Ekuklanyeni kwe PCB ibhodi, ngokunyuka okusheshayo kwemvamisa, kuzoba nokuphazamiseka okuningi okuhlukile kunalokho kwebhodi le-PCB yemvamisa ephansi. Ngaphezu kwalokho, nokwanda kwemvamisa nokuphikisana phakathi kwe-miniaturization nezindleko eziphansi zebhodi le-PCB, lokhu kuphazamiseka kuzoba nzima kakhulu.

Ocwaningweni lwangempela, singaphetha ngokuthi kunezici ezine kakhulu zokuphazamiseka, kufaka phakathi umsindo wokuphakelwa kwamandla kagesi, ukuphazanyiswa kolayini wokuhambisa, ukuhlangana nokuphazanyiswa ngogesi (i-EMI). Ngokuhlaziya izinkinga ezahlukahlukene zokuphazamiseka ze-PCB ephezulu kakhulu nokuhlanganisa nokwenza emsebenzini, kubekwa phambili izixazululo ezisebenzayo.

Okokuqala, umsindo wokuphakelwa kwamandla

Esifundeni semvamisa ephezulu, umsindo wokuphakelwa kwamandla unethonya elisobala kusiginali yemvamisa ephezulu. Therefore, the first requirement of the power supply is low noise. Izitezi ezihlanzekile zibaluleke kakhulu njengogesi ohlanzekile. Kungani? Izici zamandla zikhonjisiwe kuMdwebo 1. Ngokusobala, ukuphakelwa kukagesi kune-impedance ethile, futhi i-impedance isatshalaliswa kuwo wonke amandla kagesi, ngakho-ke, umsindo uzongezwa kokuphakelwa kwamandla.

Then we should minimize the impedance of the power supply, so it is best to have a dedicated power supply layer and grounding layer. Ekuklanyeni kwesifunda se-hf, kungcono kakhulu ukuklama ukunikezwa kwamandla njengongqimba kunebhasi ezimweni eziningi, ukuze iluphu lihlale lilandela indlela ye-impedance encane.

Ngaphezu kwalokho, ibhodi yamandla kufanele inikeze iluphu yesiginali yawo wonke amasiginali akhiqiziwe futhi atholiwe ku-PCB. Lokhu kunciphisa iluphu yesiginali futhi ngaleyo ndlela kunciphise umsindo, ovame ukunganakwa ngabaqambi besekethe abanemvamisa ephansi.

Idizayini ephezulu kakhulu ye-PCB yenzeka izixazululo zokuphazamiseka

Umdwebo 1: Izici zamandla

Kunezindlela eziningana zokuqeda umsindo wamandla ekwakhiweni kwe-PCB:

1. Note the through hole on the board: the through hole requires etched openings on the power supply layer to leave space for the through hole to pass through. Uma ukuvulwa kocingo lokuphakelwa kwamandla kukhulu kakhulu, nakanjani kuzothinta iluphu yesiginali, isignali iphoqeleka ukudlula, indawo yeluphu iyanda, nomsindo uyanda. At the same time, if several signal lines are clustered near the opening and share the same loop, the common impedance will cause crosstalk. Bheka Umfanekiso 2.

Idizayini ephezulu kakhulu ye-PCB yenzeka izixazululo zokuphazamiseka

Umdwebo 2: Indlela ejwayelekile yokudlula kwesiginali yesiginali

2. The connection line needs enough ground: each signal needs to have its own proprietary signal loop, and the loop area of the signal and loop is as small as possible, that is to say, the signal and loop should be parallel.

3. Ukunikezwa kwamandla we-analog nedijithali ukwahlukanisa: amadivayisi anemvamisa ephezulu ngokuvamile ayazwela kakhulu kumsindo wedijithali, ngakho-ke bobabili kufanele bahlukaniswe, baxhumane ndawonye emnyango wokuphakelwa kwamandla, uma isignali yonkana izingxenye ze-analog nezidijithali ze amagama, angabekwa kusignali enqamula iluphu ukunciphisa indawo yeluphu. Ububanzi be-digital-analog obusetshenziselwa i-loop yesiginali buyakhonjiswa kuMdwebo 3.

Idizayini ephezulu kakhulu ye-PCB yenzeka izixazululo zokuphazamiseka

Figure 3: Digital – analog span for signal loop

4. Avoid overlapping of separate power supplies between layers: otherwise circuit noise can easily pass through parasitic capacitive coupling.

5. Isolate sensitive components: such as PLL.

6. Place the power cable: To reduce the signal loop, place the power cable on the edge of the signal line to reduce the noise, as shown in Figure 4.

Idizayini ephezulu kakhulu ye-PCB yenzeka izixazululo zokuphazamiseka

Umdwebo 4: Beka intambo yamandla eceleni kolayini wesiginali

Two, transmission line

Kunemigqa emibili kuphela yokudlulisela ku-PCB:

Inkinga enkulu yomugqa weribhoni nomugqa we-microwave kukhombisa. Ukuzindla kuzodala izinkinga eziningi. Isibonelo, isignali yokulayisha izoba yindawo ephezulu yesiginali yangempela nesiginali ye-echo, ezokwandisa ubunzima bokuhlaziywa kwesiginali. Ukucabanga kubangela ukulahleka kokubuyisa (ukubuya kokulahleka), okuthinta isignali kabi njengokuphazamiseka komsindo okufakwayo:

1. Isiginali eboniswe emuva emthonjeni wesiginali izokwandisa umsindo wohlelo, kwenze kube nzima kakhulu kumamukeli ukuhlukanisa umsindo kulisiginali;

2. Any reflected signal will basically degrade the signal quality and change the shape of the input signal. Generally speaking, the solution is mainly impedance matching (for example, the impedance of the interconnection should very match the impedance of the system), but sometimes the calculation of impedance is more troublesome, you can refer to some transmission line impedance calculation software. The methods of eliminating transmission line interference in PCB design are as follows:

(a) Gwema ukuyekiswa kwe-impedance kolayini bokuhambisa. Iphuzu le-impedance enganqamuki iphuzu lokuguqulwa kolayini wokudlulisa, njengekhoneni eliqondile, ngembobo, njll., Kufanele kugwenywe ngangokunokwenzeka. Izindlela: Ukugwema izingakhona eziqondile zomugqa, ngangokunokwenzeka ukuya ku-45 ° Angle noma i-arc, i-Angle enkulu nayo ingaba; Sebenzisa okumbalwa ngezimbobo ngangokunokwenzeka, ngoba umgodi ngamunye ukuyekiswa kwe-impedance, njengoba kukhonjisiwe ku-FIG. 5; Signals from the outer layer avoid passing through the inner layer and vice versa.

Idizayini ephezulu kakhulu ye-PCB yenzeka izixazululo zokuphazamiseka

Figure 5: Method for eliminating transmission line interference

(b) Do not use stake lines. Ngoba noma imuphi umugqa wenqwaba ungumthombo womsindo. Uma ulayini wenqwaba mfushane, ungaxhunyaniswa ekugcineni kolayini wokudlulisa; Uma ulayini wenqwaba umude, kuzothatha ulayini omkhulu wokudlulisa njengomthombo futhi kukhiqize ukubonakaliswa okuhle, okuzokwenza inkinga ibe yinkinga. Kunconywa ukuthi ungayisebenzisi.

Okwesithathu, ukuhlanganiswa

1. Common impedance coupling: it is a common coupling channel, that is, the interference source and the interfered device often share some conductors (such as loop power supply, bus, and common grounding), as shown in Figure 6.

Idizayini ephezulu kakhulu ye-PCB yenzeka izixazululo zokuphazamiseka

Umdwebo 6: Ukuhlangana kwe-impedance ejwayelekile

In this channel, the drop back of the Ic causes a common-mode voltage in the series current loop, affecting the receiver.

2. The field common-mode coupling will cause the radiation source to cause common-mode voltages in the loop formed by the interfered circuit and on the common reference surface.

If the magnetic field is dominant, the value of the common-mode voltage generated in the series ground circuit is Vcm=-(△B/△t)* area (where △B= change in magnetic induction intensity). If it is an electromagnetic field, when its electric field value is known, its induced voltage: Vcm=(L* H *F*E)/48, the formula is suitable for L(m)=150MHz, beyond this limit, the calculation of the maximum induced voltage can be simplified as: Vcm=2* H *E.

3. Differential mode field coupling: refers to the direct radiation by wire pair or circuit board on the lead and its loop induction received. If you get as close to the two wires as possible. Lokhu kuhlangana kuncishiswe kakhulu, ngakho-ke izintambo ezimbili zingasontwa ndawonye ukunciphisa ukuphazamiseka.

4. Inter-line coupling (crosstalk) can cause unwanted coupling between any line or parallel circuit, which will greatly damage the performance of the system. Its type can be divided into capacitive crosstalk and perceptual crosstalk.

The former is because the parasitic capacitance between the lines makes the noise on the noise source coupled to the noise receiving line through current injection. The latter can be thought of as the coupling of signals between the primary stages of an unwanted parasitic transformer. Usayizi we-crosstalk e-inductive uncike ekusondeleni kwala maluphu amabili, ubukhulu bendawo yeluphu, kanye ne-impedance yomthwalo othintekile.

5. Ukuxhuma ikhebula yamandla: Izintambo zamandla ka-ac noma ze-DC ziphazanyiswa ukuphazamiseka kukagesi

Dlulisela kwamanye amadivayisi.

There are several ways to eliminate crosstalk in PCB design:

1. Zombili izinhlobo ze-crosstalk ziyanda ngokwanda kwe-impedance yomthwalo, ngakho-ke izintambo zesiginali ezizwela ekuphazanyisweni okubangelwa yi-crosstalk kufanele zinqanyulwe kahle.

2. Khulisa ibanga phakathi kwemigqa yesiginali ukuze unciphise kahle i-capacitive crosstalk. Ukuphathwa komhlaba, isikhala phakathi kwezintambo (njengemigqa yesiginali esebenzayo kanye nolayini bomhlaba wokuzihlukanisa, ikakhulukazi esimweni sokugxuma phakathi kolayini wesiginali nomhlabathi kuya esikhaleni) futhi kunciphise ukwehliswa kokuhola.

3. Capacitive crosstalk can also be effectively reduced by inserting a ground wire between adjacent signal lines, which must be connected to the formation every quarter of a wavelength.

4. Nge-crosstalk enengqondo, indawo yeluphu kufanele incishiswe, futhi uma kuvunyelwe, iluphu kufanele lisuswe.

5. Avoid signal sharing loops.

6. Naka ubuqotho besiginali: umklami kufanele asebenzise ukuphela kwenqubo yokushisela ukuxazulula ubuqotho besiginali. Abaqambi abasebenzisa le ndlela bangagxila kubude be-microstrip woqweqwe lwethusi oluvikelwe ukuze bathole ukusebenza okuhle kobuqotho besiginali. For systems with dense connectors in the communication structure, the designer can use a PCB as the terminal.

Four, electromagnetic interference

As the speed increases, EMI becomes more and more serious and presents in many aspects (such as electromagnetic interference at interconnects). High-speed devices are particularly sensitive to this and will receive high-speed spurious signals, while low-speed devices will ignore such spurious signals.

Kunezindlela eziningana zokuqeda ukuphazamiseka kwe-electromagnetic ekwakhiweni kwe-PCB:

1. Nciphisa amaluphu: Iluphu ngayinye ilingana ne-antenna, ngakho-ke kudingeka sinciphise inani lamaluphu, indawo yamaluphu nomphumela we-antenna wezihibe. Make sure the signal has only one loop path at any two points, avoid artificial loops and use the power layer whenever possible.

2. Filtering: Filtering can be used to reduce EMI on both the power line and the signal line. There are three methods: decoupling capacitor, EMI filter and magnetic element. EMI filter is shown in Figure 7.

Idizayini ephezulu kakhulu ye-PCB yenzeka izixazululo zokuphazamiseka

Umdwebo 7: Izinhlobo zokuhlunga

3. The shielding. Njengomphumela wobude benkinga kanye nezindatshana eziningi zokuvikela izingxoxo, akusasingeniso esinqunyiwe.

4. Reduce the speed of high-frequency devices.

5. Khulisa ukungaguquguquki kwe-dielectric kwebhodi le-PCB, elingavimbela izingxenye ezinemvamisa ephezulu njengentambo yokudlulisela eduze kwebhodi ukuthi ingakhanyi ngaphandle; Increase the thickness of PCB board, minimize the thickness of microstrip line, can prevent electromagnetic line spillover, can also prevent radiation.

At this point, we can conclude that in hf PCB design, we should follow the following principles:

1. Unification and stability of power supply and ground.

2. Carefully considered wiring and proper terminations can eliminate reflections.

3. Ukuyekiswa kwentambo nokunqanyulwa okufanele kunganciphisa i-crosstalk enamandla ne-inductive.

4. Ukucindezelwa komsindo kuyadingeka ukuhlangabezana nezidingo ze-EMC.