Umklamo we high-frequency PCB kuyinqubo eyinkimbinkimbi, futhi izici eziningi zingase zithinte ngokuqondile ukusebenza kokusebenza kwesifunda esinemvamisa ephezulu. Idizayini ye-high-frequency circuit circuit kanye ne-wiring kubaluleke kakhulu kuwo wonke umklamo. Amathiphu alandelayo ayishumi okwakhiwa kwesekethe ye-PCB ephezulu anconywa ikakhulukazi:

1. Multilayer board wiring

High-frequency circuits tend to have high integration and high wiring density. The use of multi-layer boards is not only necessary for wiring, but also an effective means to reduce interference. In the PCB Layout stage, a reasonable selection of the printed board size with a certain number of layers can make full use of the intermediate layer to set up the shield, better realize the nearest grounding, and effectively reduce the parasitic inductance and shorten the signal transmission length, while still maintaining a large All of these methods are beneficial to the reliability of high-frequency circuits, such as the amplitude reduction of signal cross-interference. Some data show that when the same material is used, the noise of the four-layer board is 20dB lower than that of the double-sided board. However, there is also a problem. The higher the number of PCB half-layers, the more complex the manufacturing process, and the higher the unit cost. This requires us to select PCB boards with the appropriate number of layers when performing PCB Layout. Reasonable component layout planning, and use correct wiring rules to complete the design.

2. The less the lead bends between the pins of high-speed electronic devices, the better

The lead wire of high-frequency circuit wiring is best to adopt a full straight line, which needs to be turned. It can be turned by a 45-degree broken line or a circular arc. This requirement is only used to improve the fixing strength of the copper foil in low-frequency circuits, while in high-frequency circuits, this requirement is met. One requirement can reduce the external emission and mutual coupling of high-frequency signals.

3. Ukuthi umthofi ube mfishane phakathi kwezikhonkwane zedivayisi yesekethe ye-high-frequency, kungcono

The radiation intensity of the signal is proportional to the trace length of the signal line. The longer the high-frequency signal lead, the easier it is to couple to the components close to it. Therefore, for the signal clock, crystal oscillator, DDR data, LVDS lines, USB lines, HDMI lines and other high-frequency signal lines are required to be as short as possible.

4. The less the lead layer alternate between the pins of the high-frequency circuit device, the better

Okubizwa ngokuthi “lapho kuncane ukushintshaniswa kwezingqimba zomkhondo, kungcono” kusho ukuthi i-vias embalwa (Via) esetshenziswa enqubweni yokuxhuma ingxenye, iba ngcono. Ngokusho kohlangothi, eyodwa nge-via ingaletha cishe i-0.5pF i-capacitance esabalalisiwe, futhi ukunciphisa inani le-vias kungakhuphula kakhulu isivinini futhi kunciphise amathuba okuba namaphutha edatha.

5. Naka “i-crosstalk” eyethulwe umugqa wesignali emzileni osondelene ohambisanayo

Izintambo zesekethe ye-high-frequency kufanele inake “i-crosstalk” eyethulwe umzila oseduze ohambisanayo wemigqa yesignali. I-Crosstalk ibhekisela kwinto yokuhlanganisa phakathi kwemigqa yesignali engaxhumekile ngokuqondile. Njengoba amasignali amaza aphezulu edluliswa ngendlela yamaza kagesi eduze komugqa wokudlulisela, ulayini wesiginali uzosebenza njengothi, futhi amandla enkambu ka-electromagnetic azokhishwa eduze kolayini wokudlulisela. Izimpawu zomsindo ezingafuneki zikhiqizwa ngenxa yokuhlangana okuhlangene kwezinkambu ze-electromagnetic phakathi kwamasignali. Ibizwa nge-crosstalk (Crosstalk). Amapharamitha ongqimba lwe-PCB, ukuhlukaniswa kwemigqa yesignali, izici zikagesi zokuphela kokushayela kanye nesiphetho sokwamukela, kanye nendlela yokunqamula umugqa wesignali konke kunomthelela othile ku-crosstalk. Ngakho-ke, ukuze kuncishiswe i-crosstalk yamasiginali we-high-frequency, kuyadingeka ukwenza okulandelayo ngangokunokwenzeka lapho ufaka izintambo:

Uma isikhala sezintambo sivuma, ukufaka intambo yaphansi noma indiza yaphansi phakathi kwezintambo ezimbili ezine-crosstalk engathi sína kakhulu kungabamba iqhaza ekuhlukaniseni futhi kunciphise i-crosstalk. Uma kunenkambu ye-electromagnetic eshintshashintshayo isikhathi esikhaleni esizungeze umugqa wesignali, uma ukusatshalaliswa okufanayo kungenakugwenywa, indawo enkulu “yomhlaba” ingahlelwa ngakolunye uhlangothi lomugqa wesignali ofanayo ukuze kuncishiswe kakhulu ukuphazamiseka.

Ngaphansi kwesisekelo sokuthi isikhala sezintambo siyasivumela, khulisa isikhala phakathi kwemigqa yesignali eseduze, unciphise ubude obuhambisanayo bemigqa yesignali, bese uzama ukwenza umugqa wewashi ube perpendicular umugqa wesiginali ukhiye esikhundleni parallel. Uma i-wiring ehambisanayo kungqimba olufanayo cishe ayinakugwenywa, ezingxenyeni ezimbili eziseduze, izinkomba ze-wiring kufanele zibe perpendicular komunye nomunye.

Kumasekhethi edijithali, amasiginali wewashi avamile amasignali anezinguquko ezisheshayo, ane-crosstalk yangaphandle ephezulu. Ngakho-ke, ekwakhiweni, umugqa wewashi kufanele uzungezwe umugqa ophansi futhi ubhoboze izimbobo zomugqa ophansi ukuze kuncishiswe amandla asabalalisiwe, ngaleyo ndlela kuncishiswe i-crosstalk. Kumawashi esignali yefrikhwensi ephezulu, zama ukusebenzisa amasiginali wewashi ane-voltage ephansi bese usonga imodi yaphansi, futhi unake ubuqotho bephakeji yokushaya phansi.

Itheminali yokufaka engasetshenzisiwe akufanele imiswe okwesikhashana, kodwa imiswe phansi noma ixhunywe kugesi (ugesi nawo usekelwe kuluphu yesignali yefrikhwensi ephezulu), ngenxa yokuthi ulayini omisiwe ungase ulingane nothi oludlulisayo, futhi ukubeka phansi kungavimbela. ukukhishwa. Ukuzijwayeza kufakazele ukuthi ukusebenzisa le ndlela ukuqeda i-crosstalk kwesinye isikhathi kungaveza imiphumela esheshayo.

6. Engeza i-high-frequency decoupling capacitor ephinikhodi yokuhlinzeka amandla yebhulokhi yesifunda ehlanganisiwe

I-high-frequency decoupling capacitor yengezwa kuphinikhodi yokuphakela amandla yebhulokhi ngayinye ehlanganisiwe yesekethe eseduze. Ukwenyusa i-high-frequency decoupling capacitor yephinikhodi yokuphakela amandla kungacindezela ngempumelelo ukugxambukela kwama-harmonics wemvamisa ephezulu kuphinikhodi yokuphakela amandla.

7. Hlukanisa intambo yaphansi yesiginali yedijithali yemvamisa ephezulu kanye nentambo yaphansi yesiginali ye-analogi

Uma intambo yaphansi ye-analogi, intambo yaphansi yedijithali, njll. kuxhunywe ocingweni olusesidlangalaleni olusemhlabathini, sebenzisa ubuhlalu obuzibuthe obuminyanisa imvamisa ephezulu ukuze uxhume noma uhlukanise ngokuqondile futhi ukhethe indawo efanelekile yokuxhumanisa iphuzu elilodwa. Amandla aphansi entambo yaphansi yesiginali yedijithali yefrikhwensi ephezulu ngokuvamile awahambisani. Kuvame ukuba nomehluko othile we-voltage phakathi kwalokhu okubili ngokuqondile. Ngaphezu kwalokho, intambo yaphansi yesiginali yedijithali yemvamisa ephezulu imvamisa iqukethe izingxenye ezinothe kakhulu zesiginali yefrikhwensi ephezulu. Uma intambo yaphansi yesignali yedijithali kanye nentambo yaphansi yesignali ye-analogi kuxhunywe ngokuqondile, ama-harmonics wesiginali yefrikhwensi izophazamisa isignali ye-analogi ngokuhlanganisa intambo yaphansi. Ngakho-ke, ngaphansi kwezimo ezijwayelekile, intambo yaphansi yesiginali yedijithali ye-high-frequency kanye nentambo yaphansi yesiginali ye-analogi kufanele ibekwe yodwa, futhi indlela yokuxhumana yephoyinti elilodwa ingasetshenziswa endaweni efanelekile, noma indlela ephezulu- imvamisa choke kazibuthe ubuhlalu interconnection ingasetshenziswa.

8. Gwema izihibe ezakhiwe ngezintambo

Zonke izinhlobo zokulandela isignali yemvamisa ephezulu akufanele zenze iluphu ngangokunokwenzeka. Uma kungenakugwema, indawo ye-loop kufanele ibe yincane ngangokunokwenzeka.

9. Kumele iqinisekise ukufana okuhle kwesiginali ye-impedance

In the process of signal transmission, when the impedance does not match, the signal will reflect in the transmission channel, and the reflection will cause the synthesized signal to form an overshoot, causing the signal to fluctuate near the logic threshold.

Indlela eyisisekelo yokuqeda ukucabangisisa iwukufanisa kahle nokuphazamiseka kwesiginali yokudlulisela. Njengoba umehluko omkhulu phakathi kwe-impedance yomthwalo kanye ne-impedance yesici yomugqa wokudlulisa, ukubonakaliswa okukhulu, ngakho-ke ukukhubazeka kwesici somugqa wokudlulisa isignali kufanele kwenziwe kulingane nokuvinjelwa komthwalo ngangokunokwenzeka. Ngesikhathi esifanayo, sicela uqaphele ukuthi ulayini wokudlulisela ku-PCB awukwazi ukuba nezinguquko ezingazelelwe noma amakhona, futhi uzame ukugcina ukuthintana kwephuzu ngalinye lolayini wokudlulisela kuqhubeke, ngaphandle kwalokho kuzoba nokubonisa phakathi kwezigaba ezihlukahlukene zolayini wokudlulisela. Lokhu kudinga ukuthi ngesikhathi sezintambo ze-PCB ezinesivinini esikhulu, kufanele kubhekwe imithetho elandelayo yokufaka izintambo:

Imithetho yezintambo ze-USB. Idinga umzila ohlukile wesiginali ye-USB, ububanzi bomugqa ngu-10mil, isikhala somugqa ngu-6mil, kanti umugqa ophansi nesikhala somugqa wesignali ngu-6mil.

Imithetho yezintambo ze-HDMI. Kudingeka umzila ohlukile wesignali ye-HDMI, ububanzi bomugqa bungu-10mil, isikhala somugqa singu-6mil, futhi isikhala phakathi kwamasethi amabili wamapheya esignali ahlukile we-HDMI sidlula u-20mil.

LVDS wiring rules. Requires LVDS signal differential routing, the line width is 7mil, the line spacing is 6mil, the purpose is to control the differential signal impedance of HDMI to 100+-15% ohm

Imithetho yezintambo ze-DDR. Ukulandelela kwe-DDR1 kudinga amasiginali ukuthi angadluli emigodini ngangokunokwenzeka, imigqa yesignali inobubanzi obulinganayo, futhi imigqa ihlukaniswe ngokulinganayo. Imikhondo kufanele ihlangabezane nomgomo we-2W ukuze kuncishiswe i-crosstalk phakathi kwamasignali. Kumadivayisi anesivinini esiphezulu se-DDR2 nangaphezulu, idatha yefrikhwensi ephezulu nayo iyadingeka. Imigqa iyalingana ngobude ukuze kuqinisekiswe ukufana kwe-impedance yesiginali.

10. Guarantee the integrity of transmission

Maintain the integrity of signal transmission and prevent the “ground bounce phenomenon” caused by ground splitting.