流(liu)經(jing)所(suo)布(bu)線(xian)路(lu)的(de)所(suo)有(you)電(dian)流(liu)都(dou)有(you)相(xiang)等(deng)的(de)回(hui)流(liu)。耦(ou)合(he)策(ce)略(lve)固(gu)然(ran)很(hen)多(duo)，不(bu)過(guo)回(hui)流(liu)通(tong)常(chang)流(liu)經(jing)相(xiang)鄰(lin)的(de)接(jie)地(di)層(ceng)或(huo)與(yu)信(xin)號(hao)線(xian)路(lu)並(bing)行(xing)布(bu)置(zhi)的(de)接(jie)地(di)。在(zai)參(can)考(kao)層(ceng)繼(ji)續(xu)時(shi)
，所(suo)有(you)耦(ou)合(he)都(dou)僅(jin)限(xian)於(yu)傳(chuan)輸(shu)線(xian)路(lu)，一(yi)切(qie)都(dou)非(fei)常(chang)正(zheng)常(chang)。不(bu)過(guo)，如(ru)果(guo)信(xin)號(hao)線(xian)路(lu)從(cong)頂(ding)層(ceng)切(qie)換(huan)至(zhi)內(nei)部(bu)或(huo)底(di)層(ceng)時(shi)

，回(hui)流(liu)也(ye)必(bi)須(xu)獲(huo)得(de)路(lu)徑(jing)。

 

圖1jiushiyigeshili。dingcengxinhaoxianludianliuxiamianjinaizhejiushihuiliu。dangtazhuanyidaodicengshi，huiliujiutongguofujindetongkong。buguo，ruguofujinmeiyouyongyuhuiliudetongkongshi，huiliujiuyaotongguozuijinkeyongdejieditongkong。gengyuandejulihuichanshengdianliuhuanlu，xingchengdianganqi。ruguozhezhongbubiyaodedianliulujingpianyi，pengqiaoyoutonglingyitiaoxianlujiaocha，nameganraojiuhuigengyanzhong。zhezhongdianliuhuanluqishixiangdangyuxingchengleyigetianxian！

 

圖1：信號電流從器件引腳經過通孔流到較低層。

 

回流在被迫流向最近通孔改變至不同參考層之前位於信號之下。

 

jiedicankaoshizuijiacelve

，dangaosuxianluyoushihoukebuzhizaineibucengshang。jiedicankaocengshangxiadoufangzhifeichangkunnan
，bandaotichangshangkenenghuishoudaoyinjiaoxianzhi

，badianyuanxiananfangzaigaosuxianlupangbian。cankaodianliuyaoshixuyaozaifeiDC耦合的各層或各網之間切換，應緊挨著開關點安放去耦電容。

 

 

許多器件在器件封裝底部都采用散熱接地焊盤。在RFqijianshang，zhexietongchangdoushidianqijiedi，erxianglinhanpandianyoujieditongkongzhenlie。kejiangqijianhanpanzhijielianjiezhijiediyinjiao
，bingtongguodingcengjiedilianjiezhirenheguantong。ruyouduogelujing
，huiliuhuianlujingzukangbilichaifen。tongguohanpanjinxingjiedilianjiexiangduiyuyinjiaojiedieryan
，lujinggengduan、阻抗更低。

 

電dian路lu板ban與yu器qi件jian焊han盤pan之zhi間jian良liang好hao的de電dian氣qi連lian接jie至zhi關guan重zhong要yao。裝zhuang配pei時shi
，電dian路lu板ban通tong孔kong陣zhen列lie中zhong的de未wei填tian充chong通tong孔kong也ye可ke能neng會hui抽chou走zou器qi件jian的de焊han膏gao，留liu下xia空kong隙xi。填tian滿man通tong孔kong是shi保bao證zheng焊han接jie到dao位wei的de好hao辦ban法fa。在zai評ping測ce中zhong，還hai要yao打da開kai焊han接jie掩yan模mo層ceng確que認ren沒mei有you焊han接jie掩yan模mo在zai器qi件jian下xia方fang的de電dian路lu板ban接jie地di上shang，因yin為wei焊han接jie掩yan模mo可ke能neng會hui抬tai高gao器qi件jian或huo使shi其qi搖yao擺bai。

 

 

qijianzhoubiandaochudoushitongkong。dianyuanwangfenjiechengbendiquou，ranhoujiangzhidianyuanceng，tongchangtigongduogetongkongyizuidaxiandujianshaodiangan
，tigaozailiurongliang
，tongshikongzhizongxiankejiangzhineiceng。suoyouzhexiefenjiezuizhongdouhuizaiqijianfujinwanquanbeiqianzhu。

 

meigezhexietongkongdouhuizaineijiedicengshangchanshengdayutongkongzhijingzishendejinruqu

，tigongzhizaokongxi。zhexiejinruquhenrongyizaihuiliulujingshangzaochengzhongduan。yixietongkongbicikaojinzehuixingchengjiedicenggou，dingcengCAD視圖看不見，這將導致情況進一步複雜化。圖2兩liang個ge電dian源yuan層ceng通tong孔kong的de接jie地di層ceng空kong隙xi可ke產chan生sheng重zhong疊die的de禁jin入ru區qu，並bing在zai返fan回hui路lu徑jing上shang造zao成cheng中zhong斷duan。回hui流liu隻zhi能neng轉zhuan道dao繞rao過guo接jie地di層ceng禁jin入ru區qu
，形xing成cheng現xian在zai常chang見jian的de發fa射she感gan應ying路lu徑jing問wen題ti。

 

圖2：通孔周圍接地層的禁入區可能重疊，迫使回流遠離信號路徑。

 

即便沒有重疊，禁入區也會在接地層形成鼠咬阻抗中斷。

 

甚至“友好型”接jie地di通tong孔kong也ye會hui為wei相xiang關guan金jin屬shu焊han盤pan帶dai來lai電dian路lu板ban製zhi造zao工gong藝yi要yao求qiu的de最zui小xiao尺chi寸cun規gui格ge。通tong孔kong如ru果guo非fei常chang靠kao近jin信xin號hao線xian路lu，就jiu會hui產chan生sheng好hao像xiang頂ding層ceng接jie地di空kong隙xi被bei老lao鼠shu咬yao掉diao一yi塊kuai一yi樣yang的de侵qin蝕shi。圖tu2是鼠咬示意圖。

 

由於禁入區由CADruanjianzidongshengcheng
，tongkongzaixitongdianlubanshangdeshiyongyouhenpinfan，yincixianqibujuguochengjihuzonghuichuxianyixiefanhuilujingzhongduanwenti。bujupingceshiyaogenzongmeitiaogaosuxianlu，jianzhaxiangguanhuiliucengyibimianzhongduan。rangsuoyoukezairenhequyuchanshengjiedicengganraodetongkonggengkaojindingcengjiedikongxishiyigebucuodefangfa。

 

 

huiliulujingduixinhaoxianluxingnengzhiguanzhongyao，qiyingshiweixinhaolujingdeyibufen。yucitongshi，chafenduitongchangmeiyoujinmiouhe，huiliukenengliujingxianglinceng。lianggehuiliubixutongguoxiangdengdedianqilujingbuxian。

 

jibianzaichafenduideliangtiaoxianlubujinmiouheshi，linjinyugongxiangxingshejixianzhiyehuiranghuiliuchuyuxiangtongceng。yaozhenzhengbaochidijishengxinhao
，xuyaogenghaodepipei。chafenzujianxiajiedicengdeduanliuqidengrenhejihuajiegoudouyingshiduichengde。tongyang，changdushifoupipeikenengyehuichanshengxinhaoxianluzhongdeboxingquxianwenti。huiliubuhuiyinqiboxingquxianwenti。yitiaochafenxianludechangdupipeiqingkuangyingzaiqitachafenxianluzhongtixian。

 

 

時鍾和控製線路有時可視為沒什麼影響的鄰居，因為其工作速度低
，甚至接近DC。不bu過guo，其qi開kai關guan特te性xing幾ji乎hu接jie近jin方fang波bo
，可ke在zai奇qi數shu諧xie波bo頻pin率lv下xia生sheng成cheng獨du特te的de音yin調tiao。方fang波bo發fa射she能neng源yuan的de基ji本ben頻pin率lv雖sui然ran不bu會hui產chan生sheng什shen麼me影ying響xiang，但dan其qi銳rui利li的de邊bian緣yuan可ke能neng會hui有you影ying響xiang。在zai數shu字zi係xi統tong設she計ji中zhong，轉zhuan折zhe頻pin率lv可ke估gu算suan必bi須xu要yao考kao慮lv的de最zui高gao頻pin率lv諧xie波bo，計ji算suan方fang式shi為wei：Fknee=0.5/Tr，這裏的Tr是shi上shang升sheng時shi間jian。請qing注zhu意yi，是shi上shang升sheng時shi間jian
，而er不bu是shi信xin號hao頻pin率lv。不bu過guo銳rui利li邊bian緣yuan的de方fang波bo也ye有you強qiang大da的de高gao階jie奇qi數shu諧xie波bo，其qi可ke能neng隻zhi在zai錯cuo誤wu頻pin率lv下xia下xia降jiang並bing耦ou合he在zaiRF線路上
，違反嚴格的傳輸掩模要求。

 

時鍾和控製線路應由內部接地層或頂層接地灌流（ground pour）與RF信xin號hao線xian路lu隔ge離li。如ru果guo不bu能neng使shi用yong接jie地di隔ge離li信xin號hao，那na麼me線xian路lu布bu線xian應ying確que保bao直zhi角jiao交jiao叉cha。因yin為wei時shi鍾zhong或huo控kong製zhi線xian路lu發fa射she的de磁ci通tong線xian路lu會hui圍wei繞rao幹gan擾rao源yuan線xian路lu的de電dian流liu形xing成cheng放fang射she柱zhu形xing等deng高gao線xian，它ta們men將jiang不bu會hui在zai接jie收shou器qi線xian路lu中zhong產chan生sheng電dian流liu。放fang慢man上shang升sheng時shi間jian不bu但dan可ke降jiang低di轉zhuan折zhe頻pin率lv，而er且qie還hai有you助zhu於yu減jian少shao幹gan擾rao源yuan的de幹gan擾rao
，但dan時shi鍾zhong或huo控kong製zhi線xian路lu也ye可ke充chong當dang接jie收shou器qi線xian路lu。接jie收shou器qi線xian路lu仍reng可ke作zuo為wei將jiang寄ji生sheng信xin號hao導dao入ru器qi件jian的de導dao管guan。

 

 

weibochuanshudaiyudaixiandaduoshudouyuxianglinjiedicengouhe。yixietongliangxianlurengyanshuipingfangxiangsanfa
，bingduanjieyuxianglinjixian。yitiaogaosuxianluhuochafenduishangdeyintiaozaixiayitiaojixianshangzhongjie
，danxinhaocengshangdejiediguanliuhuiweitongliangxianludailaijiaodizukangdezhongdian，ranglinjinjixianbushouyintiaoganrao。

 

時鍾分布或合成器設備路由出來

、用yong於yu承cheng載zai相xiang同tong頻pin率lv的de跡ji線xian集ji群qun可ke能neng相xiang鄰lin而er行xing

，因yin為wei幹gan擾rao源yuan音yin調tiao已yi經jing存cun在zai於yu接jie收shou器qi線xian路lu上shang。不bu過guo，分fen組zu的de線xian路lu最zui終zhong會hui分fen散san。分fen散san時shi
，應ying在zai分fen散san線xian路lu之zhi間jian提ti供gong接jie地di灌guan流liu，並bing在zai其qi開kai始shi分fen散san的de地di方fang灌guan入ru通tong孔kong，以yi便bian感gan應ying回hui流liu沿yan著zhe額e定ding回hui流liu路lu徑jing流liu回hui。在zai圖tu3中(zhong)，接(jie)地(di)島(dao)末(mo)端(duan)的(de)通(tong)孔(kong)可(ke)使(shi)感(gan)應(ying)電(dian)流(liu)流(liu)到(dao)參(can)考(kao)層(ceng)上(shang)。接(jie)地(di)灌(guan)流(liu)上(shang)其(qi)它(ta)通(tong)孔(kong)之(zhi)間(jian)的(de)間(jian)隔(ge)不(bu)要(yao)超(chao)過(guo)一(yi)個(ge)波(bo)長(chang)的(de)十(shi)分(fen)之(zhi)一(yi)，以(yi)確(que)保(bao)接(jie)地(di)不(bu)會(hui)成(cheng)為(wei)共(gong)振(zhen)結(jie)構(gou)。

 

圖3：差分線路分散處的頂層接地通孔為回流提供流動路徑。

 

 

音調進入電源層就會擴散到每個地方。如果雜散音調進入電源、緩衝器
、混頻器

、衰減器和振蕩器，就會對幹擾頻率進行調製。同樣

，當電源到達電路板時，它還沒有徹底被清空而實現對RF電路係統的驅動。應最大限度減少RF線路在電源層的暴露，特別是未過濾的電源層。

 

鄰近接地的大型電源層可創建高質量嵌入式電容
，使寄生信號衰減，並用於數字通信係統與某些RF係統。另一種方法是使用最小化電源層

，有時更像是肥大跡線而不能說是層，這樣RF線路更容易徹底避開電源層。這兩種方法都可行，不過決不能將二者的最差特性湊在一起，也就是既使用小型電源層，又在頂部走線RF線路。

 

 

去qu耦ou不bu僅jin有you助zhu於yu避bi免mian雜za散san噪zao聲sheng進jin入ru器qi件jian，還hai可ke幫bang助zhu消xiao除chu器qi件jian內nei部bu生sheng成cheng的de音yin調tiao，避bi免mian其qi耦ou合he到dao電dian源yuan層ceng上shang。去qu耦ou電dian容rong越yue靠kao近jin工gong作zuo電dian路lu係xi統tong，效xiao率lv就jiu越yue高gao。本ben地di去qu耦ou受shou電dian路lu板ban跡ji線xian的de寄ji生sheng阻zu抗kang幹gan擾rao較jiao小xiao，較jiao短duan的de跡ji線xian支zhi持chi較jiao小xiao的de天tian線xian，減jian少shao有you害hai音yin調tiao發fa射she。電dian容rong器qi安an放fang要yao結jie合he最zui高gao自zi共gong振zhen頻pin率lv

，通tong常chang最zui小xiao值zhi、最小外殼尺寸
、最靠近器件
，以及越大的電容器，離器件越遠。在RF頻率下，電路板背麵的電容器會產生通孔串連接地路徑的寄生電感，損失大量噪聲衰減優勢。

 

 

通過電路板布局評測
，我們可發現可能發射或接收雜散RFyintiaodejiegou。yaogenzongmeiyitiaoxianlu
，youyishidimingqueqihuiliulujing，quebaotanenggouyuxianlubingxing，tebieshiyaochedijianzhaguodu。ciwai
，haiyaojiangqianzaiganraoyuanyujieshouqigeli。anzhaoyixiejiandanzhiguandeguizejiangdijishengxinhao，kejiasuchanpinfabu
，jiangditiaoshichengben。