Amin’ny famolavolana Birao PCB, miaraka amin’ny fitomboan’ny haingam-pandeha haingana, dia hisy ny fanelingelenana betsaka izay tsy mitovy amin’ny an’ny tabilao PCB ambany matetika. Ankoatr’izay, miaraka amin’ny fitomboan’ny matetika sy ny fifanoheran-kevitra eo amin’ny miniaturization sy ny vidiny ambany amin’ny birao PCB, dia ho lasa sarotra kokoa ireo fanelingelenana ireo.

Amin’ny fikarohana marina dia afaka mamintina isika fa misy lafiny efatra amin’ny fitsabahana, ao anatin’izany ny tabataban’ny herinaratra, ny fanelingelenana amin’ny tsipika fandefasana, ny fitambarana ary ny fanelingelenana elektromagnetika (EMI). Amin’ny alàlan’ny famakafakana ireo olana isan-karazany amin’ny fanelingelenana an’ny PCB matetika sy ny fampifangaroana amin’ny fampiharana amin’ny asa dia aroso ny vahaolana mahomby.

Voalohany, tabataban’ny herinaratra

Ao amin’ny fizaran-tany avo lenta, ny tabataba amin’ny famatsian-kery dia misy fiantraikany miharihary amin’ny famantarana matetika. Therefore, the first requirement of the power supply is low noise. Ny gorodona madio dia manan-danja mitovy amin’ny herinaratra madio. Fa maninona Ny toetra mampiavaka ny herinaratra dia aseho amin’ny sary 1. Mazava ho azy, ny herinaratra dia manana impedance sasany, ary ny impedance dia zaraina amin’ny famatsian-jiro rehetra, noho izany, ny tabataba dia ho ampiana amin’ny herinaratra.

Then we should minimize the impedance of the power supply, so it is best to have a dedicated power supply layer and grounding layer. Amin’ny famolavolana hf circuit, tsara kokoa ny mamolavola herinaratra ho sosona toy izay bus amin’ny ankamaroan’ny tranga, amin’izay ny loop dia afaka manaraka hatrany ny lalan’ny impedance kely.

Ankoatr’izay, ny tabilao herinaratra dia tsy maintsy manome fantsom-pifandraisana ho an’ireo signal rehetra novokarina sy voaray tamin’ny PCB. Izany dia mampihena ny fantsom-pifandraisana ary mampihena ny tabataba, izay matetika no tsy raharahi’ireo mpamorona faritra matetika.

Ny famolavolana PCB matetika dia misy vahaolana fanelingelenana

Sary 1: Toetra mampiavaka ny herinaratra

Misy fomba maro hanafoanana ny tabataba herinaratra amin’ny famolavolana 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. Raha lehibe loatra ny fanokafana ny sosona famatsiana herinaratra dia voatery hisy fiantraikany amin’ny tadin’ny signal, voatery mamaky ny signal, mitombo ny faritry ny loop ary mitombo ny tabataba. At the same time, if several signal lines are clustered near the opening and share the same loop, the common impedance will cause crosstalk. Jereo ny sary 2.

Ny famolavolana PCB matetika dia misy vahaolana fanelingelenana

Sary 2: Làlana mahazatra an’ny loop famantarana signal bypass

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. Ny famatsiana herinaratra analog sy nomerika hampisaraka: ny fitaovana matetika dia mazàna no mora tohina amin’ny tabataba nomerika, noho izany dia tokony hosarahana izy roa, mifandray miaraka amin’ny fidirana amin’ny famatsiana herinaratra, raha toa ka misy ny signal manerana ny faritra analog sy digital an’ny teny, azo apetraka ao amin’ny famantarana manerana loop iray hampihenana ny faritry loop. Ny elanelan’ny nomerika-analog ampiasaina amin’ny loop signal dia aseho amin’ny sary 3.

Ny famolavolana PCB matetika dia misy vahaolana fanelingelenana

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.

Ny famolavolana PCB matetika dia misy vahaolana fanelingelenana

Sary 4: Apetraho eo akaikin’ny tsipika famantarana ny tadin’ny herinaratra

Two, transmission line

Roa ihany ny tsipika fampitana azo atao ao amin’ny PCB:

Ny olana lehibe indrindra amin’ny tsipika ribbon sy tsipika mikraoba dia ny fisaintsainana. Ny fisaintsainana dia hiteraka olana maro. Ohatra, ny famantarana ny enta-mavesatra dia ho mpanara-maso ny famantarana tany am-boalohany sy ny famantarana ny akony, izay hampitombo ny fahasahiranan’ny famakafakana famantarana. Ny fisaintsainana dia miteraka fatiantoka miverina (fatiantoka miverina), izay misy fiatraikany ratsy amin’ny famantarana toy ny fanelingelenana ny tabataba fanampiny:

1. Ny fambara taratra miverina amin’ny loharano famantarana dia hampitombo ny tabataban’ny rafitra, ka ho sarotra kokoa ho an’ny mpandray ny manavaka ny tabataba amin’ny signal;

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) Fadio ny fampijanonana tsy tapaka ny tsipika fandefasana. Ny teboka impedance tsy miato dia ny teboka fiovan’ny tsipika fampitana, toy ny zoro mahitsy, amin’ny alàlan’ny lavaka, sns., Tokony hialana araka izay tratra. Fomba: hisorohana ny zorony mahitsy amin’ny andalana, araka izay azo atao raha mandeha amin’ny 45 ° Angle na arc, mety misy ihany koa ny Angle lehibe; Ampiasao vitsivitsy araka izay azo atao, satria ny tsirairay amin’ny alàlan’ny lavaka dia fahatapahan-jiro, toy ny aseho amin’ny FIG. 5; Signals from the outer layer avoid passing through the inner layer and vice versa.

Ny famolavolana PCB matetika dia misy vahaolana fanelingelenana

Figure 5: Method for eliminating transmission line interference

(b) Do not use stake lines. Satria loharanom-tabataba daholo ny tsipika misy antontany. Raha fohy ny tsipika miavosa dia azo ampifandraisina amin’ny faran’ny tsipika fandefasana; Raha lava ny tsipika fivangongo, dia handray ny tsipika fampitana lehibe indrindra ho loharano ary hamoaka taratra lehibe, izay hanasarotra ny olana. Ampirisihina tsy hampiasa azy io.

Fahatelo, ny fampiraisana

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.

Ny famolavolana PCB matetika dia misy vahaolana fanelingelenana

Sary 6: Fampifangaroana impedance mahazatra

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. Mihena be ity fitambarana ity, ka azo ahodinkodina ireo tariby roa mba hampihena ny fitsabatsabahana.

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. Ny haben’ny crosstalk inductive dia miankina amin’ny akaiky ny tadivavarana roa, ny haben’ny faritry ny loop ary ny fijanonan’ny enta-mavesatra voakasik’izany.

5. Fitambarana tariby herinaratra: ny telegrama mandeha amin’ny herinaratra ac na DC dia voasakana amin’ny fitsabahan’ny elektromagnetika

Alefaso amin’ny fitaovana hafa.

There are several ways to eliminate crosstalk in PCB design:

1. Ireo karazana crosstalk roa ireo dia mitombo miaraka amin’ny fitomboan’ny impedance amin’ny enta-mavesatra, noho izany dia tokony hatsahatra ara-dalàna ireo tsipika famantarana izay mora tohina amin’ny fitsabahana vokatry ny crosstalk.

2. Ampitomboy ny elanelana misy eo amin’ny tsipika famantarana mba hampihenana ny crosstalk capacitive. Fitantanana ny tany, elanelam-potoana eo anelanelan’ny tariby (toy ny tsipika famantarana mavitrika sy ny tsipika fitadiavana toerana mitokana, indrindra amin’ny fanjakan’ny fitsambikinana eo anelanelan’ny tsipika famantarana sy ny tany anelanelan’ny elanelam-potoana) ary mampihena ny fidiran’ny firaka.

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. Ho an’ny crosstalk manan-tsaina dia tokony hahena ny faritra tadiavina ary raha avela dia esorina ny tadivavarana.

5. Avoid signal sharing loops.

6. Tandremo ny fahamendrehana famantarana: ny mpamorona dia tokony hampihatra ny fiafarany amin’ny fizotran’ny welding mba hamahana ny tsy fivadihana famantarana. Ireo mpamorona mampiasa an’io fomba io dia afaka mifantoka amin’ny halavan’ny microstrip amin’ny foil varahina miaro mba hahazoana fahombiazana tsara amin’ny tsy fivadihana famantarana. 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.

Misy fomba maro hanafoanana ny fitsabahana elektromagnetika amin’ny famolavolana PCB:

1. Ahena ny tadivavarana: ny tadiny tsirairay dia mitovy amin’ny antena, noho izany dia mila ahenantsika ny isan’ny tadivavarana, ny faritry ny tadivavarana ary ny vokatry ny tadivavarana. 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.

Ny famolavolana PCB matetika dia misy vahaolana fanelingelenana

Sary 7: Karazan-sivana

3. The shielding. Vokatry ny halavan’ny olana miampy lahatsoratra miaro adihevitra marobe, tsy fampidirana manokana intsony.

4. Reduce the speed of high-frequency devices.

5. Ampitomboy ny dielectric tsy tapaka ny takelaka PCB, izay afaka misoroka ireo faritra avo lenta toy ny tsipika fandefasana eo akaikin’ny tabilao tsy hiposaka ivelany; 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. Ny tariby voadinika tsara sy ny famaranana mety dia mety hampihena ny crosstalk capacitive sy inductive.

4. Ilaina ny fanakanana ny tabataba mba hahafeno ny fepetra takin’ny EMC.