器件的選用

器件的選用在設計的產品運行中起到至關重要的作用，從電機、開關

、繼電器
、電纜組件及連接器等
，甚至到電源、晶振、變(bian)壓(ya)器(qi)等(deng)都(dou)應(ying)該(gai)下(xia)功(gong)夫(fu)進(jin)行(xing)精(jing)心(xin)地(di)篩(shai)選(xuan)
，否(fou)則(ze)，在(zai)選(xuan)型(xing)中(zhong)稍(shao)有(you)不(bu)慎(shen)
，就(jiu)會(hui)對(dui)設(she)備(bei)自(zi)身(shen)或(huo)周(zhou)圍(wei)將(jiang)設(she)備(bei)造(zao)成(cheng)嚴(yan)重(zhong)的(de)不(bu)利(li)影(ying)響(xiang)。電(dian)磁(ci)兼(jian)容(rong)設(she)計(ji)從(cong)三(san)個(ge)方(fang)麵(mian)考(kao)慮(lv)：1)幹擾源
；2)傳播耦合路徑

；3)敏(min)感(gan)設(she)備(bei)。電(dian)磁(ci)兼(jian)容(rong)設(she)計(ji)從(cong)這(zhe)三(san)個(ge)方(fang)麵(mian)做(zuo)工(gong)作(zuo)。其(qi)中(zhong)濾(lv)波(bo)連(lian)接(jie)器(qi)是(shi)解(jie)決(jue)耦(ou)合(he)路(lu)徑(jing)的(de)絕(jue)佳(jia)方(fang)法(fa)之(zhi)一(yi)。濾(lv)波(bo)連(lian)接(jie)是(shi)一(yi)種(zhong)具(ju)備(bei)濾(lv)波(bo)功(gong)能(neng)的(de)連(lian)接(jie)器(qi)。通(tong)常(chang)工(gong)程(cheng)上(shang)使(shi)用(yong)的(de)信(xin)號(hao)電(dian)纜(lan)是(shi)屏(ping)蔽(bi)電(dian)纜(lan)，但(dan)仍(reng)不(bu)能(neng)滿(man)足(zu)電(dian)磁(ci)兼(jian)容(rong)標(biao)準(zhun)，對(dui)於(yu)高(gao)頻(pin)幹(gan)擾(rao)的(de)屏(ping)蔽(bi)

，主(zhu)要(yao)原(yuan)因(yin)是(shi)屏(ping)蔽(bi)電(dian)纜(lan)是(shi)金(jin)屬(shu)編(bian)製(zhi)網(wang)，上(shang)麵(mian)的(de)孔(kong)洞(dong)會(hui)在(zai)高(gao)頻(pin)時(shi)產(chan)生(sheng)泄(xie)露(lu)，另(ling)外(wai)一(yi)個(ge)原(yuan)因(yin)是(shi)屏(ping)蔽(bi)電(dian)纜(lan)的(de)高(gao)屏(ping)蔽(bi)效(xiao)能(neng)取(qu)決(jue)於(yu)電(dian)纜(lan)屏(ping)蔽(bi)層(ceng)的(de)端(duan)接(jie)情(qing)況(kuang)
，隻(zhi)有(you)當(dang)電(dian)纜(lan)屏(ping)蔽(bi)層(ceng)的(de)端(duan)接(jie)為(wei)360度(du)低(di)阻(zu)抗(kang)搭(da)接(jie)時(shi)，才(cai)會(hui)有(you)較(jiao)理(li)想(xiang)的(de)高(gao)屏(ping)蔽(bi)效(xiao)果(guo)，很(hen)多(duo)場(chang)合(he)下(xia)都(dou)無(wu)法(fa)保(bao)證(zheng)。濾(lv)波(bo)連(lian)接(jie)器(qi)能(neng)夠(gou)有(you)效(xiao)的(de)濾(lv)除(chu)不(bu)必(bi)要(yao)的(de)高(gao)頻(pin)成(cheng)分(fen)，彌(mi)補(bu)了(le)屏(ping)蔽(bi)電(dian)纜(lan)對(dui)於(yu)高(gao)頻(pin)幹(gan)擾(rao)屏(ping)蔽(bi)的(de)不(bu)足(zu)"。

電子設備的電磁兼容分析

電(dian)纜(lan)是(shi)係(xi)統(tong)的(de)最(zui)薄(bo)弱(ruo)環(huan)節(jie)
，兩(liang)台(tai)獨(du)立(li)進(jin)行(xing)電(dian)磁(ci)幹(gan)擾(rao)測(ce)試(shi)完(wan)全(quan)合(he)格(ge)的(de)設(she)備(bei)通(tong)過(guo)電(dian)纜(lan)連(lian)接(jie)後(hou)，係(xi)統(tong)往(wang)往(wang)在(zai)電(dian)磁(ci)兼(jian)容(rong)環(huan)境(jing)下(xia)測(ce)試(shi)不(bu)通(tong)過(guo)，這(zhe)是(shi)忽(hu)略(lve)了(le)電(dian)纜(lan)的(de)輻(fu)射(she)作(zuo)用(yong)。實(shi)踐(jian)表(biao)明(ming)，按(an)照(zhao)屏(ping)蔽(bi)設(she)計(ji)規(gui)範(fan)設(she)計(ji)的(de)屏(ping)蔽(bi)機(ji)箱(xiang)可(ke)達(da)到(dao)60～80dB的屏蔽效能，電纜處置不當
，造成係統產生嚴重的電磁幹擾問題。90％dedianciganraowentishiyouyudianlanzaochengde。dianlanshigaoxiaodediancibojieshoutianxianhefushetianxian
，dianlanchanshengdefusheyouqiyanzhong。dianlanduankouchuyougongmodianyacunzai，dianlanzaizhegegongmodianyadequdongxia，rutongyigendanjitianxian。tachanshengdedianchangfusheruxiashisuoshi：

E=12．6×10-7(fIL)(1／r)

式中：J是電纜中的共模電流強度，L是電纜的長度，
，是共模信號的頻率，rshiguancediandaofusheyuandejuli。ketongguojianxiaogaopingongmodianliuqiangdu
，suoduandianlanchangdujianxiaodianlandefushe。dianlandechangdubunengsuiyijianxiao，kongzhidianlangongmofushedezuihaodefangfashijianxiaogaopingongmodianliudefudu，yinweigaopingongmodianliudefushexiaolvhengao，shizaochengdianlanchaobiaofushedezhuyaoyinsu。jianxiaodianlanshanggongmogaopindianliudeyigeyouxiaofangfashizaidianlandeduankouchushiyongditonglvboqi，lvchudianlanshangdegaopingongmodianliu。chuantongshangdoushijianglvboqianzhuangzaixianlubanshangdedianlanduankouchu，zhezhonganzhuangfangshijingguolvbohoudexinhaoxianzaijixiangneijiaochang，rongyizaiciganyingshangqianraoxinhao
，xingchengxindegongmodianliu


，daozhidianlanfushe。zaiciganyingdexinhaoyoulianggelaiyuan：1)機箱內的電磁波會感應到電纜上，2)lvboqiqiandeganraoxinhaohuitongguojishengdianrongzhijieouhedaodianlanduankoushang。jiejuezhegewentidefangfashijinliangjianxiaolvbohoubaoluzaijixiangneidaoxianchangdu。lvbolianjieqishijiejuezhegewentidelixiangqijian。lvbolianjieqidemeigechazhenshangyouyigeditonglvboqi
，nenggoujiangchazhenshangdegongmodianliulvdiao。zhexielvbolianjieqiwangwangzaiwaixinghechicunshangyuputonglianjieqixiangtong
，keyizhijietidaiputonglianjieqi。youyulianjieqianzhuangzaidianlanjinrujixiangdeduankouchu，yincilvbohoudedaoxianbuhuizaiganyingshangganraoxinhao。

濾波連接器較屏蔽電纜優點

濾波連接器較屏蔽電纜使用的優點有如下三個優點：1)濾(lv)波(bo)連(lian)接(jie)器(qi)能(neng)將(jiang)電(dian)纜(lan)中(zhong)的(de)幹(gan)擾(rao)電(dian)流(liu)濾(lv)除(chu)掉(diao)
，徹(che)底(di)消(xiao)除(chu)電(dian)纜(lan)的(de)輻(fu)射(she)因(yin)素(su)。屏(ping)蔽(bi)電(dian)纜(lan)僅(jin)僅(jin)是(shi)防(fang)止(zhi)幹(gan)擾(rao)通(tong)過(guo)電(dian)纜(lan)輻(fu)射(she)，實(shi)際(ji)這(zhe)些(xie)幹(gan)擾(rao)電(dian)流(liu)還(hai)在(zai)電(dian)纜(lan)中(zhong)；2)濾(lv)波(bo)連(lian)接(jie)器(qi)抑(yi)製(zhi)電(dian)纜(lan)輻(fu)射(she)的(de)效(xiao)果(guo)比(bi)屏(ping)蔽(bi)電(dian)纜(lan)更(geng)穩(wen)定(ding)。屏(ping)蔽(bi)電(dian)纜(lan)的(de)效(xiao)果(guo)在(zai)很(hen)大(da)程(cheng)度(du)上(shang)決(jue)定(ding)於(yu)電(dian)纜(lan)的(de)端(duan)接(jie)。由(you)於(yu)電(dian)纜(lan)頻(pin)繁(fan)的(de)拆(chai)裝(zhuang)或(huo)較(jiao)長(chang)時(shi)間(jian)後(hou)搭(da)接(jie)點(dian)的(de)氧(yang)化(hua)，端(duan)接(jie)阻(zu)抗(kang)會(hui)增(zeng)加(jia)
，造(zao)成(cheng)屏(ping)蔽(bi)效(xiao)能(neng)下(xia)降(jiang)；3)濾波連接器的使用，可降低對電纜端接的要求
，降低生產成本，避免使用價格昂貴的高質量屏蔽電纜
，降低成本。

設計使用濾波連接器的試驗情況

分fen別bie使shi用yong普pu通tong連lian接jie器qi和he濾lv波bo連lian接jie器qi進jin行xing輻fu射she發fa射she研yan究jiu。從cong試shi驗yan結jie果guo可ke以yi看kan出chu，當dang使shi用yong屏ping蔽bi機ji箱xiang時shi
，主zhu要yao的de輻fu射she源yuan是shi電dian纜lan。這zhe時shi使shi用yong濾lv波bo連lian接jie器qi可ke以yi使shi輻fu射she發fa射she強qiang度du降jiang低di10～30dB。

特te別bie在zai電dian磁ci環huan境jing複fu雜za的de今jin天tian
，電dian磁ci兼jian容rong技ji術shu顯xian得de越yue發fa重zhong要yao。在zai實shi際ji工gong程cheng應ying用yong中zhong使shi用yong濾lv波bo連lian接jie器qi對dui抗kang電dian磁ci幹gan擾rao，可ke以yi起qi到dao良liang好hao的de效xiao果guo。設she計ji人ren員yuan隻zhi要yao在zai產chan品pin的de設she計ji初chu期qi考kao慮lv到dao產chan品pin的de電dian磁ci兼jian容rong性xing，在zai可ke能neng產chan生sheng幹gan擾rao的de地di方fang采cai取qu相xiang應ying的de抗kang幹gan擾rao措cuo施shi。這zhe樣yang，設she計ji的de係xi統tong就jiu能neng夠gou在zai複fu雜za的de電dian磁ci環huan境jing下xia正zheng常chang運yun行xing。