womendouzhidaoshizhongyuankeyitongguoliangzhongfangshichanshengdianciganrao。tongbushizhongdezhongfutexingyijimeiyouzhengqueduanjiedexianludouhuichanshengdianciganrao。shizhongdenengliangshitongguotianxianfushejinrudiancichangde。zhelizhidetianxianbaokuogezhongxingshi：PCB線路
、PCB返工線、未經充分屏蔽的元件、連接器、纜線(屏蔽或非屏蔽)yijiweizhengquejiedideshebeideng。zaigaosushuzixitongzhong
，gudingpinlvdeshizhongshizhuyaodedianciganraoyuan。zheshiyinwei，zhexieshizhongzongshizaiyigegudingdepinlvxiagongzuo，zhejiangshinengliangzengjiadaogenggaodejibie。erfeizhongfuxingxinhaohuoshiyibuxinhaobuhuichanshengruciduodedianciganrao。suizhegenggaodeshujusulvyaoqiugengkuaideshizhongpinlv，xinhaodebianyanlv(即上升時間和下降時間)yesuizhitigao。jiaokuaidebianyanlvjiangshifushexinhaodenengliangjibiezengjiagengduo。daozhidianciganraodediergeyuanyinshishizhongxianlumeiyouzhengqueduanjie。zukangbupipeijianghuidaozhixianluxinhaochuxianzhengxianghuofuxiangdeguochong
，zaizhezhongqingkuangxiafushenengliangjianghuizengjia
，zengjiadefuduqujueyuzhengfuxiangguochongdeyanzhongchengdu。ruguoyanzhongdeguochongdaozhileshidaoershigejiedian，kenengjiuwufatongguoFCC符合標準測試。

 

對於經驗豐富的工程師來說
，在數字係統中有許多種方法可用於解決電磁幹擾問題。設計者可以選擇屏蔽設計
、信(xin)號(hao)過(guo)濾(lv)或(huo)是(shi)消(xiao)除(chu)幹(gan)擾(rao)源(yuan)能(neng)量(liang)的(de)方(fang)法(fa)來(lai)解(jie)決(jue)問(wen)題(ti)
，這(zhe)些(xie)方(fang)案(an)可(ke)以(yi)單(dan)獨(du)使(shi)用(yong)，也(ye)可(ke)以(yi)和(he)其(qi)他(ta)方(fang)案(an)配(pei)合(he)使(shi)用(yong)。第(di)一(yi)種(zhong)方(fang)法(fa)為(wei)屏(ping)蔽(bi)，這(zhe)並(bing)不(bu)是(shi)一(yi)種(zhong)電(dian)氣(qi)解(jie)決(jue)方(fang)案(an)，而(er)隻(zhi)能(neng)稱(cheng)得(de)上(shang)是(shi)一(yi)種(zhong)機(ji)械(xie)上(shang)的(de)執(zhi)行(xing)方(fang)案(an)。屏(ping)蔽(bi)是(shi)采(cai)用(yong)金(jin)屬(shu)包(bao)裝(zhuang)的(de)方(fang)式(shi)將(jiang)元(yuan)器(qi)件(jian)、電路、組合件、電纜或整個係統的幹擾源包圍起來，防止幹擾電磁場向外擴散。過去經常采用屏蔽方案，但是有時這種方案的成本較高
；而er且qie對dui於yu發fa熱re量liang比bi較jiao大da的de電dian路lu係xi統tong
，加jia上shang屏ping蔽bi盒he會hui影ying響xiang散san熱re
，沒mei有you良liang好hao的de散san熱re這zhe對dui產chan品pin來lai說shuo是shi非fei常chang致zhi命ming的de，過guo熱re甚shen至zhi會hui損sun傷shang器qi件jian或huo係xi統tong。還hai有you
，一yi旦dan在zai產chan品pin發fa布bu之zhi前qian發fa現xian電dian磁ci幹gan擾rao問wen題ti
，如ru果guo采cai用yong屏ping蔽bi方fang案an，屏ping蔽bi盒he的de安an裝zhuang將jiang成cheng為wei一yi個ge難nan題ti。其qi他ta兩liang種zhong方fang法fa為wei濾lv波bo和he降jiang低di功gong率lv都dou是shi采cai用yong將jiang產chan生sheng電dian磁ci幹gan擾rao輻fu射she的de線xian路lu隔ge離li的de方fang法fa。為wei了le確que定ding究jiu竟jing是shi哪na一yi條tiao或huo是shi哪na幾ji條tiao線xian路lu導dao致zhi了le電dian磁ci幹gan擾rao
，應ying進jin行xing消xiao聲sheng室shi測ce試shi或huo是shi電dian磁ci幹gan擾rao仿fang真zhen。測ce試shi得de到dao的de輻fu射she報bao告gao將jiang確que定ding在zai哪na些xie頻pin率lv上shang的de電dian磁ci幹gan擾rao超chao標biao，這zhe些xie頻pin率lv通tong常chang被bei稱cheng為wei幹gan擾rao點dian。一yi旦dan確que定ding了le這zhe些xie頻pin率lv(以及其諧波頻率)
，就可找到導致幹擾的時鍾線路，這裏可以從時鍾信號是否端接
、時鍾驅動器的選擇、時鍾驅動器的選擇、降低時鍾邊沿轉換率來考慮。

 

因此針對時鍾電路的EMC設she計ji，我wo們men提ti出chu了le如ru下xia的de建jian議yi。由you於yu目mu前qian已yi有you許xu多duo以yi機ji械xie結jie構gou或huo是shi改gai變bian電dian路lu布bu局ju方fang式shi的de電dian磁ci波bo幹gan擾rao防fang治zhi解jie決jue方fang案an，但dan是shi這zhe些xie解jie決jue方fang案an都dou耗hao時shi費fei事shi
，若ruo能neng在zai電dian路lu設she計ji上shang的de小xiao細xi節jie多duo加jia留liu意yi，就jiu可ke以yi有you效xiao地di預yu防fang電dian磁ci波bo噪zao聲sheng的de產chan生sheng。時shi鍾zhong信xin號hao若ruo是shi沒mei有you被bei正zheng確que的de端duan接jie，或huo是shi時shi鍾zhong器qi件jian具ju有you快kuai速su的de瞬shun時shi特te性xing，都dou會hui產chan生sheng大da量liang的de電dian磁ci波bo噪zao聲sheng。若ruo要yao控kong製zhi電dian磁ci波bo噪zao聲sheng的de產chan生sheng，必bi須xu考kao慮lv下xia列lie幾ji項xiang原yuan則ze：正確的端接所有的時鍾信號；盡量采用邊緣上升速率較低的時鍾緩衝器件
；在時鍾線路中采用濾波電容；在高速的電路中采用時鍾擴頻技術。

 

chuleyishangyunyongdefangfa，womenhaikeyiyongyixiecuoshilaijianxiaoshizhongdianluyijishizhongxianludediancifushe
，rushizhongxinhaozouxianchangdujinkenengduan，xiankuanjinkenengda
，yuqitaxianjianjujinkenengda，jinkaoqijianbujubuxian，biyaoshikeyizouneiceng；時(shi)鍾(zhong)產(chan)生(sheng)器(qi)盡(jin)量(liang)靠(kao)近(jin)使(shi)用(yong)該(gai)時(shi)鍾(zhong)的(de)器(qi)件(jian)。在(zai)某(mou)些(xie)情(qing)況(kuang)下(xia)，可(ke)以(yi)采(cai)取(qu)對(dui)時(shi)鍾(zhong)線(xian)路(lu)添(tian)加(jia)保(bao)護(hu)性(xing)線(xian)路(lu)，即(ji)在(zai)時(shi)鍾(zhong)線(xian)兩(liang)邊(bian)鋪(pu)設(she)兩(liang)條(tiao)接(jie)地(di)線(xian)進(jin)行(xing)屏(ping)蔽(bi)。時(shi)鍾(zhong)電(dian)路(lu)和(he)高(gao)頻(pin)電(dian)路(lu)是(shi)主(zhu)要(yao)的(de)幹(gan)擾(rao)和(he)輻(fu)射(she)源(yuan)，一(yi)定(ding)要(yao)單(dan)獨(du)安(an)排(pai)、遠離敏感電路。時鍾輸出布線時不要采用向多個器件直接串行地連接(稱為菊花式連接)；而應該經時鍾緩衝器分發後向多個器件直接提供時鍾信號。石英晶體下麵以及對噪聲敏感的器件下麵不要走線
，且石英晶體振蕩器外殼要接地。時鍾線要嚴格地控製阻抗，如果能從內層走線則最好(可減小幹擾)，盡量少用過孔。保證時鍾信號返回路徑的完整性
，使信號返回路徑的環路麵積最小，減小電磁輻射。各類時鍾IC芯(xin)片(pian)的(de)接(jie)地(di)引(yin)腳(jiao)要(yao)就(jiu)近(jin)接(jie)地(di)。隻(zhi)要(yao)在(zai)電(dian)路(lu)設(she)計(ji)上(shang)遵(zun)守(shou)這(zhe)些(xie)簡(jian)單(dan)的(de)規(gui)則(ze)，就(jiu)可(ke)以(yi)最(zui)低(di)的(de)成(cheng)本(ben)和(he)最(zui)短(duan)的(de)時(shi)間(jian)內(nei)有(you)效(xiao)地(di)控(kong)製(zhi)電(dian)磁(ci)波(bo)輻(fu)射(she)，提(ti)高(gao)產(chan)品(pin)的(de)競(jing)爭(zheng)力(li)。