電(dian)(dian)(dian)(dian)(dian)磁(ci)干(gan)擾（Electromagnetic Interference 簡稱EMI），是(shi)(shi)指電(dian)(dian)(dian)(dian)(dian)磁(ci)波與電(dian)(dian)(dian)(dian)(dian)子元件作用后(hou)而產生的(de)干(gan)擾現象，有傳(chuan)導(dao)干(gan)擾和(he)輻(fu)射(she)干(gan)擾兩種。傳(chuan)導(dao)干(gan)擾是(shi)(shi)指通(tong)過(guo)導(dao)電(dian)(dian)(dian)(dian)(dian)介質把(ba)一(yi)個電(dian)(dian)(dian)(dian)(dian)網絡上的(de)信(xin)號耦合(干(gan)擾)到另一(yi)個電(dian)(dian)(dian)(dian)(dian)網絡。輻(fu)射(she)干(gan)擾是(shi)(shi)指干(gan)擾源(yuan)通(tong)過(guo)空間把(ba)其(qi)信(xin)號耦合(干(gan)擾)到另一(yi)個電(dian)(dian)(dian)(dian)(dian)網絡，在高速PCB及系統設計中，高頻信(xin)號線、集成電(dian)(dian)(dian)(dian)(dian)路的(de)引腳、各類接插(cha)件等都可能成為具有天(tian)線特性的(de)輻(fu)射(she)干(gan)擾源(yuan)，能發射(she)電(dian)(dian)(dian)(dian)(dian)磁(ci)波并影響其(qi)他(ta)系統或本(ben)系統內其(qi)他(ta)子系統的(de)正(zheng)常工(gong)作。

所謂“干(gan)擾(rao)(rao)”,指設備受(shou)到(dao)(dao)干(gan)擾(rao)(rao)后性能降(jiang)低(di)以及對設備產(chan)生干(gan)擾(rao)(rao)的(de)干(gan)擾(rao)(rao)源這(zhe)二層(ceng)意思(si)。*層(ceng)意思(si)如雷電(dian)使收音(yin)機產(chan)生雜音(yin),摩托(tuo)車在附(fu)近行駛后電(dian)視畫面出現雪花,拿起電(dian)話后聽到(dao)(dao)無線電(dian)聲音(yin)等,這(zhe)些(xie)可以簡稱其(qi)為與“BC I”“TV I”“Tel I”,這(zhe)些(xie)縮寫中都有相同的(de)“I”（干(gan)擾(rao)(rao)）那么EMI標準和EMI檢測(ce)是EMI的(de)哪(na)部(bu)分呢？理(li)所當然(ran)是第二層(ceng)含義,即干(gan)擾(rao)(rao)源,也包括(kuo)受(shou)到(dao)(dao)干(gan)擾(rao)(rao)之前的(de)電(dian)磁能量(liang)。