Radiation interference filter design method and system based on transfer function method
By converting radiated interference into a conducted common-mode current target using the transfer function method, the problem of the disconnect between filter design theory and radiation suppression effect is solved, enabling quantitative design of radiated interference filters, shortening the R&D cycle and reducing costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-05
- Publication Date
- 2026-04-07
AI Technical Summary
The existing filter design theory is disconnected from the radiation suppression effect and lacks systematic theoretical guidance, which leads to the reliance on experience in the design of radiation interference filters, increasing the research and development cycle and cost.
The transfer function method is used to convert the radiated interference value into a measurable conducted common-mode current target. The radiated interference target suppression limit is then converted into a common-mode current target suppression limit through the transfer function. The insertion loss curves of candidate filters are then used for verification to select a suitable filter.
A theoretical bridge was established between radiation and circuits, enabling the quantitative design of radiated interference filters, shortening the electromagnetic compatibility design and certification cycle, and reducing R&D costs.
Smart Images
Figure CN121809378A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of electromagnetic compatibility technology for motor systems, and in particular to a design method and system for a radiated interference filter based on the transfer function method. Background Technology
[0002] As the integration and operating frequency of electronic devices continue to increase, electromagnetic compatibility issues are becoming increasingly prominent. Radiated emission is one of the key indicators for measuring the electromagnetic compatibility of electronic equipment. If it exceeds the standard limit, it will cause interference to other surrounding equipment and even affect the reliability of the electronic equipment itself.
[0003] In engineering practice, a common method for suppressing radiated emissions is to install electromagnetic compatibility (EMC) filters on the interference side of equipment (such as power cables). Classical filter design theories, such as the insertion loss method, are typically designed for conducted interference, aiming to achieve specific conducted interference attenuation under a given source / load impedance. However, radiated emissions usually involve high-frequency currents (mainly common-mode currents) on cables radiating electromagnetic waves into space as antennas. Since the noise propagation mechanisms of radiated and conducted emissions are different, filter schemes based on conducted interference attenuation theory lack a direct theoretical connection to radiated interference suppression and are therefore unsuitable for radiated interference filter design.
[0004] Currently, the design of filters for radiated interference suppression typically relies on personal experience, involving repeated "experience-based selection-testing-adjustment" to design filter parameters. However, this approach increases development time and project costs. Research indicates that common-mode current in cables is the primary source of radiation. Therefore, common-mode current can be used as a link between conducted and radiated interference. By fully integrating the design principles of conducted electromagnetic interference (EMI) filters, it can be systematically incorporated into the forward design process of radiated interference filter parameters. Summary of the Invention
[0005] This application provides a radiated interference filter design method and system based on the transfer function method, which solves the fundamental problem of the disconnect between existing filter design theory and actual radiation suppression effect, and proposes a scientific design method that links radiated emission suppression, filter frequency characteristics and filter design.
[0006] To achieve the above objectives, the technical solution of this application embodiment is as follows:
[0007] In a first aspect, embodiments of this application provide a method for designing a radiated interference filter based on the transfer function method, the method comprising:
[0008] The electronic device under test is placed in an anechoic chamber. The power cable of the electronic device under test is connected to the power source through a line impedance stabilization network. An antenna is placed at a preset distance around the electronic device under test, and a high-frequency current probe is placed at the port of the power cable.
[0009] The antenna is used to obtain the radiated interference value generated by the electronic device under test in the target frequency band, and the high-frequency current probe is used to obtain the conducted common-mode current value generated by the power cable in the target frequency band.
[0010] The attenuation of the radiation target is determined based on the radiation interference value and the radiation interference target suppression limit; the radiation interference target suppression limit is determined based on the limit corresponding to the target frequency band range and the design margin.
[0011] The radiated interference target suppression limit corresponding to the radiated interference value is converted into a common-mode current target suppression limit through a transfer function; the common-mode current target suppression limit includes a common-mode current horizontal limit and a common-mode current vertical limit; the transfer function is determined based on the conducted common-mode current value and the radiated interference value;
[0012] The target attenuation of the common-mode current is obtained based on the conducted common-mode current test value at the power cable port and the target common-mode current suppression limit.
[0013] Based on the target attenuation of the common-mode current and the insertion loss curve of the candidate filter, the corner frequency of the candidate filter is tested; if the corner frequency meets the preset test conditions, the candidate filter is used as the filter corresponding to the electronic device under test.
[0014] In one possible approach, the radiation interference target suppression limit includes a radiation interference level limit E. LimH (f) and vertical limit of radiated interference E LimV (f) The design margin includes the horizontal design margin Y. H (f) and vertical design margin Y V (f); The radiation interference target suppression limit is determined in the following manner:
[0015] Obtain the limit value E corresponding to the target frequency band range. limit (f), and horizontal design margin Y H (f) and vertical design margin Y V (f);
[0016] The limit value E limit (f) and the horizontal design margin Y H The difference between (f) and E is taken as the radiation interference level limit.LimH (f);
[0017] The limit value E limit (f) and the vertical design margin Y V The difference between (f) and E is taken as the vertical limit of the radiated interference. LimV (f).
[0018] In one possible manner, the radiated interference value includes a horizontal radiated interference value E. H (f) and vertical radiation interference value E V (f) The radiation target attenuation includes the horizontal radiation target attenuation RIL. CMH (f) and vertical radiation target attenuation RIL CMV (f); The determination of the radiation target attenuation based on the radiation interference value and the radiation interference target suppression limit includes:
[0019] The horizontal radiation interference value E H (f) and the radiation interference level limit E LimH The difference between (f) and (f) is used as the horizontal radiation target attenuation amount RIL. CMH (f);
[0020] The vertical radiation interference value E V (f) and the vertical limit E of the radiation interference LimV The difference between (f) and (f) is taken as the vertical radiation target attenuation amount RIL. CMV (f).
[0021] In one possible approach, the transfer function includes a horizontal transfer function T. CRH (f) and vertical transfer function T CRV (f); The step of converting the radiation interference target suppression limit corresponding to the radiation interference value into a common-mode current target suppression limit through a transfer function includes:
[0022] The horizontal radiation interference value E H (f) and the horizontal transfer function T CRH The ratio of (f) is used as the common-mode current level limit I. CMLimH (f, 0);
[0023] The vertical radiation interference value E V (f) and the vertical transfer function T CRV The ratio of (f) is used as the common-mode current vertical limit I. CMLimV (f, 0).
[0024] In one possible approach, the target common-mode current attenuation includes a horizontal current attenuation of IL. CMH (f) and vertical current attenuation IL CMV (f); The step of obtaining the target common-mode current attenuation based on the conducted common-mode current test value at the power cable port and the target common-mode current suppression limit includes:
[0025] The conducted common-mode current test value I CM (f, 0) and the common-mode current level limit I CMLimH The difference between (f, 0) is used as the target attenuation amount IL of the horizontal current. CMH (f);
[0026] The conducted common-mode current test value I CM (f, 0) and the common-mode current vertical limit I CMLimV The difference between (f, 0) is used as the target attenuation amount IL of the vertical current. CMV (f).
[0027] In one possible approach, verifying the corner frequency of the candidate filter based on the target common-mode current attenuation and the insertion loss curve of the candidate filter includes:
[0028] Based on the structure of the candidate filter, determine the corresponding insertion loss;
[0029] Determine the frequency points exceeding the standard within the target frequency band, and the corresponding horizontal current target attenuation and vertical current target attenuation at the frequency points exceeding the standard;
[0030] For each frequency point exceeding the standard, the larger of the horizontal current target attenuation and the vertical current target attenuation corresponding to the frequency point exceeding the standard is taken as the design limit.
[0031] By combining the design limit with the attenuation rate corresponding to the candidate filter, the insertion loss curve is obtained, and the critical corner frequency f of the candidate filter is determined from the insertion loss curve. c ;
[0032] At the critical transition frequency f c If the value is greater than zero, the candidate filter is determined to satisfy the preset test condition; at the critical corner frequency f c If the value is less than zero, it is determined that the candidate filter does not meet the preset test condition, and a new filter is selected for test.
[0033] In one possible approach, the method further includes:
[0034] By measuring the receiver, the radiated interference value, the radiated interference target suppression limit, the limit corresponding to the target frequency band range, and the spectrum data of the design margin are obtained respectively.
[0035] A spectrum diagram is obtained based on the spectrum data.
[0036] In one possible approach, the method further includes:
[0037] The filter corresponding to the electronic device under test is installed on the electronic device under test, and the radiated interference value and conducted common-mode current test value of the electronic device under test are measured.
[0038] If the radiated interference value meets the target suppression limit for radiated interference and the conducted common-mode current test value meets the target suppression limit for common-mode current, then the filter is determined to meet the design standard.
[0039] If the radiated interference value does not meet the target suppression limit for radiated interference, and the conducted common-mode current test value does not meet the target suppression limit for common-mode current, the filter model and / or parameters are adjusted according to the target attenuation of the common-mode current corresponding to the frequency point exceeding the standard, until the filter meets the design standard.
[0040] In one possible approach, adjusting the filter model and / or parameters based on the target attenuation of the common-mode current corresponding to the out-of-specification frequency point until the filter meets design standards includes:
[0041] If the target attenuation of the common-mode current corresponding to the out-of-standard frequency point is within the operating frequency range of the filter, adjust the design margin until the filter meets the design standards.
[0042] If the target attenuation of the common-mode current corresponding to the out-of-standard frequency point is not within the operating frequency range of the filter, replace it with another type of filter and re-verify the design standards.
[0043] Secondly, embodiments of this application provide a radiation interference filter design system based on the transfer function method. The system is used to execute the method described in the first aspect above. The system includes: an electronic device under test (DUT), a line impedance stabilization network, an antenna, a high-frequency current probe, a measurement receiver, and a terminal. The DUT is disposed in an anechoic chamber, and its power cable is connected to a power source through the line impedance stabilization network. The antenna and the high-frequency current probe are respectively connected to the measurement receiver. The measurement receiver is connected to the terminal.
[0044] The antenna is positioned at a preset distance around the electronic device under test (DUT) to acquire the radiated interference value generated by the DUT within the target frequency band and to transmit the radiated interference value to the measurement receiver.
[0045] The high-frequency current probe is installed at the power cable port to acquire the conducted common-mode current value generated by the power cable in the target frequency band and send the conducted common-mode current value to the measurement receiver.
[0046] The measurement receiver is used to obtain spectral data based on the radiated interference value and the conducted common-mode current value, and to generate a spectrum diagram.
[0047] The terminal is used to determine the radiation target attenuation based on the radiated interference value and the radiated interference target suppression limit; the radiated interference target suppression limit is determined based on the limit corresponding to the target frequency band range and the design margin; the radiated interference target suppression limit corresponding to the radiated interference value is converted into a common-mode current target suppression limit through a transfer function; the common-mode current target suppression limit includes a common-mode current horizontal limit and a common-mode current vertical limit; the transfer function is determined based on the conducted common-mode current value and the radiated interference value; the common-mode current target attenuation is obtained based on the conducted common-mode current test value at the power cable port and the common-mode current target suppression limit; the corner frequency of the candidate filter is checked based on the common-mode current target attenuation and the insertion loss curve of the candidate filter; if the corner frequency meets the preset check conditions, the candidate filter is used as the filter corresponding to the electronic device under test.
[0048] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages:
[0049] The above technical solutions establish a theoretical bridge from radiation to circuits. By employing the transfer function method, the "radiated field strength" target, which cannot be directly designed, is transformed into a measurable and designable "conducted common-mode current" target. This solves the fundamental problem of the disconnect between existing filter design theory and actual radiation suppression effect. Furthermore, it overcomes the reliance on experience and trial-and-error in radiated electromagnetic interference design, providing scientific guidance for the quantification and forward design of radiated electromagnetic interference filters. This significantly shortens the electromagnetic compatibility design and certification cycle of products and reduces R&D costs. Attached Figure Description
[0050] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments of this application or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0051] Figure 1 A flowchart illustrating a radiation interference filter design method based on the transfer function method provided in this application embodiment;
[0052] Figure 2 A flowchart of another radiation interference filter design method based on the transfer function method provided in this application embodiment;
[0053] Figure 3 This is a schematic diagram of the radiated electromagnetic interference structure of an electronic device under test provided in an embodiment of this application;
[0054] Figure 4 A schematic diagram of a common-mode interference current test provided in an embodiment of this application;
[0055] Figure 5 This application provides a schematic diagram of a radiated interference emission test.
[0056] Figure 6 A spectrum diagram provided for an embodiment of this application;
[0057] Figure 7 This is a schematic diagram of an LC filter structure provided in an embodiment of this application;
[0058] Figure 8 A block diagram of a radiation interference filter design system based on the transfer function method provided in this application embodiment;
[0059] Figure 9 A block diagram of another radiation interference filter design system based on the transfer function method provided in this application embodiment. Detailed Implementation
[0060] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.
[0061] In the description of the embodiments of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the embodiments of this application and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; a mechanical connection or an electrical connection; a direct connection or an indirect connection through an intermediate medium; or a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application according to the specific circumstances.
[0062] First, the application scenario of this application is introduced. This application is applied to the selection and design of electromagnetic interference filters. Filters are a common means of radiation suppression, but the existing technology lacks design methods and systematic theoretical guidance tools for radiated interference filter parameters, thus failing to address the positive R&D needs of radiated electromagnetic interference. Furthermore, actual filter devices have specific frequency applicable ranges. For example, traditional inductors and capacitors are usually effective in the low-frequency band, while high-frequency magnetic rings and high-frequency capacitors can achieve high-frequency suppression. Therefore, filter selection and design must consider the entire frequency band.
[0063] To address the aforementioned problems, this application proposes a radiated interference filter design method and system based on the transfer function method. The method includes: placing the electronic device under test (DUT) in an anechoic chamber; connecting the DUT's power cable to a power source via a line impedance stabilization network; placing an antenna at a predetermined distance around the DUT; and placing a high-frequency current probe at the power cable port. The method involves acquiring the radiated interference value generated by the DUT within a target frequency band using the antenna and acquiring the conducted common-mode current value generated by the power cable within the target frequency band using the high-frequency current probe. Based on the radiated interference value and a radiated interference target suppression limit, the method determines the radiated interference target attenuation amount. The radiated interference target suppression limit is based on the target frequency band. The limits and design margins corresponding to the standard frequency band range are determined; the radiated interference target suppression limit corresponding to the radiated interference value is converted into a common-mode current target suppression limit through a transfer function; the common-mode current target suppression limit includes a common-mode current horizontal limit and a common-mode current vertical limit; the transfer function is determined based on the conducted common-mode current value and the radiated interference value; the common-mode current target attenuation is obtained based on the conducted common-mode current test value at the power cable port and the common-mode current target suppression limit; based on the common-mode current target attenuation and the insertion loss curve of the candidate filter, the corner frequency of the candidate filter is verified; if the corner frequency meets the preset verification conditions, the candidate filter is used as the filter corresponding to the electronic device under test.
[0064] The above technical solutions establish a theoretical bridge from radiation to circuits. By employing the transfer function method, the "radiated field strength" target, which cannot be directly designed, is transformed into a measurable and designable "conducted common-mode current" target. This solves the fundamental problem of the disconnect between existing filter design theory and actual radiation suppression effect. Furthermore, it overcomes the reliance on experience and trial-and-error in radiated electromagnetic interference design, providing scientific guidance for the quantification and forward design of radiated electromagnetic interference filters. This significantly shortens the electromagnetic compatibility design and certification cycle of products and reduces R&D costs.
[0065] Figure 1 This is a flowchart illustrating a radiation interference filter design method based on the transfer function method, provided as an embodiment of this application. Figure 1 As shown, the method may include the following steps.
[0066] S101. The electronic device under test is placed in an anechoic chamber. The power cable of the electronic device under test is connected to the power source through a line impedance stabilization network. The antenna is placed at a preset distance around the electronic device under test, and the high-frequency current probe is placed at the port of the power cable.
[0067] For example, the electronic device under test could be a brushed DC motor.
[0068] S102. Obtain the radiated interference value generated by the electronic device under test in the target frequency band using the antenna, and obtain the conducted common-mode current value generated by the power cable in the target frequency band using the high-frequency current probe.
[0069] For example, the target frequency band range could be 30MHz-1000MHz.
[0070] S103. Determine the attenuation of the radiation target based on the radiation interference value and the radiation interference target suppression limit; the radiation interference target suppression limit is determined based on the limit corresponding to the target frequency band range and the design margin.
[0071] S104. The radiation interference target suppression limit corresponding to the radiation interference value is converted into a common-mode current target suppression limit through a transfer function; the common-mode current target suppression limit includes a common-mode current horizontal limit and a common-mode current vertical limit; the transfer function is determined based on the conducted common-mode current value and the radiation interference value.
[0072] S105. Based on the conducted common-mode current test value at the power cable port and the common-mode current target suppression limit, obtain the common-mode current target attenuation amount.
[0073] S106. Based on the target attenuation of the common-mode current and the insertion loss curve of the candidate filter, the corner frequency of the candidate filter is checked; if the corner frequency meets the preset check conditions, the candidate filter is used as the filter corresponding to the electronic device under test.
[0074] The above technical solutions establish a theoretical bridge from radiation to circuits. By employing the transfer function method, the "radiated field strength" target, which cannot be directly designed, is transformed into a measurable and designable "conducted common-mode current" target. This solves the fundamental problem of the disconnect between existing filter design theory and actual radiation suppression effect. Furthermore, it overcomes the reliance on experience and trial-and-error in radiated electromagnetic interference design, providing scientific guidance for the quantification and forward design of radiated electromagnetic interference filters. This significantly shortens the electromagnetic compatibility design and certification cycle of products and reduces R&D costs.
[0075] In one possible approach, the radiation interference target suppression limit includes a radiation interference level limit E. LimH (f) and vertical limit of radiation interference E LimV (f) This design margin includes the horizontal design margin Y. H (f) and vertical design margin Y V (f); The target suppression limit for radiation interference is determined by obtaining the limit E corresponding to the target's frequency band range. limit (f), and horizontal design margin Y H (f) and vertical design margin YV (f); This limit value E limit (f) and the horizontal design margin Y H The difference between (f) and E is taken as the limit for the level of radiation interference. LimH (f); This limit value E limit (f) and the vertical design margin Y V The difference between (f) and E is taken as the vertical limit of the radiated interference. LimV (f).
[0076] For example, the radiated interference level limit E LimH (f) = E limit (f)-Y H (f); The vertical limit of the radiation interference E LimV (f)=E limit (f)-Y V (f). The limit E limit (f) can be determined based on the EMC standards that the filter needs to meet, such as EN55032. To overcome inconsistencies caused by manufacturing processes and ensure the effectiveness of radiated interference suppression, a horizontal design margin Y is specified. H (f) and vertical design margin Y V (f) can be 6-10dB.
[0077] In one possible manner, the radiated interference value includes the horizontal radiated interference value E. H (f) and vertical radiation interference value E V (f) The radiation target attenuation includes the horizontal radiation target attenuation RIL. CMH (f) and vertical radiation target attenuation RIL CMV (f); The determination of the radiation target attenuation based on the radiation interference value and the radiation interference target suppression limit includes: determining the horizontal radiation interference value E H (f) and the radiation interference level limit E LimH The difference between (f) and (f) is taken as the horizontal radiation target attenuation RIL. CMH (f); the vertical radiation interference value E V (f) and the vertical limit E of the radiation interference LimV The difference between (f) and (f) is taken as the attenuation amount RIL of the vertical radiation target. CMV (f).
[0078] For example, the horizontal radiation target attenuation RIL CMH (f)=E H (f)-E LimH(f); the vertical radiation target attenuation RIL CMV (f)=E V (f)-E LimV (f).
[0079] In one possible approach, the transfer function includes the horizontal transfer function T. CRH (f) and vertical transfer function T CRV (f); This involves converting the radiation interference target suppression limit corresponding to the radiation interference value into a common-mode current target suppression limit through a transfer function, including: converting the horizontal radiation interference value E H (f) and the horizontal transfer function T CRH The ratio of (f) is used as the common-mode current level limit I. CMLimH (f, 0); the vertical radiation interference value E V (f) and the vertical transfer function T CRV The ratio of (f) is used as the vertical limit I of the common-mode current. CMLimV (f, 0).
[0080] For example, the common-mode current level limit I CMLimH (f, 0) = E H (f) / T CRH (f); The common-mode current vertical limit I CMLimV (f, 0) = E V (f) / T CRV (f).
[0081] In another possible implementation, the transfer function can be obtained as follows: For the radiated electromagnetic interference problem of wired electronic devices, the radiation is mainly the common-mode interference current I flowing through the cable. CM (f) Generation. The conductor in the cable can be considered as composed of countless small electric dipole antennas. Therefore, the radiated electric field E at the observation point around the electronic device can be formed by the superposition of the electric fields generated by all the small electric dipoles at that point. Since the size of the conductor cannot be ignored, the current in the conductor can be expressed as: I CM (f, x) = I CM (f, 0)D(f, x); where I CM (f, x) represents the current at any point on the conductor; D(f, x) is the current distribution function, which depends only on the system characteristics. Therefore, the radiated electric field intensity at the observation point can be expressed as: Where E is the radiation field strength at the observation point, L is the length of the conductor, and R(f,0) represents the radiation factor of the current element.
[0082] For a specific system, D(f, x) and R(f, 0) are determined, then: Among them, T CR (f) is the transfer function from conducted interference to radiated interference in the test system. For a specific system T CR (f) is definite. Therefore, the radiation field of the system can be expressed as: The above formula shows that T CR (f) represents the magnitude of the radiated field strength generated by a unit common-mode current, while the electromagnetic radiation amplitude of the system can be obtained through the current element I at the conductor port. CM The magnitude of (f, 0) and the function T CR The product of (f) is obtained.
[0083] Since radiation testing includes both horizontal and vertical tests, the corresponding transfer function also includes the horizontal transfer function T. CRH (f) and vertical transfer function T CRV (f), therefore, the common-mode current I at each frequency point is calculated. CM The transfer function T from (f, 0) to the radiation field CR The formula for calculating (f) can be: T CRH (f) = E H (f) / I CM (f, 0); T CRV (f) = E V (f) / I CM (f, 0).
[0084] The transfer function described above physically represents the magnitude of the radiated field strength generated by a unit common-mode current under a specific (required) test layout. This transfer function incorporates radiation path characteristics from the cable antenna effect; therefore, it depends only on physical parameters such as the positions of the conductor and the observation point, and not on the excitation source I. CM The magnitude of (f, 0) is independent. It should be noted that, based on the physical meaning of the transfer function, it can also be obtained through simulation. The simulation environment settings need to be consistent with the parameters and environment of the radiated emission test.
[0085] In one possible approach, the target common-mode current attenuation includes the horizontal current attenuation IL. CMH (f) and vertical current attenuation IL CMV (f); The common-mode current target attenuation is obtained based on the conducted common-mode current test value at the power cable port and the common-mode current target suppression limit, including: taking the conducted common-mode current test value I... CM (f, 0) and the common-mode current level limit ICMLimH The difference between (f, 0) is taken as the current attenuation IL at that level. CMH (f); The conducted common-mode current test value I CM (f, 0) and the vertical limit I of the common-mode current CMLimV The difference between (f, 0) is taken as the vertical current attenuation IL. CMV (f).
[0086] For example, the horizontal current attenuation IL CMH (f)=I CM (f, 0)-I CMLimH (f); the vertical current attenuation IL CMV (f)=I CM (f, 0)-I CMLimV (f).
[0087] In one possible approach, S106 may include: determining the corresponding insertion loss based on the structure of the candidate filter; determining the out-of-range frequency points within the target frequency band, and the target horizontal current attenuation and target vertical current attenuation corresponding to the out-of-range frequency points; for each out-of-range frequency point, using the larger of the target horizontal current attenuation and target vertical current attenuation corresponding to the out-of-range frequency point as a design limit; combining the design limit with the attenuation rate corresponding to the candidate filter to obtain the insertion loss curve, and determining the critical corner frequency f of the candidate filter from the insertion loss curve. c At the critical transition frequency f c If the value is greater than zero, the candidate filter is determined to meet the preset test condition; at the critical corner frequency f c If the value is less than zero, the candidate filter is determined not to meet the preset test condition, and a new filter is selected for testing. For example, this new filter could be a higher-order filter; the filter type is not limited here.
[0088] In one possible approach, the method further includes: obtaining spectral data of the radiated interference value, the radiated interference target suppression limit, the limit corresponding to the target frequency band range, and the design margin using a measurement receiver; and obtaining a spectrum diagram based on the spectral data. For example, the measurement receiver may be an oscilloscope or a spectrum analyzer.
[0089] In one possible approach, the method further includes: installing a filter corresponding to the electronic device under test (DUT) on the DUT, and measuring the radiated interference value and conducted common-mode current test value of the DUT; if the radiated interference value meets the radiated interference target suppression limit and the conducted common-mode current test value meets the common-mode current target suppression limit, determining that the filter meets the design standard; if the radiated interference value does not meet the radiated interference target suppression limit and the conducted common-mode current test value does not meet the common-mode current target suppression limit, adjusting the filter model and / or parameters according to the common-mode current target attenuation corresponding to the out-of-standard frequency point until the filter meets the design standard.
[0090] In one possible approach, the filter model and / or parameters are adjusted based on the target common-mode current attenuation corresponding to the out-of-specification frequency point until the filter meets the design standards. This includes: if the target common-mode current attenuation corresponding to the out-of-specification frequency point is within the operating frequency range of the filter, adjusting the design margin until the filter meets the design standards; if the target common-mode current attenuation corresponding to the out-of-specification frequency point is not within the operating frequency range of the filter, replacing it with another type of filter and re-verifying the design standards.
[0091] Figure 2 A flowchart illustrating another radiation interference filter design method based on the transfer function method provided in this application embodiment. Refer below. Figure 2 The workflow of the above method is introduced using a brushed DC motor as the electronic device under test.
[0092] S201. Acquisition of conducted and radiated interference results.
[0093] Reference Figure 3 The device under test (EUT), such as a brushed DC motor, is placed in a predetermined position in an anechoic chamber. Its power cable (wire) is connected to the power source through a line impedance stabilization network (LISN). Observation points are set at a predetermined distance from the device under test to observe the conducted and radiated interference it generates.
[0094] Reference Figure 4 The conducted common-mode current I at any point on the power cable of the electronic device under test (EUT) is measured using a current testing magnetic ring (high-frequency current probe). CM (f, x), whose common-mode current at the port is represented by I. CM (f, 0) represents the measurement receiver and data recording device used to test and record test data in the frequency band of interest (e.g., 30MHz-1000MHz). The measurement receiver can be an oscilloscope or a spectrum analyzer, and the data recording device can be a terminal.
[0095] Reference Figure 5 A measuring antenna is placed at a preset distance (e.g., 3 meters) to measure the horizontal and vertical radiated interference E of the electronic device under test (EUT). H (f) and E V (f). By using a measuring receiver and a data recording device, the spectral data of these two physical quantities in the frequency band of interest (e.g., 30MHz-1000MHz) are recorded simultaneously.
[0096] S202, Calculation of transfer function.
[0097] The radiated electromagnetic interference (EMI) problem of electronic devices under test (EBTs) with cables mainly involves the common-mode interference current I flowing through the cables. CM (f) is generated. Figure 3 The conductor in the diagram can be considered as being composed of countless small electric dipole antennas. Therefore, the radiated electric field E at the observation point is the superposition of the electric fields generated by all the small electric dipoles at that point. Since the size of the conductor cannot be ignored, the current in the conductor can be expressed as: I CM (f, x) = I CM (f, 0)D(f, x); where I CM (f, x) represents the current at any point on the conductor; D(f, x) is the current distribution function, which depends only on the system characteristics. Therefore, the radiated electric field intensity at the observation point can be expressed as: Where E is the radiation field strength at the observation point, L is the length of the conductor, and R(f,0) represents the radiation factor of the current element.
[0098] For a specific system, D(f, x) and R(f, 0) are determined, then: Among them, T CR (f) is the transfer function from conducted interference to radiated interference in the test system. For a specific system T CR (f) is definite. Therefore, the radiation field of the system can be expressed as: The above formula shows that T CR (f) represents the magnitude of the radiated field strength generated by a unit common-mode current, while the electromagnetic radiation amplitude of the system can be obtained through the current element I at the conductor port. CM The magnitude of (f, 0) and the function T CR The product of (f) is obtained.
[0099] Radiation testing comprises two parts: horizontal testing and vertical testing. The corresponding transfer function also includes the horizontal transfer function T. CRH (f) and vertical transfer function T CRV(f), therefore, the common-mode current I at each frequency point is calculated. CM The transfer function T from (f, 0) to the radiation field CR (f), its calculation formula is: T CRH (f) = E H (f) / I CM (f, 0); T CRV (f) = E V (f) / I CM (f, 0).
[0100] The transfer function described above physically represents the magnitude of the radiated field strength generated by a unit common-mode current under a specific (required) test layout. This function incorporates radiation path characteristics from the cable antenna effect, therefore it depends only on physical parameters such as the positions of the conductor and the observation point, and not on the excitation source I. CM The magnitude of (f, 0) is independent. It should be noted that, based on the physical meaning of the transfer function, it can also be obtained through simulation. The simulation environment settings need to be consistent with the parameters and environment of the radiated emission test.
[0101] S203, Suppress target transformation and acquisition.
[0102] (1) Based on the EMC standards (e.g., EN55032) that the product (filter) needs to meet, obtain the corresponding radiated emission frequency test range and the corresponding limit E. limit (f).
[0103] (2) Based on the horizontal design margin Y H (f) and vertical design margin Y V (f) Calculate the radiation interference level limit E in the radiation interference target suppression limit. LimH (f) and vertical limit of radiated interference E LimV (f); The calculation formula is as follows: E LimH (f) = E limit (f) - Y H (f); E LimV (f) = E limit (f) - Y V (f). To overcome inconsistencies caused by product manufacturing processes and to ensure the effectiveness of radiation interference suppression, a horizontal design margin Y is specified. H (f) and vertical design margin Y V (f) is generally taken as 6-10dB.
[0104] (3) Based on the horizontal radiation interference value E H(f) and vertical radiation interference value E V (f), and the aforementioned radiation interference level limit E LimH (f) and vertical limit of radiated interference E LimV (f) Calculate the required attenuation of the radiation target provided by the filter; where the horizontal radiation target attenuation is: RIL CMH (f) = E H (f) - E LimH (f); Vertical radiation target attenuation RIL CMV (f) = E V (f) - E LimV (f).
[0105] (4) Using the above transfer function, the requirement to suppress radiated interference in the test system is transformed into the requirement to suppress the common-mode current of the test system, and the horizontal radiated interference value E is obtained. H (f) and vertical radiation interference value E V (f) corresponds to the common-mode current level limit I CMLimH (f, 0) and the common-mode current vertical limit I CMLimV (f, 0): I CMLimH (f, 0) = E H (f) / T CRH (f); I CMLimV (f, 0) = E V (f) / T CRV (f).
[0106] (5) Based on the above common-mode current test value I CM (f, 0) and the common-mode current level limit I obtained above. CMLimH (f) and common-mode current water vertical limit I CMLimV (f), calculate the target attenuation of the common-mode current required by the filter: IL CMH (f) = I CM (f, 0) - I CMLimH (f); IL CMV (f) = I CM (f, 0) - I CMLimV (f); where IL CMH (f) and IL CMV (f) represents the target attenuation of radiation interference in the horizontal and vertical directions, respectively.
[0107] (6) Display the actual radiated interference spectrum, radiated interference limits, radiated interference target suppression limits, and design margins using a spectrum diagram. (Refer to...) Figure 6 The spectrum diagram contains the actual spectrum E of radiated interference along the horizontal or vertical direction. H or E V Design margin Y H and Y V Radiated Interference Limit Standard (Limit) E limit Ideal radiation design limits (radiation interference target suppression limits) E LimH and E LimV .
[0108] IL obtained from the above process CMH (f) and IL CMV (f) can convert the system's radiation interference suppression target into the current suppression target at the cable end, and then use the idea of conduction circuit attenuation to select electromagnetic compatibility filters and quantitatively calculate parameters.
[0109] S204, Filter parameter design.
[0110] The following is based on Figure 7 The following explanation uses an LC filter structure as an example, where the filter inductor and capacitor values are L and L, respectively. x and C y The equivalent filter inductance L of its common-mode circuit xe = 0.5L x Equivalent filter capacitor C ye = 2C y .
[0111] (1) For AC power supply systems, the range of values for the filter capacitor should be determined according to the safety requirements for leakage current: Where U and f are the rated operating voltage and operating frequency of the AC power supply system, respectively, and I gmax C is the maximum leakage current allowed by safety regulations. ymax This indicates the maximum allowable value for the filter capacitor.
[0112] (2) Based on the available filter capacitors, select the equivalent filter capacitor C that satisfies condition 4.1. ye With C ymax The filter capacitor C with the closest value y C ye = 2C y .
[0113] (3) Calculate the insertion loss based on the selected filter structure, where the insertion loss expression provided by the LC filter is: Among them, V sZ represents the interference source. s and Z l These represent the source impedance and load impedance, respectively. Ideally, Z... s and Z l Take 50Ω.
[0114] (4) For the radiation interference results in the horizontal and vertical directions, based on the target attenuation IL obtained at each exceeding frequency point. CMH (f) and IL CMV (f) Of the two sets of spectrum curves, the one with the larger amplitude at each frequency point is taken as the final filter attenuation target design standard.
[0115] (5) Based on the attenuation rate of 20dB / dec of the LC filter, plot the filter insertion loss curve that meets the attenuation target, and determine the critical corner frequency f of the filter. c The insertion loss at the corner frequency is typically: .
[0116] (6) Test the critical corner frequency f c If the value is greater than zero, then it is feasible, based on the corner frequency f. c Determine the equivalent filter inductance value: .
[0117] (7) such as the critical corner frequency f c If the value is less than zero, a higher-order filter such as a CLC should be used, and the above steps should be repeated until the condition is met.
[0118] S205, Verification.
[0119] (1) Install the filter onto the electronic device under test, repeat the measurement process in S201, and verify the conducted common-mode current I after adding the filter. CM (f, 0) and radiation field strength E H (f), E V (f) Whether all limit requirements are met; if so, the design is complete. This process can also be performed through simulation.
[0120] (2) If not satisfied, recalculate the target attenuation IL at the frequency point exceeding the standard according to S203. CMH (f) and IL CMV (f) Confirm whether the frequency band exceeding the standard is within the frequency operating range of the selected filter.
[0121] (3) If the frequency point exceeding the standard is within the operating frequency range of the selected filter, adjust the design margin Y according to the magnitude of the exceeding standard. H (f) and Y V(f) and repeat the above design process. If the out-of-range frequency band is not within the operating frequency range of the selected filter, select other suppression schemes that can cover the out-of-range frequency band, such as high-frequency magnetic rings, and carry out the design according to the design idea of S204.
[0122] The above technical solutions establish a theoretical bridge from radiation to circuits. By employing the transfer function method, the "radiated field strength" target, which cannot be directly designed, is transformed into a measurable and designable "conducted common-mode current" target. This solves the fundamental problem of the disconnect between existing filter design theory and actual radiation suppression effect. Furthermore, it overcomes the reliance on experience and trial-and-error in radiated electromagnetic interference design, providing scientific guidance for the quantification and forward design of radiated electromagnetic interference filters. This significantly shortens the electromagnetic compatibility design and certification cycle of products and reduces R&D costs.
[0123] Figure 8 This is a block diagram of a radiation interference filter design system based on the transfer function method, provided as an embodiment of this application. Figure 8 As shown, the system 800 can be used to execute a radiated interference filter design method based on the transfer function method. The system 800 includes: an electronic device under test (DUT) 810, a line impedance stabilization network 820, an antenna 830, a high-frequency current probe 840, a measurement receiver 850, and a terminal 860. The DUT 810 is placed in an anechoic chamber, and the power cable 811 of the DUT 810 is connected to a power supply 870 through the line impedance stabilization network 820. The antenna 830 and the high-frequency current probe 840 are respectively connected to the measurement receiver 850. The measurement receiver 850 is connected to the terminal 860.
[0124] The antenna 830 is positioned at a predetermined distance around the electronic device under test 810 to acquire the radiated interference value generated by the electronic device under test 810 within the target frequency band and transmit the radiated interference value to the measurement receiver 850. The high-frequency current probe 840 is positioned at the port of the power cable 811 to acquire the conducted common-mode current value generated by the power cable 811 within the target frequency band and transmit the conducted common-mode current value to the measurement receiver 850. The measurement receiver 850 is used to obtain spectrum data based on the radiated interference value and the conducted common-mode current value, and generate a spectrum diagram.
[0125] For example, the measurement receiver can be an oscilloscope or a spectrum analyzer. It should be noted that the high-frequency current probe 840 is positioned on the power cable 811 near the port of the electronic device under test 810. Figure 8 The relative positions of the medium- and high-frequency current probe 840 and the power cable 811 are for illustrative purposes only and are not specifically limited.
[0126] The terminal 860 is used to determine the radiation target attenuation based on the radiated interference value and the radiated interference target suppression limit; the radiated interference target suppression limit is determined based on the limit corresponding to the target frequency band range and the design margin; the radiated interference target suppression limit corresponding to the radiated interference value is converted into a common-mode current target suppression limit through a transfer function; the common-mode current target suppression limit includes a common-mode current horizontal limit and a common-mode current vertical limit; the transfer function is determined based on the conducted common-mode current value and the radiated interference value; the common-mode current target attenuation is obtained based on the conducted common-mode current test value at the power cable 811 port and the common-mode current target suppression limit; the corner frequency of the candidate filter is checked based on the common-mode current target attenuation and the insertion loss curve of the candidate filter; if the corner frequency meets the preset check conditions, the candidate filter is used as the filter corresponding to the electronic device under test. For example, the terminal can be a computer, server, laptop, mobile phone, etc., without limitation.
[0127] Reference Figure 9 In some embodiments, the system 800 may also include a filter 880; the filter 880 may be disposed between the electronic device under test 810 and the high-frequency current probe 840.
[0128] The filter 800 can be obtained using the radiation interference filter design method based on the transfer function method described above, and corresponds to the electronic device under test 810. Specifically, the filter 800 can be designed using the workflow of radiation target attenuation → transfer function → common-mode current target attenuation → insertion loss corresponding to the electronic device under test 810. The workflow for designing this filter can be found in the relevant content of the above embodiments, and will not be repeated here.
[0129] Furthermore, the radiated interference value and conducted common-mode current test value of the electronic device under test 810 can be used to verify whether it meets the design standards. This verification process can be found in the relevant content of the above embodiments, and will not be repeated here.
[0130] The above technical solutions establish a theoretical bridge from radiation to circuits. By employing the transfer function method, the "radiated field strength" target, which cannot be directly designed, is transformed into a measurable and designable "conducted common-mode current" target. This solves the fundamental problem of the disconnect between existing filter design theory and actual radiation suppression effect. Furthermore, it overcomes the reliance on experience and trial-and-error in radiated electromagnetic interference design, providing scientific guidance for the quantification and forward design of radiated electromagnetic interference filters. This significantly shortens the electromagnetic compatibility design and certification cycle of products and reduces R&D costs.
[0131] The various embodiments in this specification are described in a progressive manner. For the same or similar parts between the various embodiments, please refer to each other. Each embodiment focuses on describing the differences from other embodiments.
[0132] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of this application.
Claims
1. A method for designing a radiated interference filter based on the transfer function method, characterized in that, The method includes: The electronic device under test is placed in an anechoic chamber. The power cable of the electronic device under test is connected to the power source through a line impedance stabilization network. An antenna is placed at a preset distance around the electronic device under test, and a high-frequency current probe is placed at the port of the power cable. The antenna is used to obtain the radiated interference value generated by the electronic device under test in the target frequency band, and the high-frequency current probe is used to obtain the conducted common-mode current value generated by the power cable in the target frequency band. The attenuation of the radiation target is determined based on the radiation interference value and the radiation interference target suppression limit; the radiation interference target suppression limit is determined based on the limit corresponding to the target frequency band range and the design margin. The radiated interference target suppression limit corresponding to the radiated interference value is converted into a common-mode current target suppression limit through a transfer function; the common-mode current target suppression limit includes a common-mode current horizontal limit and a common-mode current vertical limit; the transfer function is determined based on the conducted common-mode current value and the radiated interference value; The target attenuation of the common-mode current is obtained based on the conducted common-mode current test value at the power cable port and the target common-mode current suppression limit. Based on the target attenuation of the common-mode current and the insertion loss curve of the candidate filter, the corner frequency of the candidate filter is tested; if the corner frequency meets the preset test conditions, the candidate filter is used as the filter corresponding to the electronic device under test.
2. The method according to claim 1, characterized in that, The radiation interference target suppression limit includes the radiation interference level limit E. LimH (f) and vertical limit of radiated interference E LimV (f) The design margin includes the horizontal design margin Y. H (f) and vertical design margin Y V (f); The radiation interference target suppression limit is determined in the following manner: Obtain the limit value E corresponding to the target frequency band range. limit (f), and horizontal design margin Y H (f) and vertical design margin Y V (f); The limit value E limit (f) and the horizontal design margin Y H The difference between (f) and E is used as the radiation interference level limit. LimH (f); The limit value E limit (f) and the vertical design margin Y V The difference between (f) and E is taken as the vertical limit of the radiated interference. LimV (f).
3. The method according to claim 2, characterized in that, The radiation interference value includes the horizontal radiation interference value E. H (f) and vertical radiation interference value E V (f) The radiation target attenuation includes the horizontal radiation target attenuation RIL. CMH (f) and vertical radiation target attenuation RIL CMV (f); The determination of the radiation target attenuation based on the radiation interference value and the radiation interference target suppression limit includes: The horizontal radiation interference value E H (f) and the radiation interference level limit E LimH The difference between (f) and (f) is used as the horizontal radiation target attenuation amount RIL. CMH (f); The vertical radiation interference value E V (f) and the vertical limit E of the radiation interference LimV The difference between (f) and (f) is taken as the vertical radiation target attenuation amount RIL. CMV (f).
4. The method according to claim 3, characterized in that, The transfer function includes the horizontal transfer function T. CRH (f) and vertical transfer function T CRV (f); The step of converting the radiation interference target suppression limit corresponding to the radiation interference value into a common-mode current target suppression limit through a transfer function includes: The horizontal radiation interference value E H (f) and the horizontal transfer function T CRH The ratio of (f) is used as the common-mode current level limit I. CMLimH (f, 0); The vertical radiation interference value E V (f) and the vertical transfer function T CRV The ratio of (f) is used as the common-mode current vertical limit I. CMLimV (f, 0).
5. The method according to claim 4, characterized in that, The target common-mode current attenuation includes the horizontal current attenuation IL. CMH (f) and vertical current attenuation IL CMV (f); The step of obtaining the target common-mode current attenuation based on the conducted common-mode current test value at the power cable port and the target common-mode current suppression limit includes: The conducted common-mode current test value I CM (f, 0) and the common-mode current level limit I CMLimH The difference between (f, 0) is used as the target attenuation amount IL of the horizontal current. CMH (f); The conducted common-mode current test value I CM (f, 0) and the common-mode current vertical limit I CMLimV The difference between (f, 0) is used as the target attenuation amount IL of the vertical current. CMV (f).
6. The method according to claim 5, characterized in that, The step of verifying the corner frequency of the candidate filter based on the target attenuation of the common-mode current and the insertion loss curve of the candidate filter includes: Based on the structure of the candidate filter, determine the corresponding insertion loss; Determine the frequency points exceeding the standard within the target frequency band, and the corresponding horizontal current target attenuation and vertical current target attenuation at the frequency points exceeding the standard; For each frequency point exceeding the standard, the larger of the horizontal current target attenuation and the vertical current target attenuation corresponding to the frequency point exceeding the standard is taken as the design limit. By combining the design limit with the attenuation rate corresponding to the candidate filter, the insertion loss curve is obtained, and the critical corner frequency f of the candidate filter is determined from the insertion loss curve. c ; At the critical transition frequency f c If the value is greater than zero, the candidate filter is determined to satisfy the preset test condition; at the critical corner frequency f c If the value is less than zero, it is determined that the candidate filter does not meet the preset test condition, and a new filter is selected for test.
7. The method according to claim 6, characterized in that, The method further includes: By measuring the receiver, the radiated interference value, the radiated interference target suppression limit, the limit corresponding to the target frequency band range, and the spectrum data of the design margin are obtained respectively. A spectrum diagram is obtained based on the spectrum data.
8. The method according to claim 7, characterized in that, The method further includes: The filter corresponding to the electronic device under test is installed on the electronic device under test, and the radiated interference value and conducted common-mode current test value of the electronic device under test are measured. If the radiated interference value meets the target suppression limit for radiated interference and the conducted common-mode current test value meets the target suppression limit for common-mode current, then the filter is determined to meet the design standard. If the radiated interference value does not meet the target suppression limit for radiated interference, and the conducted common-mode current test value does not meet the target suppression limit for common-mode current, the filter model and / or parameters are adjusted according to the target attenuation of the common-mode current corresponding to the frequency point exceeding the standard, until the filter meets the design standard.
9. The method according to claim 8, characterized in that, The step of adjusting the filter model and / or parameters according to the target attenuation of the common-mode current corresponding to the out-of-specification frequency point until the filter meets the design standards includes: If the target attenuation of the common-mode current corresponding to the out-of-standard frequency point is within the operating frequency range of the filter, adjust the design margin until the filter meets the design standards. If the target attenuation of the common-mode current corresponding to the out-of-standard frequency point is not within the operating frequency range of the filter, replace it with another type of filter and re-verify the design standards.
10. A radiation interference filter design system based on the transfer function method, characterized in that, The system is used to perform the method of any one of claims 1-9, the system comprising: an electronic device under test, a line impedance stabilization network, an antenna, a high-frequency current probe, a measurement receiver, and a terminal; the electronic device under test is disposed in an anechoic chamber, and the power cable of the electronic device under test is connected to a power source through the line impedance stabilization network; the antenna and the high-frequency current probe are respectively connected to the measurement receiver; the measurement receiver is connected to the terminal; The antenna is positioned at a preset distance around the electronic device under test (DUT) to acquire the radiated interference value generated by the DUT within the target frequency band and to transmit the radiated interference value to the measurement receiver. The high-frequency current probe is installed at the power cable port to acquire the conducted common-mode current value generated by the power cable in the target frequency band and send the conducted common-mode current value to the measurement receiver. The measurement receiver is used to obtain spectral data based on the radiated interference value and the conducted common-mode current value, and to generate a spectrum diagram. The terminal is used to determine the radiation target attenuation based on the radiated interference value and the radiated interference target suppression limit; the radiated interference target suppression limit is determined based on the limit corresponding to the target frequency band range and the design margin; the radiated interference target suppression limit corresponding to the radiated interference value is converted into a common-mode current target suppression limit through a transfer function; the common-mode current target suppression limit includes a common-mode current horizontal limit and a common-mode current vertical limit; the transfer function is determined based on the conducted common-mode current value and the radiated interference value; the common-mode current target attenuation is obtained based on the conducted common-mode current test value at the power cable port and the common-mode current target suppression limit; the corner frequency of the candidate filter is checked based on the common-mode current target attenuation and the insertion loss curve of the candidate filter; if the corner frequency meets the preset check conditions, the candidate filter is used as the filter corresponding to the electronic device under test.