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)minganshebei。diancijianrongshejicongzhesangefangmianzuogongzuo。qizhonglvbolianjieqishijiejueouhelujingdejuejiafangfazhiyi。lvbolianjieshiyizhongjubeilvbogongnengdelianjieqi。tongchanggongchengshangshiyongdexinhaodianlanshipingbidianlan，danrengbunengmanzudiancijianrongbiaozhun，duiyugaopinganraodepingbi，zhuyaoyuanyinshipingbidianlanshijinshubianzhiwang，shangmiandekongdonghuizaigaopinshichanshengxielu
，lingwaiyigeyuanyinshipingbidianlandegaopingbixiaonengqujueyudianlanpingbicengdeduanjieqingkuang，zhiyoudangdianlanpingbicengdeduanjiewei360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dao60～80dB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％的(de)電(dian)磁(ci)幹(gan)擾(rao)問(wen)題(ti)是(shi)由(you)於(yu)電(dian)纜(lan)造(zao)成(cheng)的(de)。電(dian)纜(lan)是(shi)高(gao)效(xiao)的(de)電(dian)磁(ci)波(bo)接(jie)收(shou)天(tian)線(xian)和(he)輻(fu)射(she)天(tian)線(xian)，電(dian)纜(lan)產(chan)生(sheng)的(de)輻(fu)射(she)尤(you)其(qi)嚴(yan)重(zhong)。電(dian)纜(lan)端(duan)口(kou)處(chu)有(you)共(gong)模(mo)電(dian)壓(ya)存(cun)在(zai)，電(dian)纜(lan)在(zai)這(zhe)個(ge)共(gong)模(mo)電(dian)壓(ya)的(de)驅(qu)動(dong)下(xia)，如(ru)同(tong)一(yi)根(gen)單(dan)極(ji)天(tian)線(xian)。它(ta)產(chan)生(sheng)的(de)電(dian)場(chang)輻(fu)射(she)如(ru)下(xia)式(shi)所(suo)示(shi)：

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，r是shi觀guan測ce點dian到dao輻fu射she源yuan的de距ju離li。可ke通tong過guo減jian小xiao高gao頻pin共gong模mo電dian流liu強qiang度du
，縮suo短duan電dian纜lan長chang度du減jian小xiao電dian纜lan的de輻fu射she。電dian纜lan的de長chang度du不bu能neng隨sui意yi減jian小xiao

，控kong製zhi電dian纜lan共gong模mo輻fu射she的de最zui好hao的de方fang法fa是shi減jian小xiao高gao頻pin共gong模mo電dian流liu的de幅fu度du，因yin為wei高gao頻pin共gong模mo電dian流liu的de輻fu射she效xiao率lv很hen高gao
，是shi造zao成cheng電dian纜lan超chao標biao輻fu射she的de主zhu要yao因yin素su。減jian小xiao電dian纜lan上shang共gong模mo高gao頻pin電dian流liu的de一yi個ge有you效xiao方fang法fa是shi在zai電dian纜lan的de端duan口kou處chu使shi用yong低di通tong濾lv波bo器qi，濾lv除chu電dian纜lan上shang的de高gao頻pin共gong模mo電dian流liu。傳chuan統tong上shang都dou是shi將jiang濾lv波bo器qi安an裝zhuang在zai線xian路lu板ban上shang的de電dian纜lan端duan口kou處chu，這zhe種zhong安an裝zhuang方fang式shi經jing過guo濾lv波bo後hou的de信xin號hao線xian在zai機ji箱xiang內nei較jiao長chang，容rong易yi再zai次ci感gan應ying上shang千qian擾rao信xin號hao，形xing成cheng新xin的de共gong模mo電dian流liu，導dao致zhi電dian纜lan輻fu射she。再zai次ci感gan應ying的de信xin號hao有you兩liang個ge來lai源yuan：1)機箱內的電磁波會感應到電纜上
，2)濾lv波bo器qi前qian的de幹gan擾rao信xin號hao會hui通tong過guo寄ji生sheng電dian容rong直zhi接jie耦ou合he到dao電dian纜lan端duan口kou上shang。解jie決jue這zhe個ge問wen題ti的de方fang法fa是shi盡jin量liang減jian小xiao濾lv波bo後hou暴bao露lu在zai機ji箱xiang內nei導dao線xian長chang度du。濾lv波bo連lian接jie器qi是shi解jie決jue這zhe個ge問wen題ti的de理li想xiang器qi件jian。濾lv波bo連lian接jie器qi的de每mei個ge插cha針zhen上shang有you一yi個ge低di通tong濾lv波bo器qi
，能neng夠gou將jiang插cha針zhen上shang的de共gong模mo電dian流liu濾lv掉diao。這zhe些xie濾lv波bo連lian接jie器qi往wang往wang在zai外wai形xing和he尺chi寸cun上shang與yu普pu通tong連lian接jie器qi相xiang同tong
，可ke以yi直zhi接jie替ti代dai普pu通tong連lian接jie器qi。由you於yu連lian接jie器qi安an裝zhuang在zai電dian纜lan進jin入ru機ji箱xiang的de端duan口kou處chu
，因yin此ci濾lv波bo後hou的de導dao線xian不bu會hui再zai感gan應ying上shang幹gan擾rao信xin號hao。

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。

tebiezaidiancihuanjingfuzadejintian
，diancijianrongjishuxiandeyuefazhongyao。zaishijigongchengyingyongzhongshiyonglvbolianjieqiduikangdianciganrao，keyiqidaolianghaodexiaoguo。shejirenyuanzhiyaozaichanpindeshejichuqikaolvdaochanpindediancijianrongxing
，zaikenengchanshengganraodedifangcaiquxiangyingdekangganraocuoshi。zheyang，shejidexitongjiunenggouzaifuzadediancihuanjingxiazhengchangyunxing。