Fid-disinn ta ‘ Bord tal-PCB, biż-żieda mgħaġġla tal-frekwenza, se jkun hemm ħafna interferenza li hija differenti minn dik tal-bord tal-PCB ta ‘frekwenza baxxa. Barra minn hekk, biż-żieda tal-frekwenza u l-kontradizzjoni bejn il-minjaturizzazzjoni u l-ispiża baxxa tal-bord tal-PCB, dawn l-interferenzi se jsiru aktar u aktar ikkumplikati.

Fir-riċerka attwali, nistgħu nikkonkludu li hemm prinċipalment erba ‘aspetti ta’ interferenza, inklużi l-istorbju tal-provvista ta ‘l-enerġija, l-interferenza tal-linja tat-trasmissjoni, l-igganċjar u l-interferenza elettromanjetika (EMI). Permezz tal-analiżi ta ‘diversi problemi ta’ interferenza ta ‘PCB ta’ frekwenza għolja u l-kombinazzjoni mal-prattika fix-xogħol, jiġu ppreżentati soluzzjonijiet effettivi.

L-ewwel, ħoss tal-provvista tal-enerġija

Fiċ-ċirkwit ta ‘frekwenza għolja, il-ħoss tal-provvista tal-enerġija għandu influwenza ovvja fuq is-sinjal ta’ frekwenza għolja. Therefore, the first requirement of the power supply is low noise. L-art nadifa hija importanti daqs l-elettriku nadif. Għaliex? Il-karatteristiċi tal-qawwa huma murija fil-Figura 1. Ovvjament, il-provvista tal-enerġija għandha ċerta impedenza, u l-impedenza hija mqassma fuq il-provvista tal-enerġija kollha, għalhekk, il-ħoss se jiżdied mal-provvista tal-enerġija.

Then we should minimize the impedance of the power supply, so it is best to have a dedicated power supply layer and grounding layer. Fid-disinn taċ-ċirkwit hf, huwa ħafna aħjar li l-provvista tal-enerġija tiġi ddisinjata bħala saff milli bħala xarabank f’ħafna każijiet, sabiex iċ-ċirku jkun jista ‘dejjem isegwi t-triq ta’ impedenza minima.

Barra minn hekk, il-bord tal-enerġija għandu jipprovdi linja tas-sinjal għas-sinjali kollha ġġenerati u riċevuti fuq il-PCB. Dan jimminimizza s-sinjal loop u b’hekk inaqqas l-istorbju, li spiss jiġi injorat mid-disinjaturi taċ-ċirkuwiti ta ‘frekwenza baxxa.

Id-disinn tal-PCB ta ‘frekwenza għolja jseħħ soluzzjonijiet ta’ interferenza

Figura 1: Karatteristiċi tal-enerġija

Hemm diversi modi kif telimina l-istorbju tal-enerġija fid-disinn tal-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. Jekk il-ftuħ tas-saff tal-provvista tal-enerġija huwa kbir wisq, huwa marbut li jaffettwa l-linja tas-sinjal, is-sinjal huwa mġiegħel jinqabeż, iż-żona tal-linja tiżdied, u l-ħoss jiżdied. At the same time, if several signal lines are clustered near the opening and share the same loop, the common impedance will cause crosstalk. Ara l-Figura 2.

Id-disinn tal-PCB ta ‘frekwenza għolja jseħħ soluzzjonijiet ta’ interferenza

Figura 2: Passaġġ komuni tal-linja tas-sinjal tal-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. Provvista ta ‘enerġija analoga u diġitali biex tissepara: apparati ta’ frekwenza għolja huma ġeneralment sensittivi ħafna għall-istorbju diġitali, allura t-tnejn għandhom ikunu separati, imqabbdin flimkien fid-daħla tal-provvista ta ‘enerġija, jekk is-sinjal madwar il-partijiet analogi u diġitali tal- kliem, jistgħu jitqiegħdu fis-sinjal tul linja biex tnaqqas iż-żona tal-linja. Il-firxa diġitali-analoga użata għall-linja tas-sinjal tidher fil-Figura 3.

Id-disinn tal-PCB ta ‘frekwenza għolja jseħħ soluzzjonijiet ta’ interferenza

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.

Id-disinn tal-PCB ta ‘frekwenza għolja jseħħ soluzzjonijiet ta’ interferenza

Figura 4: Poġġi l-korda tad-dawl ħdejn il-linja tas-sinjal

Two, transmission line

Hemm biss żewġ linji ta ‘trasmissjoni possibbli f’PKB:

L-akbar problema tal-linja taż-żigarella u l-linja tal-majkrowejv hija r-riflessjoni. Ir-riflessjoni se tikkawża ħafna problemi. Pereżempju, is-sinjal tat-tagħbija jkun is-superpożizzjoni tas-sinjal oriġinali u s-sinjal tal-eku, li jżidu d-diffikultà tal-analiżi tas-sinjal. Riflessjoni tikkawża telf ta ‘ritorn (telf ta’ ritorn), li jaffettwa s-sinjal ħażin daqs l-interferenza ta ‘storbju addittiv:

1. Is-sinjal rifless lura għas-sors tas-sinjal iżid il-ħoss tas-sistema, u jagħmilha aktar diffiċli għar-riċevitur li jiddistingwi l-ħoss mis-sinjal;

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) Evita d-diskontinwità tal-impedenza tal-linji tat-trasmissjoni. Il-punt ta ‘impedenza mhux kontinwa huwa l-punt ta’ mutazzjoni tal-linja ta ‘trasmissjoni, bħal kantuniera dritta, minn toqba, eċċ., Għandu jiġi evitat kemm jista’ jkun. Metodi: Biex tevita kantunieri dritti tal-linja, kemm jista ‘jkun biex tmur Angolu jew ark ta’ 45 °, Angolu kbir jista ‘jkun ukoll; Uża kemm jista ‘jkun ftit toqob li jgħaddu, għax kull toqba li tgħaddi hija diskontinwità ta’ impedenza, kif muri fil-FIG. 5; Signals from the outer layer avoid passing through the inner layer and vice versa.

Id-disinn tal-PCB ta ‘frekwenza għolja jseħħ soluzzjonijiet ta’ interferenza

Figure 5: Method for eliminating transmission line interference

(b) Do not use stake lines. Minħabba li kull linja ta ‘munzelli hija sors ta’ storbju. Jekk il-linja tal-pil hija qasira, tista ‘tkun imqabbda fit-tarf tal-linja tat-trasmissjoni; Jekk il-linja tal-pil hija twila, tieħu l-linja tat-trasmissjoni ewlenija bħala s-sors u tipproduċi riflessjoni kbira, li tikkomplika l-problema. Huwa rrakkomandat li ma tużax.

It-tielet, l-igganċjar

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.

Id-disinn tal-PCB ta ‘frekwenza għolja jseħħ soluzzjonijiet ta’ interferenza

Figura 6: Igganċjar ta ‘impedenza komuni

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. Dan l-igganċjar jitnaqqas ħafna, allura ż-żewġ wajers jistgħu jiġu mibruma flimkien biex inaqqsu l-interferenza.

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. Id-daqs tal-krosstalk induttiv jiddependi fuq il-prossimità taż-żewġ linji, id-daqs taż-żona tal-linja, u l-impedenza tat-tagħbija affettwata.

5. L-igganċjar tal-kejbil tal-enerġija: Il-kejbils tal-enerġija ac jew DC huma interferiti minn interferenza elettromanjetika

Ittrasferixxi għal apparati oħra.

There are several ways to eliminate crosstalk in PCB design:

1. Iż-żewġ tipi ta ‘krosstalk jiżdiedu biż-żieda ta’ impedenza tat-tagħbija, għalhekk il-linji tas-sinjali sensittivi għall-interferenza kkawżata mill-krosstalk għandhom jintemmu sewwa.

2. Immassimizza d-distanza bejn il-linji tas-sinjali biex tnaqqas b’mod effettiv il-krosstalk abilità. Ġestjoni tal-art, spazjar bejn il-wajers (bħal linji tas-sinjali attivi u linji tal-art għall-iżolament, speċjalment fl-istat tal-qabża bejn il-linja tas-sinjal u l-art għall-intervall) u tnaqqas l-induttanza taċ-ċomb.

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. Għal krosstalk sensibbli, iż-żona tal-linja għandha tkun minimizzata, u jekk permessa, il-linja għandha tiġi eliminata.

5. Avoid signal sharing loops.

6. Oqgħod attent għall-integrità tas-sinjal: id-disinjatur għandu jimplimenta truf fil-proċess tal-iwweldjar biex isolvi l-integrità tas-sinjal. Id-disinjaturi li jużaw dan l-approċċ jistgħu jiffokaw fuq it-tul tal-mikrostrip tal-fojl tar-ram ta ‘lqugħ sabiex jiksbu prestazzjoni tajba ta’ integrità tas-sinjal. 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.

Hemm diversi modi kif telimina l-interferenza elettromanjetika fid-disinn tal-PCB:

1. Naqqas il-linji: Kull linja hija ekwivalenti għal antenna, għalhekk għandna nnaqqsu kemm jista ‘jkun in-numru ta’ linji, iż-żona tal-linji u l-effett ta ‘l-antenna tal-linji. 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.

Id-disinn tal-PCB ta ‘frekwenza għolja jseħħ soluzzjonijiet ta’ interferenza

Figura 7: Tipi ta ‘filtri

3. The shielding. Bħala riżultat tat-tul tal-ħarġa flimkien ma ‘ħafna artikoli ta’ lqugħ ta ‘diskussjoni, m’għadhomx introduzzjoni speċifika.

4. Reduce the speed of high-frequency devices.

5. Żid il-kostanti dielettrika tal-bord tal-PCB, li tista ‘tipprevjeni li l-partijiet ta’ frekwenza għolja bħal-linja ta ‘trasmissjoni ħdejn il-bord joħorġu’ l barra; 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. Wajers ikkunsidrati bir-reqqa u terminazzjonijiet xierqa jistgħu jeliminaw ir-riflessjonijiet.

3. Wajers ikkunsidrati bir-reqqa u terminazzjonijiet xierqa jistgħu jnaqqsu l-krosstalk abilità u induttiv.

4. It-trażżin tal-istorbju huwa meħtieġ biex jissodisfa r-rekwiżiti tal-EMC.