![]() The only way to know if a lowpass filter design is adequate or not is by trial and error experiments performed during EMC compliance testing, or more preferably, by trying out different low-pass filterĬomponent values very early in the product development cycle. It is impossible to model the filter exactly if the load impedance is not known. This is the situation with common mode emissions emanating off of a cable during a RE test where the impedance of the cable changes as it is rearranged in order to maximize emissions ( Reference ). Unfortunately, circuit impedances are not always well understood or impossible to know, making it more difficult to determine which values of passive low-pass filter components to choose from in order to pass the EMC compliance tests. Consult the references for more information on these other filter types. The other types of passive filters, such as high-pass,īand-pass, and band-reject are not as common as the low-pass filter is for EMC work and will not be covered in this paper. For most cases, in order to achieve EMC compliance, we really only need to know how to apply passive low-pass filter types to our circuits. If you find yourself stuck in any of the above situations, this article on passive filter basics for EMC compliance should help remove the mystery, and allow you to quickly find the best passive component filter solution that allows product to ship on time.īASICS OF PASSIVE FILTERS FOR EMC COMPLIANCEįortunately, designing filters for EMC compliance is not as difficult as it may seem. The time to learn how to properly design filters for EMC compliance is not when schedules are tight, and the product’s ship date is rapidly approaching. They may also want to know how they can get more attenuation out of their filter design in order to pass an emissions or immunity test. ![]() However, selecting the proper filter for a given situation may be confusing to some, especially if they are new to the EMC field or have not dealt with the subject in some time.ĮMC practitioners may be asking themselves what filter configuration is the best one to use for any given application or how to correctly choose the values of components given the frequency, circuit impedance, and other parameters of the circuit. The purpose of a filter is to establish either a low-impedance path for RF current to return back to the local source of energy, and/or to provide a high impedance to prevent RF currents from flowing on a cable. ![]() One of the roles of the practicing EMC engineer or product designer is to be able to design filters to add to circuits in order to get them to pass various EMC immunity and emissions standards such as IEC 6 for ESD immunity, IEC 6 for Radiated RF immunity and IEC 6 for Electrical Fast Transient/Burst immunity and other various international standards covering Radiated Emissions (RE) or Conducted Emissions (CE).ĮMI filters are often used along with proper shielding in order to achieve EMC compliance.
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