Electromagnetic compatibility conduction immunity calibration system and calibration method

Abstract

The invention relates to the technical field of electromagnetic compatibility conducted immunity testing, and discloses an electromagnetic compatibility conducted immunity calibration system and method, and the system comprises a signal generation module, a coupling and decoupling network adaptive assembly system, a calibration load access system, an auxiliary equipment terminating system, and a grounding protection system. The method can adapt to different types of coupling and decoupling networks, normalizes the calibration process, reduces the calibration uncertainty, and reduces the introduced uncertainty by 17.9% compared with a conventional method. The invention further discloses an automatic calibration method, the calibration process of conduction immunity is optimized, the initial level can be set through an algorithm, the target level addressing time can be reduced, the calibration time can be shortened, the effective detection time proportion can be improved, and various parameters of an actually measured product are embedded in all links of the calibration process, so that the calibration accuracy is improved. The device can better simulate the testing process of an actually measured product, and improves the calibration accuracy and applicability.

Description

Technical Field

[0001] The present invention relates to the technical field of electromagnetic compatibility conducted immunity testing, and in particular to an electromagnetic compatibility conducted immunity calibration system and calibration method. Background Art

[0002] Conducted immunity testing is an important electromagnetic compatibility test item, widely used in various fields such as multimedia equipment, medical equipment, rail transportation, new energy vehicles, and robots. This test is the mainstream test item for power line immunity testing in the electromagnetic compatibility testing field of various industries, and plays a decisive role in the power line immunity performance of related products.

[0003] Electromagnetic compatibility laboratories often need to invest a lot of time and costs when performing conducted immunity calibration. The calibration system has poor stability and repeatability, the calibration time is long, and the personnel experience requirements are also very high. However, the accuracy is generally not high, which introduces large uncertainties into the conducted immunity test, and there is room for improvement in efficiency and accuracy. Summary of the Invention

[0004] The purpose of the present invention is to solve the deficiencies in the prior art and to provide an electromagnetic compatibility conducted immunity calibration system and method thereof.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] An electromagnetic compatibility conducted immunity calibration system includes a signal generation module, a coupling and decoupling network adaptive assembly system, a calibration load path system, and an auxiliary equipment termination system;

[0007] A signal generating module is connected to the coupling-decoupling network adaptive assembly system and is used to generate a calibrated radio frequency signal to the coupling-decoupling network adaptive assembly system;

[0008] The coupling and decoupling network adaptive assembly system is respectively connected to the calibration load path system and the auxiliary equipment termination system, couples the radio frequency signal in common mode to the calibration load path system, and performs radio frequency shielding and decoupling on the auxiliary equipment termination system;

[0009] Calibration load path system, used to simulate test samples, complete impedance matching and obtain calibrated RF power;

[0010] Auxiliary equipment termination system is used to simulate the auxiliary equipment environment of the product during testing.

[0011] As a further preferred solution, the signal generation module includes a radio frequency signal source, a power amplifier, an attenuator, a radio frequency switch, and a network analyzer; the radio frequency signal source, the power amplifier, the attenuator, and the radio frequency switch are sequentially connected in circuit; the radio frequency switch is further connected in circuit to the network analyzer and the coupling and decoupling network adaptive assembly system;

[0012] The coupling and decoupling network adaptive assembly system includes a coupling and decoupling network, the coupling and decoupling network can be replaced with an applicable model according to the test product, and the coupling and decoupling network is connected to a radio frequency switch circuit;

[0013] The calibration load path system includes a common-mode port merging device, an impedance converter, a radio frequency switch, a power meter, an adaptive matching load, and a network analyzer. The common-mode port merging device, the impedance converter, and the radio frequency switch are sequentially connected in circuit. The radio frequency switch is further connected to the probes of the network analyzer and the power meter through a circuit. The adaptive matching load is located on the probe.

[0014] The power meter probe measures and records the RF power during the calibration process, and the adaptive matching load matches the RF impedance during the calibration process.

[0015] The auxiliary equipment termination system includes a common mode port merging device 2, an impedance converter 2, a radio frequency switch 3, and a load impedance which are connected in sequence. The radio frequency switch 3 opens and closes the connection between the impedance converter 2 and the load impedance.

[0016] As a further preferred solution, the calibration system also includes a grounding protection system, which includes a metal grounding plate. The coupling and decoupling network adaptive assembly system, the calibration load path system, and the auxiliary equipment termination system are all located on the metal grounding plate; a digital multimeter is arranged on the metal grounding plate, and the probes of the digital multimeter are respectively connected to the ground and the casing of the coupling and decoupling network.

[0017] A calibration method for an electromagnetic compatibility conducted immunity calibration system comprises the following steps:

[0018] Step 1: According to the actual test target voltage, select the same calibration target voltage U0, frequency change step k, k ≤ 1%, calibration starting frequency f min and calibration stop frequency f max , set the current calibration frequency f=f min ; Select the matching coupling and decoupling network according to the actual test product power line type, i.e. CDN-M1~M5;

[0019] Step 2: Calculate the initial level setting value U of the corresponding RF signal source S0 , set the frequency of the RF signal source to f and the level to U S=U S0 ;

[0020] Step 3: Connect the RF output port of the RF signal source to the RF input port of the power amplifier, and the RF output port of the power amplifier to the input port of the attenuator. Switch RF switch 1 to connect to network analyzer 1 and test the standing wave ratio of the attenuator output port. If the standing wave ratio is less than 2dB, proceed to step 4.

[0021] Step 4: Determine the electrical parameters of the power cord of the actual test product: resistance R pl , inductance L pl , capacitor C pl , determine the electrical parameters of the output port of the coupling and decoupling network that matches the actual test product type: resistance R 201 , inductance L 201 , capacitor C 201 , through the formula:

[0022]

[0023] Calculate the RF impedance of the calibration output port, switch RF switch 1 to connect to the coupling-decoupling network, switch RF switch 2 to connect to network analyzer 2, and measure the RF impedance corresponding to frequency f at the output port of impedance converter 1. If the deviation from the RF impedance of the calibration output port is less than 20%, complete automatic impedance matching through the subsequent adaptive matching load and proceed to step 5.

[0024] Step 5: Switch the RF switch 2 to connect the probe, connect the output port of the common-mode port merging device 2 to the input port of the RF switch 3 through the impedance converter 2, connect the RF switch 3 to the load impedance to achieve the RF performance of the simulated power supply, and then use the power meter probe test to obtain the first level value U1;

[0025] Step 6: If the first level value U1 meets the Scope requirements, continue to step seven;

[0026] Step 7: Disconnect RF switch 3 from the load impedance and use the power meter probe to measure the second level value U2; if |U1-U2|≤1.6dB, select the larger value between U1 and U2 as the test level U, and record the corresponding calibration frequency f, test level U, calibration target voltage U0, signal source level U S And continue with step eight;

[0027] Step 8: Adjust the calibration frequency f to f×(1+k) and check whether the adjustment result is ≤f max If yes, repeat steps 2 to 7; if no, end the calibration task;

[0028] Step 9: Derive the calibration frequency f, test level U, calibration target voltage U0, signal source level U for all calibration frequency points S This forms the calibration database.

[0029] As a further preferred solution, before step 1, measure the resistance between the metal casing of the coupling-decoupling network and the grounding point using a digital multimeter. If it is ≤4Ω, proceed to step 2. If it is >4Ω, check the grounding protection system until it meets the requirements and proceed to step 1.

[0030] In step 3, if the standing wave ratio is ≥ 2dB, shut down the system and check whether the connections of each port of the signal generation module are normal, and repeat step 2;

[0031] In step 4, if the deviation exceeds 20%, shut down the system and check the RF connection between the signal generation system, coupling and decoupling network, common mode port merging device and impedance converter, and then repeat step 4 until the requirements are met;

[0032] In step 6, if the first level value U1 does not meet the If the range is greater than the requirement, then the signal source level U S Lower the level by 1.5dB and repeat step 5. If it is less than the required range, increase the signal source level to S Increase the setting by 1.5dB and repeat step 5 until the result meets the range requirement.

[0033] In step 7, if |U1-U2|>1.6dB, it means that the decoupling function of the coupling-decoupling network has degraded, and it is necessary to terminate the calibration and check the coupling-decoupling network.

[0034] As a further preferred solution, the calibration parameters and arrangement need to be adjusted according to the performance parameters of the test product. During the calibration process, the power line phase type, including single-phase single-wire, single-phase two-wire, single-phase three-wire, three-phase four-wire, three-phase five-wire, power line shielding type, including shielded wire and unshielded wire, and power line electrical parameters, including resistance, inductance, and capacitance, are respectively measured to optimize the calibration process, so as to more accurately simulate the actual test scenario and improve the accuracy of the calibration results.

[0035] If it is an unshielded cable, the calibration load path system is in an unshielded state during the calibration process. If it is a shielded cable, the calibration load path system needs to be covered with a metal shielding mesh and connected to the metal shell of the coupling and decoupling network and the metal grounding plate during the calibration process. The power meter and network analyzer are outside the metal shielding mesh and connected to the metal shielding mesh cover through shielded cables. To avoid short circuit, a thin layer of shielding material is added between the calibration load path system and the metal shielding mesh cover.

[0036] As a further preferred solution, in step 2, the initial level setting value of the RF signal source is:

[0037]

[0038] Among them, U s0 is the initial level setting value of the RF signal source, U0 is the calibration target voltage, G A is the voltage gain of the power amplifier, T is the voltage attenuation factor of the attenuator, R 103 is the output impedance of the attenuator, R 201 is the common-mode impedance of the coupling-decoupling network, R 302 is the conversion resistance of impedance converter 1, R 306 is the resistance value of the adaptive matching load.

[0039] Beneficial effects: The electromagnetic compatibility conducted immunity calibration system and calibration method disclosed in the present invention optimize the calibration process of conducted immunity. The initial level can be set by an algorithm, the target level addressing time can be reduced, the calibration time can be reduced, and the effective detection time ratio can be increased. By embedding various parameters of the measured product in each link of the calibration process, the measured product testing process can be better simulated, the calibration accuracy and applicability can be improved, and the calibration uncertainty can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Schematic diagram of the connection structure of the components of the calibration system of the present invention;

[0041] Figure 2 is a flow chart of the calibration method of the present invention;

[0042] Figure 3 is a circuit equivalent diagram of the present invention;

[0043] In the figure: 101, RF signal source; 102, power amplifier; 103, attenuator; 104, RF switch 1; 105, network analyzer 1; 201, coupling and decoupling network; 301, common-mode port merging device 1; 302, impedance converter 1; 303, RF switch 2; 304, probe; 305, power meter; 306, adaptive matching load; 307, network analyzer 2; 401, common-mode port merging device 2; 402, impedance converter 2; 403, RF switch 3; 404, load impedance; 5, grounding protection system; 501, grounding bolt; 502, insulated moving handle; 503, grounding copper tape; 504, digital multimeter; 505, metal grounding plate. DETAILED DESCRIPTION

[0044] The technical solutions 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, rather than all the embodiments.

[0045] like Figure 1 As shown, an electromagnetic compatibility conducted immunity calibration system of the present invention includes a signal generation module, a coupling and decoupling network adaptive assembly system, a calibration load path system, and an auxiliary equipment termination system.

[0046] A signal generating module is connected to the coupling and decoupling network adaptive assembly system, and is used to generate a calibrated radio frequency signal to the coupling and decoupling network adaptive assembly system, and is used to generate a radio frequency power signal and ensure that the standing wave ratio at the signal end meets the requirements;

[0047] The signal generation module includes a radio frequency signal source 101, a power amplifier 102, an attenuator 103, a radio frequency switch 104, and a network analyzer 105; the radio frequency signal source 101, the power amplifier 102, the attenuator 103, and the radio frequency switch 104 are connected in sequence; the radio frequency switch 104 also selects a circuit to the network analyzer 105 and the coupling and decoupling network adaptive assembly system.

[0048] When the RF switch 104 is connected to the network analyzer 105 , it is used to monitor the standing wave ratio of the RF signal output port; when the RF switch 104 is connected to the coupling and decoupling network 201 , it is used to output the RF signal.

[0049] The sweep frequency range of the RF signal source 101 is 150kHz-80MHz (this frequency range is the frequency range of the conducted immunity test item. Under normal circumstances, the frequency range of the RF signal source 101 and the network analyzer exceeds this frequency band, but generally only this frequency band needs to be calibrated according to the test requirements). The input port of the network analyzer 105 needs to pay attention to the RF energy and add an attenuator.

[0050] The network analyzer 105 can provide standing wave warning. The existence of RF standing waves can cause a large capacity loss in the RF line and lead to impedance mismatch. The standing wave ratio test formula is as follows: Represents the ratio of the maximum voltage to the minimum voltage in the system circuit. In this solution, the standing wave ratio is required to be less than 2.

[0051] The working principle of the signal generation module is to transmit a stable signal source with stable and controllable impedance and standing wave ratio that meets the requirements through the combination of RF components, so as to provide a guarantee for the stable transmission of RF energy to the RF input end of the coupling and decoupling network.

[0052] The coupling and decoupling network adaptive assembly system is connected to the calibration load path system and the auxiliary equipment termination system respectively, couples the RF signal in common mode to the calibration load path system, and performs RF shielding and decoupling on the auxiliary equipment termination system, ensuring that the RF path only passes through the load end and does not leak to the auxiliary equipment end;

[0053] The coupling and decoupling network adaptive assembly system includes a coupling and decoupling network 201, a 90° metal grounding fixture, and an M8 fixing screw. The coupling and decoupling network 201 can be replaced according to the test product, that is, the type of coupling and decoupling network 201 (M1 to M5) can be replaced according to the test power line type. The coupling and decoupling network 201 is connected to the RF switch 104 circuit. The electrical parameters of the coupling and decoupling network 201 are generally different from those of the test product. In subsequent formula calculations, the two are added together to simulate the RF impedance during the actual test environment. Therefore, a judgment criterion is set: if the corresponding RF impedance of the output port of the impedance converter 302 deviates by no more than 20% from the RF impedance during the actual test environment, it is considered that the actual test environment can be simulated, the requirements are met, and the next step can be continued.

[0054] The 90° metal grounding fixture is an L-shaped structure, with its vertical side clamped to the side of the coupling and decoupling network 201 and its horizontal side fixed to the metal grounding plate 505 via M8 fixing screws;

[0055] To strengthen grounding requirements, increase grounding area, improve conductivity, and reduce grounding impedance, copper screws and nuts are required. The contact surfaces of the screws and nuts need to be polished smooth to increase the contact area. The tightening torque is 7N.m to 10N.m.

[0056] The housing of the coupling and decoupling network 201 forms a reference ground for the common-mode path through various grounding methods. The coupling and decoupling network 201 includes (CDN-Mx, x=1-5), where x represents the total number of testable phase lines, neutral lines, and protective earth lines. For example, M3 can be used to test single-phase three-wire products with protective earth.

[0057] Specifically, the calibration parameters and layout need to be adjusted according to the performance parameters of the test product. During the calibration process, the power line phase types M1-M5 (single-phase single-wire, single-phase two-wire, single-phase three-wire, three-phase four-wire, three-phase five-wire), power line shielding type (shielded wire, unshielded wire), and power line electrical parameters (resistance, inductance, capacitance) are respectively adjusted to more accurately simulate the actual test scenario and improve the accuracy of the calibration results.

[0058] If it is an unshielded line, during the calibration process, the calibration load path system is in an unshielded state; if it is a shielded line, during the calibration process, the calibration load path system needs to be covered with a metal shielding mesh and connected to the metal shell of the coupling decoupling network 201 and the metal grounding plate 505. The power meter 305 and the network analyzer 307 are outside the metal shielding mesh and connected to the metal shielding mesh cover through the shielded line. To avoid short circuit, a thin layer of shielding material is added between the calibration load path system and the metal shielding mesh cover.

[0059] Specifically, the impedance design of the common-mode path of the coupling-decoupling network 201 allows for adaptability to different power line specifications, thereby connecting to the common-mode port merging device 301. For CDN-Mx, where x = 1-5, the resistance of each power line is designed to be R = 100*x, ensuring a bus-to-ground impedance of 100Ω in common mode. Due to the influence of parasitic inductance and capacitance, achieving a completely ideal impedance across the entire test frequency band of 0.15-80MHz is difficult; a generally feasible design target is 100Ω ± 20Ω.

[0060] The calibration load path system is used to simulate the ideal test sample, complete the impedance matching function to obtain the calibrated RF power. The working principle of the calibration load path system 3 is to complete the impedance matching function, so that the calibrated RF power can be obtained according to the calibrated load path system. Figure 3 Derived the initial level calculation of the signal source, see the derivation process of formula 1 below for details;

[0061] The calibration load path system includes a common-mode port merging device 1 301, an impedance converter 1 302, a radio frequency switch 2 303, a power meter 305, an adaptive matching load 306, and a network analyzer 2 307. The common-mode port merging device 1 301, the impedance converter 1 302, and the radio frequency switch 2 303 are sequentially connected in circuits. The radio frequency switch 2 303 is further connected to a probe 304 of the network analyzer 2 307 and the power meter 305 through a circuit. The adaptive matching load 306 is located on the probe 304.

[0062] Common-mode port merging device 301 is a device that merges different phase lines into a single phase line. To adapt to different coupling and decoupling networks, different common-mode port merging devices 301 are used for M1-M5 to adapt to the same specifications of impedance converters 302. When the RF switch 303 is switched, it connects to the network analyzer 307 for impedance testing; when it switches to the probe 304, it uses the calibration load path for calibration;

[0063] The probe 304 of the power meter 305 measures and records the radio frequency power during the calibration process, and the adaptive matching load 306 matches the radio frequency impedance during the calibration process.

[0064] The auxiliary equipment termination system is used to simulate the auxiliary equipment environment of the product during testing. Its working principle is to simulate the auxiliary equipment environment of the product during testing. The general requirement is that the impact of the auxiliary equipment terminal on the results should not exceed 1.6dB. In the present invention, two working conditions, no-load and loaded, are tested using the RF switch 403 to complete the verification task of whether the impact of the auxiliary equipment terminal is controllable;

[0065] The auxiliary equipment termination system includes a common-mode port merging device 2 401, an impedance converter 2 402, an RF switch 3 403, and a load impedance 404 connected in sequence. The common-mode port merging device 2 401 realizes the common-mode merging function of the auxiliary equipment end RF path of the coupling decoupling network 201, and the impedance converter 2 402 realizes impedance matching. A feasible embodiment is a 150-50Ω converter. The RF switch 3 403 opens and closes the connection between the impedance converter 2 402 and the load impedance 404.

[0066] The calibration system also includes a grounding protection system for strengthening the grounding of the calibration system and monitoring leakage current. The grounding protection system includes a metal grounding plate 505. The coupling and decoupling network adaptive assembly system, the calibration load path system, and the auxiliary equipment termination system are all located on the metal grounding plate 505.

[0067] A digital multimeter 504 is placed on the metal grounding plate 505. The probes of the digital multimeter 504 are connected to the ground and the housing of the coupling and decoupling network 201. In the present invention, when the impedance exceeds 0.5 ohms, it indicates that the grounding effect is not ideal and calibration is stopped.

[0068] The metal grounding plate 505 is also provided with a grounding bolt 501 for fixing to the ground, an insulating movable handle 502 for changing the placement area, and a grounding copper tape 503 for connecting to the ground.

[0069] During the calibration process, the leakage current is monitored by a digital multimeter 504. The entire calibration system is protected by an insulating acrylic shell (not shown in the structure diagram) to ensure the stability and safety of the calibration system.

[0070] A calibration method for an electromagnetic compatibility conducted immunity calibration system can be used to control the entire process through test software to achieve efficient automatic calibration tasks. During the entire conducted immunity automatic calibration process, the power meter, network analyzer, and signal source are frequency synchronized. The automatic calibration method includes the following steps:

[0071] Before step 1, measure the resistance between the metal casing of the coupling-decoupling network 201 and the ground point using a digital multimeter 504. If the resistance is ≤4Ω, proceed to step 2. If the resistance is >4Ω, check the grounding protection system until it meets the requirements, then proceed to step 1.

[0072] Step 1: According to the actual test target voltage, select the same calibration target voltage U0, the frequency change step k (the calibration process cannot traverse all frequency points, so it is completed through selected frequency points, and the frequency of the next point of these frequency points is equal to the previous frequency point * (1 + k)), k ≤ 1%, the calibration start frequency f min and calibration stop frequency f max, set the current calibration frequency f=f min ; Select the matching coupling and decoupling network 201 according to the actual test product power line type, i.e. CDN-M1~M5;

[0073] Step 2: Calculate the initial level setting value U corresponding to the RF signal source 101 S0 , set the frequency of RF signal source 101 to f and the level to U S =U S0 ;

[0074] Step 3: Connect the RF output port of the RF signal source 101 to the RF input port of the power amplifier 102, connect the RF output port of the power amplifier 102 to the input port of the attenuator 103, and switch the RF switch 104 to connect to the network analyzer 105. The formula for the standing wave ratio test of the network analyzer 105 is as follows: Represents the ratio of the maximum voltage to the minimum voltage in the system circuit. The standing wave ratio is required to be less than 2. Test the standing wave ratio of the output port of the attenuator 103. If the standing wave ratio is less than 2dB, continue with step 4. If the standing wave ratio is greater than or equal to 2dB, shut down the system and check whether the connections of each port of the signal generation module are normal, and repeat step 2.

[0075] Step 4: Determine the actual test product power line electrical parameters: resistance R pl , inductance L pl , capacitor C pl , determine the electrical parameters of the output port of the coupling decoupling network (201) that matches the actual test product type: resistance R 201 , inductance L 201 , capacitor C 201 , through the formula:

[0076]

[0077] Calculate the RF impedance of the calibration output port, switch 104 to connect to the coupling-decoupling network 201, switch 2 RF switch 303 to connect to the network analyzer 2 307, and measure the RF impedance corresponding to the frequency f of the output port of impedance converter 1 302. If the deviation from the RF impedance of the calibration output port is less than 20%, complete automatic impedance matching through the subsequent adaptive matching load 306, and proceed to step 5. However, the larger the difference, the greater the uncertainty, so it is still necessary to minimize the impact of the difference. Therefore, it is necessary to adjust the adaptive matching load 306 to achieve a better match.

[0078] If the deviation exceeds 20%, shut down the system and check the RF connection between the signal generation system, the coupling and decoupling network 201, the common mode port merging device 301 and the impedance converter 302, and then repeat step 4 until the requirements are met;

[0079] Step 5: Switch the RF switch 2 303 to the connection probe 304, connect the output port of the common mode port merging device 2 401 to the input port of the RF switch 3 403 through the impedance converter 2 402, connect the RF switch 3 403 to the load impedance 404 to achieve the RF performance of the simulated power supply, and then use the probe 304 of the power meter 305 to test and obtain the first level value U1;

[0080] Step 6: If the first level value U1 meets the If the first level value U1 does not meet the range requirements, continue to step seven; If the range is greater than the requirement, then the signal source level U S Lower the level by 1.5dB and repeat step 5. If it is less than the required range, increase the signal source level to S Increase the setting by 1.5dB and repeat step 5 until the result meets the range requirement.

[0081] Step 7: Disconnect the RF switch 3 403 from the load impedance 404, and use the probe 304 of the power meter 305 to measure and obtain the second level value U2; if |U1-U2|≤1.6dB, select the larger result between U1 and U2 as the test level U, and record the corresponding calibration frequency f, test level U, calibration target voltage U0, signal source level U S And continue to step eight; if |U1-U2|>1.6dB, it means that the decoupling function of the coupling-decoupling network 201 has decreased, and it is necessary to terminate the calibration and check the coupling-decoupling network 201;

[0082] Step 8: Adjust the calibration frequency f to f×(1+k) and check whether the adjustment result is ≤f max If yes, repeat steps 2 to 7; if no, end the calibration task;

[0083] Step 9: Derive the calibration frequency f, test level U, calibration target voltage U0, signal source level U for all calibration frequency points S The calibration database is formed, as shown in Table 1.

[0084] Table 1 Example of calibration data results

[0085]

[0086] The conventional calibration process is to gradually increase the signal source level from a low initial value and stop when the requirements are met. The adjustment process increases the calibration time and reduces the calibration efficiency. The present invention improves the accuracy of the calibration initial value through formula 1. The derivation process of formula 1 is as follows: First, draw the equivalent diagram of the circuit according to the schematic diagram as follows Figure 3 As shown, it can be obtained that the attenuator output voltage U1=Us0 ×G A / T, according to the circuit voltage division principle, Thus, the formula 1 in step 2 can be obtained, which is the initial level setting value of the RF signal source 101:

[0087]

[0088] Among them, U s0 is the initial level setting value of the RF signal source 101, U0 is the calibration target voltage, G A is the voltage gain of the power amplifier 102, T is the voltage attenuation factor of the attenuator 103, R 103 is the output impedance of attenuator 103, R 201 is the common mode impedance of the coupling decoupling network 201, R 302 is the conversion resistance of the impedance converter 302, R 306 is the resistance value of the adaptive matching load 306 .

[0089] The following data is an example. In actual scenarios, it is necessary to obtain a data array of parameters changing with frequency through metering reports. For the sake of demonstration, some parameters are simplified. U0 = 10V, G A =105dB,T=6dB,R 103 =50Ω, R 302 =100Ω, R 306 =50Ω.

[0090] Table 2 Typical common-mode impedance of coupling-decoupling network (excluding termination impedance)

[0091]

[0092]

[0093] The signal source level value U at this time can be calculated by formula 1 s0 The setting parameters are shown in Table 3:

[0094] Table 3: U s0 Initial setting value

[0095]

[0096] In one embodiment of the present invention, the radio frequency impedance of the calibration system can be tested by a network analyzer, and the test frequency range is 150kHz-80MHz. The calibration uncertainty can be reduced by adaptive impedance compensation.

[0097] Assume that the mathematical model of the calibration process is:

[0098] V=V RMS +VLAW +P D +P AN +M VC +M AC +R S +R EUT

[0099] The symbols used are explained in Table 4 below:

[0100] Table 4: Calibration digital model symbol description

[0101]

[0102]

[0103] The calculation formula 2 for the combined standard uncertainty is as follows

[0104]

[0105] The uncertainty can be analyzed and evaluated based on the source as shown in Table 5 and Table 6.

[0106] Table 5 Uncertainty evaluation of pre-calibrated conducted immunity (without adaptive impedance compensation)

[0107]

[0108]

[0109] Through impedance compensation, M VC Can be greatly improved, in the case of impedance matching, M VC It can be reduced to the test error of the network analyzer. According to the product manual, the test error is 0.1dB.

[0110] Table 6: Uncertainty assessment of pre-calibrated conducted immunity (including adaptive impedance compensation)

[0111]

[0112] In summary, the uncertainty is reduced by 17.9% through adaptive impedance compensation.

[0113] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. An electromagnetic compatibility conducted immunity calibration system, characterized by: It includes signal generation module, coupling and decoupling network adaptive assembly system, calibration load path system, and auxiliary equipment termination system; A signal generating module is connected to the coupling-decoupling network adaptive assembly system and is used to generate a calibrated radio frequency signal to the coupling-decoupling network adaptive assembly system; The coupling and decoupling network adaptive assembly system is respectively connected to the calibration load path system and the auxiliary equipment termination system, couples the radio frequency signal in common mode to the calibration load path system, and performs radio frequency shielding and decoupling on the auxiliary equipment termination system; Calibration load path system, used to simulate test samples, complete impedance matching and obtain calibrated RF power; Auxiliary equipment termination system is used to simulate the auxiliary equipment environment of the product during testing.

2. The electromagnetic compatibility conducted immunity calibration system according to claim 1, characterized in that: The signal generation module comprises a radio frequency signal source (101), a power amplifier (102), an attenuator (103), a radio frequency switch (104), and a network analyzer (105); the radio frequency signal source (101), the power amplifier (102), the attenuator (103), and the radio frequency switch (104) are sequentially connected in circuit; the radio frequency switch (104) further selects a circuit to connect to the network analyzer (105) and the coupling and decoupling network adaptive assembly system; The coupling-decoupling network adaptive assembly system comprises a coupling-decoupling network (201), wherein the coupling-decoupling network (201) can be replaced with an applicable model according to a test product, and the coupling-decoupling network (201) is connected to a radio frequency switch (104) circuit; The calibration load path system comprises a common mode port merging device (301), an impedance converter (302), a radio frequency switch (303), a power meter (305), an adaptive matching load (306), and a network analyzer (307); the common mode port merging device (301), the impedance converter (302), and the radio frequency switch (303) are connected in sequence; the radio frequency switch (303) is further connected to a probe (304) of the network analyzer (307) and the power meter (305) through a circuit; the adaptive matching load (306) is located on the probe (304); The probe (304) of the power meter (305) measures and records the radio frequency power during the calibration process, and the adaptive matching load (306) performs matching work on the radio frequency impedance during the calibration process; The auxiliary equipment termination system comprises a common mode port merging device 2 (401), an impedance converter 2 (402), a radio frequency switch 3 (403), and a load impedance (404) which are sequentially connected in lines. The radio frequency switch 3 (403) controls the connection between the impedance converter 2 (402) and the load impedance (404).

3. The electromagnetic compatibility conducted immunity calibration system according to any one of claim 2, characterized in that: The calibration system further comprises a grounding protection system, which comprises a metal grounding plate (505). The coupling-decoupling network adaptive assembly system, the calibration load path system, and the auxiliary equipment termination system are all located on the metal grounding plate (505). A digital multimeter (504) is arranged on the metal grounding plate (505), and probes of the digital multimeter (504) are respectively connected to the ground and the housing of the coupling-decoupling network (201).

4. The calibration method of the electromagnetic compatibility conducted immunity calibration system according to claim 3, characterized in that: The following steps are involved: Step 1: According to the actual test target voltage, select the same calibration target voltage U0, frequency change step k, k ≤ 1%, calibration starting frequency f min and calibration stop frequency f max , set the current calibration frequency f=f min ; Selecting a matching coupling and decoupling network (201) according to the actual test product power line type; Step 2: Calculate the initial level setting value U corresponding to the radio frequency signal source (101) S0 , set the frequency of the RF signal source (101) to f and the level to U S =U S0 ; Step 3: The RF output port of the RF signal source (101) is connected to the RF input port of the power amplifier (102), and the RF output port of the power amplifier (102) is connected to the input port of the attenuator (103). The RF switch 1 (104) is switched to connect to the network analyzer 1 (105), and the standing wave ratio of the output port of the attenuator (103) is tested. If the standing wave ratio is less than 2dB, proceed to step 4. Step 4: Determine the electrical parameters of the power cord of the actual test product: resistance R pl , inductance L pl , capacitor C pl , determine the electrical parameters of the output port of the coupling decoupling network (201) that matches the actual test product type: resistance R 201 , inductance L 201 , capacitor C 201 , through the formula: Calculate the radio frequency impedance of the calibration output port, switch the radio frequency switch 1 (104) to connect to the coupling decoupling network (201), switch the radio frequency switch 2 (303) to connect to the network analyzer 2 (307), test the radio frequency impedance corresponding to the frequency f of the output port of the impedance converter 1 (302), and if the deviation from the radio frequency impedance of the calibration output port is less than 20%, complete the automatic impedance matching through the subsequent adaptive matching load (306), and proceed to step 5; Step 5: Switch the RF switch 2 (303) to the connection probe (304), connect the output port of the common mode port merging device 2 (401) to the input port of the RF switch 3 (403) through the impedance converter 2 (402), connect the RF switch 3 (403) to the load impedance (404), realize the RF performance of the simulated power supply, and then use the probe (304) of the power meter (305) to test and obtain the first level value U1; Step 6: If the first level value U1 meets the Scope requirements, continue to step seven; Step 7: Disconnect the RF switch 3 (403) from the load impedance (404), and use the probe (304) of the power meter (305) to test and obtain the second level value U2; if |U1-U2|≤1.6dB, select the larger result between U1 and U2 as the test level U, and record the corresponding calibration frequency f, test level U, calibration target voltage U0, signal source level U S And continue with step eight; Step 8: Adjust the calibration frequency f to f×(1+k) and check whether the adjustment result is ≤f max If yes, repeat steps 2 to 7; if no, end the calibration task; Step 9: Derive the calibration frequency f, test level U, calibration target voltage U0, signal source level U for all calibration frequency points S This forms the calibration database.

5. The calibration method of the electromagnetic compatibility conducted immunity calibration system according to claim 4, characterized in that: Before the step starts, the resistance between the metal shell of the coupling-decoupling network (201) and the grounding point is measured by a digital multimeter (504). If the resistance is less than or equal to 4Ω, the step 2 is continued. If the resistance is greater than or equal to 4Ω, the grounding protection system is checked until it meets the requirements, and the step 1 is continued. In step 3, if the standing wave ratio is ≥ 2dB, shut down the system and check whether the connections of the various ports of the signal generating module are normal, and repeat step 2; In step 4, if the deviation exceeds 20%, shut down the system to check the RF connection between the signal generation system, the coupling and decoupling network 201, the common mode port merging device 301 and the impedance converter 302, and then repeat step 4 until the requirements are met; In step 6, if the first level value U1 does not meet the If the range is greater than the requirement, then the signal source level U S Lower the level by 1.5dB and repeat step 5. If it is less than the required range, increase the signal source level to S Increase the setting by 1.5dB and repeat step 5 until the result meets the range requirement. In the step seven, if |U1-U2|>1.6dB, it indicates that the decoupling function of the coupling-decoupling network (201) has decreased, and it is necessary to terminate the calibration to check the coupling-decoupling network (201).

6. The calibration method of an electromagnetic compatibility conducted immunity calibration system according to claim 4 or 5, characterized in that: Adjust the calibration parameters and layout according to the performance parameters of the test product. During the calibration process, the power line phase type, including single-phase single-wire, single-phase two-wire, single-phase three-wire, three-phase four-wire, three-phase five-wire, power line shielding type, including shielded wire and unshielded wire, and power line electrical parameters, including resistance, inductance, and capacitance, are measured to more accurately simulate the actual test scenario and improve the accuracy of the calibration results. If it is an unshielded line, during the calibration process, the calibration load path system is in an unshielded state; If it is a shielded line, during the calibration process, the calibration load path system needs to be covered with a metal shielding net and connected to the metal shell of the coupling and decoupling network (201) and the metal grounding plate (505). The power meter (305) and the network analyzer (307) are outside the metal shielding net and connected to the metal shielding net cover through the shielded line. In order to avoid short circuit, a thin layer of shielding material is added between the calibration load path system and the metal shielding net cover.

7. The calibration method of an electromagnetic compatibility conducted immunity calibration system according to claim 4 or 5, characterized in that: In the step 2, the initial level setting value of the radio frequency signal source (101) is: Among them, U s0 is the initial level setting value of the RF signal source (101), U0 is the calibration target voltage, G A is the voltage gain of the power amplifier (102), T is the voltage attenuation factor of the attenuator (103), R 103 is the output impedance of the attenuator (103), R 201 is the common mode impedance of the coupling decoupling network (201), R 302 is the conversion resistance of the impedance converter 1 (302), R 306 is the resistance value of the adaptive matching load (306).

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