M’mapangidwe a PCB bolodi, ndikuchulukirachulukira kwakanthawi, padzakhala zosokoneza zambiri zomwe ndizosiyana ndi bolodi ya PCB yotsika kwambiri. Kuphatikiza apo, ndikuchulukirachulukira komanso kutsutsana pakati pa miniaturization ndi mtengo wotsika wa board ya PCB, kusokonekera uku kudzakhala kovuta kwambiri.

Pakufufuza kwenikweni, titha kunena kuti pali zinthu zinayi zosokoneza, kuphatikiza phokoso lamagetsi, kulowererapo kwa zingwe, kuphatikiza ndi kusokoneza kwamagetsi (EMI). Pogwiritsa ntchito kusanthula mavuto osiyanasiyana osokonekera a PCB yochulukirapo ndikuphatikiza ndikuchita bwino pantchito, njira zabwino zimayendetsedwa.

Choyamba, phokoso lamagetsi

Munthawi yamafupipafupi, phokoso lamagetsi limakhudza chiwonetsero chazizindikiro pafupipafupi. Therefore, the first requirement of the power supply is low noise. Pansi paukhondo palinso zofunika monga magetsi oyera. Chifukwa chiyani? Makhalidwe amagetsi akuwonetsedwa mu Chithunzi 1. Zachidziwikire, magetsi ali ndi impedance inayake, ndipo impedance imagawidwa pamphamvu yonse, chifukwa chake, phokoso liziwonjezeredwa pamagetsi.

Then we should minimize the impedance of the power supply, so it is best to have a dedicated power supply layer and grounding layer. Pakapangidwe kake ka hf, ndibwino kupanga magetsi ngati wosanjikiza kuposa momwe mabasi amathandizira nthawi zambiri, kuti chizunguliro chizitha kutsatira njira yopanda malire.

Kuphatikiza apo, bolodi lamagetsi liyenera kupereka chiwonetsero chazizindikiro kwa onse opangidwa ndikulandila pa PCB. Izi zimachepetsa kuzungulira kwa ma siginolo ndipo motero kumachepetsa phokoso, lomwe nthawi zambiri amanyalanyazidwa ndi opanga madera ocheperako.

Kupanga kwapafupipafupi kwa PCB kumachitika zothetsera mavuto

Chithunzi 1: Makhalidwe amagetsi

Pali njira zingapo zothetsera phokoso lamphamvu pakupanga kwa 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. Ngati kutsegula kwa magetsi kumakhala kochuluka kwambiri, kumakhudza chizindikirocho, chizindikirocho chimakakamizidwa kudutsa, malo ozungulirawo amakula, ndipo phokoso limakulirakulira. At the same time, if several signal lines are clustered near the opening and share the same loop, the common impedance will cause crosstalk. Onani Chithunzi 2.

Kupanga kwapafupipafupi kwa PCB kumachitika zothetsera mavuto

Chithunzi 2: Njira yodziwika yodutsa chizindikiro

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. Mphamvu yama Analog ndi digito kuti ipatukane: zida zama frequency ambiri nthawi zambiri zimakhudzidwa kwambiri ndi phokoso la digito, chifukwa chake awiriwo ayenera kupatulidwa, kulumikizidwa limodzi pakhomo lolowera magetsi, ngati chizindikirocho chikudutsa mbali za analog ndi digito za mawu, atha kuyikidwa mchizindikiro kudumpha kuzungulira kuti muchepetse malo ozungulira. Kutalika kwa digito-analog komwe kumagwiritsidwa ntchito potulutsa chizindikiro kukuwonetsedwa mu Chithunzi 3.

Kupanga kwapafupipafupi kwa PCB kumachitika zothetsera mavuto

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.

Kupanga kwapafupipafupi kwa PCB kumachitika zothetsera mavuto

Chithunzi 4: Ikani chingwe champhamvu pambali pa mzere wazizindikiro

Two, transmission line

Pali mizere iwiri yokha yotsegulira mu PCB:

Vuto lalikulu kwambiri pamzere wa riboni ndi mzere wama microwave ndikuwonetsa. Kusinkhasinkha kumabweretsa mavuto ambiri. Mwachitsanzo, chizindikirocho chidzakhala chiwonetsero cha chizindikiro choyambirira komanso cholozera, chomwe chidzawonjezera kuvuta kwa kusanthula kwa siginolo. Kusinkhasinkha kumapangitsa kubweza kubwerera (kutaya kubwerera), komwe kumakhudza chizindikirocho moyipa ngati kusokonekera kwamawu owonjezera:

1. Chizindikirocho chimawonekeranso ku gwero lazizindikiro chidzawonjezera phokoso la makina, zomwe zimapangitsa kuti zikhale zovuta kuti wolandirayo azitha kusiyanitsa phokoso ndi mbendera;

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) Pewani kutha kwa maimidwe othamangitsa mosalekeza. Mfundo yodziletsa ndiyo njira yosinthira mzere, monga ngodya yowongoka, kudzera pabowo, ndi zina zambiri, ziyenera kupewedwa momwe zingathere. Njira: Kupewa ngodya zowongoka za mzere, momwe mungathere kupita 45 ° Angle kapena arc, Angle yayikulu itha kukhalanso; Gwiritsani ntchito ochepa kudzera m’mabowo momwe mungathere, chifukwa chilichonse kudzera mu dzenje ndi kutha kwa impedance, monga akuwonetsera mu FIG. 5; Signals from the outer layer avoid passing through the inner layer and vice versa.

Kupanga kwapafupipafupi kwa PCB kumachitika zothetsera mavuto

Figure 5: Method for eliminating transmission line interference

(b) Do not use stake lines. Chifukwa mulu uliwonse wa mulu ndi gwero la phokoso. Ngati muluwo ndi waufupi, ukhoza kulumikizidwa kumapeto kwa chingwe chotumizira; Ngati muluwo ndi wautali, zimatengera chingwe chachikulu chotumizira ngati gwero ndikupanga kuwunikira kwakukulu, komwe kudzasokoneze vutoli. Ndibwino kuti musagwiritse ntchito.

Chachitatu, kulumikiza

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.

Kupanga kwapafupipafupi kwa PCB kumachitika zothetsera mavuto

Chithunzi 6: Kuphatikiza kwa impedance wamba

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. Kuphatikizana uku kumachepa kwambiri, chifukwa chake zingwe ziwirizi zimatha kupindika limodzi kuti zisasokoneze.

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. Kukula kwa crosstalk inductive kutengera kuyandikira kwa malupu awiri, kukula kwa malo ozungulira, komanso kupindika kwa katunduyo.

5. Kuphatikiza chingwe chamagetsi: Zingwe zamphamvu za ac kapena DC zimasokonezedwa ndi kusokonekera kwamagetsi

Tumizani ku zida zina.

There are several ways to eliminate crosstalk in PCB design:

1. Mitundu iwiri ya crosstalk imakula ndikuchulukirachulukira kwa katundu, chifukwa chake mizere yolumikizana ndi ma crosstalk iyenera kuthetsedwa moyenera.

2. Kwezani mtunda pakati pamizere yolumikizira kuti muchepetse mtanda wokwera kwambiri. Kuwongolera kwapansi, kutalikirana pakati pa zingwe (monga mizere yolumikizira ndi mizere yapansi yodzipatula, makamaka pakadumpha pakati pa mzere wazizindikiro ndi nthaka mpaka nthawi) ndikuchepetsa kutsogolera.

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. Pamtanda wanzeru, malo ozungulirako ayenera kuchepetsedwa, ndipo ngati aloledwa, kuzungulira kuyenera kuthetsedwa.

5. Avoid signal sharing loops.

6. Samalani ndi chizindikiritso: wopanga akuyenera kugwiritsa ntchito malekezero pakuwotcha kuti athetse kukhulupirika kwa siginecha. Opanga omwe amagwiritsa ntchito njirayi atha kuyang’ana kutalika kwa zingwe zazing’ono zazitsulo zotetezera mkuwa kuti athe kuchita bwino posonyeza kukhulupirika. 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.

Pali njira zingapo zothetsera kusokonekera kwamagetsi mu kapangidwe ka PCB:

1. Chepetsani malupu: Chingwe chilichonse chimafanana ndi tinyanga, chifukwa chake tifunika kuchepetsa kuchuluka kwa malupu, dera lamalupu ndi kulumikizana kwa tinyanga. 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.

Kupanga kwapafupipafupi kwa PCB kumachitika zothetsera mavuto

Chithunzi 7: Mitundu Yosefera

3. The shielding. Chifukwa cha kutalika kwa nkhaniyo kuphatikiza zokambirana zambiri zoteteza, sizowonjezeranso mawu oyamba.

4. Reduce the speed of high-frequency devices.

5. Wonjezerani ma dielectric mosalekeza a board ya PCB, yomwe ingalepheretse magawo othamanga kwambiri monga chingwe chotengera kufupi ndi bolodi kuti chisatuluke kunja; 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. Kulingalira mosamala kwa zingwe ndi kuchotsa koyenera kumatha kuthetsa ziwonetsero.

3. Kulingalira mosamalitsa kwa zingwe ndi kuyimitsidwa koyenera kumatha kuchepetsa mtunda wa crosstalk.

4. Kupondereza phokoso kumafunikira kukwaniritsa zofunikira za EMC.