In naqshadaynta Guddiga PCB, iyadoo si xawli ah u kordheysa soo noqnoqoshada, waxaa jiri doona faragelin fara badan oo ka duwan ta guddiga PCB ee soo noqnoqda. Waxaa intaa dheer, iyadoo ay sii kordhayso soo noqnoqoshada iyo iska horimaadka u dhexeeya miniaturization -ka iyo qiimaha jaban ee guddiga PCB, faragelintaani waxay noqon doontaa mid aad u sii murugsan.

Cilmi -baarista dhabta ah, waxaan ku soo gabagabeyn karnaa inay jiraan afar dhinac oo faragelin ah, oo ay ku jiraan buuqa korontada, faragelinta xarigga gudbinta, isku -xirnaanta iyo faragelinta elektromagnetic (EMI). Iyada oo la falanqeynayo dhibaatooyinka faragelinta kala duwan ee PCB-ga oo noqnoqda oo la isku daro ku-dhaqanka shaqada, xalal wax-ku-ool ah ayaa la soo bandhigaa.

Marka hore, qaylada korontada

Wareegga soo noqnoqoshada sare, buuqa korontada ayaa saamayn cad ku leh calaamadda soo noqnoqoshada sare. Therefore, the first requirement of the power supply is low noise. Dabaqyada nadiifka ah ayaa muhiim u ah sida korontada nadiifka ah. Waayo? Astaamaha awoodda waxaa lagu muujiyey Jaantuska 1. Sida iska cad, korontadu waxay leedahay cillad gaar ah, oo caqabaddu waxay u qaybsan tahay korontada oo dhan, sidaa darteed, buuqa ayaa lagu dari doonaa korontada.

Then we should minimize the impedance of the power supply, so it is best to have a dedicated power supply layer and grounding layer. Naqshadeynta wareegga ee hf, waxaa aad u fiican in loo naqshadeeyo korontada sida lakab marka loo eego sida basaska inta badan, si loop -ku mar walba u raaco waddada is -hortaag yar.

In addition, the power board must provide a signal loop for all generated and received signals on the PCB. This minimizes the signal loop and thus reduces noise, which is often overlooked by low-frequency circuit designers.

Naqshadaynta PCB-ga ee aadka u badan ayaa dhacda xalalka faragelinta

Jaantuska 1: Astaamaha Awoodda

Waxaa jira dhowr siyaabood oo looga takhalusi karo buuqa awoodda naqshadeynta 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. If the opening of the power supply layer is too large, it is bound to affect the signal loop, the signal is forced to bypass, the loop area increases, and the noise increases. At the same time, if several signal lines are clustered near the opening and share the same loop, the common impedance will cause crosstalk. Eeg jaantuska 2.

Naqshadaynta PCB-ga ee aadka u badan ayaa dhacda xalalka faragelinta

Jaantus 2: Wadada guud ee wareegga signalada wareega

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. Analog iyo korontada dhijitaalka ah si ay u kala soocaan: aaladaha soo noqnoqda guud ahaan aad bay ugu nugul yihiin dhawaaqa dhijitaalka ah, markaa waa in labadooda la kala saaraa, oo lagu wada xidhaa albaabka korontada, haddii ishaarta ku jirta qaybaha analogga iyo dhijitaalka ah ereyada, waxaa lagu dhejin karaa signalada guud ahaan loop si loo yareeyo aagga loop -ka. Dhererka dhijitaalka-analogga ah ee loo adeegsaday loop signalka waxaa lagu muujiyey Jaantuska 3.

Naqshadaynta PCB-ga ee aadka u badan ayaa dhacda xalalka faragelinta

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.

Naqshadaynta PCB-ga ee aadka u badan ayaa dhacda xalalka faragelinta

Jaantuska 4: Xarigga korontada dhig xariiqda signalada

Two, transmission line

Waxaa jira laba khad oo keliya oo suurtogal ah oo gudbinta PCB -ga:

Dhibaatada ugu weyn ee xarriiqda xarriiqda iyo khadka microwave waa milicsiga. Dib -u -milicsigu wuxuu keeni doonaa dhibaatooyin badan. Tusaale ahaan, signalada culeysku wuxuu noqon doonaa kor -u -qaadista astaanta asalka ah iyo farta echo, taas oo kordhin doonta dhibka falanqaynta signalada. Milicsigu wuxuu keenaa lumis soo noqosho (lumis soo noqosho), taas oo saamaynaysa signal -ka si xun sida faragalinta qaylada dheeriga ah:

1. Calaamadda dib loogu milicsaday isha isha waxay kordhin doontaa buuqa nidaamka, taasoo ku adkaynaysa qofka wax qaata inuu kala saaro buuqa iyo signalada;

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) Ka fogow joojinta joojinta khadadka gudbinta. Barta carqaladaynta aan joogsiga lahayn waa barta is -beddelidda xarriiqda gudbinta, sida geeska tooska ah, daloolka, iwm, waa in laga fogaadaa intii suurtogal ah. Hababka: Si looga fogaado geesaha toosan ee xarriiqda, intii suurtogal ah in la aado 45 ° Angle or arc, Angle weyn sidoo kale waxay noqon kartaa; U isticmaal waxoogaa daloollo ah intii suurtogal ah, maxaa yeelay mid kasta oo daloolku waa joojinta joojinta, sida ku cad FIG. 5; Signals from the outer layer avoid passing through the inner layer and vice versa.

Naqshadaynta PCB-ga ee aadka u badan ayaa dhacda xalalka faragelinta

Figure 5: Method for eliminating transmission line interference

(b) Do not use stake lines. Sababtoo ah xarig kasta oo raso ah waa il buuq. Haddii xariiqda raso ay gaaban tahay, waxaa lagu xiri karaa dhammaadka khadka gudbinta; Haddii xarriiqda raaggu ay dheer tahay, waxay qaadan doontaa khadka ugu weyn ee gudbinta oo ah isha waxayna soo saari doontaa milicsiga weyn, taas oo dhibka sii adkayn doonta. Waxaa lagu talinayaa inaadan isticmaalin.

Saddexaad, isku xidhka

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.

Naqshadaynta PCB-ga ee aadka u badan ayaa dhacda xalalka faragelinta

Jaantus 6: Isku -dhafka is -dhaafsiga ee caadiga ah

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. Isku -xidhkan si weyn ayaa loo dhimay, sidaa darteed labada fiilo waa la wada qalloocin karaa si loo yareeyo faragelinta.

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. Cabbirka crosstalk -ku -kicinta wuxuu ku xiran yahay u dhawaanshaha labada loops, cabbirka aagga loop -ka, iyo is -hortaaga culeyska uu saameeyay.

5. Xidhiidhka fiilada korontada: Xadhkaha korontada ac ama DC waxaa farageliya faragelinta elektromagnetka

U wareejinta aaladaha kale.

There are several ways to eliminate crosstalk in PCB design:

1. Labada nooc ee crosstalk -ku waxay kordhaan korodhka culayska culayska, markaa khadadka signalada ee xasaasiga u ah faragelinta ay keento dariiqa waa in si habboon loo joojiyaa.

2. Ballaadhi masaafada u dhexaysa khadadka signalada si wax -ku -ool ah loo yareeyo waddo -mareenka awoodda leh. Maaraynta dhulka, kala fogaanshaha u dhexeeya fiilooyinka (sida khadadka signalada firfircoon iyo khadadka dhulka ee go’doominta, gaar ahaan marka la boodo inta u dhexaysa xariiqda signalada iyo dhulka ilaa inta u dhexaysa) oo la yareeyo kicinta rasaasta.

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. Si aad u hesho crosstalk macquul ah, aagga loop waa in la yareeyaa, oo haddii la oggolaado, loop waa in la tirtiraa.

5. Avoid signal sharing loops.

6. U fiirso daacadnimada signalada: nashqadeeyuhu waa inuu hirgeliyaa dhammaadka geedi -socodka alxanka si loo xalliyo daacadnimada signalada. Naqshadayaasha isticmaalaya habkan waxay diiradda saari karaan dhererka microstrip -ka ee foornada naxaasta gaashaaman si loo helo waxqabad wanaagsan oo ah daacadnimada signalada. 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.

There are several ways to eliminate electromagnetic interference in PCB design:

1. Iska yaree siddooyinka: Loop kasta wuxuu u dhigmaa anteeno, sidaa darteed waxaan u baahannahay inaan yareyno tirada loopyada, aagga loopyada iyo saamaynta anteenooyinka ee siddooyinku. 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.

Naqshadaynta PCB-ga ee aadka u badan ayaa dhacda xalalka faragelinta

Jaantus 7: Noocyada shaandhaynta

3. The shielding. Natiijada dhererka arrinta oo lagu daray doodo badan oo maqaallo gaashaaman ah, hadda ka dib ma aha hordhac gaar ah.

4. Reduce the speed of high-frequency devices.

5. Kordhi joogteynta korontada ee guddiga PCB, taas oo ka hortagi karta in qaybo badan oo soo noqnoqda sida khadka gudbinta ee u dhow guddiga ay ka soo dillaacdo dibadda; 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. Carefully considered wiring and proper terminations can reduce capacitive and inductive crosstalk.

4. Cabbinta buuqa ayaa loo baahan yahay si loo buuxiyo shuruudaha EMC.