represents ampere.

[0049] S2: Normalize the amplitude sequence of the device to be evaluated at different frequencies using the selected amplitude normalization method;

[0050] For example, if a device has CE101 data, a 50Hz power supply, and a 10A current, all corresponding amplitude data should be subtracted by 20, as shown in Tables 1 and 2. Because there is only one CE101 data point, the normalized data is the maximum data under the device's power supply (50Hz).

[0051] Table 1 Original spectrum data

[0052] f(Hz) A (dBμA) 25 70.64 30 62.85 35 68.61 40 78.35 45 120.00 50 140.00 ... ... 10000 66.09

[0053] Table 2 Normalized spectrum data

[0054] f(Hz) A (dBμA) 25 50.64 30 42.85 35 48.61 40 58.35 45 100.00 50 120.00 ... ... 10000 46.09

[0055] S3: Extract the maximum amplitude from the amplitude sequence at different frequency points to obtain the maximum amplitude of the device to be evaluated at different frequency points;

[0056] After all CE101 data from all devices are normalized using the selected amplitude normalization method, a data table is formed showing the frequencies and multiple amplitudes. The amplitudes are then sorted in ascending order at each frequency point, as shown in Tables 3 and 4.

[0057] Table 3 Data table before sorting

[0058] f(Hz) A1 A2 A3 A4 A5 ... AN 25 51 60 32 44 56 ... 90 30 43 55 42 58 68 ... 78 35 49 57 36 51 50 ... 34 40 58 93 59 53 82 ... 74 45 100 62 67 46 57 ... 58 50 120 81 74 60 79 ... 37 ... ... ... ... ... ... ... ... 10000 46 90 58 99 96 ... 96

[0059] Table 4 Sorted data table

[0060] f(Hz) 1 2 3 4 5 N 25 32 44 51 56 60 ... 90 30 42 43 55 58 68 ... 78 35 34 36 49 50 51 ... 57 40 53 58 59 74 82 ... 93 45 46 57 58 62 67 ... 100 50 37 60 74 79 81 ... 120 ... ... ... ... ... ... ... ... 10000 46 58 90 96 97 ... 99

[0061] S4: Select the corresponding risk margin based on whether the device to be evaluated operates in the risk frequency band, and use the difference between the maximum value of each amplitude and the risk margin as the evaluation data of the device to be evaluated at different frequency points;

[0062] Optionally, the risk frequency band of the equipment to be evaluated is determined based on the engineering electromagnetic characteristics, such as 1k-10kHz as the risk frequency band, and 25Hz-1kHz as the non-risk frequency band, where the electromagnetic interference risk of the risk frequency band is greater than that of the non-risk frequency band. Based on this, the risk margin corresponding to the risk frequency band has a value range of 0-6dB (generally set to 3dB), and the frequency band is strongly constrained, and the margin sum mode is executed, and the lower limit of the level is taken; at the same time, the risk margin corresponding to the non-risk frequency band has a value range of 0-10dB (generally set to 6dB), and the frequency band is weakly constrained, and the margin difference mode is executed, and the upper limit of the level is taken.

[0063] S5: Determine the engineering level of the power cord conducted emission test results of the device under evaluation based on the level of the data under evaluation at each frequency point.

[0064] Furthermore, the data to be evaluated is divided into levels one, two, three, and four from high to low. The level division method corresponding to any frequency point is:

[0065] Sort all amplitudes in the amplitude sequence at the current frequency point from low to high, and use the amplitude at the 10% position as the dividing point AMP between the first and second levels 12 , the amplitude at the 20% position is used as the dividing point AMP between the second and third levels 23 , the amplitude at the 30% position is used as the dividing point AMP between level 3 and level 4 34 , the amplitude at the 40% position is used as the dividing point AMP4 of the fourth level; it should be noted that the smaller the amplitude of the electromagnetic signal at each frequency point, the better, and the larger the amplitude, the lower the score;

[0066] Then, the amplitude range [0,AMP 12 ) corresponds to the first level, the amplitude range [AMP 12 ,AMP 23 ) corresponds to the second level, the amplitude range [AMP 23 ,AMP 34 ) corresponds to level three, amplitude range [AMP 34 , Spec max ) corresponds to level 4, among which Spec max Indicates the maximum amplitude in the amplitude sequence at the current frequency point.

[0067] For example, for each frequency point, the amplitude data of the first 10% (level 1), 20% (level 2), 30% (level 3), and 40% (level 4) are taken respectively. That is, if there are 100 data, the amplitudes corresponding to the 10th, 20th, 30th, and 40th positions are taken respectively (in dB) to obtain the level interval data table, as shown in Table 5.

[0068] Table 3 Grade interval table

[0069] f(Hz) 10% (Level 1) 20% (secondary) 30% (Level 3) 40% (Level 4) 25 32 38 42 66 30 42 45 50 60 35 34 48 55 65 40 53 55 65 75 45 46 50 58 66 50 37 44 64 80 ... ... ... ... ... 10000 46 51 60 80

[0070] The engineering grades of the power cord conducted emission test results of the equipment to be evaluated are divided into Class A, Class B, Class C, and Class D from best to worst. Class A is further divided into Class A+ and Class A- according to the excellent level, Class B is further divided into Class B+ and Class B- according to the excellent level, Class C is further divided into Class C+ and Class C- according to the excellent level, and Class D is further divided into Class D+ and Class D- according to the excellent level. Among them, Class A, Class B, Class C, and Class D are all Class I, and Class A+, Class A-, Class B+, Class B-, Class C+, Class C-, Class D+, and Class D- are all Class II.

[0071] The method for determining the engineering grade of the power line conducted emission test result of the device to be evaluated in step S5 is as follows:

[0072] Determine whether the device to be evaluated is operating in a risky frequency band. If the device to be evaluated is operating in a non-risky frequency band, perform operation 1. If the device to be evaluated is operating in a risky frequency band, perform operation 2.

[0073] The first operation is to obtain the number of data to be evaluated at each frequency point that belongs to level 1, level 2, level 3, and level 4, respectively. If any data to be evaluated at any frequency point belongs to level 4, the engineering grade of the power line conducted emission test result of the device to be evaluated is D+. If no data to be evaluated at any frequency point belongs to level 4, the first level with the largest number of data to be evaluated is used as the alternative level, and the second level with a good attribute in the first level one level above the alternative level is used as the engineering grade of the power line conducted emission test result of the device to be evaluated. If the first level with the largest number of data to be evaluated is level A, level A+ is used as the engineering grade of the power line conducted emission test result of the device to be evaluated.

[0074] The second operation is: obtaining the number of data to be evaluated at each frequency point that belongs to level 1, level 2, level 3, and level 4, respectively; wherein, if the data to be evaluated at any frequency point belongs to level 4, the engineering grade of the power line conducted emission test result of the device to be evaluated is D-; if no data to be evaluated at any frequency point belongs to level 4, the first level with the largest number of data to be evaluated is used as an alternative level, and the second level with an excellent attribute in the first level ranked one level below the alternative level is used as the engineering grade of the power line conducted emission test result of the device to be evaluated; wherein, if the first level with the largest number of data to be evaluated is level A, level A- is used as the engineering grade of the power line conducted emission test result of the device to be evaluated.

[0075] For example, in the 1kHz-10kHz frequency band, for a device CE101 to be evaluated, after executing steps S1 to S5, only one frequency point is in the fourth-level interval [30%-40%], while the others are in the third-level interval [20%-30%]. Furthermore, 1kHz-10kHz is a risky frequency band, so CE101 is evaluated as D-.

[0076] For example, in the 25Hz-1kHz frequency band, 10 frequency points of the device under evaluation, CE101, fall within the third-level interval (20%-30%), while the rest fall within the second-level interval (10-20%). Since 25Hz-1kHz is a non-risk band with a margin of 6dB, the amplitudes corresponding to the 10 frequency points, after subtracting 6dB, fall within the second-level interval (10%-20%). The second-level interval (10%-20%) has the most frequency points, and the previous level of the second-level interval corresponding to the second-level interval is A. Therefore, the evaluation score for CE101 of the device under evaluation is A-.

[0077] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art may of course make various corresponding changes and modifications based on the present invention, but these corresponding changes and modifications should all fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for evaluating the engineering grade of power line conducted emission test results, characterized in that: The following steps are involved: S1: Select the corresponding amplitude normalization method according to the power system used by the device to be evaluated; S2: Normalize the amplitude sequence of the device to be evaluated at different frequencies using the selected amplitude normalization method; S3: Extract the maximum amplitude from the amplitude sequence at different frequency points to obtain the maximum amplitude of the device to be evaluated at different frequency points; S4: Select the corresponding risk margin based on whether the device to be evaluated operates in the risk frequency band, and use the difference between the maximum value of each amplitude and the risk margin as the evaluation data of the device to be evaluated at different frequency points; S5: Determine the engineering level of the power cord conducted emission test results of the device under evaluation based on the level of the data under evaluation at each frequency point.

2. The engineering grade evaluation method for power line conducted emission test results according to claim 1, characterized in that: In step S1, the corresponding amplitude normalization method is selected according to the power system used by the device to be evaluated: If the power system used by the device to be evaluated is 50Hz, the amplitude normalization method is as follows: AMP norm =AMP-20log(I) Among them, AMP is the amplitude sequence of the device to be evaluated at different frequencies. norm is the normalized amplitude sequence, I is the current of the device to be evaluated; If the power system used by the device to be evaluated is DC, the amplitude normalization method is as follows: AMP norm =AMP I≤3A AMP norm =AMP-20log(I / 3) 3<I≤185A AMP norm =AMP-35 I>185A Here, A represents ampere.

3. The engineering grade evaluation method for power line conducted emission test results according to claim 1, characterized in that: The data to be evaluated is divided into levels 1, 2, 3, and 4 from high to low. The level division method for any frequency point is as follows: Sort all amplitudes in the amplitude sequence at the current frequency point from low to high, and use the amplitude at the 10% position as the dividing point AMP between the first and second levels 12 , the amplitude at the 20% position is used as the dividing point AMP between the second and third levels 23 , the amplitude at the 30% position is used as the dividing point AMP between level 3 and level 4 34 , the amplitude at the 40% position is used as the dividing point AMP4 of the fourth level; Then, the amplitude range [0,AMP 12 ) corresponds to the first level, the amplitude range [AMP 12 ,AMP 23 ) corresponds to the second level, the amplitude range [AMP 23 ,AMP 34 ) corresponds to level three, amplitude range [AMP 34 , Spec max ) corresponds to level 4, among which Spec max Indicates the maximum amplitude in the amplitude sequence at the current frequency point.

4. The engineering grade evaluation method for power line conducted emission test results according to claim 3, wherein: The engineering grades of the power cord conducted emission test results of the equipment to be evaluated are divided into Class A, Class B, Class C, and Class D from best to worst. Class A is further divided into Class A+ and Class A- according to the excellent level, Class B is further divided into Class B+ and Class B- according to the excellent level, Class C is further divided into Class C+ and Class C- according to the excellent level, and Class D is further divided into Class D+ and Class D- according to the excellent level. Among them, Class A, Class B, Class C, and Class D are all Class I, and Class A+, Class A-, Class B+, Class B-, Class C+, Class C-, Class D+, and Class D- are all Class II. The method for determining the engineering grade of the power line conducted emission test result of the device to be evaluated in step S5 is as follows: Determine whether the device to be evaluated is operating in a risky frequency band. If the device to be evaluated is operating in a non-risky frequency band, perform operation 1. If the device to be evaluated is operating in a risky frequency band, perform operation 2. The first operation is to obtain the number of data to be evaluated at each frequency point that belongs to level 1, level 2, level 3, and level 4, respectively. If any data to be evaluated at any frequency point belongs to level 4, the engineering grade of the power line conducted emission test result of the device to be evaluated is D+. If no data to be evaluated at any frequency point belongs to level 4, the first level with the largest number of data to be evaluated is used as the alternative level, and the second level with a good attribute in the first level one level above the alternative level is used as the engineering grade of the power line conducted emission test result of the device to be evaluated. If the first level with the largest number of data to be evaluated is level A, level A+ is used as the engineering grade of the power line conducted emission test result of the device to be evaluated. The second operation is: obtaining the number of data to be evaluated at each frequency point that belongs to level 1, level 2, level 3, and level 4, respectively; wherein, if the data to be evaluated at any frequency point belongs to level 4, the engineering grade of the power line conducted emission test result of the device to be evaluated is D-; if no data to be evaluated at any frequency point belongs to level 4, the first level with the largest number of data to be evaluated is used as an alternative level, and the second level with an excellent attribute in the first level ranked one level below the alternative level is used as the engineering grade of the power line conducted emission test result of the device to be evaluated; wherein, if the first level with the largest number of data to be evaluated is level A, level A- is used as the engineering grade of the power line conducted emission test result of the device to be evaluated.

5. The engineering grade evaluation method for power line conducted emission test results according to claim 1, characterized in that: The risk frequency band of the equipment to be evaluated is determined based on the engineering electromagnetic characteristics, where the electromagnetic interference risk of the risk frequency band is greater than the electromagnetic interference risk of the non-risk frequency band.

6. The engineering grade evaluation method for power line conducted emission test results according to claim 5, characterized in that: 1k-10kHz is the risky frequency band, and 25Hz-1kHz is the non-risky frequency band.

7. The engineering grade evaluation method for power line conducted emission test results according to claim 1, characterized in that: In step S4, the risk margin corresponding to the risk band is in the range of 0-6 dB, while the risk margin corresponding to the non-risk band is in the range of 0-10 dB.

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